Droughts of Indian summer monsoon associated with El Nino and Non-El Nino years

Understanding the conditions of droughts are imperative for many purposes especially in planning and agricultural fields. In this paper an attempt is made to analyse rainfall distribution during droughts associated with El Nino and non-El Nino events using India Meteorological Department (IMD) daily rainfall data set having a spatial resolution of 0.25 degrees latitude x 0.25 degrees longitude grid. Patterns of rainfall during drought years which are not associated with El Nino have below normal rainfall over most places of Indian subcontinent, except peninsular India and eastern region. Most of the drought conditions of the Indian summer monsoon rainfall are associated with El Nino (13 of the 18 years) indicating that about 72% of the drought years are associated with the influence of Pacific Ocean. North India and most of the central Indian regions are under below normal rainfall especially over west coastal stations there the severity of drought is strong. The drought that are associated with El Nino are much intense in most parts of the subcontinent, it severely affected the entire west coastal belts, monsoon zone and eastern regions than the droughts associated with non-El Nino years. The spatial patterns of rainfall during flood years associated with La Nina events and drought years associated with El Nino reveal that the spatial structure of rainfall is highly non-linear. These results are also verified using APHRODITE rainfall data. Over central India and Western Ghats (WGs), the drought associated with El Nino gives clear indication of droughts from the early June onward, however, in the case of non-El Nino-related droughts, the indication of drought can be seen only after the first week of July. The study suggests that droughts associated with El Nino events bring severe drought conditions over WG region. However, over central India, there is no considerable difference in cumulative rainfall associated with the two types of droughts. The intraseasonal properties of rainfall are prominently different from non-El Nino to El Nino droughts. During El Nino droughts, the variance of rainfall in both the central Indian and WG regions is weaker than the droughts that are not associated with El Nino.