Heat Wave Variations Across China Tied to Global SST Modes

Progressive intensification and proliferation of heat waves impose extensively impacts on entire environment and ecology. The far-reaching implications of heat waves and the severe future projections emphasize the imperative need to explore the driving factors and their quantitative contribution to heat wave variations. In this study, a multiaspect characteristic of heat waves across China during 1961-2017 is evaluated using excess heat factor. Results showed that the number of events, frequency, duration, and intensity has heterogeneous spatial patterns, with a consistent abrupt transition in 1996-1997. The robust positive correlations between heat wave characteristics and warming sea surface temperature (SST) indicate the association of heat wave with SST anomalies. Except the number of events, the other factors (including the frequency, duration, and intensity) of heat waves are strongly influenced by El Nino-Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD). However, the influences have significant variations from region to region, with the central regions experiencing significant decreases in the frequency, duration, and intensity of heat waves during the simultaneous ENSO phases (El Nino-La Nina), in comparison with northern and western regions dominated by IOD (positive-negative) experiencing longer and more frequent heat waves. Particularly, the mild heat waves are more vulnerable to the warming SST modes than severe heat waves. The decrease of heat waves is affected by the convergent winds bringing cold air from the high latitude, while the extensively significant increase of heat waves is controlled by the anomalously sinking motions.