This title appears in the Scientific Report :
2020
Please use the identifier:
http://dx.doi.org/10.5194/acp-20-14273-2020 in citations.
Please use the identifier: http://hdl.handle.net/2128/26308 in citations.
Strong day-to-day variability of the Asian Tropopause Aerosol Layer (ATAL) in August 2016 at the Himalayan foothills
Strong day-to-day variability of the Asian Tropopause Aerosol Layer (ATAL) in August 2016 at the Himalayan foothills
The South Asian summer monsoon is associatedwith a large-scale anticyclonic circulation in the upper troposphere and lower stratosphere (UTLS), which confines the airmass inside. During boreal summer, the confinement of thisair mass leads to an accumulation of aerosol between about13 and 18 km (360...
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Personal Name(s): | Hanumanthu, Sreeharsha (Corresponding author) |
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Vogel, Bärbel (Corresponding author) / Müller, Rolf / Brunamonti, Simone / Fadnavis, Suvarna / Li, Dan / Ölsner, Peter / Naja, Manish / Singh, Bhupendra Bahadur / Kumar, Kunchala Ravi / Sonbawne, Sunil / Jauhiainen, Hannu / Vömel, Holger / Luo, Beiping / Jorge, Teresa / Wienhold, Frank G. / Dirkson, Ruud / Peter, Thomas | |
Contributing Institute: |
Stratosphäre; IEK-7 |
Published in: | Atmospheric chemistry and physics, 20 (2020) 22, S. 14273 - 14302 |
Imprint: |
Katlenburg-Lindau
EGU
2020
|
DOI: |
10.5194/acp-20-14273-2020 |
Document Type: |
Journal Article |
Research Program: |
Stratospheric and upper tropospheric processes for better climate predictions Composition and dynamics of the upper troposphere and middle atmosphere |
Link: |
Get full text OpenAccess |
Publikationsportal JuSER |
Please use the identifier: http://hdl.handle.net/2128/26308 in citations.
The South Asian summer monsoon is associatedwith a large-scale anticyclonic circulation in the upper troposphere and lower stratosphere (UTLS), which confines the airmass inside. During boreal summer, the confinement of thisair mass leads to an accumulation of aerosol between about13 and 18 km (360 and 440 K potential temperature); thisaccumulation of aerosol constitutes the Asian TropopauseAerosol Layer (ATAL). We present balloon-borne aerosolbackscatter measurements of the ATAL performed by theCompact Optical Backscatter Aerosol Detector (COBALD)instrument in Nainital in northern India in August 2016,and compare these with COBALD measurements in thepost-monsoon time in November 2016. The measurementsdemonstrate a strong variability of the ATAL’s altitude, vertical extent, aerosol backscatter intensity and cirrus cloudoccurrence frequency. Such a variability cannot be deducedfrom climatological means of the ATAL as they are derivedfrom satellite measurements. To explain this observed variability we performed a Lagrangian back-trajectory analysisusing the Chemical Lagrangian Model of the Stratosphere(CLaMS). We identify the transport pathways as well as thesource regions of air parcels contributing to the ATAL overNainital in August 2016. Our analysis reveals a variety offactors contributing to the observed day-to-day variability ofthe ATAL: continental convection, tropical cyclones (maritime convection), dynamics of the anticyclone and strato-spheric intrusions. Thus, the air in the ATAL is a mixture ofair masses coming from different atmospheric altitude layers. In addition, contributions from the model boundary layeroriginate in different geographic source regions. The location of the strongest updraft along the backward trajectoriesreveals a cluster of strong upward transport at the southernedge of the Himalayan foothills. From the top of the convective outflow level (about 13 km; 360 K) the air parcels ascendslowly to ATAL altitudes within a large-scale upward spiral driven by the diabatic heating in the anticyclonic flow ofthe South Asian summer monsoon at UTLS altitudes. Caseswith a strong ATAL typically show boundary layer contributions from the Tibetan Plateau, the foothills of the Hi-malayas and other continental regions below the Asian monsoon. Weaker ATAL cases show higher contributions fromthe maritime boundary layer, often related to tropical cyclones, indicating a mixing of clean maritime and pollutedcontinental air. On the one hand increasing anthropogenicemissions in the future are expected due to the strong growthof Asian economies; on the other hand the implementationof new emission control measures (in particular in China)has reduced the anthropogenic emissions of some pollutantscontributing to the ATAL substantially. It needs to be monitored in the future whether the thickness and intensity of theATAL will further increase, which will likely impact the surface climate. |