Development of model output statistics based on the least absolute shrinkage and selection operator regression for forecasting next-day maximum temperature in South Korea

Abstract

Regression models for model output statistics (MOS) based on least absolute shrinkage and selection operator methods were developed to forecast next-day maximum surface air temperature (TMAX) during the warm season in South Korea. The forecast fields from the operational numerical weather prediction (NWP) system of the Korean Meteorological Administration for global and local forecasts and the observed TMAX data in 225 observation stations were used as input variables for the MOS. The training period was July and August (JA) from 2015 to 2018, and the regression models were tested using data from JA 2019. As a result of hindcasting for the test period, the MOS models performed significantly better for next-day TMAX forecasting over South Korea than the numerical models during JA 2019. The mean TMAX errors were reduced by over 1 degrees C in MOSs compared to those in the numerical models. However, the TMAX forecast performance was generally lower in the higher-resolution NWP Local Data Assimilation and Prediction System (LDAPS)-based MOS (LMOS) than in the lower-resolution NWP Global Data Assimilation and Prediction System (GDAPS)-based MOS. This pattern was dominant when LDAPS simulated the TMAX more accurately than average. In particular, the random TMAX error of LDAPS was larger than that of GDAPS during the training period, and a positive random error of TMAX was magnified in LMOS. Because the other predictors forecasted from LDAPS can be associated with lower TMAX forecast performance of LMOS, in addition to TMAX effects as a predictor, a new MOS was developed using both LDAPS and GDAPS outputs. The forecast accuracy was improved by up to 0.3 degrees C when the forecast fields from the GDAPS substituted several LMOS predictors, even though TMAX was the primary predictor for LMOS.