Summer precipitation anomalies in the low-latitude highlands of China coupled with the subtropical Indian Ocean dipole-like sea surface temperature

摘要

The relationship between the subtropical Indian Ocean dipole (SIOD)-like sea surface temperature (SST) and summer precipitation in the low-latitude highlands (LLH) of China is investigated in a suite of numerical simulations using an atmospheric general circulation model (AGCM) and a coupled ocean-atmosphere model. The AGCM experiments driven by SIOD-like SST anomalies are inconsistent with the observations. However, the coupled ocean-atmosphere experiments show a good agreement with the observational results. The modeling results indicate that the air-sea interaction rather than a simple atmospheric forcing-response relationship is a crucial mechanism explaining the connection among the anomalous summer precipitation in the LLH, the anomalous divergence circulations across the Indian Ocean, and the SIOD-like SST anomalies. The effect of the enhanced interhemispheric vertical circulation variability associated with the SIOD-like SST anomalies facilitates zonal wind anomalies in the northern Bay of Bengal, and further induces anomalous water vapor convergence and precipitation anomalies in the LLH. The SST-wind-evaporation feedback mechanism could account for maintenance of the SIOD-like pattern in the coupled ocean-atmosphere experiments. These results could help to improve prediction accuracy of summer rainfall variations over the LLH of China.