Abstract
Abstract. The Model for Ozone and Related chemical Tracers-2 (MOZART-2) is used to examine the evolution of pollutant O3 in the upper troposphere over the Indian region. Vertical profiles of ozone mixing ratio retrieved from Microwave Limb Sounder (MLS) aboard Earth Observing System (EOS) AURA satellite for the period 2005–2009 and Tropospheric Emission Spectrometer (TES) aboard (EOS) AURA for the period 2006–2007 has been analyzed. The satellite observations reveal the evidence of downward propagation of ozone (100–200 ppb) due to stratospheric intrusion during the winter and pre-monsoon seasons. The regular feature of enhancement of ozone in the upper troposphere over India is presented. Results obtained by the MOZART-2 simulations (for years 2000–2005) confirm the observations and indicate stratospheric intrusion of O3 during winter and pre-monsoon seasons. Observed enhanced O3 mixing ratio in the upper troposphere is explained by, variation of Potential Vorticity (PV), tropopause pressure, relative humidity and CO-O3 correlation.
Highlights
Upper tropospheric ozone is an important greenhouse gas that affects global outgoing long wave radiations (Worden et al, 2008)
Upper tropospheric ozone enhancement would be the result of convective lifting of surface ozone, in situ production by anthropogenic NOx, lightning NOx and partly by HOx radicals produced from convectively lifted formaldehyde (Cooper et al, 2008) and stratospheric intrusion
The vertical profiles of ozone mixing ratio retrieved from Microwave Limb Sounder (MLS) during 2004–2009 and Tropospheric Emission Spectrometer (TES) for the period 2006– 2007 show evidence of enhanced ozone mixing ratio in the upper troposphere during winter and pre-monsoon
Summary
Upper tropospheric ozone is an important greenhouse gas that affects global outgoing long wave radiations (Worden et al, 2008). Baray et al (1998, 2000) discussed the ozone enhancement in the upper troposphere These studies suggest that subtropical jet stream could be the origin of tropopause folding, leading to stratospheric intrusion to the troposphere. Kim et al (2002) studied stratosphere– troposphere exchange processes over Korea They reported that ozone intrusion in the upper troposphere corresponds to central axis of the jet stream near the tropopause. This paper reports seasonal enhanced ozone in the upper troposphere over the Indian region due to stratospheric intrusion For this purpose, the vertical profiles of ozone mixing ratio obtained from two satellites (1) Microwave Limb Sounder (MLS) for the period 2005–2009, (2) Tropospheric Emission Spectrometer (TES) for the period 2006–2007 over the India region (5–40◦ N, 65–100◦ E) are analyzed. This algorithm produces tropopause estimates which vary smoothly in space and time (Randel et al, 2000)
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