A salient oceanic driver for the interannual variability of wintertime haze days over the Pearl River Delta region, China

Abstract

This study explored the effect of sea surface temperature (SST) on the interannual variations in wintertime haze days (WHDs) in the Pearl River Delta (PRD) region (WHDPRD) of China. Analyses unravel that SST anomalies in the adjoining area of the northern Indian and Pacific sector (the NIP region) can drive the interannual variations in the frequency of wintertime haze over the PRD region, which is deemed a salient oceanic driver. The SST anomalies have a stable and significant anticorrelation with the interannual component of the WHDPRD. This anticorrelation is highest in the concurrent winter and thus exerts a strong influence on the variability of localized WHDs. Further observational and simulation results suggest that the cold SST anomalies in the NIP region can induce a large-scale east–west dipole pattern by triggering diabatic cooling to the northwest. This dipole resembles the pattern tied to a higher WHDPRD, with an anticyclonic anomaly centered over the Indo-China Peninsula and a cyclonic anomaly centered over the western North Pacific. Under such circumstances, the PRD region is dominated by consistent northerly wind anomalies, facilitating the formation of two crucial processes responsible for a higher WHDPRD: the northward transportation of aerosols and a decrease in local wet deposition.