资源环境科技发展态势分析平台

A short-duration heavy rainfall events over India have been studied using hourly rainfall data of 126 stations for the period 1969-2015 for the Indian summer monsoon season. The events have been classified into two categories. The first category pertains to cloud burst (CB). The CB events have been further classified into two types, viz. CBa and CBb. CBa events are associated with heavy rainfall in the steep slope mountainous regions of Himalayas identified based on flash floods and damages to properties and human losses, irrespective of the rainfall amount. CBb events are associated with rainfall >10 cm/hr as per the definition by India Meteorological Department (IMD). The statistics of CBb events has been provided in the paper. A total of 28 CBb events have been recorded over Indian region in the study period. These are found to occur over different parts of India. A new and second category of short-term heavy rainfall event has been defined as mini-cloud burst (MCB). It is an event in which rainfall in two consecutive rain-hours is 5 cm or more. Statistical characteristics of these events have been investigated. MCB occurs in June over Western Ghats, over central India and foot hills of Himalayas in July and August. The frequency is low in the month of September. These events generally found to occur in the early morning hours at foot hills of Himalaya and along the west coast of India. In the interior of the land mass these are observed in the afternoon hours while in southern peninsula during night hours. Trend analyses indicate significant increase in these events at many places, except over northeast India. The statistics of CBb and MCB events provided in the paper will trigger numerical modelling studies for understanding the dynamics and invigoration of convection.