Extreme rainfall events: Vulnerability analysis for disaster management and observation system design

Extreme rainfall events today pose a serious threat to many populated and urbanized areas worldwide; an accurate estimate of frequency and distribution of these events can significantly aid policy planning and observation system design. We report here a first-ever high-resolution (10 KM) analysis of heavy rainfall episodes (defined as 24-hour rainfall exceeding 250 mm) over the Indian region. The data set, recently developed by National Oceanographic and Atmospheric Administration, USA (NOAA), provides daily composite rainfalls for the period 2001-2006 at locations approximately 10-km apart. A category-wise analysis reveals a number of hot spots of vulnerability in terms of annual average number of extreme rainfall events; in particular, the semiarid region in the north-west India emerges as a high vulnerability area in terms of extreme rainfall events. These findings have important implications for a number of areas like vulnerability assessment and meso-scale forecasting. The high-resolution analysis also clearly reveals the corridor of the monsoon trough (Continental Tropical Convergence Zone), lined by a flower-pot distribution of extreme rainfall events along the flanks; this can be a valuable input for precision design of field experiments on the continental trough or on localized extreme events like thunderstorms.

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