Effect of Sea Surface Temperature Errors on Snowfall in WRF: A Case Study of a Heavy Snowfall Event in Korea in December 2012

Jaein I Jeong,Rokjin J Park,Yang-Ki Cho

doi:10.3319/tao.2014.08.15.01(a)

Abstract

We examined the sensitivity of simulated snowfall to prescribed sea surface temperature (SST) data using the Weather Research and Forecasting (WRF) model and the Operational Sea Surface Temperature and Sea Ice Analysis (OSTIA) SST dataset for the Korean Peninsula. The OSTIA data were initially compared with in situ buoy measurements from three coastal sites in the Yellow Sea and was shown to be in good agreement with the in situ data with root mean square errors of 0.14-0.17 K for the daily mean values. Next, we conducted several WRF simulations, including a baseline simulation with the OSTIA data and sensitivity simulations with a temporally and spatially varying SST. The simulations were run for the Yellow Sea during December 2012 when a severe snowfall occurred in Korea. The baseline model generally captured the observed spatial and temporal variations of snowfall, surface air temperature and surface pressure in Korea. The sensitivity simulations with an increased and decreased SST resulted in a variation of +0.8/-0.7 K for the surface air temperature, ±0.6 hPa for the surface pressure, and ±0.3 m s^(-1) for the surface wind speed, in relation to the baseline simulation. The SST deviation affected the precipitation variability with changes of ±9% for snowfall and ±18% for rainfall, indicating considerable model sensitivity to SST perturbations. The change in the meteorological variables of the upper layer induced by the SST perturbations showed a symmetrical structure with respect to warmer and colder SST. Nevertheless, ice represented a nonlinear combination of the results at the low and mid-levels.

Highlights

Sea surface temperature (SST) plays an important role in synoptic weather systems by determining the exchange of moisture, heat and momentum between the atmosphere and the ocean surface
We examined the effect of the OSTIA SST errors of 1.5 - 2 K in the coastal sea on the meteorological fields for the Korean Peninsula by conducting two sensitivity simulations using increased (WSST) and decreased (CSST) OSTIA SST values according to the OSTIA SST errors
When the strong Siberian High, associated with a cold air mass, expands towards the Korean Peninsula, SST deviations play an important role in the air-sea interaction over the Yellow Sea

Summary

INTRODUCTION

Sea surface temperature (SST) plays an important role in synoptic weather systems by determining the exchange of moisture, heat and momentum between the atmosphere and the ocean surface. Park et al (2011) showed that SST perturbations significantly affect the air temperature at the sea surface, the atmospheric stability and the vertical moisture fluxes. Jeong and Park (2013) reported that ±1.1°C perturbations in SST result in changes in air temperature of +0.37/-0.38°C, and in surface pressure of ±0.31 hPa over the Yellow Sea. Cha et al (2011) showed that SST deviations affect cloud streets and snowfall formation. We first quantified the spatial and temporal errors of the Operational Sea Surface Temperature and Sea Ice Analysis (OSTIA) SST dataset by comparison with in situ buoy observations for the Yellow Sea. we examined the sensitivity of model simulations to the estimated SST errors, primarily focusing on a heavy snowfall event that occurred in December 2012. The analysis of our results will provide suggestions to improve weather forecasting systems associated with SST data

SST DATA AND MODEL DESCRIPTION

MODEL EVALUATION FOR THE HEAVY SNOWFALL EVENT OF DECEMBER 2012

SIMULATED SENSITIVITY OF SNOWFALLS TO SST VARIATION

CONCLUSIONS