Assessing the impact of soil moisture initialization on WRF model forecast performances over Türkiye

Abstract

<!--!introduction!--><b></b><p>Soil moisture plays a vital role in transferring energy and water fluxes between the earth's atmosphere and its surface through evaporation, it is a crucial variable in numerical weather prediction. This study investigated the effects of soil moisture initialization on Weather Research and Forecasting (WRF) forecasts by conducting a number of simulations to assess the forecasting performance of the WRF model over Türkiye. WRF simulations were conducted for 2007 and 2015, which were identified as dry and wet initialization years, respectively, based on an analysis of soil moisture and precipitation anomalies with respect to the 1992-2016 years mean. WRF simulations have been tailored as periods of three months (May-June-July), two months (June-July), and one month (July) for these two years to distinguish the effects of different initialization time periods of soil moisture. The study yielded several significant findings. Notably, initializing the simulations in a wet soil moisture condition led to improved precipitation in central Anatolia, and even small changes in soil moisture positively impacted the accuracy of the WRF model’s forecast compared to ERA5 reanalysis data. Additionally, the relationship between soil moisture and precipitation was found to vary across different regions of Türkiye. In the southeastern part of the country, the effect of soil moisture on precipitation was not apparent; however, a relationship was noted between soil moisture and surface temperature, which resulted in an improvement of approximately 4°C in minimum temperature. These findings offer a promising new approach for improving the WRF’s seasonal precipitation forecasting performance.</p>The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)