塔克拉玛干沙漠陆面过程参数化和地表能量通量的遥感反演及数值模拟

Taklimakan Desert is the second largest shifting sand desert in the world, also one of the main origin of the global dust storms, with severe natural environment and extremely arid climate. Therefore, it plays a vital role in weather and climate as well as environmental systems in our country. Thus, it becomes the ideal region to research on special land-surface process. The project will base on the data from the existing seven long-term observational stations which located from north to south (oasis, transitional zone, edge of desert, hinterland of desert) in the desert. Moreover, we will conduct more experiments, which focus on the characteristic parameters of the land-surface process and the surface energy fluxes in different areas over the desert, and combine methods of retrival from satelitte remote sensing images with those observed experimental data, to analyze the vertical structures and turbulent fluxes of heat and momentum between soil and atmosphere of near-surface layer. Then, in order to analyze the variations of parameterization schemes of land-surface process as well as surface energy fluxes in different spatial-temporal scale, the exchange relationship of momentum, heat, moister and radiation will be studied. Meanwhile, the interconversion to the different region scale (scale of the local observational site, scale of pixel of the satellite remote sensing and scale of the grid of satellite remote sensing) will be analyzed and explored. Based on theoretical research, numerical analysis, parameteric experiments, retrival of remote sensing, we will develop and improve the land-surface process parameterization schemes to suit for the desert regions, so as to improve the simulate accuracy of the land-surface process. Furthermore, a revised land-surface process model (such as: CoLM, CLM or Noah) will be coupled into a regional climate numerical simulation model (GRAPES or WRF). By the coupling experiments to improve the simulate accuracy of the regional climate simulation model, and make up for its deficiency to predict the air and surface temperature in the Taklimakan desert and its surrounded oasis.

塔克拉玛干沙漠是世界第二大流动沙漠，自然环境严酷，气候极端干旱，是全球沙尘暴的主要起源地之一，在我国天气气候和环境系统中占有举足轻重的地位，是特殊陆面过程研究的理想靶区。本课题在塔克拉玛干沙漠由北到南（绿洲边缘、荒漠过渡带、沙漠外围、沙漠腹地）的7个长期观测站点的基础上，增加沙漠不同区域多样点的陆面过程特征参数和地表能量通量的观测试验，结合卫星遥感数据反演，解析沙漠土壤和近地层大气的热力及动力的垂直结构和湍流通量，研究陆气间的动量、热量、水分和辐射的交换关系，分析沙漠区域不同时空尺度的陆面过程参数化方案和地表能量通量变化规律，探索陆面过程参数化在局部站点、像元尺度和格网尺度的转换方法，完善陆面过程参数化方案对沙漠地区陆气相互作用的表达，提高陆面过程在沙漠地区的模拟能力。通过陆面过程模块与区域气候数值模式耦合，改进数值模式对沙漠和周边绿洲天气的模拟精度，弥补其在空气和地表温度预报方面的缺陷。

塔克拉玛干沙漠是特殊陆面过程研究的理想靶区。本项目以塔中沙漠大气环境观测试验站为基地，在已有观测试验的基础上，有针对性地开展野外不同观测样点试验。利用遥感反演技术，深入分析了塔克拉玛干沙漠陆面过程特征参数和地表能量通量，发展和优化了地表参数化新方案，进行了陆面过程和区域气候数值模式耦合试验，提高了沙漠地区数值预报模式的预报精度。.本项目主要研究内容有：(1)开展陆面过程参数化方案及其遥感反演研究。(2)开展地表能量通量变化规律及其遥感反演研究。(3)开展不同时空尺度的陆面过程参数化方案对陆面过程模拟的影响研究。(4)进行陆面过程与区域气候数值模式的耦合研究。.本项目主要获得结果有：(1)扩展了沙漠陆面过程观测数据库，增加了数据样点和试验项目。(2)建立了沙漠地表动力学粗糙度的新参数化方案，获得了沙漠地表动力学和热力学粗糙度的日变化和年变化规律。(3)确定了沙漠地表环境下的整体输送系数，获得了日变化和年变化规律。(4)建立了基于遥感的地表宽波段比辐射率和反照率参数化新方案，更加适用于极端干旱的沙漠地区陆面模拟。获得了塔克拉玛干沙漠地区的宽波段地表比辐射率空间分布特征和地表反照率时空分布特征。(5)确定了估算土壤热扩散系数和土壤热通量的最优方法。(6)确定了一种基于多源遥感与再分析资料反演沙漠地表净辐射日变化的新方法。(7)基于遥感数据，利用地表参数化新方案，反演得到了塔克拉玛干沙漠地表能量通量的时空分布特征。(8)在局地尺度上，修正Noah陆面模型参数化方案，提高了模型对沙漠地表能量通量的模拟精度。(9)在网格尺度上，修正CLM陆面模型参数化方案，提高了模型对沙漠地表能量通量的模拟精度，并获得了塔克拉玛干沙漠地区地表能量通量的时空分布特征。(10)改进的陆面过程参数化方案模块已与WRF和GRAPES模式进行耦合，能够显著改善模式对南疆塔里木盆地的气温预报。