ISCCP observed large-scale cloud features over the Indo-Pacific, Southern Annular Mode and Indian summer monsoon

Abstract

The robustness of southern polar linkages with the Indian Summer Monsoon Rainfall (ISMR) is affirmed by employing the Empirical Orthogonal Function (EOF) analysis on Outgoing Longwave Radiation (OLR) over the Indian region. It is observed that the OLR's primary mode of variability (EOF1), which covers almost the entire country and holds a strong positive relationship with ISMR, is significantly associated with Southern Annular Mode (SAM). The International Satellite Cloud Climatology Project (ISCCP) generated spatial distribution of clouds during the recent three decades prominently displays formation and clustering of clouds over the central Pacific as a manifestation of the ocean-atmosphere coupled interactions associated with negative mode of SAM. Further, the northwest ward progression of the cloud-free patterns from equatorial western Pacific to the Indian region is distinctly evident in the ISCCP classified High-level clouds as compared to Middle and Low clouds during the summer monsoon season, thereby inhibiting its monsoon activity. As such, this study demonstrates an association between the southern hemispheric high latitude mode and cloud dynamics over the Indo-Pacific basin having a potential implication on the performance of Indian monsoon.