Impact of the springtime tropical North Atlantic SST on the South Asian High

As an important component of the Asian summer monsoon, the South Asian High (SAH) exhibits striking interannual variability closely related to tropical sea surface temperature (SST) forcing. For example, during post-El Niño summers, the SAH is demonstrated to be strengthened as the delayed Indian Ocean basin-wide SST mode (IOBM) having a robust capacitor enhancement effect on it. In this study, we find that the springtime SST anomalies in the tropical North Atlantic (TNA) can also exert a robust impact on the following summertime SAH intensity, with the SST warming generally accompanied by a stronger SAH and vice versa. We suggest that this influence generally involves two pathways. On the one hand, the positive TNA SST anomaly, which persists into the subsequent summer, can warm the local tropospheric column via moisture adjustment. This tropospheric warming extends eastward along with the climatological subtropical jet, leading to an elevation of the South Asian upper-level geopotential height and thus a stronger SAH. On the other hand, the TNA SST warming triggers tropical trans-basin walker circulation anomalies, causing an anomalous low-level anticyclone over the Indo-western Pacific. The Indian Ocean is featured by an evident ascending flow with intensified precipitation, which in turn generates a strengthened SAH by the resultant condensation heating. This Atlantic SST impact highlighted in this study offers a new avenue for improving the predictability of summertime atmospheric and climate anomalies over South Asia.