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1.
积雪季节变化特征的数值模拟及其敏感性试验 总被引：4，自引：0，他引：4
文中利用综合陆面模式 (ComprehensiveLandSurfaceModel,CLSM )对法国ColdePorte 1 993/ 1 994 ,1 994 / 1 995年及BOREASSSA OJP 1 994 / 1 995年积雪个例进行了模拟试验 ,通过模拟结果与观测资料的对比 ,检验了CLSM对积雪变化特征的模拟能力 ,并通过敏感性试验探讨了降雪密度、积雪持水量等积雪参数化方案及植被对积雪模拟可能产生的影响。结果表明 :(1 )CLSM能够准确地模拟出积雪的变化过程 ,对积雪的演变特征作出了合理的描述 ;(2 )降雪密度、积雪持水量参数化方案对积雪模拟结果均具有一定的影响 :降雪密度参数化主要对积雪深度的模拟产生影响 ;而积雪持水量参数化方案对积雪的演变过程 ,尤其是积雪的消融 ,具有重要的作用 ;(3)有、无植被存在的情况下 ,积雪 土壤系统的变化过程存在显著的差别 ,植被通过改变积雪 /土壤表面的能量平衡 ,对积雪及土壤的变化过程产生重要影响 :植被的存在有利于积雪的维持 ,使得积雪融化进程推迟 ,冻结土壤的增温明显偏慢 相似文献
2.
Summary The land surface model SEWAB (Surface Energy and Water Balance) is designed to be coupled to both, atmospheric and hydrological
models. Its application in mid and high latitudes requires the inclusion of freezing and thawing processes within the soil
and the accumulation and ablation of a snow cover. These winter processes are parameterised with a minimum number of empirical
formulations in order to assure reasonable computation times for an application in climate and sensitivity studies yet accounting
for all important processes. Meteorological forcing data and measurements of snow depth, soil temperature and liquid soil
water content at two locations in the mid-west of North America are used to test the model. Generally the simulated snow depth
matches the measurements, remaining differences in snow depth can be explained by uncertainties in snow density, blowing snow
and errors in precipitation measurements. The simulated soil temperature and liquid soil water content compare well with the
measurements, showing the isolating effect of the snow cover.
Received August 25, 2000 Revised January 19, 2001 相似文献
3.
《大气与海洋》2013,51(4):259-272
Abstract A physically‐based multi‐layer numerical model is developed to determine the coupled transport of heat and water in the soil and in the soil‐atmosphere boundary layer. Using inputs of standard weather data and initial soil conditions the model is capable of predicting the surface energy balance components as well as water content and temperature profiles in the soil. It is used to predict these variables for a bare silt loam soil under two tillage treatments, viz. culti‐packed and left loose after disc‐harrowing, and the predicted results are compared with measurements. Very good agreement between the model predictions and measured evaporation and heat fluxes and soil water and temperatures for a ten‐day period shows that the model is capable of simulating the coupled transport of soil heat and soil water and their transfer across the soil surface‐atmosphere interface adequately. Model predictions were compared with those of CLASS (Canadian Land Surface Scheme). It is shown that CLASS, version 2.6, provides good estimates of evaporation and hence the latent heat flux density, QE, under wetter soil conditions, but overestimates QE at moderately wet soil conditions and underestimates it under dry soil conditions. Under dry to moderately wet soil conditions the calculation of evaporation from bare soil is very sensitive to the thickness of the top layer particularly as the thickness approaches 10 cm. 相似文献
4.
By using Comprehensive Land Surface Model (CLSM), three snow cases, i.e., France Col de Porte 1993/1994, 1994/1995 and BOREAS SSA-OJP 1994/1995, were simulated. The simulated results were compared with the observations to examine the capability of the model to describe the evolutions of snow cover under two different land cover conditions. Several sensitivity experiments were performed to investigate the effects of the parameterization schemes of some snow cover internal processes and vegetation on the model results. Results suggest that the CLSM simulates the basic processes of snow cover accurately and describes the features of snow cover evolutions reasonably, indicating that the model has the potential to model the processes related to the snow cover evolution. It is also found that the different parameterization schemes of the snowfall density and snow water holding capacity have significant effects on the simulation of snow cover. The estimation of snowfall density mainly impacts the simulated snow depth, and the underestimation (overestimation) of the snowfall density increases (decreases) the snow depth simulated significantly but with little effect on the simulated snow water equivalent (SWE). The parameterization of the snow water holding capacity plays a crucial role in the evolution of snow cover, especially in the ablation of snow cover. Larger snow water holding capacity usually leads to larger snow density and heat capacity by storing more liquid water in the snow layer, and makes the temperature of snow cover and the snow ablation vary more slowly. To a smaller snow water holding capacity, contrary is the case. The results also show that the physical processes related to the snow cover variation are different, which are dependent on the vegetation existed. Vegetation plays an important role in the evolution of soil-snow system by changing the energy balance at the snow-soil surface. The existence of vegetation is favorable to the maintenance of snow cover and delays the increase of underlying soil temperature. 相似文献
5.
The surface energy balance of a snow cover: comparing measurements to two differentsimulation models 总被引：1，自引：0，他引：1
Summary We compared two one-dimensional simulation models for heat and water fluxes in the soil-snow-atmosphere system with respect
to their mathematical formulations of the surface heat exchange and the snow pack evolution. They were chosen as examples
of a simple one-layer snow model and a more detailed multiple-layer snow model (SNTHERM). The snow models were combined with
the same one-dimensional model for the heat and water balance of the underlying soil (CoupModel). Data from an arable field
in central Sweden (Marsta), covering two years (1997–1999) of soil temperature, snow depth and eddy-correlation measurements
were successfully compared with the models. Conditions with a snow pack deeper or shallower than 10 cm and bare soil resulted
in similar discrepancies. The simulated net radiation and sensible heat flux were in good agreement with that measured during
snow-covered periods, except for situations with snowmelt when the downward sensible heat flux was overestimated by 10–20 Wm−2. The results showed that the uncertainties in parameter values were more important than the model formulation and that both
models were useful in evaluating the limitations and uncertainties of the measurements.
Received November 1, 1999 Revised April 20, 2000 相似文献
6.
7.
The subsurface transport of heat and moisture and its effect on the environment: A numerical model 总被引：2，自引：0，他引：2
A numerical model was developed to study the transport of heat and vapor under the surface of bare soil and soil covered by some materials such as asphalt and concrete under no rainfall conditions. The computational results provide a good match with the experimental data. The results show that the transport of water vapor inside the soil has an important effect on the subsurface distribution of temperature, especially for bare soil. Because of evaporation, the temperature of bare soil is much lower than that under covered surfaces throughout the day and the temperature of the surface covered by asphalt is extremely high-higher than the atmospheric temperature even at night. An increase of thickness of the covering material further increases the temperature and heat stored under surfaces. The stored heat is released to the atmosphere at night, contributing to environmental effects such as the urban heat island. 相似文献
8.
Test of a simple two-layer parameterisation to simulate the energy balance and temperature of a snow pack 总被引：3，自引：0，他引：3
Summary Reasonably simple yet realistic modelling schemes simulating the heat and mass balance within a snow pack are required to
provide the necessary boundary conditions for meteorological and hydrological models. An improvement to a one-layer snow energy
balance model (UEB, Tarboton etal., 1995) is proposed to better simulate snow surface and snow pack temperatures and, as a
result, snowmelt. The modified scheme is assessed against measured snow data from the WINTEX field campaign during spring
1997 in northern Finland, and compared with results from a complex multi-layer snow energy balance scheme. The results show
that separation of a one-layer representation into two snow layers and a soil layer enables a more realistic simulation of
soil and snow temperatures as well as of the snow surface temperature. The two-layer and the multi-layer snow schemes yielded
comparable results for internal processes in the snow whenever the simulation was carried out under similar boundary forcing.
The modified scheme is proposed for use as a sub-scheme in meteorological or hydrological models, or as a tool for simulating
spatially-variable snowmelt and the surface energy balance during seasonal snow cover.
Received November 18, 1999 Revised June 17, 2000 相似文献
9.
Benjamin I. Cook Gordon B. Bonan Samuel Levis Howard E. Epstein 《Climate Dynamics》2008,31(1):107-124
We use a state of the art climate model (CAM3–CLM3) to investigate the sensitivity of surface climate and land surface processes
to treatments of snow thermal conductivity. In the first set of experiments, the thermal conductivity of snow at each grid
cell is set to that of the underlying soil (SC-SOIL), effectively eliminating any insulation effect. This scenario is compared
against a control run (CTRL), where snow thermal conductivity is determined as a prognostic function of snow density. In the
second set of experiments, high (SC-HI) and low (SC-LO) thermal conductivity values for snow are prescribed, based on upper
and lower observed limits. These two scenarios are used to envelop model sensitivity to the range of realistic observed thermal
conductivities. In both sets of experiments, the high conductivity/low insulation cases show increased heat exchange, with
anomalous heat fluxes from the soil to the atmosphere during the winter and from the atmosphere to the soil during the summer. The increase in surface heat exchange leads to soil cooling of up to 20 K in the winter, anomalies that
persist (though damped) into the summer season. The heat exchange also drives an asymmetric seasonal response in near-surface
air temperatures, with boreal winter anomalies of +6 K and boreal summer anomalies of −2 K. On an annual basis there is a
net loss of heat from the soil and increases in ground ice, leading to reductions in infiltration, evapotranspiration, and
photosynthesis. Our results show land surface processes and the surface climate within CAM3–CLM3 are sensitive to the treatment
of snow thermal conductivity. 相似文献
10.
Modeling microclimate environments: A verification study 总被引：3，自引：0，他引：3
A numerical model is developed for simulating microclimate of plants and bare soil. The model evaluates heat, mass, momentum, and radiative fluxes in the soil-plant-atmosphere system. Its vertical domain may extend throughout the whole Planetary Boundary Layer (PBL). The model requires, either, temporal meteorological data of solar radiation, wind speed, air temperature and humidity measured over the field, or, when applied to the whole PBL, initial values of the latter three at its top. Vegetation parameters (leaf area index, photometric properties, root distribution and density) as well as soil texture, hydraulic and photometric properties are considered. The model was verified with meteorological data taken from two different climatological regions, above a bare soil and two cotton fields.For all case studies, observed and calculated values of air (except for within-canopy) and soil temperatures, wind speed, net radiation, and soil-, latent-, and sensible heat fluxes, agreed well with measurements. 相似文献
11.
Snow cover on the Tibetan Plateau (TP) has been shown to be essential for the East Asian summer monsoon. In this paper, we demonstrate that tropical cyclone (TC) 04B (1999) in the northern Indian Ocean, which made landfall during the autumn of 1999, may have contributed to climate anomalies over East Asia during the following spring and summer by increasing snow cover on the TP. Observations indicate that snow cover on the TP increased markedly after TC 04B (1999) made landfall in October of 1999. Sensitivity experiments, in which the TC was removed from a numerical model simulation of the initial field, verified that TC 04B (1999) affected the distribution as well as increased the amount of snow on the TP. In addition, the short-term numerical modeling of the climate over the region showed that the positive snow cover anomaly induced negative surface temperature, negative sensible heat flux, positive latent heat flux, and positive soil temperature anomalies over the central and southern TP during the following spring and summer. These climate anomalies over the TP were associated with positive (negative) summer precipitation anomalies over the Yangtze River valley (along the southeastern coast of China). 相似文献
12.
中国西天山季节性积雪热力特征分析 总被引：3，自引：0，他引：3
利用中国天山积雪雪崩站干、湿雪雪层内每隔5min一次的10层雪温数据,探讨了一次降雪过程后干、湿雪的雪层温度特征,对比分析了干、湿雪的雪面能量平衡方程中各分量的差异。结果表明:(1)整个冬半年积雪各层温度基本<0℃,雪温日变化振幅由雪面向下逐渐减小,积雪深层温度的波峰(谷)值稍滞后于积雪浅层温度极值1～2天。(2)湿雪冷中心的出现时间早于干雪,暖中心的出现时间晚于干雪,太阳辐射对湿雪的穿透深度大于干雪。(3)雪层温度振幅变化与能量吸收随雪深都呈指数衰减分布。积雪密度越大,吸收系数越小,穿透深度越大。(4)干雪雪面的感热通量和潜热通量几乎都为负值,积雪积累。湿雪雪面的潜热通量与感热通量方向相反,互相抵消,所以净辐射是导致湿雪消融的主要因素。 相似文献
13.
利用区域气候模式Reg CM4.3(Regional Climate Mode version 4.3)对新疆地区冬季的地表状态进行了模拟分析,通过与ERA40再分析资料的对比分析发现,温度分布形势模拟较好,地面热力状态受地形影响显著,陡峭地形附近由于热性质差异大和非均匀性强会导致较大模拟误差;模式较好模拟出降水和潜热通量北疆多南疆少,山区多盆地少的分布特征,模拟出通过反照率影响,地表吸收的短波辐射呈现出沙漠腹地吸收多而天山地区吸收少的分布,对北疆呈感热通量汇而南疆呈感热通量源的感热分布形势也模拟较好;模拟的雪水当量与降水分布有较好的一致性,春季融雪径流与冬季雪水当量分布及降水均有较好的对应关系。通过模拟分析也发现,现有方案实际感热通量计算中以地面温度代替地面位温,造成感热通量偏小,因此会低估南疆感热源效应和高估北疆感热汇效应。此外,积雪量和地面温度模拟偏高可能是春季北疆主要积雪区径流偏强的原因。 相似文献
14.
15.
文中描述一个一维的积雪分层模型,目的是要刻划雪盖随季节的变化,与其下冻土变动模型一起,构成完整的雪盖模型。为了保持一定精度,并能用于大气环模式（ＧＣＭ）研究,模型对积雪内部热量及质量输送过程的描述精细程度及计算时分层多少均有所考虑。模型中,改用内能代替温度作为预报量,克服了相变时直接预报温度时造成的计算误差,有效地预报了相变过程。对于积雪密度的变化,考虑了雪花形态的破坏而引起的密度变化及由于压实过程而引起的密度变化。并对各分层自重产生压实过程推导了相应的公式,在模型中对雪盖的光学特性、热力学特性及水流流动特性参数化方案设计也进行了分析。本简化模型的模拟结果与精细积雪模型的比较,具有几乎同等的精度,与俄罗斯的Ｙｅｒ－ｓｈｏｖ站实测数据相比,吻合十分理想。 相似文献
16.
20世纪利用一维层状云模式对2002年4月4~5日河南省冷锋降水过程进行了模拟。数值模拟结果显示,此次冷锋降水属于冷云降水过程,冷锋前后云中主要以冰相粒子为主,云中水质粒自上而下的空间分布依次为冰晶、雪、云水、霰、雨水。冷锋前后,各种水质粒有着不同的含量及数密度,但形成水质粒的主要微物理过程都表现为:冰晶数密度的增加主要依靠核化、繁生,大部分雪主要靠凝华、撞冻过冷云水和冰晶增长,霰的质量增加主要靠撞冻雪、过冷云水和雪自动转化而来,大部分的雨水是由霰融化而来,因而此次冷锋降水机制表现为“水汽—雪—霰—雨水”。 相似文献
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18.
利用青海省甘德两次降雪过程的微气象观测数据,探讨了两场降雪过程雪深、雪密度、雪中含冰量、雪中含水量和雪面温度的变化情况,分析了地表反照率与雪密度、雪中含冰量及雪中含水量的关系,结合降雪过程近地面温、湿、风廓线特征分析了积雪对近地面温、湿、风梯度的影响。结果表明:积雪覆盖会导致地表反照率显著增加,降雪过后正午时地表反照率可高达0.8～0.9。随着积雪的消融,地表反照率逐渐减小;积雪反照率与雪密度和雪中含冰量呈正相关,与雪中含水量呈负相关;地表积雪覆盖会导致近地面温度梯度绝对值减小,相对湿度梯度绝对值在凌晨减小、午后增大,地表积雪覆盖对近地面风速梯度变化并无特定的影响。 相似文献
19.
A Water Balance Model for a Subarctic Sedge Fen and its Application to Climatic Change 总被引：1，自引：0，他引：1
Wayne R. Rouse 《Climatic change》1998,38(2):207-234
A model to calculate the water balance of a hummocky sedge fen in the northern Hudson Bay Lowland is presented. The model develops the potential latent heat flux (evaporation) as a function of net radiation and atmospheric temperature. It is about equally sensitive to a 2% change in net radiation and a 1°C change in temperature. The modelled potential evaporation agrees well with the Priestley–Taylor formulation of evaporation under conditions of a non-limiting water supply. The actual evaporative heat flux is modelled by expressing actual/potential evaporation as a function of potential accumulated water deficit. Model evaporation agrees well with energy balance calculations using 7 years of measured data including wet and dry extremes. Water deficit is defined as the depth of water below reservoir capacity. Modelled water table changes concur with measurements taken over a 4 year period. When net radiation, temperature and precipitation measurements are available the water balance can be projected to longer time periods. Over a 30 year interval (1965–1994) the water balance of the sedge fen showed the following. During the growing season, there was an increase in precipitation, no change in temperature and a decrease in net radiation, evapotranspiration and water deficit. There was also a decrease in winter snow depths. The fen was brought back to reservoir capacity during final snowmelt every year but one. Summer rainfall was the most important single factor affecting the water balance and the ratio actual/potential evaporation emerged as a linear function of rainfall amount. A 2 × CO2 climate warming scenario with an annual temperature increase of 4°C and no precipitation change indicates lesser snow amounts and a shorter snow cover period. A greater summer water deficit, triggered mainly by greater evaporation during the month of May, is partially alleviated by lesser evaporation magnitudes in July. The greater water deficit would be counterbalanced by a 23% increase in summer rainfall. On average, the fen's water reservoir would still be recharged after winter snowmelt but the ground would remain at reservoir capacity for a shorter time. The warming scenario with a 10% decline in summer rainfall would create a large increase in the longevity and severity of the water deficit and this would be particularly evident during drier years. The carbon budget and peat accumulation and breakdown rates are strongly affected by changes in the water balance. Some evidence implies that greater water deficits lead to an increase in net carbon emissions. This implies that the sedge peatland could lose biomass under such conditions. An example is given where increased water deficit results in large decreases in local wetland streamflow. 相似文献
20.
地气耦合系统中温湿变化的数值模拟 总被引：4，自引：1，他引：4
本文提出了计算地气耦合系统中温度和湿度变化的一维数值模式,在土壤中,利用热量平衡和水份平衡原理计算土壤温度和湿度,在大气中,考虑了长短波辐射、云量和凝结等因素对大气温湿变化的影响。选择一种代表性土壤对模式进行了检验,结果发现,模式能较好地模拟诸多物理量的日变化过程。计算表明,大气和土壤的初始温湿分布,对结果有较大影响。本文的原理可应用于大气环流模式中陆气相互作用过程的参数化。 相似文献