Trend and spatial distribution of rainfall & rainy days over Andaman & Nicobar Islands

Abstract

The present study examines the characteristics and climatological features of daily rainfall data over Andaman & Nicobar Islands. Analysis of rainfall data reveals a large monthly deviation over the northern latitudes as compare to southern latitudes of Andaman & Nicobar Islands. Also, it is found that rainfall increases from north to south latitudes in all the seasons except monsoon, where a reverse pattern exists. In trend analysis, a statistically significant decreasing trend (confidence level >95 %) is observed for yearly rainfall and rainy days over the region. Analysis of daily rainfall intensity for each year shows increasing trend for frequency of rather heavy rain (35.6–64.4 mm) and significant decreasing trend for frequencies of light rain (2.5–7.5 mm), and very heavy rain (>124.5 mm) over the region. Many times, very heavy rain events are associated with cyclonic disturbances affecting Andaman & Nicobar Islands region. The analysis of cyclonic disturbances over the region reveals a stronger and more significant decreasing trend. So, one of the causes for decreasing trend in very heavy rain over Andaman & Nicobar Islands may be due to significant decreasing frequency of cyclonic disturbances affecting this region.