An observational evidence of climate change during global warming era

The relationships of the Frequency of the Cyclonic Systems (FCS) over the Bay of Bengal in the Summer Monsoon (SM) season (June through September) with the North Atlantic Oscillation Index (NAOI) and the Southern Oscillation Index (SOI) from January through May for the period 1950–2005 are examined. The NAOI (January and February) and the SOI (April) showed significant inverse and positive relationships respectively with the FCS generated in SM season over the Bay of Bengal. These relationships are marked on a decadal scale. In the Global Warming (GW) era, a significant reduction in the FCS is associated with a significant increase of NAOI, relaxation of SOI and a weak vertical zonal wind shear in the domain 5°–22°N and 80°–100°E.

► NAOI (January and February) shows significant inverse relationship with FCS in SM season over the Bay of Bengal.
► SOI (April) shows significant positive relationship with FCS in SM season over the Bay of Bengal.
► Weakening of both westerlies at 850 hPa and easterlies at 100 hPa over Indian southern latitudes takes place in GW era.
► Decrease of vertical shear in the zonal wind over the monsoon depression prone area is observed in GW era.
► SOI is decreasing in GW era. Climate is changing over India.