Characteristics of observed rainfall over Odisha: An extreme vulnerable zone in the east coast of India

The present study investigates the spatiotemporal characteristics of rainfall events during the summer monsoon season over Odisha (one of the vulnerable zone for heavy rainfall) with the main aim for heavy-to-extreme rainfall events. India Meteorological Department (IMD) station observations and gridded rainfall analysis datasets for a period of 34 years (1980-2013) are used and four frequency indices (heavy-to-extreme, light-to-moderate, dry days, and wet spells) and four intensity indices (daily maximum rainfall, 5-day maximum rainfall, seasonal rainfall total, and daily intensity index) from both the datasets are evaluated. Furthermore, the above-stated indices are analysed over the four meteorological zones of Odisha, as classified by IMD. The analysis reveals that both the heavy-to-extreme rainfall days and dry days are increasing, while the light-to-moderate rainfall days and wet days are decreasing. It is also found that the rate of increase in rainfall amount and number of wet-day are higher in the southern than northern Odisha. This implies that the climate is becoming drier as one move from south to north and the gradient is also increasing with time. The climatological analysis suggests not only the heavy-to-extreme rainfall days and intensity are more in urban (Khordha) and highly elevated (Eastern Ghat; height ~ 1.6 km) areas but also the trend is increasing over those regions. The Murphy skill score of daily rainfall between two datasets is 0.94; however, the number of the extreme rainfall events is more in station data (297) than the gridded data (150) during the study period.