Winter Monsoon Extremes over the Deccan Plateau Associated with the Siberian High

This study shows that the seasonal precipitation extremes in the winter monsoon from October to December (OND) over Deccan Plateau (DP) are significantly affected by the variability of Siberian High (SH) in the preceding July to September (JAS) months using the Climate Forecast System Reanalysis (CFSR) and Modern-Era Retrospective Analysis for Research and Applications-2 (MERRA2) data from 1980 to 2016. Both reanalysis datasets consistently show that the pluvial (drought) conditions in the winter monsoon in the state of Telangana are extremely likely due to the negative (positive) SH anomalies in the preceding JAS season. The negative (positive) SH anomaly in JAS favors anomalous high (low) pressure over west of India, which exists mainly over Arabian Peninsula and this in turn results in a large-scale cyclonic (anti-cyclonic) flow centered over the state of Telangana. In the negative SH years of winter monsoon, the northeasterly winds blowing over to the southwest Indian subcontinent are weakened and steered into the Indian peninsula by this large-scale high pressure system over the Arabian peninsula during OND. The steering winds bring moisture from Arabian Sea and Indian Ocean and the resulting moisture convergence on DP increases the chances for pluvial episodes. Based on this study, we hypothesize that the SH variability associated with the Eurasian snow cover impacts the snow fraction through snow-albedo effect and significantly changes the troposphere temperature over the Eurasian region. The resulting baroclinic instability from the large-scale temperature gradient strengthens (weakens) the East Asian jet stream and promotes the high (low) pressure over Arabian Peninsula which is the primary cause of the anomalous steering of moisture transport into the Indian Peninsula and the associated pluvial (drought) episodes over DP. The predictability of extreme precipitation conditions over DP associated with the variations in SH should aid predictions over Telangana and adjacent regions and improve water resources planning and could further improve the resilience planning for rapidly growing suburban regions of Hyderabad.