scholarly journals Space-Time Variability of UTLS Chemical Distribution in the Asian Summer Monsoon Viewed by Limb and Nadir Satellite Sensors

2017 ◽  
Author(s):  
Jiali Luo ◽  
Laura L. Pan ◽  
Shawn B. Honomichl ◽  
John W. Bergman ◽  
William J. Randel ◽  
...  
Keyword(s):  
Information Content ◽  
Summer Monsoon ◽  
Seasonal Variability ◽  
Asian Summer Monsoon ◽  
Trace Gas ◽  
Time Variability ◽  
Dynamical Structure ◽  
Upper Troposphere ◽  
Asian Summer ◽  
The Impact

Abstract. The Asian Summer Monsoon (ASM) creates a hemispheric scale signature in trace gas distributions in the upper troposphere and lower stratosphere (UTLS). Data from satellite retrievals are the best source of information for characterizing these large-scale signatures. Measurements from the Microwave Limb Sounder (MLS), a limb viewing satellite sensor, have been the most widely used retrieval products for these type of studies. This work explores the information content for the ASM upper troposphere from two nadir-viewing sensors, IASI and OMI. Day-to-day behaviour of carbon monoxide (CO) and ozone (O3) in the UTLS from these two nadir-viewing sensors are analysed in comparison to MLS to examine the information content for the ASM UTLS trace gas analyses. Day-to-day changes in tracer distributions in response to dynamical variability is explored, to assess whether these nadir viewing sensors provide useful information for investigating sub-seasonal variability. Our result shows that both nadir-viewing instruments capture the impact of ASM dynamics on spatial distribution of tracers in the UTLS. Despite the limited vertical resolution, tropospheric profiles from IASI are able to represent the upper tropospheric enhancement of CO in the region of ASM anticyclone. Similarly, the OMI O3 profile product is capable of distinguishing the tropospheric dominated air mass in the anticyclone from the stratospheric dominated background on a daily time scale. The high horizontal sampling density of IASI data show finer structures in the horizontal distribution of CO compared to the limb viewing MLS, including CO enhancement in the upper troposphere over the western Pacific resulting from the eastward eddy shedding of the ASM anticyclone. Sub-seasonal variability of tracers is correlated with the dynamical structure of the anticyclone as represented by the geopotential height (GPH) field, and systematic differences between the nadir and limb sounder results are discussed.

scholarly journals Transport of aerosol pollution in the UTLS during Asian summer monsoon as simulated by ECHAM5-HAMMOZ model

2012 ◽  
Vol 12 (11) ◽  
pp. 30081-30117 ◽  
Author(s):  
S. Fadnavis ◽  
K. Semeniuk ◽  
L. Pozzoli ◽  
M. G. Schultz ◽  
S. D. Ghude ◽  
...  
Keyword(s):  
Summer Monsoon ◽  
Asian Summer Monsoon ◽  
Indian Subcontinent ◽  
Aerosol Layer ◽  
Anthropogenic Aerosols ◽  
Upper Troposphere ◽  
Aerosol Pollution ◽  
Asian Summer ◽  
Cloud Ice ◽  
The Impact

Abstract. An eight member ensemble of ECHAM5-HAMMOZ simulations for the year 2003 is analyzed to study the transport of aerosols in the Upper Troposphere and Lower Stratosphere (UTLS) during the Asian Summer Monsoon (ASM). Simulations show persistent maxima in black carbon, organic carbon, sulfate, and mineral dust aerosols within the anticyclone in the UTLS throughout the ASM (period from July to September) when convective activity over the Indian subcontinent is highest. Model simulations indicate boundary layer aerosol pollution as the source of this UTLS aerosol layer and identify ASM convection as the dominant transport process. Evidence of ASM transport of aerosols into the stratosphere is observed in HALogen Occultation Experiment (HALOE) and Stratospheric Aerosol and Gas Experiment (SAGE) II aerosol extinction. The impact of aerosols in the UTLS region is analyzed by evaluating the differences between simulations with (CTRL) and without aerosol (HAM-off) loading. The transport of anthropogenic aerosols in the UTLS increases cloud ice, water vapour and temperature, indicating that aerosols play an important role in enhancement of cloud ice in the Upper-Troposphere (UT). Aerosol induced circulation changes include a weakening of the main branch of the Hadley circulation and increased vertical transport around the southern flank of the Himalayas and reduction in monsoon precipitation over the India region.

The Iimpact of the Iintraseasonal Intensity Variation of Asian Summer Monsoon Anticyclone on Chemical Constituents Distribution in the Upper Troposphere and Lower Stratosphere

2020 ◽  
Author(s):  
Jiali Luo ◽  
Kecheng Peng
Keyword(s):  
Summer Monsoon ◽  
Lower Stratosphere ◽  
Asian Summer Monsoon ◽  
Intensity Variation ◽  
Upper Troposphere ◽  
Intensity Index ◽  
Seasonal Oscillation ◽  
Asian Summer ◽  
The Impact ◽  
East West

<p>During the Asian summer monsoon (ASM) season, the stratosphere-troposphere exchange (STE) process has a significant effect on the stratospheric chemical constituent concentration and spatial distribution. In order to further explain the STE process during the ASM season, the impact of ASMA intensity on chemical species within the anticyclone escaping process during the ASM season is studied. Using the MERRA 2, NCEP reanalysis data and MLS satellite data in June, July and August (JJA) of 2004-2017, the relationship between the day-to-day intensity variation of the ASMA and the horizontal distribution of ozone (O<sub>3</sub>) and carbon monoxide (CO) during the intra-seasonal east-west oscillation is discussed based on an ASMA intensity index we defined. The results show that the intensity of the ASMA varied during the intra-seasonal east-west oscillation. The ASMA intensity index increased continuously from early June and peaked during mid-July to early August. ASMA has a constraints effect on the air inside. Its intra-seasonal oscillation and its intensity influenced the chemical distribution in the upper troposphere and lower stratosphere (UTLS). The distribution of chemical substances during its strong periods (SP) were relatively concentrated than that in weaker periods (WP). The air inside of the ASMA was easier to mix into stratosphere when the intensity was weak, and vice verse. The intensity variation of the ASMA caused by its intra-seasonal oscillation may affect the STE process during the Asian summer monsoon season.</p>

scholarly journals Space–time variability in UTLS chemical distribution in the Asian summer monsoon viewed by limb and nadir satellite sensors

2018 ◽  
Vol 18 (16) ◽  
pp. 12511-12530 ◽  
Author(s):  
Jiali Luo ◽  
Laura L. Pan ◽  
Shawn B. Honomichl ◽  
John W. Bergman ◽  
William J. Randel ◽  
...  
Keyword(s):  
Summer Monsoon ◽  
Large Scale ◽  
Asian Summer Monsoon ◽  
Time Variability ◽  
Synoptic Scale ◽  
Ozone Monitoring Instrument ◽  
Complementary Information ◽  
Asian Summer ◽  
Chemical Distribution ◽  
The Impact

Abstract. The Asian summer monsoon (ASM) creates a hemispheric-scale signature in trace-gas distributions in the upper troposphere and lower stratosphere (UTLS). Data from satellite retrievals are the best source of information for characterizing these large-scale signatures. Measurements from the Microwave Limb Sounder (MLS), a limb-viewing satellite sensor, have been the most widely used retrieval products for these types of studies. This work explores the information for the ASM influence on UTLS chemical distribution from two nadir-viewing sensors, the Infrared Atmospheric Sounding Interferometer (IASI) and the Ozone Monitoring Instrument (OMI), together with the MLS. Day-to-day changes in carbon monoxide (CO) and ozone (O3) tracer distributions in response to dynamical variability are examined to assess how well the data from different sensors provide useful information for studying the impact of sub-seasonal-scale dynamics on chemical fields. Our results, using June–August 2008 data, show that although the MLS provides relatively sparse horizontal sampling on daily timescales, interpolated daily CO distributions show a high degree of dynamical consistency with the synoptic-scale structure of and variability in the anticyclone. Our analysis also shows that the IASI CO retrieval has sufficient sensitivity to produce upper tropospheric (UT) CO with variabilities independent from the lower to middle tropospheric CO. The consistency of IASI CO field with the synoptic-scale anticyclone dynamical variability demonstrates that the IASI UT CO product is a physically meaningful dataset. Furthermore, IASI CO vertical cross sections combined with the daily maps provide the first observational evidence for a model analyses-based hypothesis on the preferred ASM vertical transport location and the subsequent horizontal redistribution via east–west eddy shedding. Similarly, the OMI O3 profile product is shown to be capable of distinguishing the tropospheric-dominated air mass in the anticyclone from the stratospheric-dominated background on a daily timescale, providing consistent and complementary information to the MLS. These results not only highlight the complementary information between nadir and limb sensors but also demonstrate the value of “process-based” retrieval evaluation for characterizing satellite data information content.

scholarly journals Characterization of non-methane hydrocarbons in Asian summer monsoon outflow observed by the CARIBIC aircraft

2011 ◽  
Vol 11 (2) ◽  
pp. 503-518 ◽  
Author(s):  
A. K. Baker ◽  
T. J. Schuck ◽  
F. Slemr ◽  
P. van Velthoven ◽  
A. Zahn ◽  
...  
Keyword(s):  
Carbon Monoxide ◽  
Summer Monsoon ◽  
Fossil Fuels ◽  
Asian Summer Monsoon ◽  
Trace Gases ◽  
Northern Region ◽  
Monsoon Circulation ◽  
Upper Troposphere ◽  
Mixing Ratios ◽  
Asian Summer

Abstract. Between April and December 2008 the CARIBIC commercial aircraft conducted monthly measurement flights between Frankfurt, Germany and Chennai, India. These flights covered the period of the Asian summer monsoon (June–September), during which enhancements in a number of atmospheric species were observed in the upper troposphere over southwestern Asia. In addition to in situ measurements of trace gases and aerosols, whole air samples were collected during the flights, and these were subsequently analyzed for a suite of trace gases that included a number of C2–C8 non-methane hydrocarbons. Non-methane hydrocarbons are relatively short-lived compounds and the large enhancements in their mixing ratios in the upper troposphere over southwestern Asia during the monsoon, sometimes more than double their spring and fall means, provides qualitative evidence for the influence of convectively uplifted boundary layer air. The particularly large enhancements of the combustion tracers benzene and ethyne, along with the similarity of their ratios with carbon monoxide and emission ratios from the burning of household biofuels, indicate a strong influence of biofuel burning to NMHC emissions in this region. Conversely, the ratios of ethane and propane to carbon monoxide, along with the ratio between i-butane and n-butane, indicate a significant source of these compounds from the use of fossil fuels, and comparison to previous campaigns suggests that this source could be increasing. Photochemical aging patterns of NMHCs showed that the CARIBIC samples were collected in two distinctly different regions of the monsoon circulation: a southern region where air masses had been recently influenced by low level contact and a northern region, where air parcels had spent substantial time in transit in the upper troposphere before being probed. Estimates of age using ratios of individual NMHCs have ranges of 3–6 days in the south and 9–12 days in the north.

scholarly journals Dynamics and composition of the Asian summer monsoon anticyclone

2017 ◽  
Author(s):  
Klaus-Dirk Gottschaldt ◽  
Hans Schlager ◽  
Robert Baumann ◽  
Duy S. Cai ◽  
Veronika Eyring ◽  
...  
Keyword(s):  
Summer Monsoon ◽  
Atmospheric Chemistry ◽  
Asian Summer Monsoon ◽  
Monsoon Season ◽  
Lower Troposphere ◽  
Equatorial Region ◽  
Ozone Production ◽  
Trace Gas ◽  
Asian Summer ◽  
Southern Fringe

Abstract. This study places HALO research aircraft observations in the upper-tropospheric Asian summer monsoon anticyclone (ASMA) obtained during the Earth System Model Validation (ESMVal) campaign in September 2012 into the context of regional, intra-annual variability by hindcasts with the ECHAM/MESSy Atmospheric Chemistry (EMAC) model. The simulations demonstrate that tropospheric trace gas profiles in the monsoon season are distinct from the rest of the year. Air uplifted from the lower troposphere to the tropopause layer dominates the eastern part of the ASMA’s interior, while the western part is characterised by subsidence down to the mid-troposphere. Soluble compounds are being washed out when uplifted by convection in the eastern part, where lightning simultaneously replenishes reactive nitrogen in the upper troposphere. Net photochemical ozone production is significantly enhanced in the ASMA, contrasted by an ozone depleting regime in the mid-troposphere and more neutral conditions in autumn and winter. An analysis of multiple monsoon seasons in the simulation shows that stratospherically influenced tropopause layer air is regularly entrained at the eastern ASMA flank, and then transported in the southern fringe around the interior region. Observed and simulated tracer-tracer relations reflect photochemical O3 production, as well as in-mixing from the lower troposphere and the tropopause layer. The simulation additionally shows entrainment of clean air from the equatorial region by northerly winds at the western ASMA flank. Although the in situ measurements were performed towards the end of summer, the main ingredients needed for their interpretation are present throughout the monsoon season. A transition between two dynamical modes of the ASMA took place during the HALO ESMVal campaign. Transport barriers of the original anticyclone are overcome effectively when it splits up. Air from the fringe is stirred into the interiors of the new anticyclones and vice versa. Instabilities of this and other types occur quite frequently. Our study emphasises their paramountcy for the trace gas composition of the ASMA and its outflow into regions around the world.

scholarly journals Transport of Asian surface pollutants to the global stratosphere from the Tibetan Plateau region during the Asian summer monsoon

2020 ◽  
Vol 7 (3) ◽  
pp. 516-533 ◽  
Author(s):  
Jianchun Bian ◽  
Dan Li ◽  
Zhixuan Bai ◽  
Qian Li ◽  
Daren Lyu ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Summer Monsoon ◽  
Asian Summer Monsoon ◽  
Global Climate ◽  
Pollutant Emissions ◽  
The Tibetan Plateau ◽  
Plateau Region ◽  
Radiative Processes ◽  
Asian Summer ◽  
The Impact

Abstract Due to its surrounding strong and deep Asian summer monsoon (ASM) circulation and active surface pollutant emissions, surface pollutants are transported to the stratosphere from the Tibetan Plateau region, which may have critical impacts on global climate through chemical, microphysical and radiative processes. This article reviews major recent advances in research regarding troposphere–stratosphere transport from the region of the Tibetan Plateau. Since the discovery of the total ozone valley over the Tibetan Plateau in summer from satellite observations in the early 1990s, new satellite-borne instruments have become operational and have provided significant new information on atmospheric composition. In addition, in situ measurements and model simulations are used to investigate deep convection and the ASM anticyclone, surface sources and pathways, atmospheric chemical transformations and the impact on global climate. Also challenges are discussed for further understanding critical questions on microphysics and microchemistry in clouds during the pathway to the global stratosphere over the Tibetan Plateau.

scholarly journals Upper tropospheric CO and O<sub>3</sub> budget during the Asian Summer Monsoon

2016 ◽  
Author(s):  
B. Barret ◽  
B. Sauvage ◽  
Y. Bennouna ◽  
E. Le Flochmoen
Keyword(s):  
South Asian ◽  
Summer Monsoon ◽  
Satellite Data ◽  
Large Scale ◽  
Transport Model ◽  
Asian Summer Monsoon ◽  
East Asian ◽  
Gangetic Plain ◽  
Upper Troposphere ◽  
Asian Summer

Abstract. During the Asian Summer Monsoon, the circulation in the Upper Troposphere-Lower Stratosphere (UTLS) is dominated by the Asian Monsoon Anticyclone (AMA). Pollutants convectively uplifted to the upper troposphere are trapped within this anticyclonic circulation that extends from the Pacific Ocean to the eastern Mediterranean basin. Among the uplifted pollutants are ozone (O3) and its precursors, such as carbon monoxide (CO) and nitrogen oxides (NOx). Many studies based on global modelisation and satellite data have documented the source regions and transport pathways of primary pollutants (CO, HCN) into the AMA. Here, we aim to quantify the O3 budget by taking into consideration anthropogenic and natural sources. We first use CO and O3 data from the Metop-A/IASI sensor to document their tropospheric distributions over Asia, taking advantage of the useful information they provide on the vertical dimension. These satellite data are used together with MOZAIC/IAGOS tropospheric profiles recorded in India to validate the distributions simulated by the global GEOS-Chem chemistry transport model. Over the Asian region, UTLS monthly CO and O3 distributions from IASI and GEOS-Chem display the same large-scale features. UTLS CO columns from GEOS-Chem are in agreement with IASI, with a low bias of 11 ± 9% and a correlation coefficient of 0.70. For O3, the model underestimates IASI UTLS columns over Asia by 14 ± 26% but the correlation between both is high (0.94). GEOS-Chem is further used to quantify the CO and O3 budget through sensitivity simulations. For CO, these simulations confirm that South-Asian anthropogenic emissions have a more important impact on enhanced concentrations within the AMA (∼25 ppbv) than East-Asian emissions (∼10 ppbv). The correlation between enhanced emissions over the Indo–gangetic–Plain and monsoon deep convection is responsible for this larger impact. Consistently, South-Asian anthropogenic NOx emissions also play a larger role in producing O3 within the AMA (∼8 ppbv) than East-Asian emissions (∼5 ppbv) but Asian lightning produced NOx are responsible for the largest O3 production (10–14 ppbv). Stratosphere to Troposphere Exchanges (STE) are also important in transporting O3 in the upper part of the AMA.

scholarly journals Dynamics and composition of the Asian summer monsoon anticyclone

2018 ◽  
Vol 18 (8) ◽  
pp. 5655-5675 ◽  
Author(s):  
Klaus-Dirk Gottschaldt ◽  
Hans Schlager ◽  
Robert Baumann ◽  
Duy Sinh Cai ◽  
Veronika Eyring ◽  
...  
Keyword(s):  
Summer Monsoon ◽  
Atmospheric Chemistry ◽  
Asian Summer Monsoon ◽  
Monsoon Season ◽  
Lower Troposphere ◽  
Trace Gas ◽  
Transport Barriers ◽  
Research Aircraft ◽  
Asian Summer ◽  
Southern Fringe

Abstract. This study places HALO research aircraft observations in the upper-tropospheric Asian summer monsoon anticyclone (ASMA) into the context of regional, intra-annual variability by hindcasts with the ECHAM/MESSy Atmospheric Chemistry (EMAC) model. The observations were obtained during the Earth System Model Validation (ESMVal) campaign in September 2012. Observed and simulated tracer–tracer relations reflect photochemical O3 production as well as in-mixing from the lower troposphere and the tropopause layer. The simulations demonstrate that tropospheric trace gas profiles in the monsoon season are distinct from those in the rest of the year, and the measurements reflect the main processes acting throughout the monsoon season. Net photochemical O3 production is significantly enhanced in the ASMA, where uplifted precursors meet increased NOx, mainly produced by lightning. An analysis of multiple monsoon seasons in the simulation shows that stratospherically influenced tropopause layer air is regularly entrained at the eastern ASMA flank and then transported in the southern fringe around the interior region. Radial transport barriers of the circulation are effectively overcome by subseasonal dynamical instabilities of the anticyclone, which occur quite frequently and are of paramount importance for the trace gas composition of the ASMA. Both the isentropic entrainment of O3-rich air and the photochemical conversion of uplifted O3-poor air tend to increase O3 in the ASMA outflow.

Investigating the sensitivity of the onset and withdrawal of the south Asian summer monsoon system to changes in anthropogenic emissions using a climate model

2020 ◽  
Author(s):  
Shiwansha Mishra ◽  
Dilip Ganguly ◽  
Puneet Sharma
Keyword(s):  
South Asian ◽  
Summer Monsoon ◽  
Climate Model ◽  
Asian Summer Monsoon ◽  
Anthropogenic Emissions ◽  
South Asian Summer Monsoon ◽  
The South ◽  
Monsoon System ◽  
Asian Summer ◽  
The Impact

&lt;p&gt;While the monsoon onset is recognized as a rapid, substantial, and sustained increase in rainfall over large parts of south Asia, the withdrawal marks the return to dry conditions. Normally, the south Asian summer monsoon onset occurs around 1&lt;sup&gt;st&lt;/sup&gt; June over extreme south of peninsular India, which gradually advances to extreme northwest of India by around 15&lt;sup&gt;th&lt;/sup&gt; July. The withdrawal starts from northwest India from around 1st September and from extreme south peninsular India by around 30th September. The determinations of the onset and withdrawal dates of monsoon have great economic significance for this region as they influence many agriculture and water resource management decisions in one of the most highly populated regions of the world. Several studies involving global model simulations have shown that changing aerosol emissions could result in significant changes in the seasonal mean precipitation distribution over India. A few studies also show that presence of absorbing aerosols in the foothills of Himalayas and over the Tibetan plateau could increase the moisture convergence over India thereby causing an advancement and intensification of the monsoon precipitation. However, most of the previous studies, which investigated the impact of anthropogenic emissions on the monsoon, are limited to understanding the impact of various emission changes on the seasonal mean monsoon characteristics. In the present study, we try to understand the sensitivity of the onset and withdrawal period of the south Asian summer monsoon system to changes in anthropogenic emissions using a climate model (CESM1.2). We diagnose the onset and withdrawal of the south Asian monsoon by analyzing the variability in vertically integrated moisture transport (VIMT) over the south Asian region and following the definition of hydrologic onset and withdrawal index (HOWI) defined by Fasullo et al. (2002). We examined the effect of changing emissions anthropogenic aerosol, greenhouse gases and both on the onset and withdrawal of the south Asian summer monsoon system. Our preliminary results suggest that increases in the emissions of aerosols and greenhouse gases from anthropogenic sources from pre-industrial to present day could possibly result in significant delay in the onset and advancement in withdrawal of the south Asian summer monsoon system thereby shortening the length of the monsoon season. More results with greater detail will be presented.&lt;/p&gt;

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