Impacts Of Initial Soil Moisture And Temperature Anomalies On Regional Climate Simulation On East Asia And Its Surrounding Area

All kinds of land surface processes have important influence on simulation results in the regional climate models. At present, there is a shortage of the soil moisture and soil temperature observation data, this makes it’s very difficult to establish initial soil moisture and temperature fields in the global or regional scale. Land surface processes used by climate models are still some earlier development schemes, in which the descriptions of land surface processes use some simple assumptions and limiting conditions, make there are many uncertain factors on the description of the initial soil moisture and temperature field. So it is necessary to investigate that whether the simple initial soil moisture and temperature field adopted by the current climate models has a great influence on the results of regional climate simulation, and affects the effect of climate prediction.By using the regional climate model RegCM4.0coupled with a land surface model CLM3.5, the possible impacts of initial soil moisture and temperature anomalies on East Asia and the surrounding area summer climate was investigated via idealized numerical experiments in a short-term time scale. Results suggest that:(1) The shallow soil moisture differences last for more than1-2months in most areas after artificially reduce the spring initial soil moisture. The net surface upward long-wave radiation flux and surface sensible heat flux enhance obviously as well as latent heat flux decreases, and the surface shortwave radiation slightly increase. The change of the surface energy balance significantly intensified surface thermal heating to the atmosphere, cause a significant warming effect in both surface temperature and air temperature near the surface in most areas, especially over East China, North India and Central Asian.(2) Low initial soil moisture anomalies can significantly decreases the regional evapotranspiration, but the impact on precipitation is small and has large uncertainties, while the change of the surface energy balance significantly intensified surface thermal heating to the atmosphere, warmer underlying surface causes warm high pressure abnormalities at middle and upper troposphere, but these effects were not significant.(3) The initial temperature anomaly decrease rapidly over time after artificially reduce the spring initial soil moisture, the initial value error of soil temperature is difficult to keep for a long time. Lower initial soil temperature initial have some impact on the surface energy balance of the region, cause the surface temperature and the air temperature slightly decrease in most areas; the impact of precipitation and evaporation is small and has large uncertainties, the impact on the atmospheric circulation showed a sensitivity to the simulate starting time, the abnormal distribution of the different simulation starting time has different characteristics, but these changes were not significant. The results show that the influence of initial soil temperature Sensitivity experiment on East Asia and the surrounding area regional climate simulation is uncertain and changes in the quantity is small.(4) The different starting time of the simulation can lead to different results, the initial soil moisture and temperature fields of different starting times have different influences on the simulation results with varying degrees. There are differences in the intensity and scope on both the change of soil moisture and temperature themselves and their impacts on climate simulation.(5) Overall, the initial soil moisture anomalies have a certain impact on the climate simulation results of RegCM4.0, mostly reflect on the temperature and energy flux, and should be considered in the following simulation. But at present it’s unnecessary to spend too much effort to consider the effect of initial soil temperature anomalies may cause.