A physically-based multi-layer snow model Snow-Atmosphere-Soil-Transfer scheme （SAST） and a land surface model Biosphere-Atmosphere Transfer Scheme （BATS） were employed to investigate how boreal forests influence ...A physically-based multi-layer snow model Snow-Atmosphere-Soil-Transfer scheme （SAST） and a land surface model Biosphere-Atmosphere Transfer Scheme （BATS） were employed to investigate how boreal forests influence snow accumulation and ablation under the canopy. Mass balance and energetics of snow beneath a Scots pine canopy in Finland at different stages of the 2003-2004 and 2004-2005 snow seasons are analyzed. For the fairly dense Scots pine forest, drop-off of the canopy-intercepted snow contributes, in some cases, twice as much to the underlying snowpack as the direct throughfall of snow. During early winter snow melting, downward turbulent sensible and condensation heat fluxes play a dominant role together with downward net longwave radiation. In the final stage of snow ablation in middle spring, downward net all- wave radiation dominates the snow melting. Although the downward sensible heat flux is comparable to the net solar radiation during this period, evaporative cooling of the melting snow surface makes the turbulent heat flux weaker than net radiation. Sensitivities of snow processes to leaf area index （LAI） indicate that a denser canopy speeds up early winter snowmelt, but also suppresses melting later in the snow season. Higher LAI increases the interception of snowfall, therefore reduces snow accumulation under the canopy during the snow season; this effect and the enhancement of downward longwave radiation by denser foliage outweighs the increased attenuation of solar radiation, resulting in earlier snow ablation under a denser canopy. The difference in sensitivities to LAI in two snow seasons implies that the impact of canopy density on the underlying snowpack is modulated by interannual variations of climate regimes.展开更多
Blowing snow is an important part of snow hydrologic processes in mountainous region, however the related researches were rare for the Qilian mountainous region where blowing snow is frequent. Using the observation da...Blowing snow is an important part of snow hydrologic processes in mountainous region, however the related researches were rare for the Qilian mountainous region where blowing snow is frequent. Using the observation dataset in 2008 snow season in Binggou wa- tershed in Qilian mountainous region, we systematically studied the energy and mass processes of blowing snow by field observation and model simulation. The results include the analysis of snow observation, the occurrence probability of blowing snow, blowing snow transport and blowing snow sublimation. It was found that blowing snow was obvious in high altitude region （4,146 m）, the snow redislribution phenomena was remarkable. In Yakou station in the study region, blowing snow was easily occurred in midwinter and early spring when no snowmelt, the blowing snow transport was dominated in this period; when snowmelt beginning, the occur- rence probability of blowing snow decreased heavily because of the increasing air temperature, melt, and refrozen phenomena. The blowing snow sublimation accounted for 41.5% of total snow sublimation at Yakou station in 2008 snow season.展开更多
[Objective] The aim was to study the formation and development of a heavy snow in Benxi area. [Method] Based on conventional meteorological data, the formation and development of a heavy snow in Benxi area from Decemb...[Objective] The aim was to study the formation and development of a heavy snow in Benxi area. [Method] Based on conventional meteorological data, the formation and development of a heavy snow in Benxi area from December 4th to 5th in 2009 were analyzed from the aspects of weather situation evolution and physical quantity field feature. [Result] The heavy snow was caused by upper trough and North China cyclone. In this process, there was upper level divergence and lower level convergence over Benxi area, and it was warm at low attitude and cold at high attitude; southwest jet at low attitude transported water vapor from Bohai Sea to eastern Liaoning, which provided good water vapor condition for snow, but it didn’t reach heavy snow due to inadequate ascending force. The development of Ural Mountains high ridge played an important role in the snow process and the strengthened high ridge moving northward was beneficial to the southward movement of cold air and deepening of upper trough. Analysis on physical quantity field could provide reference for predicting beginning and ending time and strength of heavy snow. [Conclusion] The study could provide basis for the forecast of heavy snow.展开更多
A BATS-SAST model was employed to simulate the snow processes in four snow cases of Sk_OJP 2001/2002, 2002/2003, 2003/2004 and Sk_HarvestJP 2003/2004 of Canada. At Sk_OJP site we modified the long-wave radiation and p...A BATS-SAST model was employed to simulate the snow processes in four snow cases of Sk_OJP 2001/2002, 2002/2003, 2003/2004 and Sk_HarvestJP 2003/2004 of Canada. At Sk_OJP site we modified the long-wave radiation and precipitation schemes. Considering the different interceptions between rain and snow and the effect of wind and canopy temperature on snow download, we improved the canopy interception model. At Sk_HarvestJP site we modified the snow cover fraction scheme. Results show that the model reasonably simulates the basic processes of snow cover. The modified model, which considers the part of the long-wave radiation and precipitation transmitted through the canopy at Sk_OJP site, can increase the simulation of snow depth which is closer to the observations. The improved canopy interception model, which influences the variation of snow depth under the canopy by changing canopy interception, is a great improvement on simulation of snow depth, especially on the ablation of snow cover. At Sk_HarvestJP site, there are obvious improvements on simulation of snow depth on the ablation of snow cover.展开更多
Snow cover on the Tibetan Plateau(TP)is closely related to regional and continental biological and hydrological processes.The vast snow cover,special climatic conditions,and sparse vegetative cover over the TP facilit...Snow cover on the Tibetan Plateau(TP)is closely related to regional and continental biological and hydrological processes.The vast snow cover,special climatic conditions,and sparse vegetative cover over the TP facilitate the occurrence of blowing snow,leading to substantial heterogeneities in the snow cover and great promotion in the moisture supply from the land surface to the overlying atmospheric boundary layer.However,blowing-snow processes are significantly misrepresented or even neglected in current models,which causes considerable uncertainties of numerical model simulations and leads to erroneous estimates of snow-related processes in mountainous terrain.We present in this paper a brief review of our work in the past 5 years to serve as a basis for further development and improvement of the land-surface model.These studies can be divided into three parts:detection of the problems,development of the land-surface model,and application of the coupled model over the TP(the logical framework is presented in Figure 1).The origin and advances in the development of a land-surface model with consideration of blowing-snow effects are described herein;and the importance of blowing-snow processes in the land-surface model,especially over the TP,is highlighted.We expect that the blowingsnow studies over the TP will play a key role in documenting and understanding the land-surface processes(LSPs)and the cryospheric changes over the TP.展开更多
为探究SHAW(Simultaneous heat and water)模型中输入参数不确定性在模拟积雪覆盖条件下土壤热过程中对输出结果造成的影响以及关键影响因素,以松嫩平原黑土区东北农业大学试验场为研究区域,运用SHAW模型模拟积雪覆盖条件下6个不同深度...为探究SHAW(Simultaneous heat and water)模型中输入参数不确定性在模拟积雪覆盖条件下土壤热过程中对输出结果造成的影响以及关键影响因素,以松嫩平原黑土区东北农业大学试验场为研究区域,运用SHAW模型模拟积雪覆盖条件下6个不同深度土层热过程动态变化情况,并结合拉丁超立方取样(Latin hypercube sampling,LHS)方法,采用标准秩逐步回归探究参数不确定性对土壤冻结深度和温度输出不确定性的影响。结果表明:SHAW模型能够反映土壤冻融规律,6个深度土层温度的模拟值与实测值平均绝对误差小于2℃,选取的参数对土壤温度的输出敏感性较弱,而初始积雪厚度对土壤冻结深度的输出起主导作用。总体而言,SHAW模型基于LHS抽样和标准秩逐步回归方法可用于模拟积雪覆盖条件下土壤热过程模拟研究。展开更多
文摘A physically-based multi-layer snow model Snow-Atmosphere-Soil-Transfer scheme （SAST） and a land surface model Biosphere-Atmosphere Transfer Scheme （BATS） were employed to investigate how boreal forests influence snow accumulation and ablation under the canopy. Mass balance and energetics of snow beneath a Scots pine canopy in Finland at different stages of the 2003-2004 and 2004-2005 snow seasons are analyzed. For the fairly dense Scots pine forest, drop-off of the canopy-intercepted snow contributes, in some cases, twice as much to the underlying snowpack as the direct throughfall of snow. During early winter snow melting, downward turbulent sensible and condensation heat fluxes play a dominant role together with downward net longwave radiation. In the final stage of snow ablation in middle spring, downward net all- wave radiation dominates the snow melting. Although the downward sensible heat flux is comparable to the net solar radiation during this period, evaporative cooling of the melting snow surface makes the turbulent heat flux weaker than net radiation. Sensitivities of snow processes to leaf area index （LAI） indicate that a denser canopy speeds up early winter snowmelt, but also suppresses melting later in the snow season. Higher LAI increases the interception of snowfall, therefore reduces snow accumulation under the canopy during the snow season; this effect and the enhancement of downward longwave radiation by denser foliage outweighs the increased attenuation of solar radiation, resulting in earlier snow ablation under a denser canopy. The difference in sensitivities to LAI in two snow seasons implies that the impact of canopy density on the underlying snowpack is modulated by interannual variations of climate regimes.
基金funded by the National Natural Science Foundation of China(Grant Nos.913252034100124041071227)
文摘Blowing snow is an important part of snow hydrologic processes in mountainous region, however the related researches were rare for the Qilian mountainous region where blowing snow is frequent. Using the observation dataset in 2008 snow season in Binggou wa- tershed in Qilian mountainous region, we systematically studied the energy and mass processes of blowing snow by field observation and model simulation. The results include the analysis of snow observation, the occurrence probability of blowing snow, blowing snow transport and blowing snow sublimation. It was found that blowing snow was obvious in high altitude region （4,146 m）, the snow redislribution phenomena was remarkable. In Yakou station in the study region, blowing snow was easily occurred in midwinter and early spring when no snowmelt, the blowing snow transport was dominated in this period; when snowmelt beginning, the occur- rence probability of blowing snow decreased heavily because of the increasing air temperature, melt, and refrozen phenomena. The blowing snow sublimation accounted for 41.5% of total snow sublimation at Yakou station in 2008 snow season.
文摘[Objective] The aim was to study the formation and development of a heavy snow in Benxi area. [Method] Based on conventional meteorological data, the formation and development of a heavy snow in Benxi area from December 4th to 5th in 2009 were analyzed from the aspects of weather situation evolution and physical quantity field feature. [Result] The heavy snow was caused by upper trough and North China cyclone. In this process, there was upper level divergence and lower level convergence over Benxi area, and it was warm at low attitude and cold at high attitude; southwest jet at low attitude transported water vapor from Bohai Sea to eastern Liaoning, which provided good water vapor condition for snow, but it didn’t reach heavy snow due to inadequate ascending force. The development of Ural Mountains high ridge played an important role in the snow process and the strengthened high ridge moving northward was beneficial to the southward movement of cold air and deepening of upper trough. Analysis on physical quantity field could provide reference for predicting beginning and ending time and strength of heavy snow. [Conclusion] The study could provide basis for the forecast of heavy snow.
基金supported by Chinese COPES project (GYHY200706005)by the Ministry of Science and Technology of China under Grant No.2007CB411505 and No.2010CB428400
文摘A BATS-SAST model was employed to simulate the snow processes in four snow cases of Sk_OJP 2001/2002, 2002/2003, 2003/2004 and Sk_HarvestJP 2003/2004 of Canada. At Sk_OJP site we modified the long-wave radiation and precipitation schemes. Considering the different interceptions between rain and snow and the effect of wind and canopy temperature on snow download, we improved the canopy interception model. At Sk_HarvestJP site we modified the snow cover fraction scheme. Results show that the model reasonably simulates the basic processes of snow cover. The modified model, which considers the part of the long-wave radiation and precipitation transmitted through the canopy at Sk_OJP site, can increase the simulation of snow depth which is closer to the observations. The improved canopy interception model, which influences the variation of snow depth under the canopy by changing canopy interception, is a great improvement on simulation of snow depth, especially on the ablation of snow cover. At Sk_HarvestJP site, there are obvious improvements on simulation of snow depth on the ablation of snow cover.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDA2006010101)the National Natural Science Foundation of China (41905012, 91837208 and 41661144043)+2 种基金the National Key Research and Development Program of China (2018YFC1505701)the Opening Fund of Key Laboratory for Land Surface Process and Climate Change in Cold and Arid Regions, the Chinese Academy of Sciences (LPCC2018002)the China Postdoctoral Science Foundation (2018M641489)
文摘Snow cover on the Tibetan Plateau(TP)is closely related to regional and continental biological and hydrological processes.The vast snow cover,special climatic conditions,and sparse vegetative cover over the TP facilitate the occurrence of blowing snow,leading to substantial heterogeneities in the snow cover and great promotion in the moisture supply from the land surface to the overlying atmospheric boundary layer.However,blowing-snow processes are significantly misrepresented or even neglected in current models,which causes considerable uncertainties of numerical model simulations and leads to erroneous estimates of snow-related processes in mountainous terrain.We present in this paper a brief review of our work in the past 5 years to serve as a basis for further development and improvement of the land-surface model.These studies can be divided into three parts:detection of the problems,development of the land-surface model,and application of the coupled model over the TP(the logical framework is presented in Figure 1).The origin and advances in the development of a land-surface model with consideration of blowing-snow effects are described herein;and the importance of blowing-snow processes in the land-surface model,especially over the TP,is highlighted.We expect that the blowingsnow studies over the TP will play a key role in documenting and understanding the land-surface processes(LSPs)and the cryospheric changes over the TP.
