Linkage between global sea surface temperature and hydroclimatology of a major river basin of India before and after 1980

The frequent occurrence of flood and drought worldwide has drawn attention to assessing whether the hydroclimatology of major river basins has changed. The Mahanadi river basin (MRB) is the major source of fresh water for both Chattisgarh and Odisha states (71 million people approximately) in India. The MRB (141 600 km2 area) is one of the most vulnerable to climate change and variations in temperature and precipitation. In recent years, it has repeatedly faced adverse hydrometeorological conditions. Large-scale ocean-atmospheric phenomena have a substantial influence on river hydroclimatology. Hence global sea surface temperature (SST) linkage with the precipitation and surface temperature of the MRB was analyzed over the period 1950-2012. Significant changes in seasonal correlation patterns were witnessed from 1950-1980 (PR-80) to 1981-2012 (PO-80). The correlation was higher during PR-80 compared to PO-80 between the El Niño region SST versus the maximum temperature (Tmax) in all seasons except the pre-monsoon season and the minimum temperature (Tmin) in all seasons except the monsoon season. However, precipitation correlation changes are not prominent. Like the SST, the correlation patterns of sea level pressure with precipitation, Tmax and Tmin shifted conspicuously from PR-80 to PO-80. These shifts could be related to change in Pacific decadal SST patterns and anthropogenic effects. Fingerprint-based detection and attribution analysis revealed that the observed changes in Tmin (pre-monsoon and monsoon season) during the second half of the 20th century cannot be explained solely by natural variability and can be attributed to an anthropogenic effect.