MODIS BRDF/Albedo数据在中国温度模拟中的应用

地表反照率直接影响地表辐射平衡，进而改变当地温度(2 m气温，下同)，然后还可能通过大气平流过程影响下游地区的温度。为揭示利用实时更新的地表反照率替换WRF (Weather Research and Forecasting) 模式的静态地表反照率对中国大陆温度模拟结果的影响，本文进行了两组为期6 年(2002-2007 年) 的连续积分试验：控制试验(CT试验) 采用短波波段地表反照率，取自WRF模式推荐的地表参数数据集；敏感试验(MD试验) 采用分波段的(可见光和近红外) 地表反照率，取自MODIS BRDF/Albedo数据产品。试验结果表明，CT试验能够模拟中国温度的基本空间格局，但是模拟温度相对于观测温度有明显偏差，青藏高原南部的模拟温度偏低(负偏差)，最大偏低幅度为1.03oC，出现在秋季，东部地区的模拟温度偏高(正偏差)，最大偏高幅度达3.4oC，出现在春季；MD试验模拟结果的正、负偏差格局与CT试验基本相似，但是与CT试验相比，MD试验模拟的青藏高原南部温度的负偏差更大，最大为1.32oC，而模拟的东部地区温度的正偏差明显减小，最大为2.97oC，这说明MD试验比CT试验模拟的温度普遍偏低。在青藏高原，这主要归因于MD试验比CT试验的地表反照率大，使得地表净辐射少，地表感热少，致使温度偏低；在中国东部的黄淮海至江南丘陵区，这主要归因于MD试验中北方蒙古高原的地表反照率比CT试验的大，使得MD试验中该地区的地表净辐射少，地表感热少，温度低，然后通过南下冷平流过程致使位于其下游的黄淮海至江南丘陵区温度降低。

Application of MODIS BRDF/Albedo Dataset in the Regional Temperature Simulation of China

Surface albedo determines the surface radiation budget directly and causes a local radiation forcing, thus the local temperature (2 m temperature, the same below) could be modified; and then, through atmospheric advection, the temperature of lower reach would be impacted. To study the effects of using MODIS BRDF/Albedo in the regional climate simulation with WRF (Weather Research and Forecasting) model, we carried out two 6-year (2002-2007) simulations on climate of China with WRF model. The Control Run (CT) was forced by surface albedo derived from Static Surface Dataset suggested by WRF model; the MODIS Run (MD) was forced by spectral surface albedo derived from MODIS BRDF/Albedo dataset. The results show the CT run could reproduce the general spatial pattern of temperature with evident biases. In southern Tibetan Plateau, the CT's simulation is lower than observation, with the maximum biases of 1.03oC in autumn; while, in eastern China, the CT's simulation is higher than observation, with the maximum biases of 3.4oC in spring. MD's biases pattern is similar with CT run. However, the MD's cooling biases in southern Tibetan Plateau are larger than CT run, with the maximum biases of 1.32oC; the MD's warming biases in eastern China is lower than CT run, with the maximum biases of 2.97oC. The differences between the CT's biases and MD's biases demonstrate MD's simulation is generally lower than CT's simulation. On the Tibetan Plateau, the lower simulation from MD is attributed to local higher surface albedo. The higher surface albedo causes a less net solar radiation and then a less sense heat from surface to atmosphere bottom; as a consequence, the lower temperature happened. In eastern China, the lower temperature was attributed to colder airflow from north, which is caused by higher albedo and thus cooling effects occur on the Mongolia Plateau.