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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
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Volume 18, issue 21 | Copyright
Atmos. Chem. Phys., 18, 15937-15957, 2018
https://doi.org/10.5194/acp-18-15937-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 07 Nov 2018

Research article | 07 Nov 2018

Balloon-borne measurements of temperature, water vapor, ozone and aerosol backscatter on the southern slopes of the Himalayas during StratoClim 2016–2017

Simone Brunamonti1, Teresa Jorge1, Peter Oelsner2, Sreeharsha Hanumanthu3,4, Bhupendra B. Singh3, K. Ravi Kumar3,a, Sunil Sonbawne3, Susanne Meier2, Deepak Singh5, Frank G. Wienhold1, Bei Ping Luo1, Maxi Boettcher1, Yann Poltera1, Hannu Jauhiainen8, Rijan Kayastha6, Jagadishwor Karmacharya9, Ruud Dirksen2, Manish Naja5, Markus Rex7, Suvarna Fadnavis3, and Thomas Peter1 Simone Brunamonti et al.
  • 1Institute for Atmospheric and Climate Science (IAC), Swiss Federal Institute of Technology (ETH), Zürich, Switzerland
  • 2Deutscher Wetterdienst (DWD) / GCOS Reference Upper Air Network (GRUAN) Lead Center, Lindenberg, Germany
  • 3Indian Institute of Tropical Meteorology (IITM), Pune, India
  • 4Forschungszentrum Jülich (FZJ), Institute of the Energy and Climate Research – Stratosphere (IEK-7), Jülich, Germany
  • 5Aryabhatta Research Institute of Observational Sciences (ARIES), Nainital, India
  • 6Kathmandu University (KU), Dhulikhel, Nepal
  • 7Alfred Wegener Institute (AWI) for Polar and Marine Research, Potsdam, Germany
  • 8Vaisala Oyj, Vantaa, Finland
  • 9Department of Hydrology and Meteorology (DHM), Meteorological Forecasting Division, Kathmandu, Nepal
  • anow at: Centre for Atmospheric Sciences, Indian Institute of Technology (IIT), Delhi, India

Abstract. The Asian summer monsoon anticyclone (ASMA) is a major meteorological system of the upper troposphere–lower stratosphere (UTLS) during boreal summer. It is known to contain enhanced tropospheric trace gases and aerosols, due to rapid lifting from the boundary layer by deep convection and subsequent horizontal confinement. Given its dynamical structure, the ASMA represents an efficient pathway for the transport of pollutants to the global stratosphere. A detailed understanding of the thermal structure and processes in the ASMA requires accurate in situ measurements. Within the StratoClim project we performed state-of-the-art balloon-borne measurements of temperature, water vapor, ozone and aerosol backscatter from two stations on the southern slopes of the Himalayas. In total, 63 balloon soundings were conducted during two extensive monsoon-season campaigns, in August 2016 in Nainital, India (29.4°N, 79.5°E), and in July–August 2017 in Dhulikhel, Nepal (27.6°N, 85.5°E); one shorter post-monsoon campaign was also carried out in November 2016 in Nainital. These measurements provide unprecedented insights into the UTLS thermal structure, the vertical distributions of water vapor, ozone and aerosols, cirrus cloud properties and interannual variability in the ASMA. Here we provide an overview of all of the data collected during the three campaign periods, with focus on the UTLS region and the monsoon season. We analyze the vertical structure of the ASMA in terms of significant levels and layers, identified from the temperature and potential temperature lapse rates and Lagrangian backward trajectories, which provides a framework for relating the measurements to local thermodynamic properties and the large-scale anticyclonic flow. Both the monsoon-season campaigns show evidence of deep convection and confinement extending up to 1.5–2km above the cold-point tropopause (CPT), yielding a body of air with high water vapor and low ozone which is prone to being lifted further and mixed into the free stratosphere. Enhanced aerosol backscatter also reveals the signature of the Asian tropopause aerosol layer (ATAL) over the same region of altitudes. The Dhulikhel 2017 campaign was characterized by a 5K colder CPT on average than in Nainital 2016 and a local water vapor maximum in the confined lower stratosphere, about 1km above the CPT. Data assessment and modeling studies are currently ongoing with the aim of fully exploring this dataset and its implications with respect to stratospheric moistening via the ASMA system and related processes.

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Based on balloon-borne measurements performed in India and Nepal in 2016–2017, we infer the vertical distributions of water vapor, ozone and aerosols in the atmosphere, from the surface to 30 km altitude. Our measurements show that the atmospheric dynamics of the Asian summer monsoon system over the polluted Indian subcontinent lead to increased concentrations of water vapor and aerosols in the high atmosphere (approximately 14–20 km altitude), which can have an important effect on climate.
Based on balloon-borne measurements performed in India and Nepal in 2016–2017, we infer the...
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