为了利用有限的气象观测资料来快速推算无观测资料地区的山地近地表风速,在Microsoft Visual Studio 2008平台上,用C#语言和ArcEngine组件开发了山地近地表风速网格化系统,实现了近地表风速影响因子提取、风速模拟、残差订正等功能,提...为了利用有限的气象观测资料来快速推算无观测资料地区的山地近地表风速,在Microsoft Visual Studio 2008平台上,用C#语言和ArcEngine组件开发了山地近地表风速网格化系统,实现了近地表风速影响因子提取、风速模拟、残差订正等功能,提高了风速网格化效率,可以为山地风资源评估、生态环境保护等方面提供细致的风速数据。展开更多
Land-surface conditions, such as surface roughness and SWC （soil-water content）, control the saltation activity and dust emission in northeast Asia. Information on spatial and temporal changes in surface SWC is need...Land-surface conditions, such as surface roughness and SWC （soil-water content）, control the saltation activity and dust emission in northeast Asia. Information on spatial and temporal changes in surface SWC is needed for dust-modeling systems used to predict dust events with the aim of preventing the damage they cause. A MTVDI （modified temperature-vegetation dryness index） was tested to see if it could reproduce the surface SWC observed in Zhangye, China, and the Tottori Sand Dunes of Japan, and the threshold wind speed at the Tottori Sand Dunes. MTVDI was calculated from land-surface temperature using the MODIS （moderate resolution imaging spectroradiometer） product, and the aerodynamic minimum and maximum surface temperatures were estimated based on meteorological data. A greater correlation is seen between MTVDI and SWC than between SWC from AMSR-E （advanced microwave scanning radiometer-earth observing system） and SWC in Zhangye. The threshold wind speed for saltation activity decreased with increasing MTVDI, that is, with drying of the soil surface of the Tottori Sand Dunes. The correlation between MTVDI and threshold wind speed is statistically significant （R2 = 0.2987）.展开更多
Over the last three decades, the Tibetan Plateau has exhibited a significant increase in air temperature and a significant decrease in wind speed. How the surface heat source has changed is an important issue in monso...Over the last three decades, the Tibetan Plateau has exhibited a significant increase in air temperature and a significant decrease in wind speed. How the surface heat source has changed is an important issue in monsoon research. Based on routine meteorological data, this study investigates the differences between methods for estimating trends in surface sensible heat flux on the Tibetan Plateau for the period 1984-2006. One is a physical method based on micro-meteorological theory and experi- ments, and takes into account both atmospheric stability and thermal roughness length. The other approach includes conven- tional empirical methods that assume the heat transfer coefficient is a constant value or a simple function of wind speed. The latter method is used widely in climatologic studies. Results from the physical method show that annual mean sensible heat flux has weakened by 2% per decade, and flux seasonal mean has weakened by -2%--4% except in winter. The two commonly used empirical methods showed high uncertainties in heat flux trend estimates, although they produced similar climatologies. Annual mean heat flux has weakened by 7% per decade when a fixed transfer coefficient is used, whereas the trend is negligible when the transfer coefficient is assumed a function of wind speed. Conventional empirical methods may therefore misrepresent the trend in sensible heat flux.展开更多
文摘为了利用有限的气象观测资料来快速推算无观测资料地区的山地近地表风速,在Microsoft Visual Studio 2008平台上,用C#语言和ArcEngine组件开发了山地近地表风速网格化系统,实现了近地表风速影响因子提取、风速模拟、残差订正等功能,提高了风速网格化效率,可以为山地风资源评估、生态环境保护等方面提供细致的风速数据。
文摘Land-surface conditions, such as surface roughness and SWC （soil-water content）, control the saltation activity and dust emission in northeast Asia. Information on spatial and temporal changes in surface SWC is needed for dust-modeling systems used to predict dust events with the aim of preventing the damage they cause. A MTVDI （modified temperature-vegetation dryness index） was tested to see if it could reproduce the surface SWC observed in Zhangye, China, and the Tottori Sand Dunes of Japan, and the threshold wind speed at the Tottori Sand Dunes. MTVDI was calculated from land-surface temperature using the MODIS （moderate resolution imaging spectroradiometer） product, and the aerodynamic minimum and maximum surface temperatures were estimated based on meteorological data. A greater correlation is seen between MTVDI and SWC than between SWC from AMSR-E （advanced microwave scanning radiometer-earth observing system） and SWC in Zhangye. The threshold wind speed for saltation activity decreased with increasing MTVDI, that is, with drying of the soil surface of the Tottori Sand Dunes. The correlation between MTVDI and threshold wind speed is statistically significant （R2 = 0.2987）.
基金supported by National Natural Science Foundation of China (Grant Nos. 40875009, 40810059006)Key Innovation Project of Chinese Academy of Sciences (Grant No. KZCX2-YW-Q11-01),"100-Talent" Program of Chinese Academy of Sciences
文摘Over the last three decades, the Tibetan Plateau has exhibited a significant increase in air temperature and a significant decrease in wind speed. How the surface heat source has changed is an important issue in monsoon research. Based on routine meteorological data, this study investigates the differences between methods for estimating trends in surface sensible heat flux on the Tibetan Plateau for the period 1984-2006. One is a physical method based on micro-meteorological theory and experi- ments, and takes into account both atmospheric stability and thermal roughness length. The other approach includes conven- tional empirical methods that assume the heat transfer coefficient is a constant value or a simple function of wind speed. The latter method is used widely in climatologic studies. Results from the physical method show that annual mean sensible heat flux has weakened by 2% per decade, and flux seasonal mean has weakened by -2%--4% except in winter. The two commonly used empirical methods showed high uncertainties in heat flux trend estimates, although they produced similar climatologies. Annual mean heat flux has weakened by 7% per decade when a fixed transfer coefficient is used, whereas the trend is negligible when the transfer coefficient is assumed a function of wind speed. Conventional empirical methods may therefore misrepresent the trend in sensible heat flux.
