Unprecedented warming in Northwestern India during April of 2022: roles of local forcing and atmospheric Rossby wave

Abstract

Abstract A high surface air temperature (SAT) record over Northwestern India was reported in April 2022. This study examines the contribution of interannual variability on Indian SAT and possible reasons for the extreme SAT during April 2022. Result shows that the interannual variability of SAT is captured by the first two leading modes using the empirical orthogonal function (EOF) analysis. Both of them show highest values over the Northwestern India and are simultaneous energetic during 2022. The EOF1 is related to the Indian Ocean Basin Mode (IOBM) and an anomalous anti-cyclone in the troposphere, while the Rossby wave train from the North Atlantic to the north of India controls the EOF2. The active IOBM and strong Rossby wave source account for the extreme SAT over northwestern India during April 2022. In addition, the Indian regional mean SAT during April is well represented by the indices of IOBM and tropospheric anomalous anti-cyclone, which can help to improve the prediction of SAT over India.