利用中尺度模式WRF和1981年、1990年卫星遥感地表分类数据,模拟分析了典型年份农牧交错带内地表植被变化对2001-2010年中国区域气候的影响。结果表明:(1)相对于1981年,1990年交错带内38°N以北(南)植被覆盖增加(减小),地表粗糙度增...利用中尺度模式WRF和1981年、1990年卫星遥感地表分类数据,模拟分析了典型年份农牧交错带内地表植被变化对2001-2010年中国区域气候的影响。结果表明:(1)相对于1981年,1990年交错带内38°N以北(南)植被覆盖增加(减小),地表粗糙度增加(减小)。(2)当植被覆盖度增加(减小)、地表粗糙度增加(减小)时,交错带相应地区及附近地区温度升高(降低)。(3)交错带植被演变导致我国降水量差值场存在自东向西的"正-负-正"分布,地表粗糙度增加(减小)对应降水量差值增加(减少),且降水量越大,水循环越充足,植被演变对降水量的影响表现越突出。(4)交错带的植被演变主要影响中高层风场,且存在明显的季节性差异。500 h Pa气旋状(反气旋状)偏差风场环流中心对应着降水量差值场的正值(负值)。展开更多
The flux-variance similarity relation and the vertical transfer of scalars exhibit dissimilarity over different types of surfaces, resulting in different parameterization approaches of relative transport efficiency am...The flux-variance similarity relation and the vertical transfer of scalars exhibit dissimilarity over different types of surfaces, resulting in different parameterization approaches of relative transport efficiency among scalars to estimate turbulent fluxes using the flux-variance method. We investigated these issues using eddycovariance measurements over an open, homogeneous and flat grassland in the eastern Tibetan Plateau in summer under intermediate hydrological conditions during rainy season. In unstable conditions, the temperature, water vapor, and CO2 followed the flux-variance similarity relation, but did not show in precisely the same way due to different roles （active or passive） of these scalars. Similarity constants of temperature, water vapor and CO2 were found to be 1.12, 1.19 and 1.17, respectively. Heat transportation was more eft% cient than water vapor and CO2. Based on the estimated sensible heat flux, five parameterization methods of relative transport efficiency of heat to water vapor and CO2 were examined to estimate latent heat and CO2 fluxes. The strategy of local determination of flux-variance similarity relation is recommended for the estimation of latent heat and CO2 fluxes. This approach is better for representing the averaged relative transport efficiency, and technically easier to apply, compared to other more complex ones.展开更多
为了改进陆面过程模式对青藏高原高寒草甸下垫面的模拟能力,选取玛曲站、阿柔站、那曲站3个典型高原高寒草甸观测站6-9月的观测资料,特别是实测土壤属性数据,并将实测土壤属性数据代入陆面过程模式CLM4.5(Community Land Model)进行单...为了改进陆面过程模式对青藏高原高寒草甸下垫面的模拟能力,选取玛曲站、阿柔站、那曲站3个典型高原高寒草甸观测站6-9月的观测资料,特别是实测土壤属性数据,并将实测土壤属性数据代入陆面过程模式CLM4.5(Community Land Model)进行单点数值模拟试验,为改进模式参数化方案提供依据。研究表明:(1)CLM4.5模式能较好地再现高寒草甸下垫面的土壤温湿度、辐射通量和湍流通量的季节变化,修改土壤属性后模拟效果明显优于修改前,但较观测值还存在一定偏差。(2)修改土壤属性后CLM4.5模式在玛曲站和那曲站对各层土壤湿度的模拟值更接近观测值,在阿柔站对浅层土壤湿度模拟效果的改善优于深层土壤。修改土壤属性后,模式地表虽然与各站点实际地表更为接近,但对土壤温度的改进不明显。(3)修改土壤属性前后反射辐射的模拟值在三个站点均偏低,但修改土壤属性后模拟效果优于修改前。模式对地表长波辐射的改进不显著,其中阿柔站的模拟值与观测值的相关性较高,且偏差较小。(4)CLM4.5模式对各站感热通量的模拟值均高于观测值,修改土壤属性后,感热通量的模拟值更接近实测值且在玛曲站和那曲站的潜热通量模拟值与观测值更为接近。展开更多
Wavelet regression(WR)models are used commonly for hydrologic time series forecasting,but they could not consider uncertainty evaluation.In this paper the AM-MCMC(adaptive Metropolis-Markov chain Monte Carlo)algorithm...Wavelet regression(WR)models are used commonly for hydrologic time series forecasting,but they could not consider uncertainty evaluation.In this paper the AM-MCMC(adaptive Metropolis-Markov chain Monte Carlo)algorithm was employed to wavelet regressive modeling processes,and a model called AM-MCMC-WR was proposed for hydrologic time series forecasting.The AM-MCMC algorithm is used to estimate parameters’uncertainty in WR model,based on which probabilistic forecasting of hydrologic time series can be done.Results of two runoff data at the Huaihe River watershed indicate the identical performances of AM-MCMC-WR and WR models in gaining optimal forecasting result,but they perform better than linear regression models.Differing from the WR model,probabilistic forecasting results can be gained by the proposed model,and uncertainty can be described using proper credible interval.In summary,parameters in WR models generally follow normal probability distribution;series’correlation characters determine the optimal parameters values,and further determine the uncertain degrees and sensitivities of parameters;more uncertain parameters would lead to more uncertain forecasting results and hard predictability of hydrologic time series.展开更多
文摘利用中尺度模式WRF和1981年、1990年卫星遥感地表分类数据,模拟分析了典型年份农牧交错带内地表植被变化对2001-2010年中国区域气候的影响。结果表明:(1)相对于1981年,1990年交错带内38°N以北(南)植被覆盖增加(减小),地表粗糙度增加(减小)。(2)当植被覆盖度增加(减小)、地表粗糙度增加(减小)时,交错带相应地区及附近地区温度升高(降低)。(3)交错带植被演变导致我国降水量差值场存在自东向西的"正-负-正"分布,地表粗糙度增加(减小)对应降水量差值增加(减少),且降水量越大,水循环越充足,植被演变对降水量的影响表现越突出。(4)交错带的植被演变主要影响中高层风场,且存在明显的季节性差异。500 h Pa气旋状(反气旋状)偏差风场环流中心对应着降水量差值场的正值(负值)。
基金funding frown the Chinese National Key Programme for Developing Basic Sciences，the National Natural Science Foundation of China，the Key Program of the Chinese Academy of Sciences，the National Natural Science Foundation of China，the Foundation for Excellent Young Scholars of CAREERI
文摘The flux-variance similarity relation and the vertical transfer of scalars exhibit dissimilarity over different types of surfaces, resulting in different parameterization approaches of relative transport efficiency among scalars to estimate turbulent fluxes using the flux-variance method. We investigated these issues using eddycovariance measurements over an open, homogeneous and flat grassland in the eastern Tibetan Plateau in summer under intermediate hydrological conditions during rainy season. In unstable conditions, the temperature, water vapor, and CO2 followed the flux-variance similarity relation, but did not show in precisely the same way due to different roles （active or passive） of these scalars. Similarity constants of temperature, water vapor and CO2 were found to be 1.12, 1.19 and 1.17, respectively. Heat transportation was more eft% cient than water vapor and CO2. Based on the estimated sensible heat flux, five parameterization methods of relative transport efficiency of heat to water vapor and CO2 were examined to estimate latent heat and CO2 fluxes. The strategy of local determination of flux-variance similarity relation is recommended for the estimation of latent heat and CO2 fluxes. This approach is better for representing the averaged relative transport efficiency, and technically easier to apply, compared to other more complex ones.
文摘为了改进陆面过程模式对青藏高原高寒草甸下垫面的模拟能力,选取玛曲站、阿柔站、那曲站3个典型高原高寒草甸观测站6-9月的观测资料,特别是实测土壤属性数据,并将实测土壤属性数据代入陆面过程模式CLM4.5(Community Land Model)进行单点数值模拟试验,为改进模式参数化方案提供依据。研究表明:(1)CLM4.5模式能较好地再现高寒草甸下垫面的土壤温湿度、辐射通量和湍流通量的季节变化,修改土壤属性后模拟效果明显优于修改前,但较观测值还存在一定偏差。(2)修改土壤属性后CLM4.5模式在玛曲站和那曲站对各层土壤湿度的模拟值更接近观测值,在阿柔站对浅层土壤湿度模拟效果的改善优于深层土壤。修改土壤属性后,模式地表虽然与各站点实际地表更为接近,但对土壤温度的改进不明显。(3)修改土壤属性前后反射辐射的模拟值在三个站点均偏低,但修改土壤属性后模拟效果优于修改前。模式对地表长波辐射的改进不显著,其中阿柔站的模拟值与观测值的相关性较高,且偏差较小。(4)CLM4.5模式对各站感热通量的模拟值均高于观测值,修改土壤属性后,感热通量的模拟值更接近实测值且在玛曲站和那曲站的潜热通量模拟值与观测值更为接近。
基金supported by the National Natural Science Foundation of China(41201036)the Opening Fund of Key Laboratory for Land Surface Process and Climate Change in Cold and Arid Regions,Chinese Academy of Sciences(LPCC201203)
文摘Wavelet regression(WR)models are used commonly for hydrologic time series forecasting,but they could not consider uncertainty evaluation.In this paper the AM-MCMC(adaptive Metropolis-Markov chain Monte Carlo)algorithm was employed to wavelet regressive modeling processes,and a model called AM-MCMC-WR was proposed for hydrologic time series forecasting.The AM-MCMC algorithm is used to estimate parameters’uncertainty in WR model,based on which probabilistic forecasting of hydrologic time series can be done.Results of two runoff data at the Huaihe River watershed indicate the identical performances of AM-MCMC-WR and WR models in gaining optimal forecasting result,but they perform better than linear regression models.Differing from the WR model,probabilistic forecasting results can be gained by the proposed model,and uncertainty can be described using proper credible interval.In summary,parameters in WR models generally follow normal probability distribution;series’correlation characters determine the optimal parameters values,and further determine the uncertain degrees and sensitivities of parameters;more uncertain parameters would lead to more uncertain forecasting results and hard predictability of hydrologic time series.
