634 / 2024-09-18 17:47:50

Precipitation Anomaly over the Tibetan Plateau affected by Tropical Sea-Surface Temperatures and Mid-Latitude Atmospheric Circulation in September

Tibetan Plateau precipitation, interannual variability, Indian Ocean Dipole, Silk Road pattern

Tibetan Plateau (TP) precipitation is affected by anomalous circulation systems in both the tropics and mid-latitudes, due to the TP’s unique geographical location. By using observational, reanalysis, and CMIP6 model datasets, this study reveals the individual and joint effects of the Indian Ocean Dipole (IOD) and Silk Road pattern (SRP) on the interannual variability of TP precipitation in September. In the positive IOD phase, the zonal gradient of the sea-surface temperature anomalies (SSTAs) drives a Gill-type response with an anticyclonic anomaly over the Indian subcontinent and Bay of Bengal. To the north, anomalous westerlies induce a shallow trough, and the associated anomalous southwesterlies transport moisture to the southeastern TP, resulting in surplus precipitation there. Meanwhile, the westerly jet disturbances over the North Atlantic excite an SRP-like pattern, resulting in a baroclinic structure in northern India with the upper (lower) tropospheric anomalous anticyclone (cyclone) over west-central Asia (northern India). The anomalous southwesterlies to the east of the low-level cyclone transport abundant moisture to the southeastern TP, which results in increased precipitation there. The joint effects of IOD and SRP can explain nearly 52% of the TP precipitation anomaly, exceeding the contribution of IOD (19%) and SRP (27%) alone. Our results highlight the necessity of considering the joint effects of drivers in the tropics and mid-latitudes, providing a basis for more accurate simulations and predictions of TP precipitation.