The IAP (Institute of Atmospheric Physics) land-surface model (IAP94) is described. This model is a comprehensive one with detailed description for the processes of vegetation, snow and soil. Particular attention has ...The IAP (Institute of Atmospheric Physics) land-surface model (IAP94) is described. This model is a comprehensive one with detailed description for the processes of vegetation, snow and soil. Particular attention has been paid to the cases with three water phases in the surface media. On the basis of the mixture theory and the theory of fluid dynamics of porous media, the system of universal conservational equations for water and heat of soil, snow and vegetation canopy has been constructed. On this background, all important factors that may affect the water and heat balance in media can be considered naturally, and each factor and term possess distinct physical meaning. In the computation of water content and temperature, the water phase change and the heat transportation by water flow are taken into account. Moreover, particular attention has been given to the water vapor diffusion in soil for arid or semi-arid cases, and snow compaction. In the treatment of surface turbulent fluxes, the difference between aerodynamic and thermal roughness is taken into account. The aerodynamic roughness of vegetation is calculated as a function of canopy density, height and zero-plane displacement. An extrapolation of log linear and exponential relationship is used when calculating the wind profile within canopy. The model has been validated against field measurements in off-line simulations. The desirable model′s performance leads to the conclusion that the IAP94 is able to reproduce the main physical mechanisms governing the energy and water balances in the global land surface. Part II of the present study will concern the validation in a 3-D experiment coupled with the IAP Two-Level AGCM.展开更多
In order to further understand the land surface processes over the northern Tibetan Plateau, this study produced an off-line simulated examination at the Bujiao site on the northern Tibetan Plateau from June 2002 to A...In order to further understand the land surface processes over the northern Tibetan Plateau, this study produced an off-line simulated examination at the Bujiao site on the northern Tibetan Plateau from June 2002 to April 2004, using the Noah Land Surface Model （Noah LSM） and observed data from the CAMP/Tibet experiment. The observed data were neces- sarily corrected and the number of soil layers in the Noah LSM was changed from 4 to 10 to enable this off-line simulation and analysis. The main conclusions are as follows： the Noah LSM performed well on the northern Tibetan Plateau. The simulated net radiation, upward longwave radiation, and upward shortwave radiation demonstrated the same remarkable annual and seasonal variation as the observed data, especially the upward longwave radiation. The simulated soil temperatures were acceptably close to the observed temperatures, especially in the shallow soil layers. The simulated freezing and melting processes were shown to start from the surface soil layer and spread down to the deep soil layers, but they took longer than the observed processes. However, Noah LSM did not adequately simulate the soil moisture. Therefore, additional high-quality, long-term observations of land surface-atmosphere processes over the Tibetan Plateau will be a key factor in proper adiustments of the model parameters in the future.展开更多
Based on the existing Land Surface Physical Process Models(Deardorff, Dickinson, LIU, Noilhan, Seller, ZHAO), a Comprehensive Land Surface Physical Process Model (CLSPPM) is developed by considering the different phys...Based on the existing Land Surface Physical Process Models(Deardorff, Dickinson, LIU, Noilhan, Seller, ZHAO), a Comprehensive Land Surface Physical Process Model (CLSPPM) is developed by considering the different physical processes of the earth's surface-vegetation-atmosphere system more completely. Compared with SiB and BATS, which are famous for their detailed parameterizations of physical variables, this simplified model is more convenient and saves much more computation time. Though simple, the feas...展开更多
Two land surface schemes, one the standard Biosphere / Atmosphere Transfer Scheme Version ie (BOZ) and the other B1Z based on B0Z and heterogeneously-treated by' combined approach' , were co 'pled to the m...Two land surface schemes, one the standard Biosphere / Atmosphere Transfer Scheme Version ie (BOZ) and the other B1Z based on B0Z and heterogeneously-treated by' combined approach' , were co 'pled to the meso-scale model MM4, respectively. Through the calculations of equations from the companion paper, parameters representing land surface heterogeneity and suitable for the coupling models were found out. Three cases were simulated for heavy rainfalls during 36 hours, and the sensitivity of short-term weather modeling to the land surface heterogeneity was tested. Through the analysis of the simulations of the three heavy rainfalls, it was demonstrated that BIZ, compared with BOZ, could more realistically reflect the features of the land surface heterogeneity, therefore could more realistically reproduce the circulation and precipitation amount in the heavy rainfall processes of the three cases. This shows that even short-term weather is sensitive to the land surface heterogeneity, which is more obvious with time passing, and whose influence is more pronounced in the lower layer and gradually extends to the middle and upper layer. Through the analysis of these simulations with BlZ, it is suggested that the bulk effect of smaller-scale fluxes (i.e., the momentum, water vapor and sensible heat fluxes) near the s ig nificantly-heterogeneous land surface is to change the larger-scale (i.e., meso-scale) circulation, and then to influence the development of the low-level jets and precipitation. And also, the complexity of the land-atmosphere interaction was shown in these simulations.展开更多
Based on the existing land-surface schemes and models,an improved Land-surface Process Model(LPM-ZD)has been developed.It has the following major characteristics:(1)The combination of physical equations and empirical ...Based on the existing land-surface schemes and models,an improved Land-surface Process Model(LPM-ZD)has been developed.It has the following major characteristics:(1)The combination of physical equations and empirical analytical formulae are used to construct the governing equations of soil temperature and moisture.Higher resolution of model level and physical equations are adopted for the upper soil layers,and for the lower soil layers,lower resolution of model level is adopted and empirical analytical formulae are used.(2)In land surface hydrological process,the sub-grid distribution of rainfall and its effects are taken into account. (3)A simple snow cover submodel has been used,which includes effects of snow cover on soil thermodynamics and hydrology,as well as albedo. By use of this model and three groups of point observation data,a series of“off-line”tests have been carried out.The simulation results indicate that land-surface process model has good performance and can well simulate diurnal and seasonal variation of land surface processes for many kinds of land surface covers(forest,grass,crops and desert)in different climate zone.The results simulated by the model are consistent with the observations.Later,by use of one group of observation data and the model,a series of sensitivity experiments have been done.It is shown that the model is much sensitive to some parameters,such as initial soil moisture,vegetation physical parameters as well as the proportion of the grid covered with rain.Therefore it is much important for land-surface process model to define these parameters as accurately as possible.展开更多
The effect on climate due to seasonal variation of vegetation and roughness length was simulated in Part Ⅰ of this essay.In Part Ⅱ,the individual effect of albedo and the joint effect of all those factors (vegetatio...The effect on climate due to seasonal variation of vegetation and roughness length was simulated in Part Ⅰ of this essay.In Part Ⅱ,the individual effect of albedo and the joint effect of all those factors (vegetation,roughness length and albedo) were calculated by numerical sensitivity experiments.The results showed that:(1)There is no significant effect on precipitation if the albedo of 4 seasons is used to replace the CRCM's climate average data,but the effect on land surface temperature can be seen clearly.And the effect also can be seen in adjacent regions.(2)If all these three factors are used to replace the CRCM's climate average data at the same time,the effect on precipitation is significant,the most variation value is 300mm.And the effect on temperature is similar to what we can see if only one of these factors in CRCM is replaced by monthly or seasonal data.(3)Seasonal variation of land surface parameters has important effect not only on regional climate,but also on global environment.展开更多
Sensitivity experiment is an important method to study the effect on regional climate due to seasonal variation of land surface parameters.Using China Regional Climate Model(CRCM) nested in CCM1.we first simulate Chin...Sensitivity experiment is an important method to study the effect on regional climate due to seasonal variation of land surface parameters.Using China Regional Climate Model(CRCM) nested in CCM1.we first simulate Chinese regional climate,then two numerical sensitivity experiments on the effect of vegetation and roughness length are made.The results show that: (1)If the vegetation is replaced with the monthly data of 1997.precipitation and land-surface temperature are both changed clearly,precipitation decreases and land surface temperature increases,but there is no regional correspondence between these changes.And the results are much better than the results when climate average vegetation was used in the CRCM.(2)If the roughness length is replaced with the monthly data of 1997,there is significant change on land surface temperature,and there is very good regional correspondence between these changes.But the effect on precipitation is very small.展开更多
陆面模式CLM(Community Land Model)是目前国际上发展较为完善并被广泛应用的陆面过程模式。本文使用中国科学院寒区旱区环境与工程研究所位于青藏高原东部的若尔盖高原湿地生态系统研究站的观测资料,对CLM3.0版本及CLM4.0版本在上述地...陆面模式CLM(Community Land Model)是目前国际上发展较为完善并被广泛应用的陆面过程模式。本文使用中国科学院寒区旱区环境与工程研究所位于青藏高原东部的若尔盖高原湿地生态系统研究站的观测资料,对CLM3.0版本及CLM4.0版本在上述地区的模拟性能进行了检验与对比。通过比较观测值与模拟值,验证了模式在高原季节性冻土地区的适用性,发现CLM4.0较CLM3.0在模拟结果上有了一定提高。CLM4.0加入了未冻水参数化方案,使模式可以模拟到冬季土壤冻结后存留的未冻水,显著增加了冻融期间土壤含水量的模拟,同时减小了土壤含冰量的模拟值。并因此增大了模拟的冻土热容量,减小了热导率,使冻融期间土壤温度的模拟也有了一定改善。但是模拟中也发现对于较深层土壤,温度模拟值在冻融期间较观测显著偏低。另外,在消融(冻结)过程阶段CLM4.0模拟的土壤含水量骤增(骤降)的时间均较观测提前。消融过程、冻结过程阶段模拟时间偏短,而完全冻结、完全消融阶段模拟时间偏长。因此CLM对于高原冻土地区的模拟仍是其需要重点改进的地方之一。展开更多
Off-line experiments have been conducted with IAP94 land surface model on different surface types (cropland, forest and paddy field) in different seasons (spring, summer and autumn) over the Huaihe River basin. The si...Off-line experiments have been conducted with IAP94 land surface model on different surface types (cropland, forest and paddy field) in different seasons (spring, summer and autumn) over the Huaihe River basin. The simulated energy fluxes and canopy temperature by IAP94 agree quite well with the observations, simulation results also show that IAP94 can successfully simulate the tendency of total soil water content variation. The comparison;results between simulation and observation indicate that strong evaporation at the paddy field in summer should be paid more attention to within the land surface models, and model's performance leads to the conclusion that IAP94 is capable of reproducing the main physical mechanisms governing the land-surface processes in the East Asian semi-humid monsoon region.展开更多
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 simulatedresults were compared with the observations ...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 simulatedresults were compared with the observations to examine the capability of the model to describe theevolutions of snow cover under two different land cover conditions. Several sensitivity experimentswere performed to investigate the effects of the parameterization schemes of some snow coverinternal processes and vegetation on the model results. Results suggest that the CLSM simulates thebasic processes of snow cover accurately and describes the features of snow cover evolutionsreasonably, indicating that the model has the potential to model the processes related to the snowcover evolution. It is also found that the different parameterization schemes of the snowfalldensity 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 simulatedsignificantly but with little effect on the simulated snow water equivalent (SWE). Theparameterization of the snow water holding capacity plays a crucial role in the evolution of snowcover, especially in the ablation of snow cover. Larger snow water holding capacity usually leads tolarger snow density and heat capacity by storing more liquid water in the snow layer, and makes thetemperature of snow cover and the snow ablation vary more slowly. To a smaller snow water holdingcapacity, contrary is the case. The results also show that the physical processes related to thesnow cover variation are different, which are dependent on the vegetation existed. Vegetation playsan important role in the evolution of soil-snow system by changing the energy balance at thesnow-soil surface. The existence of vegetation is favorable to the maintenance of snow cover anddelays the increase of underlying soil temperature.展开更多
文摘The IAP (Institute of Atmospheric Physics) land-surface model (IAP94) is described. This model is a comprehensive one with detailed description for the processes of vegetation, snow and soil. Particular attention has been paid to the cases with three water phases in the surface media. On the basis of the mixture theory and the theory of fluid dynamics of porous media, the system of universal conservational equations for water and heat of soil, snow and vegetation canopy has been constructed. On this background, all important factors that may affect the water and heat balance in media can be considered naturally, and each factor and term possess distinct physical meaning. In the computation of water content and temperature, the water phase change and the heat transportation by water flow are taken into account. Moreover, particular attention has been given to the water vapor diffusion in soil for arid or semi-arid cases, and snow compaction. In the treatment of surface turbulent fluxes, the difference between aerodynamic and thermal roughness is taken into account. The aerodynamic roughness of vegetation is calculated as a function of canopy density, height and zero-plane displacement. An extrapolation of log linear and exponential relationship is used when calculating the wind profile within canopy. The model has been validated against field measurements in off-line simulations. The desirable model′s performance leads to the conclusion that the IAP94 is able to reproduce the main physical mechanisms governing the energy and water balances in the global land surface. Part II of the present study will concern the validation in a 3-D experiment coupled with the IAP Two-Level AGCM.
基金the National Natural Science Foundation of China (Nos. 41075053 and 41275016)
文摘In order to further understand the land surface processes over the northern Tibetan Plateau, this study produced an off-line simulated examination at the Bujiao site on the northern Tibetan Plateau from June 2002 to April 2004, using the Noah Land Surface Model （Noah LSM） and observed data from the CAMP/Tibet experiment. The observed data were neces- sarily corrected and the number of soil layers in the Noah LSM was changed from 4 to 10 to enable this off-line simulation and analysis. The main conclusions are as follows： the Noah LSM performed well on the northern Tibetan Plateau. The simulated net radiation, upward longwave radiation, and upward shortwave radiation demonstrated the same remarkable annual and seasonal variation as the observed data, especially the upward longwave radiation. The simulated soil temperatures were acceptably close to the observed temperatures, especially in the shallow soil layers. The simulated freezing and melting processes were shown to start from the surface soil layer and spread down to the deep soil layers, but they took longer than the observed processes. However, Noah LSM did not adequately simulate the soil moisture. Therefore, additional high-quality, long-term observations of land surface-atmosphere processes over the Tibetan Plateau will be a key factor in proper adiustments of the model parameters in the future.
基金National Natural Science Foundation of China (No. 40275004)State Key Laboratory of Atmosphere Physics and Chemistry
文摘Based on the existing Land Surface Physical Process Models(Deardorff, Dickinson, LIU, Noilhan, Seller, ZHAO), a Comprehensive Land Surface Physical Process Model (CLSPPM) is developed by considering the different physical processes of the earth's surface-vegetation-atmosphere system more completely. Compared with SiB and BATS, which are famous for their detailed parameterizations of physical variables, this simplified model is more convenient and saves much more computation time. Though simple, the feas...
基金the NKBRSF Project! G 1999043400 the CNSF Project! 49735180.
文摘Two land surface schemes, one the standard Biosphere / Atmosphere Transfer Scheme Version ie (BOZ) and the other B1Z based on B0Z and heterogeneously-treated by' combined approach' , were co 'pled to the meso-scale model MM4, respectively. Through the calculations of equations from the companion paper, parameters representing land surface heterogeneity and suitable for the coupling models were found out. Three cases were simulated for heavy rainfalls during 36 hours, and the sensitivity of short-term weather modeling to the land surface heterogeneity was tested. Through the analysis of the simulations of the three heavy rainfalls, it was demonstrated that BIZ, compared with BOZ, could more realistically reflect the features of the land surface heterogeneity, therefore could more realistically reproduce the circulation and precipitation amount in the heavy rainfall processes of the three cases. This shows that even short-term weather is sensitive to the land surface heterogeneity, which is more obvious with time passing, and whose influence is more pronounced in the lower layer and gradually extends to the middle and upper layer. Through the analysis of these simulations with BlZ, it is suggested that the bulk effect of smaller-scale fluxes (i.e., the momentum, water vapor and sensible heat fluxes) near the s ig nificantly-heterogeneous land surface is to change the larger-scale (i.e., meso-scale) circulation, and then to influence the development of the low-level jets and precipitation. And also, the complexity of the land-atmosphere interaction was shown in these simulations.
文摘Based on the existing land-surface schemes and models,an improved Land-surface Process Model(LPM-ZD)has been developed.It has the following major characteristics:(1)The combination of physical equations and empirical analytical formulae are used to construct the governing equations of soil temperature and moisture.Higher resolution of model level and physical equations are adopted for the upper soil layers,and for the lower soil layers,lower resolution of model level is adopted and empirical analytical formulae are used.(2)In land surface hydrological process,the sub-grid distribution of rainfall and its effects are taken into account. (3)A simple snow cover submodel has been used,which includes effects of snow cover on soil thermodynamics and hydrology,as well as albedo. By use of this model and three groups of point observation data,a series of“off-line”tests have been carried out.The simulation results indicate that land-surface process model has good performance and can well simulate diurnal and seasonal variation of land surface processes for many kinds of land surface covers(forest,grass,crops and desert)in different climate zone.The results simulated by the model are consistent with the observations.Later,by use of one group of observation data and the model,a series of sensitivity experiments have been done.It is shown that the model is much sensitive to some parameters,such as initial soil moisture,vegetation physical parameters as well as the proportion of the grid covered with rain.Therefore it is much important for land-surface process model to define these parameters as accurately as possible.
文摘The effect on climate due to seasonal variation of vegetation and roughness length was simulated in Part Ⅰ of this essay.In Part Ⅱ,the individual effect of albedo and the joint effect of all those factors (vegetation,roughness length and albedo) were calculated by numerical sensitivity experiments.The results showed that:(1)There is no significant effect on precipitation if the albedo of 4 seasons is used to replace the CRCM's climate average data,but the effect on land surface temperature can be seen clearly.And the effect also can be seen in adjacent regions.(2)If all these three factors are used to replace the CRCM's climate average data at the same time,the effect on precipitation is significant,the most variation value is 300mm.And the effect on temperature is similar to what we can see if only one of these factors in CRCM is replaced by monthly or seasonal data.(3)Seasonal variation of land surface parameters has important effect not only on regional climate,but also on global environment.
文摘Sensitivity experiment is an important method to study the effect on regional climate due to seasonal variation of land surface parameters.Using China Regional Climate Model(CRCM) nested in CCM1.we first simulate Chinese regional climate,then two numerical sensitivity experiments on the effect of vegetation and roughness length are made.The results show that: (1)If the vegetation is replaced with the monthly data of 1997.precipitation and land-surface temperature are both changed clearly,precipitation decreases and land surface temperature increases,but there is no regional correspondence between these changes.And the results are much better than the results when climate average vegetation was used in the CRCM.(2)If the roughness length is replaced with the monthly data of 1997,there is significant change on land surface temperature,and there is very good regional correspondence between these changes.But the effect on precipitation is very small.
文摘陆面模式CLM(Community Land Model)是目前国际上发展较为完善并被广泛应用的陆面过程模式。本文使用中国科学院寒区旱区环境与工程研究所位于青藏高原东部的若尔盖高原湿地生态系统研究站的观测资料,对CLM3.0版本及CLM4.0版本在上述地区的模拟性能进行了检验与对比。通过比较观测值与模拟值,验证了模式在高原季节性冻土地区的适用性,发现CLM4.0较CLM3.0在模拟结果上有了一定提高。CLM4.0加入了未冻水参数化方案,使模式可以模拟到冬季土壤冻结后存留的未冻水,显著增加了冻融期间土壤含水量的模拟,同时减小了土壤含冰量的模拟值。并因此增大了模拟的冻土热容量,减小了热导率,使冻融期间土壤温度的模拟也有了一定改善。但是模拟中也发现对于较深层土壤,温度模拟值在冻融期间较观测显著偏低。另外,在消融(冻结)过程阶段CLM4.0模拟的土壤含水量骤增(骤降)的时间均较观测提前。消融过程、冻结过程阶段模拟时间偏短,而完全冻结、完全消融阶段模拟时间偏长。因此CLM对于高原冻土地区的模拟仍是其需要重点改进的地方之一。
基金National Key Porgramme for Developing Basic Sciences! (G1998040900-part1)Supported by the National Natural Science Foundatio
文摘Off-line experiments have been conducted with IAP94 land surface model on different surface types (cropland, forest and paddy field) in different seasons (spring, summer and autumn) over the Huaihe River basin. The simulated energy fluxes and canopy temperature by IAP94 agree quite well with the observations, simulation results also show that IAP94 can successfully simulate the tendency of total soil water content variation. The comparison;results between simulation and observation indicate that strong evaporation at the paddy field in summer should be paid more attention to within the land surface models, and model's performance leads to the conclusion that IAP94 is capable of reproducing the main physical mechanisms governing the land-surface processes in the East Asian semi-humid monsoon region.
基金Supported by the National Natural Science Foundation of China under Grant No. 40405018.
文摘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 simulatedresults were compared with the observations to examine the capability of the model to describe theevolutions of snow cover under two different land cover conditions. Several sensitivity experimentswere performed to investigate the effects of the parameterization schemes of some snow coverinternal processes and vegetation on the model results. Results suggest that the CLSM simulates thebasic processes of snow cover accurately and describes the features of snow cover evolutionsreasonably, indicating that the model has the potential to model the processes related to the snowcover evolution. It is also found that the different parameterization schemes of the snowfalldensity 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 simulatedsignificantly but with little effect on the simulated snow water equivalent (SWE). Theparameterization of the snow water holding capacity plays a crucial role in the evolution of snowcover, especially in the ablation of snow cover. Larger snow water holding capacity usually leads tolarger snow density and heat capacity by storing more liquid water in the snow layer, and makes thetemperature of snow cover and the snow ablation vary more slowly. To a smaller snow water holdingcapacity, contrary is the case. The results also show that the physical processes related to thesnow cover variation are different, which are dependent on the vegetation existed. Vegetation playsan important role in the evolution of soil-snow system by changing the energy balance at thesnow-soil surface. The existence of vegetation is favorable to the maintenance of snow cover anddelays the increase of underlying soil temperature.
