Simulating the soil temperature of Egypt using a high-resolution regional climate model: sensitivity to soil moisture and temperature initial conditions

Daily forecast of soil temperature in arid region (e.g., Egypt) is important for monitoring agricultural activity. In this study, a high-resolution regional climate model (RegCM4) was used to forecast the daily soil temperature of depth 40 cm (hereafter ST40). The RegCM4 was downscaled by the Global Forecast System (GFS of one degree horizontal resolution) to 25 km grid spacing. Because the ST40 is sensitive to different initial conditions of the soil moisture and temperature, four experiments were conducted and grouped to two cases. The first case considered the comparison between initialing the RegCM4 from bare soil and from the global satellite soil moisture product (ESACCI). On the other hand, the second case examined the influence of initializing the soil temperature from the Century reanalysis product (Century) versus initializing from zero values. The results showed that initializing the RegCM4 with the ESACCI has a notable impact on the simulated ST40 with respect to the bare soil. Furthermore, when the RegCM4 is initialized with the Century product, the simulated ST40 is improved in the sense that the ST40 trend becomes smoother than when the RegCM4 is initialized with zero values. Such behavior is indicated as the difference the Century and zero values decreases with the forecast time. In conclusion, it can be recommended that the RegCM4 can be initialized by the ESACCI satellite soil moisture and Century reanalysis soil temperature products to ensure a reliable forecast of the ST40