Aerosol characteristics in the upper troposphere and lower stratosphere region during successive and contrasting Indian summer monsoon season

2018 ◽  
Vol 173 ◽  
pp. 46-52 ◽  
Author(s):  
A.K. Srivastava ◽  
D. Kumar ◽  
A. Misra ◽  
V.P. Kanawade ◽  
V. Pathak ◽  
...  
Keyword(s):  
Summer Monsoon ◽  
Indian Summer Monsoon ◽  
Lower Stratosphere ◽  
Monsoon Season ◽  
Summer Monsoon Season ◽  
Upper Troposphere

scholarly journals Trends in peroxyacetyl nitrate (PAN) in the upper troposphere and lower stratosphere over southern Asia during the summer monsoon season: regional impacts

2014 ◽  
Vol 14 (23) ◽  
pp. 12725-12743 ◽  
Author(s):  
S. Fadnavis ◽  
M. G. Schultz ◽  
K. Semeniuk ◽  
A. S. Mahajan ◽  
L. Pozzoli ◽  
...  
Keyword(s):  
Summer Monsoon ◽  
Lower Stratosphere ◽  
Monsoon Season ◽  
Michelson Interferometer ◽  
Temporal Trends ◽  
Nox Emissions ◽  
Summer Monsoon Season ◽  
Peroxyacetyl Nitrate ◽  
Upper Troposphere ◽  
India And China

Abstract. We analyze temporal trends of peroxyacetyl nitrate (PAN) retrievals from the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) during 2002–2011 in the altitude range 8–23 km over the Asian summer monsoon (ASM) region. The greatest enhancements of PAN mixing ratios in the upper troposphere and lower stratosphere (UTLS) are seen during the summer monsoon season from June to September. During the monsoon season, the mole fractions of PAN show statistically significant (at 2σ) positive trends from 0.2 ± 0.05 to 4.6 ± 3.1 ppt yr−1 (except between 12 and 14 km) which is higher than the annual mean trends of 0.1 ± 0.05 to 2.7 ± 0.8 ppt yr−1. These rising concentrations point to increasing NOx (= NO + NO2) and volatile organic compound (VOC) emissions from developing nations in Asia, notably India and China. We analyze the influence of monsoon convection on the distribution of PAN in UTLS with simulations using the global chemistry–climate model ECHAM5-HAMMOZ. During the monsoon, transport into the UTLS over the Asian region primarily occurs from two convective zones, one the South China Sea and the other over the southern flank of the Himalayas. India and China host NOx-limited regimes for ozone photochemical production, and thus we use the model to evaluate the contributions from enhanced NOx emissions to the changes in PAN, HNO3 and O3 concentrations in the UTLS. From a set of sensitivity experiments with emission changes in particular regions, it can be concluded that Chinese emissions have a greater impact on the concentrations of these species than Indian emissions. According to SCanning Imaging Absorption SpectroMeter for Atmospheric CHartographY (SCIAMACHY) NO2 retrievals NOx emissions increases over India have been about half of those over China between 2002 and 2011.

scholarly journals Trends in Peroxyacetyl Nitrate (PAN) in the upper troposphere and lower stratosphere over Southern Asia during the summer monsoon season: regional impacts

2014 ◽  
Vol 14 (13) ◽  
pp. 19055-19094 ◽  
Author(s):  
S. Fadnavis ◽  
M. G. Schultz ◽  
K. Semeniuk ◽  
A. S. Mahajan ◽  
L. Pozzoli ◽  
...  
Keyword(s):  
Summer Monsoon ◽  
Lower Stratosphere ◽  
Monsoon Season ◽  
Michelson Interferometer ◽  
Temporal Trends ◽  
Nox Emissions ◽  
Summer Monsoon Season ◽  
Peroxyacetyl Nitrate ◽  
Upper Troposphere ◽  
India And China

Abstract. We analyze temporal trends of Peroxyacetyl Nitrate (PAN) retrievals from the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) during 2002–2011 in the altitude range 8–23 km over the Asian summer monsoon (ASM) region. The greatest enhancements of PAN mixing ratios in the upper troposphere and lower stratosphere (UTLS) are seen during the summer monsoon season from June to September. During the monsoon season, the mole fractions of PAN show statistically significant (at 2 sigma level) positive trends from 0.2 ± 0.05 to 4.6 ± 3.1 ppt year−1 (except between 12–14 km) which is higher than the annual mean trends of 0.1 ± 0.05 to 2.7 ± 0.8 ppt year−1. These rising concentrations point to increasing NOx (=NO+NO2) and volatile organic compound (VOC) emissions from developing nations in Asia, notably India and China. We analyze the influence of monsoon convection on the distribution of PAN in UTLS with simulations using the global chemistry-climate model ECHAM5-HAMMOZ. During the monsoon, transport into the UTLS over the Asian region primarily occurs from two convective zones, one extending from the Bay of Bengal to the South China Sea and the other over the southern flank of the Himalayas. India and China are NOx limited regions, and thus we use the model to evaluate the contributions from enhanced NOx emissions to the changes in PAN, HNO3 and O3 concentrations in the UTLS. From a set of sensitivity experiments with emission changes in particular regions it can be concluded that Chinese emissions have a greater impact on the concentrations of these species than Indian emissions. NOx emissions increases over India are about half of those over China.

IMDAA Regional Reanalysis: Performance Evaluation During Indian Summer Monsoon Season

2020 ◽  
Vol 125 (2) ◽  
Author(s):  
Raghavendra Ashrit ◽  
S. Indira Rani ◽  
Sushant Kumar ◽  
S. Karunasagar ◽  
T. Arulalan ◽  
...  
Keyword(s):  
Performance Evaluation ◽  
Summer Monsoon ◽  
Indian Summer Monsoon ◽  
Monsoon Season ◽  
Summer Monsoon Season ◽  
Regional Reanalysis

scholarly journals Weakening Trend of the Tropical Easterly Jet Stream of the Boreal Summer Monsoon Season 1950–2009

2013 ◽  
Vol 26 (23) ◽  
pp. 9408-9414 ◽  
Author(s):  
B. Abish ◽  
P. V. Joseph ◽  
Ola M. Johannessen
Keyword(s):  
Indian Ocean ◽  
Summer Monsoon ◽  
Monsoon Season ◽  
Equatorial Indian Ocean ◽  
Boreal Summer ◽  
Jet Stream ◽  
Moist Convection ◽  
Summer Monsoon Season ◽  
Upper Troposphere ◽  
Tropical Easterly Jet

Recent research has reported that the tropical easterly jet stream (TEJ) of the boreal summer monsoon season is weakening. The analysis herein using 60 yr (1950–2009) of data reveals that this weakening of the TEJ is due to the decreasing trend in the upper tropospheric meridional temperature gradient over the area covered by the TEJ. During this period, the upper troposphere over the equatorial Indian Ocean has warmed due to enhanced deep moist convection associated with the rapid warming of the equatorial Indian Ocean. At the same time, a cooling of the upper troposphere has taken place over the Northern Hemisphere subtropics including the Tibetan anticyclone. The simultaneous cooling of the subtropics and the equatorial heating has caused a decrease in the upper tropospheric meridional thermal gradient. The consequent reduction in the strength of the easterly thermal wind has resulted in the weakening of the TEJ.

scholarly journals Transport pathways of peroxyacetyl nitrate in the upper troposphere and lower stratosphere from different monsoon systems during the summer monsoon season

2015 ◽  
Vol 15 (20) ◽  
pp. 11477-11499 ◽  
Author(s):  
S. Fadnavis ◽  
K. Semeniuk ◽  
M. G. Schultz ◽  
M. Kiefer ◽  
A. Mahajan ◽  
...  
Keyword(s):  
Summer Monsoon ◽  
Lower Stratosphere ◽  
Asian Summer Monsoon ◽  
Monsoon Season ◽  
Peroxyacetyl Nitrate ◽  
Transport Pathways ◽  
Upper Troposphere ◽  
Asian Summer ◽  
Emission Change ◽  
Transport Patterns

Abstract. The Asian summer monsoon involves complex transport patterns with large-scale redistribution of trace gases in the upper troposphere and lower stratosphere (UTLS). We employ the global chemistry–climate model ECHAM5–HAMMOZ in order to evaluate the transport pathways and the contributions of nitrogen oxide species peroxyacetyl nitrate (PAN), NOx and HNO3 from various monsoon regions, to the UTLS over southern Asia and vice versa. Simulated long-term seasonal mean mixing ratios are compared with trace gas retrievals from the Michelson Interferometer for Passive Atmospheric Sounding aboard ENVISAT(MIPAS-E) and aircraft campaigns during the monsoon season (June–September) in order to evaluate the model's ability to reproduce these transport patterns. The model simulations show that there are three regions which contribute substantial pollution to the South Asian UTLS: the Asian summer monsoon (ASM), the North American monsoon (NAM) and the West African monsoon (WAM). However, penetration due to ASM convection reaches deeper into the UTLS compared to NAM and WAM outflow. The circulation in all three monsoon regions distributes PAN into the tropical latitude belt in the upper troposphere (UT). Remote transport also occurs in the extratropical UT where westerly winds drive North American and European pollutants eastward where they can become part of the ASM convection and lifted into the lower stratosphere. In the lower stratosphere the injected pollutants are transported westward by easterly winds. Sensitivity experiments with ECHAM5–HAMMOZ for simultaneous NOx and non-methane volatile organic compounds (NMVOCs) emission change (−10 %) over ASM, NAM and WAM confirm similar transport. Our analysis shows that a 10 % change in Asian emissions transports ~ 5–30 ppt of PAN in the UTLS over Asia, ~ 1–10 ppt of PAN in the UTLS of northern subtropics and mid-latitudes, ~ 7–10 ppt of HNO3 and ~ 1–2 ppb of ozone in UT over Asia. Comparison of emission change over Asia, North America and Africa shows that the highest transport of HNO3 and ozone occurs in the UT over Asia and least over Africa. The intense convective activity in the monsoon regions is associated with lightning and thereby the formation of additional NOx. This also affects the distribution of PAN in the UTLS. Simulations with and without lightning show an increase in the concentrations of PAN (~ 40 %), HNO3 (75 %), NOx (70 %) and ozone (30 %) over the regions of convective transport. Lightning-induced production of these species is higher over equatorial Africa and America compared to the ASM region. This indicates that the contribution of anthropogenic emissions to PAN in the UTLS over the ASM is higher than that of lightning.

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