Hot Extremes over India and their Driving Mechanisms
Assessing Changes in Characteristics of Hot Extremes Over India in a Warming Environment and their Driving Mechanisms
This study diagnoses the change in the characteristics of hot extremes over India before and after the 1976 climate shift and explores the driving mechanisms (including atmospheric patterns, local factors, and natural variability associated with El Niño/Southern Oscillation) responsible for such hot extremes. Furthermore, the results discussed in this study have important implications for developing appropriate mitigation and adaptation strategies related to the consequences of such extremes.
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This study infers a clear shift in the climate towards warmer temperatures, i.e., most parts of India, except the Indo-Gangetic plains, have experienced more frequent hot days having higher temperatures in the recent climate.
In the recent climate, the amplified mid-tropospheric geopotential height is directly associated with hot extremes over India. This high-pressure system over the northern parts of India causes sinking motion that leads to surface warming due to adiabatic compression, which in turn causes more hot extremes. Furthermore, this sinking motion is associated with reduced cloud cover, which has allowed more solar radiation reaching the Earth’s surface that in turn leads to warmer temperatures over the Indian landmass.
The reduced soil moisture in the recent period has led to the larger proportion of sensible heat flux than latent heat into the atmosphere, inducing positive feedback between the atmospheric heating and further drying of the soil, which have resulted in an augmentation of near-surface air temperatures in the recent period.
The preceding winter El Niño/Southern Oscillation conditions provide substantial forcing for the hot days over India and the mechanism for the lag of several months is related to 3 to 4 months delayed response of Indian Ocean sea surface temperatures to ENSO. Thus, post-Niño hot extremes over India can be potentially anticipated in advance and this will help society to prepare for such extremes.