Spatiotemporal Characteristics and Physical Drivers of Heatwaves in India

In this study, we analyze the spatiotemporal patterns of propagation of pre-monsoon heatwaves and their drivers in India. Using complex networks, we find that heatwaves originate most frequently in northwest India and propagate in the northeast or southeast direction. Heatwaves propagating in the northeast direction have a higher intensity, lower moving distance, smaller areal coverage, and shorter duration than heatwaves moving in the southeast. We find that the larger area and duration of heatwaves propagating southeast are a result of development of larger and more persistent high-pressure systems extending over entire northern and eastern India, which are influenced by El Ni & ntilde;o Southern Oscillation. On the other hand, higher radiative fluxes and larger heat entrainment in the boundary layer in the heatwaves propagating northeast contribute to their higher intensities. We analyze the spatial patterns of where heatwaves originate and how they spread in the pre-monsoon period in India. We find that most heatwaves originate in northwest India. Some of these heatwaves spread to north and central India while some propagate to south India. Heatwaves in northern and central India have higher intensity and last for a shorter period of time as compared to those which spread to south India. The area and duration of heatwaves moving toward south India are influenced by El Nino events. On the other hand, the intensity of heatwaves of central and north India is higher due to greater shortwave radiation and heat entrainment in the boundary layer. Regions of origin and termination of pre-monsoon heatwaves in India are identified using complex networks and event synchronization Majority of heatwaves originate from northwest India and propagate in the northeast or southeast direction Heatwaves propagating southwards have larger duration and areal extent and are influenced by El Ni & ntilde;o Southern Oscillation