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© 2018. This work is published under https://creativecommons.org/licenses/by/4.0/ (the “License”). Notwithstanding the ProQuest Terms and Conditions, you may use this content in accordance with the terms of the License.

Abstract

Lower tropospheric (surface to 600 hPa) ozone over India poses serious risks to both human health and crops, and potentially affects global ozone distribution through frequent deep convection in tropical regions. Our current understanding of the processes controlling seasonal and long-term variations in lower tropospheric ozone over this region is rather limited due to spatially and temporally sparse observations. Here we present an integrated process analysis of the seasonal cycle, interannual variability, and long-term trends of lower tropospheric ozone over India and its linkage to the South Asian monsoon using the Ozone Monitoring Instrument (OMI) satellite observations for years 2006–2014 interpreted with a global chemical transport model (GEOS-Chem) simulation for 1990–2010. OMI observed lower tropospheric ozone over India averaged for 2006–2010, showing the highest concentrations (54.1 ppbv) in the pre-summer monsoon season (May) and the lowest concentrations (40.5 ppbv) in the summer monsoon season (August). Process analyses in GEOS-Chem show that hot and dry meteorological conditions and active biomass burning together contribute to 5.8 Tg more ozone being produced in the lower troposphere in India in May than January. The onset of the summer monsoon brings ozone-unfavorable meteorological conditions and strong upward transport, which all lead to large decreases in the lower tropospheric ozone burden. Interannually, we find that both OMI and GEOS-Chem indicate strong positive correlations (r=0.55–0.58) between ozone and surface temperature in pre-summer monsoon seasons, with larger correlations found in high NOx emission regions reflecting NOx-limited production conditions. Summer monsoon seasonal mean ozone levels are strongly controlled by monsoon strengths. Lower ozone concentrations are found in stronger monsoon seasons mainly due to less ozone net chemical production. Furthermore, model simulations over 1990–2010 estimate a mean annual trend of 0.19 ± 0.07 (p value < 0.01) ppbv yr-1 in Indian lower tropospheric ozone over this period, which are mainly driven by increases in anthropogenic emissions with a small contribution (about 7 %) from global methane concentration increases.

Details

Title
Lower tropospheric ozone over India and its linkage to the South Asian monsoon
Author
Lu, Xiao 1   VIAFID ORCID Logo  ; Zhang, Lin 2 ; Liu, Xiong 3 ; Gao, Meng 4   VIAFID ORCID Logo  ; Zhao, Yuanhong 2 ; Shao, Jingyuan 2 

 Laboratory for Climate and Ocean-Atmosphere Studies, Department of Atmospheric and Oceanic Sciences, School of Physics, Peking University, Beijing 100871, China; School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA 
 Laboratory for Climate and Ocean-Atmosphere Studies, Department of Atmospheric and Oceanic Sciences, School of Physics, Peking University, Beijing 100871, China 
 Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, USA 
 School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA 
Pages
3101-3118
Publication year
2018
Publication date
2018
Publisher
Copernicus GmbH
ISSN
16807316
e-ISSN
16807324
Source type
Scholarly Journal
Language of publication
English
ProQuest document ID
2305530869
Copyright
© 2018. This work is published under https://creativecommons.org/licenses/by/4.0/ (the “License”). Notwithstanding the ProQuest Terms and Conditions, you may use this content in accordance with the terms of the License.