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.

scholarly journals Lower-stratospheric aerosol measurements in eastward shedding vortices over Japan from the Asian summer monsoon anticyclone during the summer of 2018

2020 ◽  
Author(s):  
Masatomo Fujiwara ◽  
Tetsu Sakai ◽  
Koichi Shiraishi ◽  
Yoichi Inai ◽  
Sergey Khaykin ◽  
...  
Keyword(s):  
Summer Monsoon ◽  
Forest Fires ◽  
Lower Stratosphere ◽  
Asian Summer Monsoon ◽  
Volcanic Eruptions ◽  
Stratospheric Aerosol ◽  
Aerosol Layer ◽  
Upper Troposphere ◽  
Asian Summer ◽  
The Japanese Archipelago

Abstract. Eastward airmass transport from the Asian summer monsoon (ASM) anticyclone in the upper troposphere and lower stratosphere (UTLS) often involves eastward shedding vortices, which can cover most of the Japanese archipelago. We investigated the aerosol characteristics of these vortices by analysing data from two lidar systems in Japan, at Tsukuba (36.1° N, 140.1° E) and Fukuoka (33.55° N, 130.36° E), during the summer of 2018. We observed several events with enhanced particle signals at Tsukuba at 15.5–18 km altitude (at or above the local tropopause) during August–September 2018, with a backscattering ratio of ~1.10 and particle depolarization of ~5 % (i.e., not spherical, but more spherical than ice crystals). These particle characteristics may be consistent with those of solid aerosol particles, such as ammonium nitrate. Each event had a timescale of a few days. During the same study period, we also observed similar enhanced particle signals in the lower stratosphere at Fukuoka. The upper troposphere is often covered by cirrus clouds at both lidar sites. Backward trajectory calculations for these sites for days with enhanced particle signals in the lower stratosphere and days without indicate that the former airmasses originated within the ASM anticyclone, and the latter more from edge regions. Reanalysis carbon-monoxide and satellite water-vapour data indicate that eastward shedding vortices were involved in the observed aerosol enhancements. Satellite aerosol data confirm that the period and latitudinal region were free from the direct influence of documented volcanic eruptions and high latitude forest fires. Our results indicate that the Asian Tropopause Aerosol Layer (ATAL) over the ASM region extends east towards Japan in association with the eastward shedding vortices, and that lidar systems in Japan can detect at least the lower stratospheric portion of the ATAL during periods when the lower stratosphere is undisturbed by volcanic eruptions and forest fires. The upper tropospheric portion of the ATAL is either depleted by tropospheric processes (convection and wet scavenging) during eastward transport or is obscured by much stronger cirrus cloud signals.

scholarly journals Lower-stratospheric aerosol measurements in eastward-shedding vortices over Japan from the Asian summer monsoon anticyclone during the summer of 2018

2021 ◽  
Vol 21 (4) ◽  
pp. 3073-3090
Author(s):  
Masatomo Fujiwara ◽  
Tetsu Sakai ◽  
Tomohiro Nagai ◽  
Koichi Shiraishi ◽  
Yoichi Inai ◽  
...  
Keyword(s):  
Summer Monsoon ◽  
Forest Fires ◽  
Lower Stratosphere ◽  
Asian Summer Monsoon ◽  
Volcanic Eruptions ◽  
Stratospheric Aerosol ◽  
Aerosol Layer ◽  
Upper Troposphere ◽  
Asian Summer ◽  
The Japanese Archipelago

Abstract. Eastward air-mass transport from the Asian summer monsoon (ASM) anticyclone in the upper troposphere and lower stratosphere (UTLS) often involves eastward-shedding vortices, which can cover most of the Japanese archipelago. We investigated the aerosol characteristics of these vortices by analysing data from two lidar systems in Japan, at Tsukuba (36.1∘ N, 140.1∘ E) and Fukuoka (33.55∘ N, 130.36∘ E), during the summer of 2018. We observed several events with enhanced particle signals at Tsukuba at 15.5–18 km of altitude (at or above the local tropopause) during August–September 2018, with a backscattering ratio of ∼ 1.10 and particle depolarization of ∼ 5 % (i.e. not spherical, but more spherical than ice crystals). These particle characteristics may be consistent with those of solid aerosol particles, such as ammonium nitrate. Each event had a timescale of a few days. During the same study period, we also observed similar enhanced particle signals in the lower stratosphere at Fukuoka. The upper troposphere is often covered by cirrus clouds at both lidar sites. Backward trajectory calculations for these sites for days with enhanced particle signals in the lower stratosphere and days without indicate that the former air masses originated within the ASM anticyclone and the latter more from edge regions. Reanalysis carbon monoxide and satellite water vapour data indicate that eastward-shedding vortices were involved in the observed aerosol enhancements. Satellite aerosol data confirm that the period and latitudinal region were free from the direct influence of documented volcanic eruptions and high-latitude forest fires. Our results indicate that the Asian tropopause aerosol layer (ATAL) over the ASM region extends east towards Japan in association with the eastward-shedding vortices and that lidar systems in Japan can detect at least the lower-stratospheric portion of the ATAL during periods when the lower stratosphere is undisturbed by volcanic eruptions and forest fires. The upper-tropospheric portion of the ATAL is either depleted by tropospheric processes (convection and wet scavenging) during eastward transport or is obscured by much stronger cirrus cloud signals.

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 Efficient transport of tropospheric aerosol into the stratosphere via the Asian summer monsoon anticyclone

2017 ◽  
Vol 114 (27) ◽  
pp. 6972-6977 ◽  
Author(s):  
Pengfei Yu ◽  
Karen H. Rosenlof ◽  
Shang Liu ◽  
Hagen Telg ◽  
Troy D. Thornberry ◽  
...  
Keyword(s):  
Summer Monsoon ◽  
Lower Stratosphere ◽  
Model Simulation ◽  
Asian Summer Monsoon ◽  
Volcanic Eruptions ◽  
Aerosol Layer ◽  
Upper Troposphere ◽  
Tropospheric Aerosol ◽  
Asian Summer

An enhanced aerosol layer near the tropopause over Asia during the June–September period of the Asian summer monsoon (ASM) was recently identified using satellite observations. Its sources and climate impact are presently not well-characterized. To improve understanding of this phenomenon, we made in situ aerosol measurements during summer 2015 from Kunming, China, then followed with a modeling study to assess the global significance. The in situ measurements revealed a robust enhancement in aerosol concentration that extended up to 2 km above the tropopause. A climate model simulation demonstrates that the abundant anthropogenic aerosol precursor emissions from Asia coupled with rapid vertical transport associated with monsoon convection leads to significant particle formation in the upper troposphere within the ASM anticyclone. These particles subsequently spread throughout the entire Northern Hemispheric (NH) lower stratosphere and contribute significantly (∼15%) to the NH stratospheric column aerosol surface area on an annual basis. This contribution is comparable to that from the sum of small volcanic eruptions in the period between 2000 and 2015. Although the ASM contribution is smaller than that from tropical upwelling (∼35%), we find that this region is about three times as efficient per unit area and time in populating the NH stratosphere with aerosol. With a substantial amount of organic and sulfur emissions in Asia, the ASM anticyclone serves as an efficient smokestack venting aerosols to the upper troposphere and lower stratosphere. As economic growth continues in Asia, the relative importance of Asian emissions to stratospheric aerosol is likely to increase.

Long-term trends and transport of surface pollutants to UTLS  during the Asian summer monsoon

2021 ◽  
Author(s):  
William K.M. Lau ◽  
Kyu-Myong Kim
Keyword(s):  
Summer Monsoon ◽  
Asian Summer Monsoon ◽  
Linear Trend ◽  
Monsoon Season ◽  
Radiative Heating ◽  
Aerosol Layer ◽  
Near Surface ◽  
Upper Troposphere ◽  
Asian Summer

<p>Using MERRA2 reanalyses, we have examined the long-term (2000-2019) trends and transport of surface pollutants, CO, BC and OC from surface to the upper troposphere and lower stratosphere (UTLS) during the Asian summer monsoon.    We find a strong linear trend indicating an expansion and strengthening of the Asian Monsoon Anticyclone (AMA), in conjunction with increased concentration of CO, BC and OC in the UTLS, including the Aerosol Tropopause Aerosol Layer (ATAL). </p><p>The UTLS trend in CO can be tracked to increased upward transport primarily from surface sources near 25-35<sup>o</sup>N, in association with the expansion/strengthening of the AMA, and a northward displacement of ascending branch of the monsoon meridional circulation.  In contrast, near 25-35<sup>o</sup>N, BC and OC trends show significant reduction from surface to mid-troposphere, coupled a weak increase at UTLS (above 250 -100 hPa).  The reduction in surface and tropospheric BC and OC likely reflects reduced emission due to the clean air acts in East Asia.  Additionally, heavier rainfall associated with the enhanced ascent and wet scavenging may also contribute to the strong reduction in tropospheric BC and OC.  The increase in UTLS OC/BC appears to stem from increased and extended biomass burning near surface sources located in extratropical latitudes (70-130<sup>o</sup> E, 55-70<sup>o</sup> N).  The OC/BC aerosols are transported upward by vertical mixing over the source regions, and enter the tropical UTLS through horizonal diffusive processes.   Additionally, enhanced penetrative convection in the anomalous ascent regions during the peak monsoon season may also play a role in further enhancing the monsoon ascent, lifting ambient hydrophobic OC/BC and water vapor in the mid-to-upper troposphere to higher elevations, resulting in enhanced ice-cloud fraction, increased latent and radiative heating in the UTLS/ATAL region.</p><p> </p>

scholarly journals First detection of ammonia (NH<sub>3</sub>) in the Asian summer monsoon upper troposphere

2016 ◽  
Vol 16 (22) ◽  
pp. 14357-14369 ◽  
Author(s):  
Michael Höpfner ◽  
Rainer Volkamer ◽  
Udo Grabowski ◽  
Michel Grutter ◽  
Johannes Orphal ◽  
...  
Keyword(s):  
Summer Monsoon ◽  
Asian Summer Monsoon ◽  
Michelson Interferometer ◽  
Emission Spectra ◽  
Global Scale ◽  
Aerosol Layer ◽  
Upper Troposphere ◽  
Mixing Ratios ◽  
Monsoon Area ◽  
Asian Summer

Abstract. Ammonia (NH3) has been detected in the upper troposphere by the analysis of averaged MIPAS (Michelson Interferometer for Passive Atmospheric Sounding) infrared limb-emission spectra. We have found enhanced amounts of NH3 within the region of the Asian summer monsoon at 12–15 km altitude. Three-monthly, 10° longitude  ×  10° latitude average profiles reaching maximum mixing ratios of around 30 pptv in this altitude range have been retrieved, with a vertical resolution of 3–8 km and estimated errors of about 5 pptv. These observations show that loss processes during transport from the boundary layer to the upper troposphere within the Asian monsoon do not deplete the air entirely of NH3. Thus, ammonia might contribute to the so-called Asian tropopause aerosol layer by the formation of ammonium aerosol particles. On a global scale, outside the monsoon area and during different seasons, we could not detect enhanced values of NH3 above the actual detection limit of about 3–5 pptv. This upper bound helps to constrain global model simulations.

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

&lt;p&gt;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&lt;sub&gt;3&lt;/sub&gt;) 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.&lt;/p&gt;

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 Anthropogenic Aerosols Cause Recent Pronounced Weakening of Asian Summer Monsoon Relative to Last Four Centuries

2019 ◽  
Vol 46 (10) ◽  
pp. 5469-5479 ◽  
Author(s):  
Yu Liu ◽  
Wenju Cai ◽  
Changfeng Sun ◽  
Huiming Song ◽  
Kim M. Cobb ◽  
...  
Keyword(s):  
Summer Monsoon ◽  
Asian Summer Monsoon ◽  
Anthropogenic Aerosols ◽  
Asian Summer
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