Spatial and temporal variation in long-term temperature and water vapor in the mesopause Region

Abstract. Mesopause is the zone of minimum temperature in Earth’s atmosphere. Temperature variation in this region is one of the important responsible factors for chemical and physical changes including spatiotemporal variability in water vapor content. Twenty-two years of monthly temperature and water vapor data were used from Sounding of the Atmosphere using Broadband Emission Radiometry. Eight months per year (excluding transitional months) were selected for temporal analysis. Spatially the region is classified into four parts including Northern, and Southern Poles. Long-term variations in water vapor and temperature in the selected domains of time and space as well as at equinoxes and solstices are presented. A decreasing, and increasing trend in temperature and water vapor respectively was observed during the study period. Yearly averaged temperature and water vapor content showed that 2002 was the hottest year (193 K) and had minimum water vaper content (0.89 ppmv) and 2018 was the coldest year (187 K) and had maximum water vapor content (1.14 ppmv). June and July were the coldest months and January and December were hotter months throughout the year over the North Pole and Equator. The vertical gradient of temperature and water vapor (80 to 100 km) changes with space and time however, has a strong negative relation in all selected locations and seasons. Around the equinoxes, the monthly average distribution of mesopause temperature was highest (191 K), followed by winter solstice and then summer solstice. The decreasing trend in temperature and an increasing trend in water vapor can be an early warning indication for future climate change.