Atmospheric patterns and winter precipitation over north-western South Asia

Mid-latitude storms act as crucial atmospheric bridges between global teleconnection patterns and regional precipitation distribution during boreal winter over South Asia. In this work, we study the spatio-temporal variability of seasonal precipitation over South Asia over the last four decades, which reveals distinct regional precipitation patterns across seasons. For the winter region of South Asia (WRSA), the second Empirical orthogonal function (EOF2) of 500 hPa geopotential heights shows a significant positive correlation with precipitation. Furthermore, using regression analysis, we estimate that the first six EOFs explain most of the interannual variability in winter precipitation during the positive phase of AMO. The results show that six standard climate indices influence winter precipitation over WRSA. We observed a decadal variability in the relationship between ENSO and winter precipitation over WRSA that is modulated by Pacific Decadal Oscillation (PDO) and Atlantic Multidecadal Oscillation (AMO). The positive phase of AMO strengthens the positive relationship between ENSO and winter precipitation over WRSA. The model results also show that two other oscialltions, DMI and AAO, significantly explain the variability of winter precipitation over WRSA. The atmospheric patterns extracted in this study significantly improve winter precipitation forecasting skill of linear regression models compared to those based on standard climate indices, especially during positive AMO winters. The results from this study can be used to improve seasonal predictability of winter precipitation over WRSA.

Automated summary

Mid-latitude storms play a crucial role in connecting global teleconnection patterns and regional precipitation distribution in South Asia during boreal winter. This study examines the spatio-temporal variability of seasonal precipitation over South Asia in the past four decades, revealing distinct regional precipitation patterns across seasons. The results show that various climate indices influence winter precipitation in the region, and the relationship between ENSO and winter precipitation is modulated by PDO and AMO. The atmospheric patterns identified in this study significantly improve winter precipitation forecasting compared to traditional climate indices, especially during positive AMO winters.