Diurnal variability of lower and middle atmospheric water vapour over the Asian summer monsoon region: first results from COSMIC-1 and TIMED-SABER measurements

Abstract

First observations on the vertical structure of diurnal variability of tropospheric water vapour in the lower and middle atmosphere using 13 years of COSMIC and 18 years of SABER observations are presented in this paper. The most significant and new observation is that the middle stratospheric water vapour (SWV) enhancement is observed between 9-18 LT, whereas it is between 6-15 LT near tropopause in all the seasons. The diurnal amplitude of water vapour near tropopause is between 0.3-0.4 ppmv. Bimodal peaks are found in the diurnal amplitude of SWV, maximizing between 25-30 km (~0.4 ppmv) and 45-50 km (~0.6 ppmv). The analysis reveals that the diurnal variability in the lower SWV is controlled by the tropical tropopause temperature, whereas the middle and upper SWV is controlled by methane oxidation. The results are presented and discussed in the light of present understanding.

Impact of Annular Solar Eclipse on the Trace Gases and Dynamics of the Lower and Middle Atmosphere: Results Inferred From an Integrated Campaign “Suryagrahan‐2019”

“…Tropopause is cooler during the post‐eclipse and no isothermal structures are observed over Pune, Balasore, and Nainital, which are outside the maximum obscuration. Diurnal variability of temperature is found to be <±0.5 K in the troposphere and <2 K in the stratosphere for the tropical Indian region (e.g., S. S. Das et al., 2022) as well for the global tropical region (e.g., Sakazaki et al., 2018; Seidel et al., 2005). During the episode of 26 December 2019 eclipse, we observed temperature changes of ±6 K between the tropopause and 32 km, which is significantly higher than the normal diurnal variability over the tropical region.…”