Variability of Convective Activity over the North Indian Ocean and its Associations with Monsoon Rainfall over India |
| |
| Authors: | D R Pattanaik |
| |
| Institution: | (1) India Meteorological Department, NHAC (NWP), Mausam Bhawan, Lodhi Road, New Delhi, 110003, India |
| |
| Abstract: | The present study is an attempt to examine the variability of convective activity over the north Indian Ocean (Bay of Bengal
and Arabian Sea) on interannual and longer time scale and its association with the rainfall activity over the four different
homogeneous regions of India (viz., northeast India, northwest India, central India and south peninsular India) during the
monsoon season from June to September (JJAS) for the 26 year period (1979 to 2004). The monthly mean Outgoing Long-wave Radiation
(OLR) data obtained from National Oceanic and Atmospheric Administration (NOAA) polar orbiting spacecraft are used in this
study and the 26-year period has been divided into two periods of 13 years each with period-i from 1979 to 1991 and period
-ii from 1992 to 2004. It is ascertained that the convective activity increases over the Arabian Sea and the Bay of Bengal
in the recent period (period -ii; 1992 to 2004) compared to that of the former period (period -i; 1979 to 1991) during JJAS
and is associated with a significantly increasing trend (at 95% level) of convective activity over the north Bay of Bengal
(NBAY). On a monthly scale, July and August also show increase in convective activity over the Arabian Sea and the Bay of
Bengal during the recent period and this is associated with slight changes in the monsoon activity cycle over India. The increase
in convective activity particularly over the Arabian Sea during the recent period of June is basically associated with about
three days early onset of the monsoon over Delhi and relatively faster progress of the monsoon northward from the southern
tip of India. Over the homogeneous regions of India the correlation coefficient (CC) of OLR anomalies over the south Arabian
Sea (SARA) is highly significant with the rainfall over central India, south peninsular India and northwest India, and for
the north Arabian Sea (NARA), it is significant with northwest India rainfall and south peninsular rainfall. Similarly, the
OLR anomalies over the south Bay of Bengal (SBAY) have significant CC with northwest India and south peninsular rainfall,
whereas the most active convective region of the NBAY is not significantly correlated with rainfall over India. It is also
found that the region over northeastern parts of India and its surroundings has a negative correlation with the OLR anomalies
over the NARA and is associated with an anomalous sinking (rising) motion over the northeastern parts of India during the
years of increase (decrease) of convective activity over the NARA. |
| |
| Keywords: | Outgoing long-wave radiation (OLR) convection north Indian Ocean homogeneous region all India summer monsoon rainfall (AISMR) |
| 本文献已被 SpringerLink 等数据库收录！ |
|
