FRONTIER Newsletter No.9 Jan.2000

The unusual event of 1994 in the Asia-Pacific region

Swadhin Kumar Behera (Climate Variations Research Program)
The Asia- Pacific sector experienced unusual weather conditions during the boreal summer of 1994. Extremely dry and hot summer prevailed over Japan whereas Indian sub- continent and East Asia experienced heavy monsoon rain leading to flood in many parts. Such climate variability in the monsoon rains in the Indian sub- continent is often believed to be related to ENSO event in the Pacific. Though there was some indication of a weak warm ENSO in the Pacific during 1994, this cannot explain heavy monsoon rains over India as the warm phase of ENSO is statistically inversely related with the monsoon rain. On the other hand, the southeastern tropical Indian Ocean was anomalously cold during the event with warm anomalies in the central region which is now known as a part of Indian Ocean dipole mode (see Frontier Newsletter No. 8).

As found out by Behera, Krishnan and Yamagata (GRL, October 1, 1999) a positive feed- back between the convection, wind, evaporation along with the ocean dynamics helped maintain the dipole structure in the SST anomalies. The resulted anomalous moisture transport from southeastern tropical Indian Ocean gave rise to the enhanced convection over Indian sub-continent and East Asia.As it is already known that enhanced convection north of Philippines is inversely related with the rainfall over Japan,it is suggested that such anomalous condition in the eastern Indian Ocean is linked to the 1994 dry summer condition over Japan.