Impact of Climate Change on Northeast Monsoon System of India - Role of Siberian Teleconnection

Abstract

The Northeast monsoon (NEM) precipitation has undergone a significant change in pattern over the last half century. The changing pattern of climatic variables over the moisture source (i.e. west Pacific High) and the heat sink (Siberian High) of the winter monsoon dynamics over time has caused a shift in the pattern of NEM precipitation over the southern peninsular region of India. There is no significant trend in NEM precipitation in the Indian region whereas the surface temperature has a significantly increasing trend over India during the NEM season. There is no significant trend in outgoing long wave radiation (OLR) of Siberian High (SH) while the west Pacific High (WPH) has a significantly increasing trend in OLR. Surface pressure of both the SH & WPH has no significant trend for the last 59 years (1948-2006). Surface temperature over SH & WPH has a significantly increasing trend for the last 59 years (1948-2006).There is a high correlation of NEM precipitation with El Nino & Southern Oscillation (ENSO), Indian Ocean Dipole(IOD) and OLR of WPH during the period 1970-2000. It signifies that convectional activity in the moisture source region of the NEM, warm SST in the western Indian Ocean and the ENSO have a deep bearing on the NEM precipitation during the three decades 1970-2000. The correlation of NEM precipitation with ENSO, IOD during the last period 2000-2006 has undergone changes where the NEM precipitation has shown a shift that is negatively correlated with ENSO & IOD. The change is much more in IOD than ENSO which signifies that the conventional trend of bearing of warm or cold SST of West Indian ocean on NEM precipitation has decreased during this period of 2000-2006. The correlation of NEM precipitation with the convectional activity of the moisture sink region of the NEM has been gradually decreasing since the 1970s and the moisture source of NEM has a significantly decreasing convectional activity trend. The correlation of NEM precipitation with all three variables (OLR, surface pressure & surface temperature) has shown a comparatively higher value for the heat sink regions (Siberian High) than for the moisture source region (West Pacific High) during the period 2000-2006. Thus the NEM precipitation over India has faced a deep bearing by the role of Siberian High interference.