Understanding the spatio-temporal structure of recent heat waves over India

Major heat waves are occurring over India during the hottest months of May and June. Since the temperature extremes have major impact on human health and agriculture, better understanding the dynamics behind its evolution and propagation will help us to develop effective mitigation strategies. Understanding the spatio-temporal distribution, evolution and dynamics associated with heat waves is lacking over this region, due to the lack of high-resolution weather information. Here, we developed a high-resolution (4 × 4 km) dynamically downscaled hourly climate data for April to June during period of 2001–2016. The downscaled daily surface temperature is in good agreement with station observations, which is also in agreement with the observed features of temperature distribution during this period. Based on the Indian meteorological department definition, intensity of the heat waves is identified and re-classified into minor and severe category. The spatio-temporal distribution of each heat wave shows variation in its spatial coverage and also in its intensity. The distributions of heat waves are mainly over central India, North-West India and states such as Odisha, Andhra Pradesh and Telangana during pre-monsoon season. Results show that the increase in meridional heat transport is higher than the zonal advection component, and intensification of heat waves is linked with heat accumulation over a particular region associated with weakening of heat transport. The further amplification associated with depletion of soil moisture will result in the reduction in evaporative cooling, and it will further amplify the surface air temperature.