Impact of Local Sea Surface Temperature on Heavy Snowfall in Yeongdong Region

Abstract

This research investigates the impact of local sea surface temperature (SST) on the intensity of snowfall in Yeongdong region which is strongly affected by a synoptic scale factor (East Asian Winter Monsoon, EAWM). Characteristics of snowfall in Yeongdong region, in particular the relationship with EAWM and SST were examined based on observational analysis, and sensitivity experiments with a regional climate model (RCM) were conducted. In sensitivity experiments, local SST was replaced with the climatological SST in winter season for 33 years (1982~2014). Analyses of the composite maps for each strong and weak EAWM year demonstrate that favorable synoptic condition (eastward surge of Siberian High over the northeastern part of the Korean Peninsula, enhanced easterly wind anomaly, and anomalous warm SST over the East Sea) makes a large amount of snowfall during the weak monsoon year. The observational analysis shows both atmospheric and oceanic conditions are important to occur abnormal heavy snowfall in Yeongdong region and analyses of SST experiment suggest that the intensity of snowfall can be significantly affected by local SST when the synoptic condition is favorable. Local SST acts as a source of energy for the formation of heavy snowfall, and it regulates heat and moisture fluxes. When positive SST anomaly exists, latent heat fluxes over the East Sea and moisture convergence on Yeongdong region are enhanced. On the contrary, negative SST anomaly leads to reduced latent heat fluxes and decreased moisture convergence. However, these results are necessarily accompanied with a favorable synoptic condition for heavy snowfall in Yeongdong region. Without the surge of Siberian High and the inflow of easterly wind, SST has no significant impact on the amount of snowfall in Yeongdong region. In addition, both atmospheric and oceanic conditions should be completely favorable to occur a large amount of snowfall.