基于卫星遥感数据的Noah-MP地表反照率关键参数优化

Toward Optimization of Key Parameters in Noah-MP Surface Albedo Using Satellite Remote Sensing Products

地表反照率是影响地–气相互作用的关键因子,而准确描述地表反照率是改进陆面模型水热模拟能力的关键。当前Noah-MP (the Noah land surface model with Multiple Parameterizations)土壤反照率估算主要依赖于查找表方法,该方法基于土壤颜色获得不同土壤类型的反照率,但在区域尺度上土壤颜色等级尚未得到有效率定,直接影响了区域反照率模拟水平。此外,裸土反照率的计算还高度依赖于土壤水分。针对这一问题,以同化得到的土壤水分数据作为输入,计算得到不同土壤颜色等级对应的反照率时间序列。在此基础上,以MODIS反照率为参照,同时排除高植被覆盖和积雪的影响,逐步筛选得到青藏高原区域0.25°格点尺度下最优的土壤颜色等级。评估结果表明,优化得到的土壤颜色等级空间分布规律符合土壤质地与反照率之间的物理规律,且改进了研究区域70%空间网格内的Noah-MP模型反照率估计。

Surface albedo is a key factor affecting land-air interactions.The accurate estimate of sur-face albedo is of great value for improving land model’s capability in hydrothermal simulation.In the Noah-MP(the Noah land surface model with multiple parameterizations)land surface model,estimation of soil albedo mainly relies on a look-up table-based method that characterize the albedo of different soil types with the so-called soil color.However,the soil color has not yet been calibrated at the regional or global scale,which greatly hinders the regional albedo simulation.In addition,the calculation of bare soil albedo is highly sensitive to surface soil moisture.To this end,this study first produces an ensemble of albedo time series with regard to different soil types with data assimilation generated soil moisture as in-put.Then,the optimal 0.25°soil color for the Tibetan Plateau region were screened by referring MODIS albedo and excluding the impacts from dense vegetation and snow cover.The evaluation results show that the spatial distribution of optimized soil color can reasonably reflect the relationship between soil texture and albedo,and improved Noah-MP albedo estimation in over 70%of the grid cells in the study area.