Since the early 2000s, many satellite passive microwave brightness temperature (BT) archives, such as the Advanced Microwave Scanning Radiometer for the Earth Observing System (AMSR-E) BTs, have become the useful ...Since the early 2000s, many satellite passive microwave brightness temperature (BT) archives, such as the Advanced Microwave Scanning Radiometer for the Earth Observing System (AMSR-E) BTs, have become the useful resources for assessing the changes in the surface and deep soil moistures over both arid and semi-arid regions. In this study, we used a new soil effective temperature (T scheme and the archived AMSR-E BTs to estimate surface soil moisture (SM) over the Nagqu region in the central Tibetan Plateau, China. The surface and deep soil temperatures required for the calculation of regional-scale T were obtained from outputs of the Community Land Model version 4.5 (CLM4.5). In situ SM measurements at the CEOP-CAMP/Tibet (Coordinated Enhanced Observing Period Asia-Australia Monsoon Project on the Tibetan Plateau) experimental sites were used to validate the AMSR-E-based SM estimations at regional and single-site scales. Furthermore, the spatial distribution of monthly mean surface SM over the Nagqu region was obtained from 16 daytime AMSR-E BT observations in July 2004 over the Nagqu region. Results revealed that the AMSR-E-based surface SM estimations agreed well with the in situ-based surface SM measurements, with the root mean square error (RMSE) ranging from 0.042 to 0.066 m3/m3 and the coefficient of determination (R2) ranging from 0.71 to 0.92 during the nighttime and daytime. The regional surface soil water state map showed a clear spatial pattern related to the terrain. It indicated that the lower surface SM values occurred in the mountainous areas of the northern, mid-western and southeastern parts of Nagqu region, while the higher surface SM values appeared in the low elevation areas such as the Tongtian River Basin, Namco Lake and bog meadows in the central part of Nagqu region. Our analysis also showed that the new T^scheme does not require special fitting parameters or additional assumptions, which simplifies the data requirements for regional-scale applications. This scheme combined with the archived satellite passive microwave BT observations can be used to estimate the historical surface SM for hydrological process studies over the Tibetan Plateau regions.展开更多
基于黄河流域101个气象站点的实测气象数据和国际耦合模式比较计划第5阶段(coupled model intercomparison project phase 5,CMIP5)3种排放情景下的6个模型1961—2099年的降水和气温数据,采用等距离累积分布函数法(equidistant cumulati...基于黄河流域101个气象站点的实测气象数据和国际耦合模式比较计划第5阶段(coupled model intercomparison project phase 5,CMIP5)3种排放情景下的6个模型1961—2099年的降水和气温数据,采用等距离累积分布函数法(equidistant cumulative distribution function matching method,EDCDFm)进行统计降尺度;通过历史阶段(1961—2005年)实测站点数据对降尺度后的降水和气温进行精度评估;在此基础上,通过标准化降水指数(standardprecipitation index,SPI)对黄河流域气象干旱进行预估。结果表明,EDCDFm的降尺度方法能够明显提高气候模式所模拟的气温和降水精度,尤其对极值的模拟精度;黄河流域气象干旱的预估显示,3种气候情景下21世纪初的干旱情况相对于基准期均变得比较严重,但是世纪末的干旱程度均明显减轻,近期黄河流域的防旱工作形势仍然严峻。展开更多
基金supported by the National Natural Science Foundation of China (41575013)the National Supercomputer Center in Guangzhou, China
摘要Since the early 2000s, many satellite passive microwave brightness temperature (BT) archives, such as the Advanced Microwave Scanning Radiometer for the Earth Observing System (AMSR-E) BTs, have become the useful resources for assessing the changes in the surface and deep soil moistures over both arid and semi-arid regions. In this study, we used a new soil effective temperature (T scheme and the archived AMSR-E BTs to estimate surface soil moisture (SM) over the Nagqu region in the central Tibetan Plateau, China. The surface and deep soil temperatures required for the calculation of regional-scale T were obtained from outputs of the Community Land Model version 4.5 (CLM4.5). In situ SM measurements at the CEOP-CAMP/Tibet (Coordinated Enhanced Observing Period Asia-Australia Monsoon Project on the Tibetan Plateau) experimental sites were used to validate the AMSR-E-based SM estimations at regional and single-site scales. Furthermore, the spatial distribution of monthly mean surface SM over the Nagqu region was obtained from 16 daytime AMSR-E BT observations in July 2004 over the Nagqu region. Results revealed that the AMSR-E-based surface SM estimations agreed well with the in situ-based surface SM measurements, with the root mean square error (RMSE) ranging from 0.042 to 0.066 m3/m3 and the coefficient of determination (R2) ranging from 0.71 to 0.92 during the nighttime and daytime. The regional surface soil water state map showed a clear spatial pattern related to the terrain. It indicated that the lower surface SM values occurred in the mountainous areas of the northern, mid-western and southeastern parts of Nagqu region, while the higher surface SM values appeared in the low elevation areas such as the Tongtian River Basin, Namco Lake and bog meadows in the central part of Nagqu region. Our analysis also showed that the new T^scheme does not require special fitting parameters or additional assumptions, which simplifies the data requirements for regional-scale applications. This scheme combined with the archived satellite passive microwave BT observations can be used to estimate the historical surface SM for hydrological process studies over the Tibetan Plateau regions.
摘要基于黄河流域101个气象站点的实测气象数据和国际耦合模式比较计划第5阶段(coupled model intercomparison project phase 5,CMIP5)3种排放情景下的6个模型1961—2099年的降水和气温数据,采用等距离累积分布函数法(equidistant cumulative distribution function matching method,EDCDFm)进行统计降尺度;通过历史阶段(1961—2005年)实测站点数据对降尺度后的降水和气温进行精度评估;在此基础上,通过标准化降水指数(standardprecipitation index,SPI)对黄河流域气象干旱进行预估。结果表明,EDCDFm的降尺度方法能够明显提高气候模式所模拟的气温和降水精度,尤其对极值的模拟精度;黄河流域气象干旱的预估显示,3种气候情景下21世纪初的干旱情况相对于基准期均变得比较严重,但是世纪末的干旱程度均明显减轻,近期黄河流域的防旱工作形势仍然严峻。