Application of MODIS Albedo Data in the Simulation of Land Surface and Rainfall Processes over the Yellow River Water Source Region
-
-
Abstract
Land surface albedo (LSA) is a very important geophysical variable in the land surface process. The change of LSA has a direct impact on the surface energy balance, and then can make air temperature and precipitation change by land-atmosphere interaction. To investigate the influence of LSA changes under different surface conditions over the Yellow River water source region, two sets of numerical simulation experiments are conducted by using the WRF (Weather Research and Forecasting) model. Firstly, the impact of LSA changes on the distribution of latent heat and sensible heat is discussed, and then the mechanism of precipitation changes is also explored in detail. At last, the original LSA with low spatial and temporal resolution in this model is substituted by the EOS/MODIS LSA product for improving the simulation ability of the model. The results indicate that: (1) When LSA decreases (or increases), the simulated sensible heat and latent heat increase (or decrease). When LSA decreases 0.1, the ratio of sensible to latent heat increments is approximate to 3∶1.(2) It has the biggest impact on the amount of precipitation in the downriver grassland of the Yellow River water source region and has the smallest impact in the region north of the Yellow River water source region where the land cover is mainly sparse vegetation. The mechanism that the change of LSA leads to the change of precipitation, taking the decrease of LSA as an example, is embodied in three aspects. First, the decrease of surface air pressure induced by the decrease of LSA increases the low-level atmospheric convergent flow, and then enhances the upward movement of air. Second, the increase of 2.0-m temperature accelerates the thermal instability in the low-level atmosphere. Third, the increase in 2.0-m specific humidity indicates more water vapor content in the near-surface layer.(3) Compared with observed monthly rainfall, the assimilation experiment which uses the EOS/MODIS LSA product could improve the accuracy of precipitation simulation.〖WTHZ〗Key words〖WTBZ〗〓ZK(land surface albedo, the Yellow River water source region, WRF model, satellite remote sensing data assimilation, precipitation
-
-