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|Title:||ENSO and monsoon induced sea level changes and their impacts along the Indian coastline|
|Keywords:||Mean sea level;Mean tidal level;El Nino / Southern Oscillation (ENSO);Monsoon;Southern oscillation index (SOI);Sea surface temperature;Sea level;Tidal level|
|Abstract:||For preparedness programmes aimed at combating sea level - associated disasters, it is necessary to carry out comprehensive studies on different aspects of sea level variability. On many occasions the interannual modes dominate the long term trends of mean sea level (MSL). In South Asian region El Niño-Southern Oscillation (ENSO) induced variation is an important component of sea level variability on the interannual time scale. In the present paper focus is on the ENSO and monsoon modes of interannual variability of MSL along the Indian coast. The results have revealed that good concurrent correlations exist between the Southern Oscillation Index (SOI) and the Mean Tidal Level (MTL) at Visakhapatnam during the intense cyclone period of the year, i.e. May, October and November. Also, in the end phase of the southwest monsoon (i.e. during September) MTL is significantly correlated to the SOI. During the cold phase of ENSO (i.e. positive SOI) MSL is higher over the east coast of India enhancing the hazardous potential of the Bay of Bengal tropical cyclones. ENSO seems to have relatively lesser impact on the MSL variation over the west coast of India. However, during September (southwest monsoon) the correlations between the MTL and SOI are significant, both at Mumbai and Kochi. Thus ENSO appears to influence the MSL along the west coast of India during the ending phase of the southwest monsoon. The SOI-sea level relationship has prognostic utility also. High positive correlations exist between MSL along the east coast of India during the intense cyclone period (May, October and November) and the SOI of preceding month which can provide predictive indications of sea level one month in advance. Significant concurrent correlations have been found between monthly rainfall and MSL over the west coast of India during the southwest monsoon season. The correlation coefficients of the order of ~ +0.5 have been observed between the seasonal monsoon rainfall over Konkan and Goa coast and seasonal MSL at Mumbai; and seasonal monsoon rainfall over Kerala and seasonal MSL at Kochi. It is interesting to note that correlations between the monsoon rainfall and MSL over the east coast of India are poor, implying that the southwest monsoon rainfall has very little influence on the sea level variations over the east coast of India. It may be pointed out that southeast coast of India receives substantial amount of rainfall during the northeast monsoon season (October to December) during which northeasterly winds prevail there. The lag correlations between the southwest monsoon rainfall and sea level over the west coast and the northeast monsoon rainfall and sea level over the east coast could also be looked into for the purpose of predictability aspect of the sea level along the Indian coast.|
|Appears in Collections:|| IJMS Vol.35(2) [June 2006]|
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