According to the need of popular land surface process models, characteristics and rules of some key land surface process and soil parameters over Gobi in typical arid region of Northwest China are analyzed by using th...According to the need of popular land surface process models, characteristics and rules of some key land surface process and soil parameters over Gobi in typical arid region of Northwest China are analyzed by using the data observed during the intensive observation period of the Dunhuang Land–Surface Process Field Experiment (DLSPFE) (May–June 2000). Using the relative reflection as weighting factor, the weighted mean of the surface albedo over Dunhuang Gobi in typical arid region is calculated and its values are 0.255 ± 0.021. After canceling the interference of the buildings, the mean values of the roughness length averaged with logarithm is 0.0019 ± 0.00071 m. After removing the influence of the oasis, the soil wetness factor computed with data under condition of no precipitation is 0.0045. After removing the influence of the precipitation , the mean values of the soil heat capacity over Dunhuang Gobi in typical arid region is 1.12 × 10<SUP>6</SUP> J m<SUP>−3</SUP>K<SUP>−1</SUP>, a bit smaller than the values observed in HEIFE. But the soil heat diffusivity and conductivity are about one of those observed in HEIFE. The soil water content over Dunhuang Gobi in typical synoptic condition is very little and does not exceed 1% basically.展开更多
Land cover change affects surface radiation budget and energy balance by chang- ing surface albedo and further impacts the regional and global climate. In this article, high spatial and temporal resolution satellite p...Land cover change affects surface radiation budget and energy balance by chang- ing surface albedo and further impacts the regional and global climate. In this article, high spatial and temporal resolution satellite products were used to analyze the driving mechanism for surface albedo change caused by land cover change during 1990-2010. In addition, the annual-scale radiative forcing caused by surface albedo changes in China＇s 50 ecological regions were calculated to reveal the biophysical mechanisms of land cover change affecting climate change at regional scale. Our results showed that the national land cover changes were mainly caused by land reclamation, grassland desertification and urbanization in past 20 years, which were almost induced by anthropogenic activities. Grassland and forest area decreased by 0.60% and 0.11%, respectively. The area of urban and farmland increased by 0.60% and 0.19%, respectively. The mean radiative forcing caused by land cover changes during 1990-2010 was 0.062 W/m2 in China, indicating a warming climate effect. However, spatial heterogeneity of radiative forcing was huge among different ecological regions. Farmland conversing to urban construction land, the main type of land cover change for the urban and suburban agricultural ecological region in Beijing-Tianjin-Tangshan region, caused an albedo reduction by 0.00456 and a maximum positive radiative forcing of 0.863 WIm2, which was presented as warming climate effects. Grassland and forest conversing to farmland, the main type of land cover change for the temperate humid agricultural and wetland ecological region in Sanjiang Plain, caused an albedo increase by 0.00152 and a maximum negative radiative forcing of 0.184 W/m2, implying cooling climate effects.展开更多
地表反照率是陆面过程中一个重要的物理量,其变化直接影响地表能量的收支状况,进而可以影响气温和降水等其它气象要素。本文利用WRF(Weather Research and Forecasting)模式,通过两组数值模拟试验分别探讨了地表反照率改变在黄河源区不...地表反照率是陆面过程中一个重要的物理量,其变化直接影响地表能量的收支状况,进而可以影响气温和降水等其它气象要素。本文利用WRF(Weather Research and Forecasting)模式,通过两组数值模拟试验分别探讨了地表反照率改变在黄河源区不同下垫面情况下潜热、感热的分配关系,详细分析了地表反照率改变对降水变化的影响机制,最后应用EOS/MODIS地表反照率产品替代原模式低时空分辨率的地表反照率。研究结果表明:(1)当地表反照率减少(增加)时,模拟的区域平均地表温度、感热、潜热数值相应增大(减少)。当地表反照率减少0.1时,地表温度上升约1.0K,感热和潜热量增量比约为3∶1。(2)地表反照率改变对降水量变化影响最大的区域是黄河源区下游的草场区域,其次是黄河源头区域,最小的是黄河源区北部的稀疏植被区域。地表反照率通过对大气动力、热力以及水汽条件的影响,使得降水发生的环境改变,主要体现在:当地表反照率减少时,地表气压的减少使得大气低层的辐合气流增强,有利于上升运动的发生;2.0m气温的升高增强了大气近地层的热力不稳定度;2.0m比湿的增加表明近地层空气水汽含量增加。(3)与实况对比分析发现,使用卫星遥感产品后在月尺度上能够更准确地模拟降水量的变化过程。展开更多
基金This research was sponsored by the National Key Program for Developing Basic Sciences Research on the Formation Mechanism and Pr
文摘According to the need of popular land surface process models, characteristics and rules of some key land surface process and soil parameters over Gobi in typical arid region of Northwest China are analyzed by using the data observed during the intensive observation period of the Dunhuang Land–Surface Process Field Experiment (DLSPFE) (May–June 2000). Using the relative reflection as weighting factor, the weighted mean of the surface albedo over Dunhuang Gobi in typical arid region is calculated and its values are 0.255 ± 0.021. After canceling the interference of the buildings, the mean values of the roughness length averaged with logarithm is 0.0019 ± 0.00071 m. After removing the influence of the oasis, the soil wetness factor computed with data under condition of no precipitation is 0.0045. After removing the influence of the precipitation , the mean values of the soil heat capacity over Dunhuang Gobi in typical arid region is 1.12 × 10<SUP>6</SUP> J m<SUP>−3</SUP>K<SUP>−1</SUP>, a bit smaller than the values observed in HEIFE. But the soil heat diffusivity and conductivity are about one of those observed in HEIFE. The soil water content over Dunhuang Gobi in typical synoptic condition is very little and does not exceed 1% basically.
基金National Key Program for Developing Basic Science,No.2010CB950902Strategic Priority Research Program of the Chinese Academy of Sciences,No.XDA05090303
文摘Land cover change affects surface radiation budget and energy balance by chang- ing surface albedo and further impacts the regional and global climate. In this article, high spatial and temporal resolution satellite products were used to analyze the driving mechanism for surface albedo change caused by land cover change during 1990-2010. In addition, the annual-scale radiative forcing caused by surface albedo changes in China＇s 50 ecological regions were calculated to reveal the biophysical mechanisms of land cover change affecting climate change at regional scale. Our results showed that the national land cover changes were mainly caused by land reclamation, grassland desertification and urbanization in past 20 years, which were almost induced by anthropogenic activities. Grassland and forest area decreased by 0.60% and 0.11%, respectively. The area of urban and farmland increased by 0.60% and 0.19%, respectively. The mean radiative forcing caused by land cover changes during 1990-2010 was 0.062 W/m2 in China, indicating a warming climate effect. However, spatial heterogeneity of radiative forcing was huge among different ecological regions. Farmland conversing to urban construction land, the main type of land cover change for the urban and suburban agricultural ecological region in Beijing-Tianjin-Tangshan region, caused an albedo reduction by 0.00456 and a maximum positive radiative forcing of 0.863 WIm2, which was presented as warming climate effects. Grassland and forest conversing to farmland, the main type of land cover change for the temperate humid agricultural and wetland ecological region in Sanjiang Plain, caused an albedo increase by 0.00152 and a maximum negative radiative forcing of 0.184 W/m2, implying cooling climate effects.
文摘地表反照率是陆面过程中一个重要的物理量,其变化直接影响地表能量的收支状况,进而可以影响气温和降水等其它气象要素。本文利用WRF(Weather Research and Forecasting)模式,通过两组数值模拟试验分别探讨了地表反照率改变在黄河源区不同下垫面情况下潜热、感热的分配关系,详细分析了地表反照率改变对降水变化的影响机制,最后应用EOS/MODIS地表反照率产品替代原模式低时空分辨率的地表反照率。研究结果表明:(1)当地表反照率减少(增加)时,模拟的区域平均地表温度、感热、潜热数值相应增大(减少)。当地表反照率减少0.1时,地表温度上升约1.0K,感热和潜热量增量比约为3∶1。(2)地表反照率改变对降水量变化影响最大的区域是黄河源区下游的草场区域,其次是黄河源头区域,最小的是黄河源区北部的稀疏植被区域。地表反照率通过对大气动力、热力以及水汽条件的影响,使得降水发生的环境改变,主要体现在:当地表反照率减少时,地表气压的减少使得大气低层的辐合气流增强,有利于上升运动的发生;2.0m气温的升高增强了大气近地层的热力不稳定度;2.0m比湿的增加表明近地层空气水汽含量增加。(3)与实况对比分析发现,使用卫星遥感产品后在月尺度上能够更准确地模拟降水量的变化过程。
