2020 |
| A Gaudel; O R Cooper; K-L Chang; I Bourgeois; J R Ziemke; S A Strode; L D Oman; P Sellitto; P Nédélec; R Blot; V Thouret; C Granier: Aircraft observations since the 1990s reveal increases of tropospheric ozone at multiple locations across the Northern Hemisphere. Science Advances, 6 (34), 2020. (Type: Journal Article | Abstract | Links | BibTeX) @article{Gaudel2020, title = {Aircraft observations since the 1990s reveal increases of tropospheric ozone at multiple locations across the Northern Hemisphere}, author = {A Gaudel; O R Cooper; K-L Chang; I Bourgeois; J R Ziemke; S A Strode; L D Oman; P Sellitto; P Nédélec; R Blot; V Thouret; C Granier}, url = {https://advances.sciencemag.org/content/6/34/eaba8272.full}, doi = {10.1126/sciadv.aba8272}, year = {2020}, date = {2020-08-21}, journal = {Science Advances}, volume = {6}, number = {34}, abstract = {Tropospheric ozone is an important greenhouse gas, is detrimental to human health and crop and ecosystem productivity, and controls the oxidizing capacity of the troposphere. Because of its high spatial and temporal variability and limited observations, quantifying net tropospheric ozone changes across the Northern Hemisphere on time scales of two decades had not been possible. Here, we show, using newly available observations from an extensive commercial aircraft monitoring network, that tropospheric ozone has increased above 11 regions of the Northern Hemisphere since the mid-1990s, consistent with the OMI/MLS satellite product. The net result of shifting anthropogenic ozone precursor emissions has led to an increase of ozone and its radiative forcing above all 11 study regions of the Northern Hemisphere, despite NOx emission reductions at midlatitudes.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Tropospheric ozone is an important greenhouse gas, is detrimental to human health and crop and ecosystem productivity, and controls the oxidizing capacity of the troposphere. Because of its high spatial and temporal variability and limited observations, quantifying net tropospheric ozone changes across the Northern Hemisphere on time scales of two decades had not been possible. Here, we show, using newly available observations from an extensive commercial aircraft monitoring network, that tropospheric ozone has increased above 11 regions of the Northern Hemisphere since the mid-1990s, consistent with the OMI/MLS satellite product. The net result of shifting anthropogenic ozone precursor emissions has led to an increase of ozone and its radiative forcing above all 11 study regions of the Northern Hemisphere, despite NOx emission reductions at midlatitudes. |
| A Petzold; P Neis; M Rütimann; S Rohs; F Berkes; H G J Smit; M Krämer; N Spelten; P Spichtinger; P Nédélec; A Wahner: Ice-supersaturated air masses in the northern mid-latitudes from regular in situ observations by passenger aircraft: vertical distribution, seasonality and tropospheric fingerprint. Atmospheric Chemistry and Physics, 20 , pp. 8157–8179, 2020. (Type: Journal Article | Abstract | Links | BibTeX) @article{Wahner2020, title = {Ice-supersaturated air masses in the northern mid-latitudes from regular in situ observations by passenger aircraft: vertical distribution, seasonality and tropospheric fingerprint}, author = {A Petzold; P Neis; M Rütimann; S Rohs; F Berkes; H G J Smit; M Krämer; N Spelten; P Spichtinger; P Nédélec; A Wahner}, url = {https://doi.org/10.5194/acp-20-8157-2020}, year = {2020}, date = {2020-07-14}, journal = {Atmospheric Chemistry and Physics}, volume = {20}, pages = {8157–8179}, abstract = {The vertical distribution and seasonal variation of water vapour volume mixing ratio (H2O VMR), of relative humidity with respect to ice (RHice) and particularly of regions with ice-supersaturated air masses (ISSRs) in the extratropical upper troposphere and lowermost stratosphere are investigated at northern mid-latitudes over the eastern North American, North Atlantic and European regions for the period 1995 to 2010. Observation data originate from regular and continuous long-term measurements on board instrumented passenger aircraft in the framework of the European research programme MOZAIC (1994–2010), which continues as the European research infrastructure IAGOS (from 2011). Data used in our study result from collocated observations of O3 VMR, RHice and temperature, as well as H2O VMR deduced from RHice and temperature data. The in situ observations of H2O VMR and RHice with a vertical resolution of 30 hPa (< 750 m at the extratropical tropopause level) and a horizontal resolution of 1 km resolve detailed features of the distribution of water vapour and ice-supersaturated air relative to the thermal tropopause, including their seasonal and regional variability and chemical signatures at various distances from the tropopause layer. Annual cycles of the investigated properties document the highest H2O VMR and temperatures above the thermal tropopause in the summer months, whereas RHice above the thermal tropopause remains almost constant in the course of the year. Over all investigated regions, upper tropospheric air masses close to the tropopause level are nearly saturated with respect to ice and contain a significant fraction of ISSRs with a distinct seasonal cycle of minimum values in summer (30 % over the ocean, 20 %–25 % over land) and maximum values in late winter (35 %–40 % over both land and ocean). Above the thermal tropopause, ISSRs are occasionally observed with an occurrence probability of 1.5 ± 1.1 %, whereas above the dynamical tropopause at 2 PVU (PVU: potential vorticity unit), the occurrence probability increases 4-fold to 8.4 ± 4.4 %. In both coordinate systems related to tropopause height (TPH), the ISSR occurrence probabilities drop to values below 1 % for the next higher air mass layer with pressure levels p < pTPH−15 hPa. For both tropopause definitions, the tropospheric nature or fingerprint, based on O3 VMR, indicates the continuing tropospheric influence on ISSRs inside and above the respective tropopause layer. For the non-ISSRs, however, the stratospheric nature is clearly visible above the thermal tropopause, whereas above the dynamical tropopause the air masses show a still substantial tropospheric influence. For all three regions, seasonal deviations from the long-term annual cycle of ISSR occurrence show no significant trends over the observation period of 15 years, whereas a statistically significant correlation between the North Atlantic Oscillation (NAO) index and the deviation of ISSR occurrence from the long-term average is observed for the North Atlantic region but not for the eastern North American and European regions.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The vertical distribution and seasonal variation of water vapour volume mixing ratio (H2O VMR), of relative humidity with respect to ice (RHice) and particularly of regions with ice-supersaturated air masses (ISSRs) in the extratropical upper troposphere and lowermost stratosphere are investigated at northern mid-latitudes over the eastern North American, North Atlantic and European regions for the period 1995 to 2010. Observation data originate from regular and continuous long-term measurements on board instrumented passenger aircraft in the framework of the European research programme MOZAIC (1994–2010), which continues as the European research infrastructure IAGOS (from 2011). Data used in our study result from collocated observations of O3 VMR, RHice and temperature, as well as H2O VMR deduced from RHice and temperature data. The in situ observations of H2O VMR and RHice with a vertical resolution of 30 hPa (< 750 m at the extratropical tropopause level) and a horizontal resolution of 1 km resolve detailed features of the distribution of water vapour and ice-supersaturated air relative to the thermal tropopause, including their seasonal and regional variability and chemical signatures at various distances from the tropopause layer. Annual cycles of the investigated properties document the highest H2O VMR and temperatures above the thermal tropopause in the summer months, whereas RHice above the thermal tropopause remains almost constant in the course of the year. Over all investigated regions, upper tropospheric air masses close to the tropopause level are nearly saturated with respect to ice and contain a significant fraction of ISSRs with a distinct seasonal cycle of minimum values in summer (30 % over the ocean, 20 %–25 % over land) and maximum values in late winter (35 %–40 % over both land and ocean). Above the thermal tropopause, ISSRs are occasionally observed with an occurrence probability of 1.5 ± 1.1 %, whereas above the dynamical tropopause at 2 PVU (PVU: potential vorticity unit), the occurrence probability increases 4-fold to 8.4 ± 4.4 %. In both coordinate systems related to tropopause height (TPH), the ISSR occurrence probabilities drop to values below 1 % for the next higher air mass layer with pressure levels p < pTPH−15 hPa. For both tropopause definitions, the tropospheric nature or fingerprint, based on O3 VMR, indicates the continuing tropospheric influence on ISSRs inside and above the respective tropopause layer. For the non-ISSRs, however, the stratospheric nature is clearly visible above the thermal tropopause, whereas above the dynamical tropopause the air masses show a still substantial tropospheric influence. For all three regions, seasonal deviations from the long-term annual cycle of ISSR occurrence show no significant trends over the observation period of 15 years, whereas a statistically significant correlation between the North Atlantic Oscillation (NAO) index and the deviation of ISSR occurrence from the long-term average is observed for the North Atlantic region but not for the eastern North American and European regions. |
| C J Corwin, T P Banyard: Multidecadal Measurements of UTLS Gravity Waves Derived From Commercial Flight Data. Journal of Geophysical Research, 125 (19), 2020. (Type: Journal Article | Abstract | Links | BibTeX) @article{Corwin2020, title = {Multidecadal Measurements of UTLS Gravity Waves Derived From Commercial Flight Data}, author = {C J Corwin, T P Banyard}, url = {https://doi.org/10.1029/2020JD033445}, year = {2020}, date = {2020-09-21}, journal = {Journal of Geophysical Research}, volume = {125}, number = {19}, abstract = {Gravity waves (GWs) are key drivers of atmospheric dynamics, with major impacts on climate and weather processes. However, they are challenging to measure in observational data, and as a result no large‐area multidecadal GW time series yet exist. This has prevented us from quantifying the interactions between GWs and long–timescale climate processes. Here, we exploit temperatures measured by commercial aircraft since 1994 as part of the In‐Service Aircraft for a Global Observing System (IAGOS) atmospheric chemistry research program to produce a novel 26‐year time series of upper troposphere/lower stratosphere (UTLS) GW measurements across most of the Northern Hemisphere. We analyze 90,342 flight hours (76.2 million flight kilometers) of data, typically at a temporal resolution of seconds and with high temperature precision. We show that GW activity in the Northern Hemisphere UTLS is consistently strongest north of and above the upper tropospheric jet. We also show that GW sources not typically observed in stratospheric data but assumed in model schemes, such as the Rocky Mountains, are visible at these altitudes, suggesting that wave momentum from these sources is deposited specifically between ∼200 and 50 hPa. Our data show no significant impact of the Quasi‐Biennial Oscillation, the Northern Annular Mode, or climate change. However, we do see strong evidence of links with the El Niño–Southern Oscillation, which modulates the measured GW signal by ∼25%, and weak evidence of links with the 11‐year solar cycle. These results have important implications for atmospheric process modeling and for understanding large‐scale climate teleconnections.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Gravity waves (GWs) are key drivers of atmospheric dynamics, with major impacts on climate and weather processes. However, they are challenging to measure in observational data, and as a result no large‐area multidecadal GW time series yet exist. This has prevented us from quantifying the interactions between GWs and long–timescale climate processes. Here, we exploit temperatures measured by commercial aircraft since 1994 as part of the In‐Service Aircraft for a Global Observing System (IAGOS) atmospheric chemistry research program to produce a novel 26‐year time series of upper troposphere/lower stratosphere (UTLS) GW measurements across most of the Northern Hemisphere. We analyze 90,342 flight hours (76.2 million flight kilometers) of data, typically at a temporal resolution of seconds and with high temperature precision. We show that GW activity in the Northern Hemisphere UTLS is consistently strongest north of and above the upper tropospheric jet. We also show that GW sources not typically observed in stratospheric data but assumed in model schemes, such as the Rocky Mountains, are visible at these altitudes, suggesting that wave momentum from these sources is deposited specifically between ∼200 and 50 hPa. Our data show no significant impact of the Quasi‐Biennial Oscillation, the Northern Annular Mode, or climate change. However, we do see strong evidence of links with the El Niño–Southern Oscillation, which modulates the measured GW signal by ∼25%, and weak evidence of links with the 11‐year solar cycle. These results have important implications for atmospheric process modeling and for understanding large‐scale climate teleconnections. |
| F Roux; H Clark; K-Y Wang; S Rohs; B Sauvage; P Nédélec;: The influence of typhoons on atmospheric composition deduced from IAGOS measurements over Taipei. Atmospheric Chemistry and Physics, 20 , pp. 3945–3963, 2020. (Type: Journal Article | Abstract | Links | BibTeX) @article{Roux2020, title = {The influence of typhoons on atmospheric composition deduced from IAGOS measurements over Taipei}, author = {F Roux; H Clark; K-Y Wang; S Rohs; B Sauvage; P Nédélec;}, url = {https://doi.org/10.5194/acp-20-3945-2020}, year = {2020}, date = {2020-04-02}, journal = {Atmospheric Chemistry and Physics}, volume = {20}, pages = {3945–3963}, abstract = {The research infrastructure IAGOS (In-Service Aircraft for a Global Observing System) equips commercial aircraft with instruments to monitor the composition of the atmosphere during flights around the world. In this article, we use data from two China Airlines aircraft based in Taipei (Taiwan) which provided daily measurements of ozone, carbon monoxide and water vapour throughout the summer of 2016. We present time series, from the surface to the upper troposphere, of ozone, carbon monoxide and relative humidity near Taipei, focusing on periods influenced by the passage of typhoons. We examine landing and take-off profiles in the vicinity of tropical cyclones using ERA-5 reanalyses to elucidate the origin of the anomalies in the vertical distribution of these chemical species. Results indicate a high ozone content in the upper- to middle-troposphere track of the storms. The high ozone mixing ratios are generally correlated with potential vorticity and anti-correlated with relative humidity, suggesting stratospheric origin. These results suggest that tropical cyclones participate in transporting air from the stratosphere to troposphere and that such transport could be a regular feature of typhoons. After the typhoons passed Taiwan, the tropospheric column was filled with substantially lower ozone mixing ratios due to the rapid uplift of marine boundary layer air. At the same time, the relative humidity increased, and carbon monoxide mixing ratios fell. Locally, therefore, the passage of typhoons has a positive effect on air quality at the surface, cleansing the atmosphere and reducing the mixing ratios of pollutants such as CO and O3.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The research infrastructure IAGOS (In-Service Aircraft for a Global Observing System) equips commercial aircraft with instruments to monitor the composition of the atmosphere during flights around the world. In this article, we use data from two China Airlines aircraft based in Taipei (Taiwan) which provided daily measurements of ozone, carbon monoxide and water vapour throughout the summer of 2016. We present time series, from the surface to the upper troposphere, of ozone, carbon monoxide and relative humidity near Taipei, focusing on periods influenced by the passage of typhoons. We examine landing and take-off profiles in the vicinity of tropical cyclones using ERA-5 reanalyses to elucidate the origin of the anomalies in the vertical distribution of these chemical species. Results indicate a high ozone content in the upper- to middle-troposphere track of the storms. The high ozone mixing ratios are generally correlated with potential vorticity and anti-correlated with relative humidity, suggesting stratospheric origin. These results suggest that tropical cyclones participate in transporting air from the stratosphere to troposphere and that such transport could be a regular feature of typhoons. After the typhoons passed Taiwan, the tropospheric column was filled with substantially lower ozone mixing ratios due to the rapid uplift of marine boundary layer air. At the same time, the relative humidity increased, and carbon monoxide mixing ratios fell. Locally, therefore, the passage of typhoons has a positive effect on air quality at the surface, cleansing the atmosphere and reducing the mixing ratios of pollutants such as CO and O3. |
| I Bourgeois; J Peischl; C R. Thompson; K C. Aikin; T Campos; H Clark; R Commane; B Daube; G W Diskin; J W Elkins; Ru-Shan Gao; A Gaudel; E J Hintsa; B J Johnson; R Kivi; K McKain; F L Moore; D D Parrish; R Querel; E Ray; R Sánchez; C Sweeney; D W Tarasick; A M Thompson; V Thouret; J C Witte; S C Wofsy; T B Ryerson: Global-scale distribution of ozone in the remote troposphere from ATom and HIPPO airborne field missions. Atmospheric Chemistry and Physics, Forthcoming. (Type: Journal Article | Abstract | Links | BibTeX) @article{Ryerson2020, title = {Global-scale distribution of ozone in the remote troposphere from ATom and HIPPO airborne field missions}, author = {I Bourgeois; J Peischl; C R. Thompson; K C. Aikin; T Campos; H Clark; R Commane; B Daube; G W Diskin; J W Elkins; Ru-Shan Gao; A Gaudel; E J Hintsa; B J Johnson; R Kivi; K McKain; F L Moore; D D Parrish; R Querel; E Ray; R Sánchez; C Sweeney; D W Tarasick; A M Thompson; V Thouret; J C Witte; S C Wofsy; T B Ryerson}, url = {https://doi.org/10.5194/acp-2020-315}, year = {2020}, date = {2020-07-25}, journal = {Atmospheric Chemistry and Physics}, abstract = {ATom and HIPPO represent the first global-scale, vertically resolved measurements of O3 distributions throughout the troposphere, with HIPPO sampling the Pacific basin and ATom sampling both the Pacific and Atlantic basins. Given the relatively limited temporal resolution of these two campaigns, we first compare ATom and HIPPO ozone data to longer-term observational records to establish the representativeness of our dataset. We show that these two airborne campaigns captured on average 53, 54, and 38 % of the ozone variability in the marine boundary layer, free troposphere, and upper troposphere/lower stratosphere (UTLS), respectively, at nine well-established ozonesonde sites. Additionally, ATom captured the most frequent ozone concentrations measured by regular commercial aircraft flights in the northern Atlantic UTLS. We then use the repeated vertical profiles carried out during these two campaigns to provide a global-scale picture of tropospheric ozone spatial and vertical distributions throughout the remote troposphere. We highlight a clear hemispheric gradient, with greater ozone in the northern hemisphere consistent with greater precursor emissions. We also show that the ozone distribution below 8 km was similar in the extra-tropics of the Atlantic and Pacific basins due to zonal circulation patterns. However, twice as much ozone was found in the tropical Atlantic than in the tropical Pacific, due to well-documented dynamical patterns transporting continental air masses over the Atlantic. We finally show that the seasonal variability of tropospheric ozone over the Pacific and the Atlantic basins is driven by transported continental plumes and photochemistry, and the vertical distribution is driven by photochemistry and mixing with stratospheric air. This new dataset is essential for improving our understanding of both ozone production and loss processes in remote regions, as well as the influence of anthropogenic emissions on baseline ozone.}, keywords = {}, pubstate = {forthcoming}, tppubtype = {article} } ATom and HIPPO represent the first global-scale, vertically resolved measurements of O3 distributions throughout the troposphere, with HIPPO sampling the Pacific basin and ATom sampling both the Pacific and Atlantic basins. Given the relatively limited temporal resolution of these two campaigns, we first compare ATom and HIPPO ozone data to longer-term observational records to establish the representativeness of our dataset. We show that these two airborne campaigns captured on average 53, 54, and 38 % of the ozone variability in the marine boundary layer, free troposphere, and upper troposphere/lower stratosphere (UTLS), respectively, at nine well-established ozonesonde sites. Additionally, ATom captured the most frequent ozone concentrations measured by regular commercial aircraft flights in the northern Atlantic UTLS. We then use the repeated vertical profiles carried out during these two campaigns to provide a global-scale picture of tropospheric ozone spatial and vertical distributions throughout the remote troposphere. We highlight a clear hemispheric gradient, with greater ozone in the northern hemisphere consistent with greater precursor emissions. We also show that the ozone distribution below 8 km was similar in the extra-tropics of the Atlantic and Pacific basins due to zonal circulation patterns. However, twice as much ozone was found in the tropical Atlantic than in the tropical Pacific, due to well-documented dynamical patterns transporting continental air masses over the Atlantic. We finally show that the seasonal variability of tropospheric ozone over the Pacific and the Atlantic basins is driven by transported continental plumes and photochemistry, and the vertical distribution is driven by photochemistry and mixing with stratospheric air. This new dataset is essential for improving our understanding of both ozone production and loss processes in remote regions, as well as the influence of anthropogenic emissions on baseline ozone. |
| K-L Chang; O R Cooper; A Gaudel; I Petropavlovskikh; V Thouret: Statistical regularization for trend detection: an integrated approach for detecting long-term trends from sparse tropospheric ozone profiles. Atmospheric Chemistry and Physics, 20 , pp. 9915–9938, 2020. (Type: Journal Article | Abstract | Links | BibTeX) @article{Thouret;2020, title = {Statistical regularization for trend detection: an integrated approach for detecting long-term trends from sparse tropospheric ozone profiles}, author = {K-L Chang; O R Cooper; A Gaudel; I Petropavlovskikh; V Thouret}, url = {https://doi.org/10.5194/acp-20-9915-2020}, year = {2020}, date = {2020-08-26}, journal = {Atmospheric Chemistry and Physics}, volume = {20}, pages = { 9915–9938}, abstract = {Detecting a tropospheric ozone trend from sparsely sampled ozonesonde profiles (typically once per week) is challenging due to the short-lived anomalies in the time series resulting from ozone's high temporal variability. To enhance trend detection, we have developed a sophisticated statistical approach that utilizes a geoadditive model to assess ozone variability across a time series of vertical profiles. Treating the profile time series as a set of individual time series on discrete pressure surfaces, a class of smoothing spline ANOVA (analysis of variance) models is used for the purpose of jointly modeling multiple correlated time series (on separate pressure surfaces) by their associated seasonal and interannual variabilities. This integrated fit method filters out the unstructured variation through a statistical regularization (i.e., a roughness penalty) by taking advantage of the additional correlated data points available on the pressure surfaces above and below the surface of interest. We have applied this technique to the trend analysis of the vertically correlated time series of tropospheric ozone observations from (1) IAGOS (In-service Aircraft for a Global Observing System) commercial aircraft profiles above Europe and China throughout 1994–2017 and (2) NOAA GML's (Global Monitoring Laboratory) ozonesonde records at Hilo, Hawaii, (1982–2018) and Trinidad Head, California (1998–2018). We illustrate the ability of this technique to detect a consistent trend estimate and its effectiveness in reducing the associated uncertainty in the profile data due to the low sampling frequency. We also conducted a sensitivity analysis of frequent IAGOS profiles above Europe (approximately 120 profiles per month) to determine how many profiles in a month are required for reliable long-term trend detection. When ignoring the vertical correlation, we found that a typical sampling strategy (i.e. four profiles per month) might result in 7 % of sampled trends falling outside the 2σ uncertainty interval derived from the full dataset with an associated 10 % of mean absolute percentage error. Based on a series of sensitivity studies, we determined optimal sampling frequencies for (1) basic trend detection and (2) accurate quantification of the trend. When applying the integrated fit method, we find that a typical sampling frequency of four profiles per month is adequate for basic trend detection; however, accurate quantification of the trend requires 14 profiles per month. Accurate trend quantification can be achieved with only 10 profiles per month if a regular sampling frequency is applied. In contrast, the standard separated fit method, which ignores the vertical correlation between pressure surfaces, requires 8 profiles per month for basic trend detection and 18 profiles per month for accurate trend quantification. While our method improves trend detection from sparse datasets, the key to substantially reducing the uncertainty is to increase the sampling frequency.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Detecting a tropospheric ozone trend from sparsely sampled ozonesonde profiles (typically once per week) is challenging due to the short-lived anomalies in the time series resulting from ozone's high temporal variability. To enhance trend detection, we have developed a sophisticated statistical approach that utilizes a geoadditive model to assess ozone variability across a time series of vertical profiles. Treating the profile time series as a set of individual time series on discrete pressure surfaces, a class of smoothing spline ANOVA (analysis of variance) models is used for the purpose of jointly modeling multiple correlated time series (on separate pressure surfaces) by their associated seasonal and interannual variabilities. This integrated fit method filters out the unstructured variation through a statistical regularization (i.e., a roughness penalty) by taking advantage of the additional correlated data points available on the pressure surfaces above and below the surface of interest. We have applied this technique to the trend analysis of the vertically correlated time series of tropospheric ozone observations from (1) IAGOS (In-service Aircraft for a Global Observing System) commercial aircraft profiles above Europe and China throughout 1994–2017 and (2) NOAA GML's (Global Monitoring Laboratory) ozonesonde records at Hilo, Hawaii, (1982–2018) and Trinidad Head, California (1998–2018). We illustrate the ability of this technique to detect a consistent trend estimate and its effectiveness in reducing the associated uncertainty in the profile data due to the low sampling frequency. We also conducted a sensitivity analysis of frequent IAGOS profiles above Europe (approximately 120 profiles per month) to determine how many profiles in a month are required for reliable long-term trend detection. When ignoring the vertical correlation, we found that a typical sampling strategy (i.e. four profiles per month) might result in 7 % of sampled trends falling outside the 2σ uncertainty interval derived from the full dataset with an associated 10 % of mean absolute percentage error. Based on a series of sensitivity studies, we determined optimal sampling frequencies for (1) basic trend detection and (2) accurate quantification of the trend. When applying the integrated fit method, we find that a typical sampling frequency of four profiles per month is adequate for basic trend detection; however, accurate quantification of the trend requires 14 profiles per month. Accurate trend quantification can be achieved with only 10 profiles per month if a regular sampling frequency is applied. In contrast, the standard separated fit method, which ignores the vertical correlation between pressure surfaces, requires 8 profiles per month for basic trend detection and 18 profiles per month for accurate trend quantification. While our method improves trend detection from sparse datasets, the key to substantially reducing the uncertainty is to increase the sampling frequency. |
| M Cussac; V Marécal; V Thouret; B Josse; B Sauvage: The impact of biomass burning on upper tropospheric carbon monoxide: a study using MOCAGE global model and IAGOS airborne data. Atmospheric Chemistry and Physics, 20 , pp. 9393–9417, 2020. (Type: Journal Article | Abstract | Links | BibTeX) @article{Sauvage2020, title = {The impact of biomass burning on upper tropospheric carbon monoxide: a study using MOCAGE global model and IAGOS airborne data}, author = {M Cussac; V Marécal; V Thouret; B Josse; B Sauvage}, url = {https://doi.org/10.5194/acp-20-9393-2020}, year = {2020}, date = {2020-08-11}, journal = {Atmospheric Chemistry and Physics}, volume = {20}, pages = {9393–9417}, abstract = {In this paper, the fate of biomass burning emissions of carbon monoxide is studied with the global chemistry–transport model MOCAGE (MOdélisation de Chimie Atmosphérique à Grande Échelle) and IAGOS (In-Service Aircraft for a Global Observing System) airborne measurements for the year 2013. The objectives are firstly to improve their representation within the model and secondly to analyse their contribution to carbon monoxide concentrations in the upper troposphere. At first, a new implementation of biomass burning injection is developed for MOCAGE, using the latest products available in Global Fire Assimilation System (GFAS) biomass burning inventory on plume altitude and injection height. This method is validated against IAGOS observations of CO made in fire plumes, identified thanks to the SOFT-IO source attribution data. The use of these GFAS products leads to improved MOCAGE skill to simulate fire plumes originating from boreal forest wildfires. It is also shown that this new biomass burning injection method modifies the distribution of carbon monoxide in the free and upper troposphere, mostly at northern boreal latitudes. Then, MOCAGE performance is evaluated in general in the upper troposphere and lower stratosphere in comparison to the IAGOS observations and is shown to be very good, with very low bias and good correlations between the model and the observations. Finally, we analyse the contribution of biomass burning to upper tropospheric carbon monoxide concentrations. This is done by comparing simulations where biomass are toggled on and off in different source regions of the world to assess their individual influence. The two regions contributing the most to upper tropospheric CO are found to be the boreal forests and equatorial Africa, in accordance with the quantities of CO they emit each year and the fact that they undergo fast vertical transport: deep convection in the tropics and pyroconvection at high latitudes. It is also found that biomass burning contributes more than 11 % on average to the CO concentrations in the upper troposphere and up to 50 % at high latitudes during the wildfire season.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this paper, the fate of biomass burning emissions of carbon monoxide is studied with the global chemistry–transport model MOCAGE (MOdélisation de Chimie Atmosphérique à Grande Échelle) and IAGOS (In-Service Aircraft for a Global Observing System) airborne measurements for the year 2013. The objectives are firstly to improve their representation within the model and secondly to analyse their contribution to carbon monoxide concentrations in the upper troposphere. At first, a new implementation of biomass burning injection is developed for MOCAGE, using the latest products available in Global Fire Assimilation System (GFAS) biomass burning inventory on plume altitude and injection height. This method is validated against IAGOS observations of CO made in fire plumes, identified thanks to the SOFT-IO source attribution data. The use of these GFAS products leads to improved MOCAGE skill to simulate fire plumes originating from boreal forest wildfires. It is also shown that this new biomass burning injection method modifies the distribution of carbon monoxide in the free and upper troposphere, mostly at northern boreal latitudes. Then, MOCAGE performance is evaluated in general in the upper troposphere and lower stratosphere in comparison to the IAGOS observations and is shown to be very good, with very low bias and good correlations between the model and the observations. Finally, we analyse the contribution of biomass burning to upper tropospheric carbon monoxide concentrations. This is done by comparing simulations where biomass are toggled on and off in different source regions of the world to assess their individual influence. The two regions contributing the most to upper tropospheric CO are found to be the boreal forests and equatorial Africa, in accordance with the quantities of CO they emit each year and the fact that they undergo fast vertical transport: deep convection in the tropics and pyroconvection at high latitudes. It is also found that biomass burning contributes more than 11 % on average to the CO concentrations in the upper troposphere and up to 50 % at high latitudes during the wildfire season. |
| P Reutter; P Neis; S Rohs; B Sauvage: Ice supersaturated regions: properties and validation of ERA-Interim reanalysis with IAGOS in situ water vapour measurements. Atmospheric Chemistry and Physics, 20 , pp. 787–804, 2020. (Type: Journal Article | Abstract | Links | BibTeX) @article{Sauvage2020b, title = {Ice supersaturated regions: properties and validation of ERA-Interim reanalysis with IAGOS in situ water vapour measurements}, author = {P Reutter; P Neis; S Rohs; B Sauvage}, url = {https://doi.org/10.5194/acp-20-787-2020}, year = {2020}, date = {2020-01-23}, journal = {Atmospheric Chemistry and Physics}, volume = {20}, pages = {787–804}, abstract = {Cirrus clouds and their potential formation regions, so-called ice supersaturated regions (ISSRs), with values of relative humidity with respect to ice exceeding 100 %, occur frequently in the tropopause region. It is assumed that ISSRs and cirrus clouds can change the tropopause structure by diabatic processes, driven by latent heating due to phase transition and interaction with radiation. For many research questions, a three-dimensional picture including a sufficient temporal resolution of the water vapour fields in the tropopause region is required. This requirement is fulfilled nowadays by reanalysis products such as the European Centre for Medium-Range Weather Forecasts (ECMWF) ERA-Interim reanalysis. However, for a meaningful investigation of water vapour in the tropopause region, a comparison of the reanalysis data with measurement is advisable, since it is difficult to measure water vapour and to assimilate meaningful measurements into reanalysis products. Here, we present an intercomparison of high-resolution in situ measurements aboard passenger aircraft within the European Research Infrastructure IAGOS (In-service Aircraft for a Global Observing System; http://www.iagos.org, last access: 15 January 2020) with ERA-Interim. Temperature and humidity data over the North Atlantic from 2000 to 2009 are compared relative to the dynamical tropopause. The comparison of the temperature shows good agreement between the measurement and ERA-Interim. While ERA-Interim also shows the main features of the water vapour measurements of IAGOS, the variability of the data is clearly smaller in the reanalysis data set. The combination of temperature and water vapour leads to the relative humidity with respect to ice (RHi). Here, ERA-Interim deviates from the measurements concerning values larger than RHi=100 %, both in number and strength of supersaturation. Also, pathlengths of ISSRs along flight tracks are investigated, representing macrophysical properties as linked to atmospheric flows. The comparison of ISSR pathlengths shows distinct differences, which can be traced back to the spatial resolution of both data sets. Also, the seasonal cycle and height dependence of pathlengths changes for the different data sets due to their spatial resolution. IAGOS shows a significantly greater amount of smaller ISSRs compared to ERA-Interim. Good agreement begins only at pathlengths on the order of the ERA-Interim spatial resolution and larger.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Cirrus clouds and their potential formation regions, so-called ice supersaturated regions (ISSRs), with values of relative humidity with respect to ice exceeding 100 %, occur frequently in the tropopause region. It is assumed that ISSRs and cirrus clouds can change the tropopause structure by diabatic processes, driven by latent heating due to phase transition and interaction with radiation. For many research questions, a three-dimensional picture including a sufficient temporal resolution of the water vapour fields in the tropopause region is required. This requirement is fulfilled nowadays by reanalysis products such as the European Centre for Medium-Range Weather Forecasts (ECMWF) ERA-Interim reanalysis. However, for a meaningful investigation of water vapour in the tropopause region, a comparison of the reanalysis data with measurement is advisable, since it is difficult to measure water vapour and to assimilate meaningful measurements into reanalysis products. Here, we present an intercomparison of high-resolution in situ measurements aboard passenger aircraft within the European Research Infrastructure IAGOS (In-service Aircraft for a Global Observing System; http://www.iagos.org, last access: 15 January 2020) with ERA-Interim. Temperature and humidity data over the North Atlantic from 2000 to 2009 are compared relative to the dynamical tropopause. The comparison of the temperature shows good agreement between the measurement and ERA-Interim. While ERA-Interim also shows the main features of the water vapour measurements of IAGOS, the variability of the data is clearly smaller in the reanalysis data set. The combination of temperature and water vapour leads to the relative humidity with respect to ice (RHi). Here, ERA-Interim deviates from the measurements concerning values larger than RHi=100 %, both in number and strength of supersaturation. Also, pathlengths of ISSRs along flight tracks are investigated, representing macrophysical properties as linked to atmospheric flows. The comparison of ISSR pathlengths shows distinct differences, which can be traced back to the spatial resolution of both data sets. Also, the seasonal cycle and height dependence of pathlengths changes for the different data sets due to their spatial resolution. IAGOS shows a significantly greater amount of smaller ISSRs compared to ERA-Interim. Good agreement begins only at pathlengths on the order of the ERA-Interim spatial resolution and larger. |
2019 |
| A H Laskar; S Mahata; S K Bhattacharya; M-C Liang: Triple Oxygen and Clumped Isotope Compositions of CO2 in the Middle Troposphere. Earth and Space Science, 2019. (Type: Journal Article | Abstract | Links | BibTeX) @article{Laskar2019, title = {Triple Oxygen and Clumped Isotope Compositions of CO2 in the Middle Troposphere}, author = { A H Laskar; S Mahata; S K Bhattacharya; M-C Liang}, url = { https://doi.org/10.1029/2019EA000573}, year = {2019}, date = {2019-06-06}, journal = {Earth and Space Science}, abstract = {We report the oxygen isotopic anomaly (Δ17O) and clumped isotopic composition (Δ47) of CO2 sampled from the middle troposphere (~10 km above ground) during two CARIBIC (Civil Aircraft for the Regular Investigation of the atmosphere Based on an Instrument Container) flights in summer and winter seasons: one from Düsseldorf to Isla Margarita on 11 August 2001 and the other from Puerto Plata to Munich on 21 February 2002. The mid‐tropospheric Δ17O values were higher than the near‐surface values by 0.051 ± 0.010 ‰, indicating enhanced stratospheric influence. The Δ47 values were also higher by 0.160 ± 0.015 ‰ compared to that from the lower troposphere. Stratospheric influence is supported by the observed correlations of the Δ17O values with the mixing ratios of N2O, O3, and 14CO, which carry stratospheric signatures. The increase in the anomaly in the free troposphere represents a balance between the stratosphere‐troposphere exchange fluxes and biogeochemical/hydrospheric isotopic resetting rates at the Earth surface. Using a simple two box model with the free tropospheric Δ17O values, an average surface exchange rate of CO2 between 327 and 772 PgC/year is inferred, giving a CO2 turnover time of 1.4 to 2.8 years in the atmosphere. The present estimates are based on a rather small set of free tropospheric data and have relatively large uncertainties, but they agree with the existing model and proxy‐based estimates.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We report the oxygen isotopic anomaly (Δ17O) and clumped isotopic composition (Δ47) of CO2 sampled from the middle troposphere (~10 km above ground) during two CARIBIC (Civil Aircraft for the Regular Investigation of the atmosphere Based on an Instrument Container) flights in summer and winter seasons: one from Düsseldorf to Isla Margarita on 11 August 2001 and the other from Puerto Plata to Munich on 21 February 2002. The mid‐tropospheric Δ17O values were higher than the near‐surface values by 0.051 ± 0.010 ‰, indicating enhanced stratospheric influence. The Δ47 values were also higher by 0.160 ± 0.015 ‰ compared to that from the lower troposphere. Stratospheric influence is supported by the observed correlations of the Δ17O values with the mixing ratios of N2O, O3, and 14CO, which carry stratospheric signatures. The increase in the anomaly in the free troposphere represents a balance between the stratosphere‐troposphere exchange fluxes and biogeochemical/hydrospheric isotopic resetting rates at the Earth surface. Using a simple two box model with the free tropospheric Δ17O values, an average surface exchange rate of CO2 between 327 and 772 PgC/year is inferred, giving a CO2 turnover time of 1.4 to 2.8 years in the atmosphere. The present estimates are based on a rather small set of free tropospheric data and have relatively large uncertainties, but they agree with the existing model and proxy‐based estimates. |
| B Martinsson; J Friberg; O S Sandvik; M Hermann; P F J van Velthoven; A Zahn: Formation and composition of the UTLS aerosol. npj Climate and Atmospheric Science, 2 (40), 2019. (Type: Journal Article | Abstract | Links | BibTeX) @article{vanZahn2019, title = {Formation and composition of the UTLS aerosol}, author = {B Martinsson; J Friberg; O S Sandvik; M Hermann; P F J van Velthoven; A Zahn}, url = {https://doi.org/10.1038/s41612-019-0097-1}, year = {2019}, date = {2019-11-06}, journal = {npj Climate and Atmospheric Science}, volume = {2}, number = {40}, abstract = {Stratospheric aerosol has long been seen as a pure mixture of sulfuric acid and water. Recent measurements, however, found a considerable carbonaceous fraction extending at least 8 km into the stratosphere. This fraction affects the aerosol optical depth (AOD) and the radiative properties, and hence the radiative forcing and climate impact of the stratospheric aerosol. Here we present an investigation based on a decade (2005–2014) of airborne aerosol sampling at 9–12 km altitude in the tropics and the northern hemisphere (NH) aboard the IAGOS-CARIBIC passenger aircraft. We find that the chemical composition of tropospheric aerosol in the tropics differs markedly from that at NH midlatitudes, and, that the carbonaceous stratospheric aerosol is oxygen-poor compared to the tropospheric aerosol. Furthermore, the carbonaceous and sulfurous components of the aerosol in the lowermost stratosphere (LMS) show strong increases in concentration connected with springtime subsidence from overlying stratospheric layers. The LMS concentrations significantly exceed those in the troposphere, thus clearly indicating a stratospheric production of not only the well-established sulfurous aerosol, but also a considerable but less understood carbonaceous component.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Stratospheric aerosol has long been seen as a pure mixture of sulfuric acid and water. Recent measurements, however, found a considerable carbonaceous fraction extending at least 8 km into the stratosphere. This fraction affects the aerosol optical depth (AOD) and the radiative properties, and hence the radiative forcing and climate impact of the stratospheric aerosol. Here we present an investigation based on a decade (2005–2014) of airborne aerosol sampling at 9–12 km altitude in the tropics and the northern hemisphere (NH) aboard the IAGOS-CARIBIC passenger aircraft. We find that the chemical composition of tropospheric aerosol in the tropics differs markedly from that at NH midlatitudes, and, that the carbonaceous stratospheric aerosol is oxygen-poor compared to the tropospheric aerosol. Furthermore, the carbonaceous and sulfurous components of the aerosol in the lowermost stratosphere (LMS) show strong increases in concentration connected with springtime subsidence from overlying stratospheric layers. The LMS concentrations significantly exceed those in the troposphere, thus clearly indicating a stratospheric production of not only the well-established sulfurous aerosol, but also a considerable but less understood carbonaceous component. |
| D Tarasick; I E Galbally; O R Cooper; M G Schultz; G Ancellet; T Leblanc; T J Wallington; J Ziemke; X Liu; M Steinbacher; J Staehelin; C Vigouroux; J W Hannigan; O García; G Foret; E Zanis P.and Weatherhead; I Petropavlovskikh; H Worden; M Osman; J Liu; K -L Chang; A Gaudel; M Lin; M Granados-Muñoz; A M Thompson; S J Oltmans; J Cuesta; G Dufour; V Thouret; B Hassler; T Trickl; J L Neu: Tropospheric Ozone Assessment Report: Tropospheric ozone from 1877 to 2016, observed levels, trends and uncertainties. Elementa Science of the Anthropocene, 7 (1), pp. 39, 2019. (Type: Journal Article | Abstract | Links | BibTeX) @article{tarasick2019, title = {Tropospheric Ozone Assessment Report: Tropospheric ozone from 1877 to 2016, observed levels, trends and uncertainties}, author = {D Tarasick and I E Galbally and O R Cooper and M G Schultz and G Ancellet and T Leblanc and T J Wallington and J Ziemke and X Liu and M Steinbacher and J Staehelin and C Vigouroux and J W Hannigan and O García and G Foret and E Zanis P.and Weatherhead and I Petropavlovskikh and H Worden and M Osman and J Liu and K -L Chang and A Gaudel and M Lin and M Granados-Muñoz and A M Thompson and S J Oltmans and J Cuesta and G Dufour and V Thouret and B Hassler and T Trickl and J L Neu}, url = {https://www.elementascience.org/article/10.1525/elementa.376/}, doi = {http://doi.org/10.1525/elementa.376}, year = {2019}, date = {2019-01-01}, journal = {Elementa Science of the Anthropocene}, volume = {7}, number = {1}, pages = {39}, abstract = {From the earliest observations of ozone in the lower atmosphere in the 19th century, both measurement methods and the portion of the globe observed have evolved and changed. These methods have different uncertainties and biases, and the data records differ with respect to coverage (space and time), information content, and representativeness. In this study, various ozone measurement methods and ozone datasets are reviewed and selected for inclusion in the historical record of background ozone levels, based on relationship of the measurement technique to the modern UV absorption standard, absence of interfering pollutants, representativeness of the well-mixed boundary layer and expert judgement of their credibility. There are significant uncertainties with the 19th and early 20th-century measurements related to interference of other gases. Spectroscopic methods applied before 1960 have likely underestimated ozone by as much as 11% at the surface and by about 24% in the free troposphere, due to the use of differing ozone absorption coefficients. There is no unambiguous evidence in the measurement record back to 1896 that typical mid-latitude background surface ozone values were below about 20 nmol mol–1, but there is robust evidence for increases in the temperate and polar regions of the northern hemisphere of 30–70%, with large uncertainty, between the period of historic observations, 1896–1975, and the modern period (1990–2014). Independent historical observations from balloons and aircraft indicate similar changes in the free troposphere. Changes in the southern hemisphere are much less. Regional representativeness of the available observations remains a potential source of large errors, which are difficult to quantify. The great majority of validation and intercomparison studies of free tropospheric ozone measurement methods use ECC ozonesondes as reference. Compared to UV-absorption measurements they show a modest (~1–5% ±5%) high bias in the troposphere, but no evidence of a change with time. Umkehr, lidar, and FTIR methods all show modest low biases relative to ECCs, and so, using ECC sondes as a transfer standard, all appear to agree to within one standard deviation with the modern UV-absorption standard. Other sonde types show an increase of 5–20% in sensitivity to tropospheric ozone from 1970–1995. Biases and standard deviations of satellite retrieval comparisons are often 2–3 times larger than those of other free tropospheric measurements. The lack of information on temporal changes of bias for satellite measurements of tropospheric ozone is an area of concern for long-term trend studies.}, keywords = {}, pubstate = {published}, tppubtype = {article} } From the earliest observations of ozone in the lower atmosphere in the 19th century, both measurement methods and the portion of the globe observed have evolved and changed. These methods have different uncertainties and biases, and the data records differ with respect to coverage (space and time), information content, and representativeness. In this study, various ozone measurement methods and ozone datasets are reviewed and selected for inclusion in the historical record of background ozone levels, based on relationship of the measurement technique to the modern UV absorption standard, absence of interfering pollutants, representativeness of the well-mixed boundary layer and expert judgement of their credibility. There are significant uncertainties with the 19th and early 20th-century measurements related to interference of other gases. Spectroscopic methods applied before 1960 have likely underestimated ozone by as much as 11% at the surface and by about 24% in the free troposphere, due to the use of differing ozone absorption coefficients. There is no unambiguous evidence in the measurement record back to 1896 that typical mid-latitude background surface ozone values were below about 20 nmol mol–1, but there is robust evidence for increases in the temperate and polar regions of the northern hemisphere of 30–70%, with large uncertainty, between the period of historic observations, 1896–1975, and the modern period (1990–2014). Independent historical observations from balloons and aircraft indicate similar changes in the free troposphere. Changes in the southern hemisphere are much less. Regional representativeness of the available observations remains a potential source of large errors, which are difficult to quantify. The great majority of validation and intercomparison studies of free tropospheric ozone measurement methods use ECC ozonesondes as reference. Compared to UV-absorption measurements they show a modest (~1–5% ±5%) high bias in the troposphere, but no evidence of a change with time. Umkehr, lidar, and FTIR methods all show modest low biases relative to ECCs, and so, using ECC sondes as a transfer standard, all appear to agree to within one standard deviation with the modern UV-absorption standard. Other sonde types show an increase of 5–20% in sensitivity to tropospheric ozone from 1970–1995. Biases and standard deviations of satellite retrieval comparisons are often 2–3 times larger than those of other free tropospheric measurements. The lack of information on temporal changes of bias for satellite measurements of tropospheric ozone is an area of concern for long-term trend studies. |
| L M David; A R Ravishankara; J F Brewer; B Sauvage; V Thouret; S Venkataramani; V Sinha: Tropospheric ozone over the Indian subcontinent from 2000 to 2015: Data set and simulation using GEOS-Chem chemical transport model. Atmospheric Environment, 219 , pp. 117039, 2019, ISSN: 1352-2310. (Type: Journal Article | Abstract | Links | BibTeX) @article{david2019, title = {Tropospheric ozone over the Indian subcontinent from 2000 to 2015: Data set and simulation using GEOS-Chem chemical transport model}, author = {L M David and A R Ravishankara and J F Brewer and B Sauvage and V Thouret and S Venkataramani and V Sinha}, url = {http://www.sciencedirect.com/science/article/pii/S1352231019306788}, doi = {https://doi.org/10.1016/j.atmosenv.2019.117039}, issn = {1352-2310}, year = {2019}, date = {2019-01-01}, journal = {Atmospheric Environment}, volume = {219}, pages = {117039}, abstract = {The Indian subcontinent (IS) is a region of increasing economic growth, urbanization, and consequently, anthropogenic emissions, altering tropospheric ozone (O3) over the region with impacts on the lives and health of 1.3 billion people. We have developed a comprehensive data set of the tropospheric O3 for 16 years (2000–2015) for the region between 50-115°E and 0–45°N, focusing on the IS. The data set included available balloon-borne, aircraft, and satellite-based measurements. We used a global three-dimensional chemical transport model, GEOS-Chem, at a 2° × 2.5° resolution to calculate daily tropospheric O3 over the region. The simulated O3 abundances in the boundary layer and lower, mid, and upper troposphere were compared with ozonesonde, aircraft, and satellite observations. The statistical analyses indicate that the model simulated boundary layer and lower, mid, and upper tropospheric O3 column abundances reasonably well with a mean bias ~1–3 DU in comparison to observations, but within the uncertainties of the observations. The model reproduced the vertical profiles of O3 and CO with a bias of less than 20% over different regions in the IS. The simulated tropospheric column NO2 was higher by a factor of ~1.5 compared to satellite observations. The model reproduced the regional difference in seasonal variations of tropospheric column O3 as observed by the Ozone Monitoring Instrument. We conclude that the CO emissions from the IS are underestimated while those of NOx are overestimated, both by around 20–30%.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The Indian subcontinent (IS) is a region of increasing economic growth, urbanization, and consequently, anthropogenic emissions, altering tropospheric ozone (O3) over the region with impacts on the lives and health of 1.3 billion people. We have developed a comprehensive data set of the tropospheric O3 for 16 years (2000–2015) for the region between 50-115°E and 0–45°N, focusing on the IS. The data set included available balloon-borne, aircraft, and satellite-based measurements. We used a global three-dimensional chemical transport model, GEOS-Chem, at a 2° × 2.5° resolution to calculate daily tropospheric O3 over the region. The simulated O3 abundances in the boundary layer and lower, mid, and upper troposphere were compared with ozonesonde, aircraft, and satellite observations. The statistical analyses indicate that the model simulated boundary layer and lower, mid, and upper tropospheric O3 column abundances reasonably well with a mean bias ~1–3 DU in comparison to observations, but within the uncertainties of the observations. The model reproduced the vertical profiles of O3 and CO with a bias of less than 20% over different regions in the IS. The simulated tropospheric column NO2 was higher by a factor of ~1.5 compared to satellite observations. The model reproduced the regional difference in seasonal variations of tropospheric column O3 as observed by the Ozone Monitoring Instrument. We conclude that the CO emissions from the IS are underestimated while those of NOx are overestimated, both by around 20–30%. |
| M Kavitha; P R Nair : Satellite-retrieved vertical profiles of methane over the Indian region: impact of synoptic-scale meteorology. International Journal of Remote Sensing, 40 , pp. 5585-5616, 2019. (Type: Journal Article | Abstract | Links | BibTeX) @article{Kavitha2019, title = {Satellite-retrieved vertical profiles of methane over the Indian region: impact of synoptic-scale meteorology}, author = {M Kavitha and P R Nair }, url = {https://www.tandfonline.com/doi/full/10.1080/01431161.2019.1580791}, year = {2019}, date = {2019-02-26}, journal = {International Journal of Remote Sensing}, volume = {40}, pages = {5585-5616}, abstract = {The altitude distribution of methane (CH4) is the least addressed topic in the greenhouse gas assessment over the Indian region. In the absence of the in-situ measurements, the satellite-based retrievals of the vertical distribution of CH4 using Atmospheric Infrared Sounder (AIRS) measurements during the period 2003–2015 were made use in this study for the first time to understand the 3D distribution (latitude-longitude-altitude) of CH4 over Indian region. Significant regional and seasonal variations are observed in the vertical distribution of CH4, even though it is a long-lived greenhouse gas and known to be well-mixed. Over most of the regions, the highest mixing ratio is observed during post-monsoon months and minimum in the pre-monsoon/monsoon season. The presence of a ‘high altitude peak’ in CH4 (around 1880 ppbv) around 300 hPa–250 hPa was noted in post-monsoon which is caused by the monsoon-associated convective updrafts and the anti-cyclonic system. The vertical profiles show seasonal variations which are region as well as altitude-dependent. Over the oceanic region, the highest seasonal amplitude of CH4 mixing ratio was observed over North–Arabian Sea due to the proximity of the source rich land regions. During the winter and pre-monsoon months, the latitudinal differences are absent throughout the troposphere. A consistent increasing trend in CH4, ranging from 1 ppbv year–1 to 6 ppbv year–1 is seen at all the tropospheric altitudes, with faster growth rates at higher altitudes, maximizing at 300 hPa–150 hPa. An approximate estimate of direct forcing due to CH4 lies in the range 0.80 W m–2–0.83 W m–2. The paper also presents a comparison of the in-situ measured upper tropospheric CH4 mixing ratio from CARIBIC (Civil Aircraft for the Regular Investigation of the atmosphere Based on an Instrument Container) flight data and AIRS retrievals.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The altitude distribution of methane (CH4) is the least addressed topic in the greenhouse gas assessment over the Indian region. In the absence of the in-situ measurements, the satellite-based retrievals of the vertical distribution of CH4 using Atmospheric Infrared Sounder (AIRS) measurements during the period 2003–2015 were made use in this study for the first time to understand the 3D distribution (latitude-longitude-altitude) of CH4 over Indian region. Significant regional and seasonal variations are observed in the vertical distribution of CH4, even though it is a long-lived greenhouse gas and known to be well-mixed. Over most of the regions, the highest mixing ratio is observed during post-monsoon months and minimum in the pre-monsoon/monsoon season. The presence of a ‘high altitude peak’ in CH4 (around 1880 ppbv) around 300 hPa–250 hPa was noted in post-monsoon which is caused by the monsoon-associated convective updrafts and the anti-cyclonic system. The vertical profiles show seasonal variations which are region as well as altitude-dependent. Over the oceanic region, the highest seasonal amplitude of CH4 mixing ratio was observed over North–Arabian Sea due to the proximity of the source rich land regions. During the winter and pre-monsoon months, the latitudinal differences are absent throughout the troposphere. A consistent increasing trend in CH4, ranging from 1 ppbv year–1 to 6 ppbv year–1 is seen at all the tropospheric altitudes, with faster growth rates at higher altitudes, maximizing at 300 hPa–150 hPa. An approximate estimate of direct forcing due to CH4 lies in the range 0.80 W m–2–0.83 W m–2. The paper also presents a comparison of the in-situ measured upper tropospheric CH4 mixing ratio from CARIBIC (Civil Aircraft for the Regular Investigation of the atmosphere Based on an Instrument Container) flight data and AIRS retrievals. |
| O S Sandvik; J Friberg ;B G Martinsson ;P F J van Velthoven; M Hermann; A Zahn;: Intercomparison of in-situ aircraft and satellite aerosol measurements in the stratosphere. npj Scientific Reports, (9), pp. 15576, 2019. (Type: Journal Article | Abstract | Links | BibTeX) @article{vanZahn;2019, title = {Intercomparison of in-situ aircraft and satellite aerosol measurements in the stratosphere}, author = {O S Sandvik; J Friberg ;B G Martinsson ;P F J van Velthoven; M Hermann; A Zahn;}, url = {https://doi.org/10.1038/s41598-019-52089-6}, doi = {10.1038/s41598-019-52089-6}, year = {2019}, date = {2019-10-30}, journal = {npj Scientific Reports}, number = {9}, pages = {15576}, abstract = {Aerosol composition and optical scattering from particles in the lowermost stratosphere (LMS) have been studied by comparing in-situ aerosol samples from the IAGOS-CARIBIC passenger aircraft with vertical profiles of aerosol backscattering obtained from the CALIOP lidar aboard the CALIPSO satellite. Concentrations of the dominating fractions of the stratospheric aerosol, being sulphur and carbon, have been obtained from post-flight analysis of IAGOS-CARIBIC aerosol samples. This information together with literature data on black carbon concentrations were used to calculate the aerosol backscattering which subsequently is compared with measurements by CALIOP. Vertical optical profiles were taken in an altitude range of several kilometres from and above the northern hemispheric extratropical tropopause for the years 2006-2014. We find that the two vastly different measurement platforms yield different aerosol backscattering, especially close to the tropopause where the influence from tropospheric aerosol is strong. The best agreement is found when the LMS is affected by volcanism, i.e., at elevated aerosol loadings. At background conditions, best agreement is obtained some distance (>2 km) above the tropopause in winter and spring, i.e., at likewise elevated aerosol loadings from subsiding aerosol-rich stratospheric air. This is to our knowledge the first time the CALIPSO lidar measurements have been compared to in-situ long-term aerosol measurements.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Aerosol composition and optical scattering from particles in the lowermost stratosphere (LMS) have been studied by comparing in-situ aerosol samples from the IAGOS-CARIBIC passenger aircraft with vertical profiles of aerosol backscattering obtained from the CALIOP lidar aboard the CALIPSO satellite. Concentrations of the dominating fractions of the stratospheric aerosol, being sulphur and carbon, have been obtained from post-flight analysis of IAGOS-CARIBIC aerosol samples. This information together with literature data on black carbon concentrations were used to calculate the aerosol backscattering which subsequently is compared with measurements by CALIOP. Vertical optical profiles were taken in an altitude range of several kilometres from and above the northern hemispheric extratropical tropopause for the years 2006-2014. We find that the two vastly different measurement platforms yield different aerosol backscattering, especially close to the tropopause where the influence from tropospheric aerosol is strong. The best agreement is found when the LMS is affected by volcanism, i.e., at elevated aerosol loadings. At background conditions, best agreement is obtained some distance (>2 km) above the tropopause in winter and spring, i.e., at likewise elevated aerosol loadings from subsiding aerosol-rich stratospheric air. This is to our knowledge the first time the CALIPSO lidar measurements have been compared to in-situ long-term aerosol measurements. |
| Y Yarragunta; S Srivastava; D Mitra; E Le Flochmoen; B Barret; P Kumar; H C Chandola: Source attribution of carbon monoxide and ozone over the Indian subcontinent using MOZART-4 chemistry transport model. Atmospheric Research, 227 , pp. 165-177, 2019, (Provided by the SAO/NASA Astrophysics Data System). (Type: Journal Article | Abstract | Links | BibTeX) @article{yarrangunta_2019, title = {Source attribution of carbon monoxide and ozone over the Indian subcontinent using MOZART-4 chemistry transport model}, author = {Y Yarragunta and S Srivastava and D Mitra and E Le Flochmoen and B Barret and P Kumar and H C Chandola}, url = {http://adsabs.harvard.edu/abs/2019AtmRe.227..165Y}, doi = {10.1016/j.atmosres.2019.04.019}, year = {2019}, date = {2019-10-01}, journal = {Atmospheric Research}, volume = {227}, pages = {165-177}, abstract = {Daily simulations of tropospheric carbon monoxide (CO) and ozone (O3) have been made using MOZART-4 (Model for OZone And Related chemical Tracers version 4) during 2007-08. The model simulated CO and O3 are evaluated against MOZAIC (Measurement of Ozone and Water Vapor by Airbus In-Service Aircraft) airborne observations over Hyderabad and IASI (Infrared Atmospheric Sounding Interferometer) retrievals over five most populous cities of India i.e. Mumbai, Delhi, Bangalore, Hyderabad, and Ahmedabad. The MOZAIC tropospheric column showed winter maxima and summer minima for CO whereas spring maxima and summer minima for O3. These seasonal features are reproduced well by model over Hyderabad. Model lower and middle tropospheric CO (O3) columns are positively biased by about 14 (8) ppbv as compared to MOZAIC observations. Model underestimated (overestimated) IASI CO columns during pre-monsoon (post-monsoon) while it overestimated IASI O3 columns throughout the year. Model simulated column of CO and O3 are positively biased by 4-13% and 23-33% respectively as compared to the IASI retrievals over five most populous cities. Tagged and sensitivity simulations of MOZART-4 have been used to quantify the contribution of different sources to the tropospheric CO and O3 distribution over the Indian landmass region. At surface, anthropogenic contribution varies from 55% to 81% during different seasons with an annual average contribution of 67%. This contribution decreases with increasing altitude up to 35% at 300 hPa. The contribution of photochemically produced CO is found to be 9-33% at surface. Unlike ANT-CO, the photochemically produced CO increases with altitude as it reaches up to 48% at 300 hPa. Surface BB-CO contributes upto 30% over parts of North East India during pre-monsoon season. Contribution of NAT-CO is found to be negligible (Approximately 6%) near surface as well as at the higher altitudes. Sensitivity simulations are used to decompose the total ozone (TO) into contributions from enhancement of ozone from Indian anthropogenic emissions, referred as Indian pollution ozone (IPO) and from the total background ozone (TBO). Annual total ozone is found to be 30 to 70 ppbv at surface and 77 to 85 ppbv at 300 hPa over the Indian landmass region. IPO and TBO contribute annually 58% and 42% at surface while 45% and 55% at 300 hPa respectively. The IPO contributes strongly at surface, with maximum (68%) impact during pre-monsoon season.}, note = {Provided by the SAO/NASA Astrophysics Data System}, keywords = {}, pubstate = {published}, tppubtype = {article} } Daily simulations of tropospheric carbon monoxide (CO) and ozone (O3) have been made using MOZART-4 (Model for OZone And Related chemical Tracers version 4) during 2007-08. The model simulated CO and O3 are evaluated against MOZAIC (Measurement of Ozone and Water Vapor by Airbus In-Service Aircraft) airborne observations over Hyderabad and IASI (Infrared Atmospheric Sounding Interferometer) retrievals over five most populous cities of India i.e. Mumbai, Delhi, Bangalore, Hyderabad, and Ahmedabad. The MOZAIC tropospheric column showed winter maxima and summer minima for CO whereas spring maxima and summer minima for O3. These seasonal features are reproduced well by model over Hyderabad. Model lower and middle tropospheric CO (O3) columns are positively biased by about 14 (8) ppbv as compared to MOZAIC observations. Model underestimated (overestimated) IASI CO columns during pre-monsoon (post-monsoon) while it overestimated IASI O3 columns throughout the year. Model simulated column of CO and O3 are positively biased by 4-13% and 23-33% respectively as compared to the IASI retrievals over five most populous cities. Tagged and sensitivity simulations of MOZART-4 have been used to quantify the contribution of different sources to the tropospheric CO and O3 distribution over the Indian landmass region. At surface, anthropogenic contribution varies from 55% to 81% during different seasons with an annual average contribution of 67%. This contribution decreases with increasing altitude up to 35% at 300 hPa. The contribution of photochemically produced CO is found to be 9-33% at surface. Unlike ANT-CO, the photochemically produced CO increases with altitude as it reaches up to 48% at 300 hPa. Surface BB-CO contributes upto 30% over parts of North East India during pre-monsoon season. Contribution of NAT-CO is found to be negligible (Approximately 6%) near surface as well as at the higher altitudes. Sensitivity simulations are used to decompose the total ozone (TO) into contributions from enhancement of ozone from Indian anthropogenic emissions, referred as Indian pollution ozone (IPO) and from the total background ozone (TBO). Annual total ozone is found to be 30 to 70 ppbv at surface and 77 to 85 ppbv at 300 hPa over the Indian landmass region. IPO and TBO contribute annually 58% and 42% at surface while 45% and 55% at 300 hPa respectively. The IPO contributes strongly at surface, with maximum (68%) impact during pre-monsoon season. |
