Short-term climatic fluctuations in North Atlantic Oscillation and frequency of cyclonic disturbances over North Indian Ocean and Northwest Pacific

Abstract

A relationship between mean sea level pressure gradient between Azores High (AH) and Icelandic Low (IL) here after called North Atlantic Oscillation Index (NAOI) and the frequency of cyclonic disturbances over North Indian Ocean is investigated using 98 years of date (1891–1988). The analysis is carried out on monthly, seasonel, annual and decadal scales. Similar studies are also done for North West Pacific ocean cyclonic disturbances. It is noticed that the number of cyclonic disturbances over North Indian Ocean during monsoon season (June–September) as well as on annual scale is significantly correlated with NAOI. However for pre (April–May) and post (October-November-December) monsoon seasons frequency of cyclonic disturbances do not bear similar relationship with NAOI. The study also shows that decadal scale variability of cyclonic disturbances during the summer monsoon over North Indian Ocean has a remarkable correspondence with the decadal variability of NAOI.