Influence of dry air intrusion from the Middle East on Indian summer monsoon variability

The dry air intrusion from the Middle East is found to influence the spatial and temporal distribution of Indian summer monsoon precipitation. Here, we suggest an index to quantify dry air intrusion towards India during summer monsoon by calculating moisture deficit transport from Western Asia. Moisture deficit is defined as the difference between saturation specific humidity and specific humidity . We compare the dry air intrusion index with the daily rainfall-based dry spells . We find that the results obtained from both analyses are consistent for July and August. Moisture deficit transport index captures the long dry spells that occurred over central India for the years 2001, 2002, and 2005 which were reported to be influenced by dry air intrusion (Krishnamurti et al., 2010, J. Atmos. Sci.) . Our analyses illustrate the co-variability between moisture deficit over West Asia and precipitation over India during summer monsoon for both active and dry spells. The variability in the lower-tropospheric blocking high over the Arabian Peninsula is found to influence the intrusion of the dry air over the Arabian Sea and Indian continental region during summer monsoon season. Further, an anomalous westward shift in the precipitation pattern over the continental India during active phases of summer monsoon is seen when an anomalous low-pressure area is developed over the eastern Arabian Peninsula adjacent to the Arabian Sea.