Analysis of Interannual Variation of Regionally Persistent High-Temperature Events in South China during 1961–2017

This study investigates the general circulation and external forcing factors that synergistically affect interannual variation in regional persistent high-temperature events (RPHs) in South China during summer. Several observational data obtained from meteorological stations over the last 60 years and the NCEP/NCAR Reanalysis data set are used. The RPH index is defined based on historical regionally persistent high-temperature events in South China. Under the control of anticyclones throughout the troposphere, deep atmospheric dynamics and thermal anomalies occurred in vertical regions over South China during the years when a large number of RPHs occurred. The interannual variation in RPHs in South China is closely associated with the eastward-propagating wave trains over Eurasia and the large circulation anomaly in the tropics owing to the combined effect of sea surface temperature anomalies (SSTA) from the tropical Indian Ocean, tropical Pacific Ocean, and North Atlantic Ocean. The generation of anticyclone anomaly over the South China Sea in the western Pacific Ocean, which led to the westward extension of strengthened western Pacific subtropical high, results from the SSTA from the tropical Indian Ocean and the tropical Pacific Ocean. The enhancement of wave trains over Eurasia in the upper troposphere, which led to the eastward extension of strengthened South Asia high, results from the SSTA of the North Atlantic Ocean. Thus, strong downdraft is generated under the control of anticyclones throughout the troposphere over South China with a combined effect of these key regions of oceans. The large number of RPHs stems from this strong downdraft, which brings adiabatic heating and strengthened solar radiation heating at the surface.