On the influence of different initial conditions on the soil temperature of Egypt using a regional climate model

Soil temperature is an important indicator for monitoring the root’s environment of natural vegetation or crops. Regional Climate Models (RCMs) are valuable tools for simulating the soil temperature profile on a hierarchy of time scales ranging from daily to annual. Focusing on the daily scale, two eight-year simulations (2011-2018) were conducted to examine the influence of different initial conditions on the simulated soil temperature profile to using a regional climate model (RegCM4). The two simulations were driven by ERA-Interim reanalysis and the output was compared with respect to in-situ observation. The first simulation was initialized with an arbitrary initial condition (i.e., from bare soil) and it was referred to as RegCM4-S1; the second one was initialized with a long-term spin-up file and it was designated as RegCM4-S2. The results showed that the RegCM4-S2 performs better than RegCM4-S1 in simulating the shallow soil temperature profile. Moreover, the RegCM4-S2 shows a poor performance in simulating the soil temperature of deep depths but still outperforms the RegCM4-S1 with respect to the in-situ observation. With a particular focus on the deep depths, the soil temperature parameterization needs to be revised and it is necessary to implement a numerical scheme to reduce the spin-up time.