Abstract
Abstract. We have investigated the long-term trends in and variabilities of stratospheric ozone, water vapor and temperature over the Indian monsoon region using the long-term data constructed from multi-satellite (Upper Atmosphere Research Satellite (UARS MLS and HALOE, 1993–2005), Aura Microwave Limb Sounder (MLS, 2004–2015), Sounding of the Atmosphere using Broadband Emission Radiometry (SABER, 2002–2015) on board TIMED (Thermosphere Ionosphere Mesosphere Energetics Dynamics)) observations covering the period 1993–2015. We have selected two locations, namely, Trivandrum (8.4∘ N, 76.9∘ E) and New Delhi (28∘ N, 77∘ E), covering northern and southern parts of the Indian region. We also used observations from another station, Gadanki (13.5∘ N, 79.2∘ E), for comparison. A decreasing trend in ozone associated with NOx chemistry in the tropical middle stratosphere is found, and the trend turned to positive in the upper stratosphere. Temperature shows a cooling trend in the stratosphere, with a maximum around 37 km over Trivandrum (−1.71 ± 0.49 K decade−1) and New Delhi (−1.15 ± 0.55 K decade−1). The observed cooling trend in the stratosphere over Trivandrum and New Delhi is consistent with Gadanki lidar observations during 1998–2011. The water vapor shows a decreasing trend in the lower stratosphere and an increasing trend in the middle and upper stratosphere. A good correlation between N2O and O3 is found in the middle stratosphere (∼ 10 hPa) and poor correlation in the lower stratosphere. There is not much regional difference in the water vapor and temperature trends. However, upper stratospheric ozone trends over Trivandrum and New Delhi are different. The trend analysis carried out by varying the initial year has shown significant changes in the estimated trend. Keywords. Atmospheric composition and structure (middle atmosphere – composition and chemistry; troposphere – composition and chemistry) – meteorology and atmospheric dynamics (climatology)
Highlights
Ozone and water vapor are two potent greenhouse gases in the atmosphere
For the present study we considered 23 years of ozone mixing ratio data by combining observations from the Microwave Limb Sounder (MLS) (1993–1999), the Halogen Occultation Experiment (HALOE) (1993–2005) on board the Upper Atmosphere Research Satellite (UARS), and the Earth Observing System (EOS) Microwave Limb Sounder (MLS) on board the Aura spacecraft (2004–2015)
The ozone concentrations at the ozone peak altitude of Trivandrum and Gadanki are nearly the same, which means that the difference which we observed in Fig. 1b is not due to the difference in latitudes of the two stations but can be the combined result of change in chemistry and dynamics
Summary
Ozone and water vapor are two potent greenhouse gases in the atmosphere. Over the tropical regions, stratospheric ozone depletion is not a critical problem but tropospheric ozone is a serious issue. A large number of ozone and temperature observations are available at different stations all over the globe (compared to water vapor, methane, nitrous oxide, etc.). These observations show that the industrial revolution has changed the ozone precursors in the troposphere through anthropogenic sources, and thereby the radiative forcing (∼ 0.40 ± 0.20 W m−2) has increased significantly due to ozone (IPCC, 2013). Long-term trend observations can give reliable evidence of the current state of the atmosphere and the effect on climate and ecosystems. They are essential for the numerical sim-
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