Influence of monsoon low pressure systems on South Asian disasters and implications for disaster prediction

Abstract

Transient atmospheric vortices called monsoon low pressure systems (LPS) generate a large fraction of total rainfall over South Asia and often produce extreme precipitation. Here, we assess the influence of these storms on the occurrence of disasters, using information from the Emergency Events Database (EM-DAT) that we geocoded and then associated with LPS tracks. We show that more than half of hydro-meteorological disasters over South Asia during summer are associated with these LPS events. Weaker LPS (which are called monsoon lows) occur more frequently than stronger LPS (called monsoon depressions), but the stronger LPS produce a larger number of disasters. Furthermore, although many prior studies have shown that the peak rainfall in LPS falls southwest of the vortex centre, the disasters are concentrated on the northern edge of the LPS tracks, along the Himalayas and upper basins of the Ganga and Brahmaputra rivers. Observations show a sharp peak in rainfall on the day of disasters, confirming the physical link between LPS and these hydro-meteorological disasters. A similar peak in rainfall is found in weather forecasts made up to five days before the disaster, suggesting that short-term precipitation forecasts can be useful in disaster preparation.