This paper uses a Modified Soil-Plant-Atmosphere Scheme (MSPAS) to study the interaction between land surface and atmospheric boundary layer processes. The scheme is composed of two main parts: atmospheric boundary la...This paper uses a Modified Soil-Plant-Atmosphere Scheme (MSPAS) to study the interaction between land surface and atmospheric boundary layer processes. The scheme is composed of two main parts: atmospheric boundary layer processes and land surface processes. 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 feasibility of the model is well proved in this paper. The numerical simulation results from MSPAS show good agreement with reality. The scheme is used to obtain reasonable simulations for diurnal variations of heat balance, potential temperature of boundary layer, and wind field, and spatial distributions of temperature, specific humidity, vertical velocity, turbulence kinetic energy, and turbulence exchange coefficient over desert and oasis. In addition, MSPAS is used to simulate the interaction between desert and oasis at night, and again it obtains reasonable results. This indicates that MSPAS can be used to study the interaction between land surface processes and the atmospheric boundary layer over various underlying surfaces and can be extended for regional climate and numerical weather prediction study.展开更多
On 12 August 2004, Typhoon Rananim （0414） moved inland over China and stagnated over the Poyang Lake area, resulting in torrential rainfall and severe geologic hazards. The Advanced Weather Research and Forecasting ...On 12 August 2004, Typhoon Rananim （0414） moved inland over China and stagnated over the Poyang Lake area, resulting in torrential rainfall and severe geologic hazards. The Advanced Weather Research and Forecasting （ARW-WRF） model and its different land surface models （LSMs） were employed to study the impacts of land surface process on the inland behavior of Typhoon Rananim. Results show that simulations, coupled with LSMs or not, have no significant differences in predicting typhoon track, intensity, and largescale circulation. However, the simulations of mesoscale structure, rainfall rate, and rainfall distribution of typhoon are more reasonable with LSMs than without LSMs. Although differences are slight among LSMs, NOAH is better than the others. Based on outputs using the NOAH scheme, the interaction between land surtace and typhoon was explored in this study. Notably, typhoon rainfall and cloud cover can cool land surface, but rainfall expands the underlying saturated wetland area, which exacerbates the asymmetric distribution of surface heat fluxes. Accordingly, an energy frontal zone may form in the lower troposphere that enhances ascending motion and local convection, resulting in heavier rainfall. Moreover, the expanded underlying saturated wetlands provide plentiful moisture and unstable energy for the maintenance of Typhoon Rananim and increased rainfall in return.展开更多
With data from the project Collaborative Observation of Semi-arid/Arid Regions in North China, collected during July and September 2008, the spatial patterns of land surface processes over arid and semiarid regions ha...With data from the project Collaborative Observation of Semi-arid/Arid Regions in North China, collected during July and September 2008, the spatial patterns of land surface processes over arid and semiarid regions have been investigated based on the ordinary Kriging interpolation approach. Generally, for the radiation processes, downward and upward short-wave radiation have a uniformly increasing trend with latitude, but the spatial patterns of long-wave radiation present notable regional differences: both upward and downward long-wave radiation increase with latitude in the west of North China, while in the east they vary inversely with latitude, suggesting surface temperature and clouds respectively have feedbacks to the long-wave radiation in the west and east of North China. The surface net radiation basically has a negative latitudinal trend. Long-wave radiation budget plays an important role in the spatial pattern of surface net radiation, particularly in the east of North China, although short-wave radiation budget largely determines the magnitude of surface net radiation. For the energy processes, latent and sensible heat flux varies conversely with latitude: more available land surface energy is consumed by evaporating soil water at lower latitudes while more is used for heating the atmosphere at higher latitudes. A soil heat flux maximum and minimum are found in Loess Plateau and Qinghai Plateau respectively, and a maximum is seen in the northeast China.展开更多
Atmospheric variability is driven not only by internal dynamics, but also by external forcing, such as soil states, SST, snow, sea-ice cover, and so on. To investigate the forecast uncertainties and effects of land su...Atmospheric variability is driven not only by internal dynamics, but also by external forcing, such as soil states, SST, snow, sea-ice cover, and so on. To investigate the forecast uncertainties and effects of land surface processes on numerical weather prediction, we added modules to perturb soil moisture and soil temperature into NCEP＇s Global Ensemble Forecast System （GEFS）, and compared the results of a set of experiments involving different configurations of land surface and atmospheric perturbation. It was found that uncertainties in different soil layers varied due to the multiple timescales of interactions between land surface and atmospheric processes. Perturbations of the soil moisture and soil temperature at the land surface changed sensible and latent heat flux obviously, as compared to the less or indirect land surface perturbation experiment from the day-to-day forecasts. Soil state perturbations led to greater variation in surface heat fluxes that transferred to the upper troposphere, thus reflecting interactions and the response to atmospheric external forcing. Various verification scores were calculated in this study. The results indicated that taking the uncertainties of land surface processes into account in GEFS could contribute a slight improvement in forecast skill in terms of resolution and reliability, a noticeable reduction in forecast error, as well as an increase in ensemble spread in an under-dispersive system. This paper provides a preliminary evaluation of the effects of land surface processes on predictability. Further research using more complex and suitable methods is needed to fully explore our understanding in this area.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
Land-atmosphere interaction,as one of the key processes affecting the atmosphere and climate over East Asia,has drawn increasing attention during the past few decades.However,the current level of understanding regardi...Land-atmosphere interaction,as one of the key processes affecting the atmosphere and climate over East Asia,has drawn increasing attention during the past few decades.However,the current level of understanding regarding the mechanisms through which land surface processes impact the East Asian climate needs to be improved.Based on existing studies,six key regions where land surface processes affect the East Asian climate are proposed in this study,which can provide a valuable reference for future research into land-atmosphere interaction in East Asia.展开更多
Many studies have explored the importance and influence of planetary boundary layer processes on tropical cyclones (TCs). However, few studies have focused on the influence of land surface processes on the activity of...Many studies have explored the importance and influence of planetary boundary layer processes on tropical cyclones (TCs). However, few studies have focused on the influence of land surface processes on the activity of TCs. To test the effect of initial perturbations of land surface processes on TCs, a land surface process perturbation module is built in a global ensemble prediction system. Ensemble experiments for the TCs that occurred from 12 UTC 22 August to 18 UTC 24 November, 2006 show that consideration of the uncertainties within the land surface process could increase the predictability of the global ensemble prediction system. Detailed analysis on TC Xangsane (2006) indicates that the perturbation of land surface processes may increase the variation of sensible heat flux and latent heat flux. Meanwhile, the effect from land surface perturbation can be transferred to the upper atmosphere, which leads to better TC forecasts.展开更多
[Objective] The research aimed to carry out numerical simulation on impact of land-surface process in a Meiyu front rainstorm.[Method] Based on the meso-scale atmospheric non-hydrostatic model GRAPES-Meso which couple...[Objective] The research aimed to carry out numerical simulation on impact of land-surface process in a Meiyu front rainstorm.[Method] Based on the meso-scale atmospheric non-hydrostatic model GRAPES-Meso which coupled with NOAH land-surface module,a Meiyu front rainstorm in Jianghuai basin during 6-8 July,2005 was simulated.Via sensitivity tests with and without land-surface process,the impact of land-surface process on Meiyu front rainstorm was studied.[Result] GRAPES-Meso which coupled with NOAH land-surface process could simulate daily variation characteristics of Meiyu front precipitation and atmospheric low-level southwest jet.The land-surface process could improve the simulations of precipitation initiation,intensity and distribution.The improvement of precipitation initiation simulation was especially obvious,which solved spin-up problem of model to some extent.When the land-atmosphere interaction wasn’t considered,the precipitation initiation of model was very slow.The intensity evolution of simulated precipitation was different from actual situation.Moreover,it couldn’t simulate daily variation characteristics of precipitation and southwest jet.[Conclusion] The land-surface process had important impact on Meiyu process in Jianghuai basin.展开更多
An analytical expression for subgrid–scale inhomogeneous runoff ratios generated by heterogeneous soil moisture content and climatic precipitation forcing is presented based on physical mechanisms for land surface hy...An analytical expression for subgrid–scale inhomogeneous runoff ratios generated by heterogeneous soil moisture content and climatic precipitation forcing is presented based on physical mechanisms for land surface hydrology and theory of statistical probability distribution. Thereby the commonly used mosaic parameterization of subgrid runoff ratio was integrated into a statistical–dynamic scheme with the bulk heterogeneity of a grid area included. Furthermore, a series of numerical experiments evaluating the reliability of the parameterization were conducted using the data generated by the emulated simulation method. All the experimental results demonstrate that the proposed scheme is feasible and practical.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
The Yellow River Basin faces water scarcity and ecological fragility.Changes on the land surface,characterized by large-scale soil and water conservation measures,have a significant impact on river runoff and ecologic...The Yellow River Basin faces water scarcity and ecological fragility.Changes on the land surface,characterized by large-scale soil and water conservation measures,have a significant impact on river runoff and ecological environment.However,there are still great uncertainties in the scientific understanding of the mechanisms by which multiple driver impact eco-hydrological processes due to the diversity of land surfaces and the complexity of the coupling processes.As an international scientific frontier on interdisciplinary studies in climatology,hydrology,ecology,and other related fields,it is significant to study the mechanisms and assess the impacts of land surface change on eco-hydrological risk to support ecological restoration plan and sustainable water resources utilization in the Yellow River Basin.Taking the Yellow River Basin as the study area,this study proposes several important research initiatives,focusing on addressing the ecological and water resources problems in the Loess Plateau.These initiatives include(1)to quantify the individual effect of land surface elements(e.g.,vegetation,terraces,and check dam)and reveal the nonlinear driving mechanisms of multiple drivers on eco-hydrological processes;(2)to construct a distributed eco-hydrological model that couples dynamic land surface features,and simulate eco-hydrological processes in a changing environment;(3)to improve the ecological risk assessment indicator system and methods for assessing the impacts of land surface changes on eco-hydrological synergistic functions and ecological risk;(4)to establish an ecological regulation model based on multiobjective game theory and adopt an adaptive regulation mode for ecological risk management.The research could enrich the scientific understanding and theory of eco-hydrology,and prompt disciplinary studies of ecology,hydrology,climatology,and other fields.The expected academic achievements will innovate eco-hydrological simulation and assessment techniques in a changing environment,and strongly support the implementation of the national strategy for ecological protection and high-quality development in the Yellow River Basin.展开更多
Using the Simple Biosphere Model （SiB2）, soil thermal properties （STP） were examined in a Tibetan prairie during the monsoon period to investigate ground surface temperature prediction. We improved the SiB2 model ...Using the Simple Biosphere Model （SiB2）, soil thermal properties （STP） were examined in a Tibetan prairie during the monsoon period to investigate ground surface temperature prediction. We improved the SiB2 model by incorporating a revised force-restore method （FRM） to take the vertical heterogeneity of soil thermal diffusivity （k） into account. The results indicate that （1） the revised FRM alleviates daytime overestimation and nighttime underestimation in modeled ground surface temperature （Tg）, and （2） its role in little rainfall events is significant because the vertical gradient of k increases with increasing surface evaporation. Since the original formula of thermal conductivity （A） in the SiB2 greatly underestimates soil thermal conductivity, we compared five Mgorithms of A involving soil moisture to investigate the cause of overestimation during the day and underestimation at night on the basis of the revised FRM. The results show that （1） the five algorithms significantly improve Tg prediction, especially in daytime, and （2） taking one of these five algorithms as an example, the simulated Tg values in the daytime are closer to the field measurements than those in the nighttime. The differences between modeled Tg and field measurements are mostly within the margin of error of -4-2 K during 3 August to 4 September 1998.展开更多
城市建成区是行政区范围内具有基本完善的市政公用设施的非农业生产建设用地,它包括市区集中连片的部分以及分散在近郊区与城市有着密切联系的部分.针对利用不透水面指数和夜间灯光数据结合的方法提取城市建成区(Built-up area of urban...城市建成区是行政区范围内具有基本完善的市政公用设施的非农业生产建设用地,它包括市区集中连片的部分以及分散在近郊区与城市有着密切联系的部分.针对利用不透水面指数和夜间灯光数据结合的方法提取城市建成区(Built-up area of urban extraction,BAUA)的结果在城市近郊工业区有缺失现象,以及市中心内部的大面积裸露土地和夜间灯光数据值较弱的地区存在大块空洞现象的问题,以2019年北京、武汉、郑州、西安4个城市建成区为研究对象,首先借助GEE(google earth engine)平台利用Weka Cobweb聚类算法以及形态学后处理,研究了基于夜间灯光数据NPP/VIIRS与Landsat-8数据计算的建筑指数和地表温度相结合的方法对城市建成区(built-up area extraction,BUAE)提取,然后利用不透水面指数和夜间灯光数据结合的方法提取城市建成区,最后对比2种方法的提取结果.研究表明:(1)在BUAE方法中加入(Landsurface temperature,LST)参数,能有效弥补市郊工业区因夜间灯光数据值损失而造成提取建成区缺失的不足.(2)BUAE方法可以一定程度上减弱提取建成区内部的大面积裸露土地和夜间灯光数据值较弱的地区存在大块空洞现象.(3)2种方法在对市郊和市中心城镇化水平差异小的特大城市北京的建成区提取轮廓基本一致,对市郊和市中心城镇化水平差异大的大城市如武汉、西安、郑州提取建成区的轮廓差异较大.相对BAUA方法,BUAE方法在北京,准确度提高了2.1%,在武汉准确度提高了13.9%,在西安准确度提高了10.6%,在郑州提高了9.7%,但BUAE的虚警率也高于BAUA的虚警率.本研究可以为建成区提取提供参考.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
Alpine wetland is one of the typical underlying surfaces on the Qinghai–Tibet Plateau.It plays a crucial role in runoff regulation.Investigations on the mechanisms of water and heat exchanges are necessary to underst...Alpine wetland is one of the typical underlying surfaces on the Qinghai–Tibet Plateau.It plays a crucial role in runoff regulation.Investigations on the mechanisms of water and heat exchanges are necessary to understand the land surface processes over the alpine wetland.This study explores the characteristics of hydro-meteorological factors with in situ observations and uses the Community Land Model 5 to identify the main factors controlling water and heat exchanges.Latent heat flux and thermal roughness length were found to be greater in the warm season(June–August)than in the cold season(December–February),with a frozen depth of 20–40 cm over the alpine wetland.The transfers of heat fluxes were mainly controlled by longwave radiation and air temperature and affected by root distribution.Air pressure and stomatal conductance were also important to latent heat flux,and soil solid water content was important to sensible heat flux.Soil temperature was dominated by longwave radiation and air temperature,with crucial surface parameters of initial soil liquid water content and total water content.The atmospheric control factors transitioned to precipitation and air temperature for soil moisture,especially at the shallow layer(5 cm).Meanwhile,the more influential surface parameters were root distribution and stomatal conductance in the warm season and initial soil liquid water content and total water content in the cold season.This work contributes to the research on the land surface processes over the alpine wetland and is helpful to wetland protection.展开更多
基金supported by the National Natural Science Foundation of China (Grant No.40275004)the State Key Laboratory of Atmosphere Physics and Chemistry,and the City University of Hong Kong(Grant No.8780046)the City University of Hong Kong Strategic Research(Grant No.7001038)
文摘This paper uses a Modified Soil-Plant-Atmosphere Scheme (MSPAS) to study the interaction between land surface and atmospheric boundary layer processes. The scheme is composed of two main parts: atmospheric boundary layer processes and land surface processes. 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 feasibility of the model is well proved in this paper. The numerical simulation results from MSPAS show good agreement with reality. The scheme is used to obtain reasonable simulations for diurnal variations of heat balance, potential temperature of boundary layer, and wind field, and spatial distributions of temperature, specific humidity, vertical velocity, turbulence kinetic energy, and turbulence exchange coefficient over desert and oasis. In addition, MSPAS is used to simulate the interaction between desert and oasis at night, and again it obtains reasonable results. This indicates that MSPAS can be used to study the interaction between land surface processes and the atmospheric boundary layer over various underlying surfaces and can be extended for regional climate and numerical weather prediction study.
基金financed by the National Grand Fundamental Research 973 Program of China (Grant No. 2009CB421504)the Natural Science Foundation of China (Grant Nos. 41175063,40975032,and 41275066)
文摘On 12 August 2004, Typhoon Rananim （0414） moved inland over China and stagnated over the Poyang Lake area, resulting in torrential rainfall and severe geologic hazards. The Advanced Weather Research and Forecasting （ARW-WRF） model and its different land surface models （LSMs） were employed to study the impacts of land surface process on the inland behavior of Typhoon Rananim. Results show that simulations, coupled with LSMs or not, have no significant differences in predicting typhoon track, intensity, and largescale circulation. However, the simulations of mesoscale structure, rainfall rate, and rainfall distribution of typhoon are more reasonable with LSMs than without LSMs. Although differences are slight among LSMs, NOAH is better than the others. Based on outputs using the NOAH scheme, the interaction between land surtace and typhoon was explored in this study. Notably, typhoon rainfall and cloud cover can cool land surface, but rainfall expands the underlying saturated wetland area, which exacerbates the asymmetric distribution of surface heat fluxes. Accordingly, an energy frontal zone may form in the lower troposphere that enhances ascending motion and local convection, resulting in heavier rainfall. Moreover, the expanded underlying saturated wetlands provide plentiful moisture and unstable energy for the maintenance of Typhoon Rananim and increased rainfall in return.
基金supported by the State Key Program of National Natural Science of China (Grant No. 40830957)
文摘With data from the project Collaborative Observation of Semi-arid/Arid Regions in North China, collected during July and September 2008, the spatial patterns of land surface processes over arid and semiarid regions have been investigated based on the ordinary Kriging interpolation approach. Generally, for the radiation processes, downward and upward short-wave radiation have a uniformly increasing trend with latitude, but the spatial patterns of long-wave radiation present notable regional differences: both upward and downward long-wave radiation increase with latitude in the west of North China, while in the east they vary inversely with latitude, suggesting surface temperature and clouds respectively have feedbacks to the long-wave radiation in the west and east of North China. The surface net radiation basically has a negative latitudinal trend. Long-wave radiation budget plays an important role in the spatial pattern of surface net radiation, particularly in the east of North China, although short-wave radiation budget largely determines the magnitude of surface net radiation. For the energy processes, latent and sensible heat flux varies conversely with latitude: more available land surface energy is consumed by evaporating soil water at lower latitudes while more is used for heating the atmosphere at higher latitudes. A soil heat flux maximum and minimum are found in Loess Plateau and Qinghai Plateau respectively, and a maximum is seen in the northeast China.
基金supported by the National Fundamental(973) Research Program of China(Grant No.2013CB430100)the Special Fund for Meteorological Scientific Research in the Public Interest(Grant No.GYHY201506005)the National Natural Science Foundation of China(Grant Nos.41475097,41075079,41275065 and 41475054)
文摘Atmospheric variability is driven not only by internal dynamics, but also by external forcing, such as soil states, SST, snow, sea-ice cover, and so on. To investigate the forecast uncertainties and effects of land surface processes on numerical weather prediction, we added modules to perturb soil moisture and soil temperature into NCEP＇s Global Ensemble Forecast System （GEFS）, and compared the results of a set of experiments involving different configurations of land surface and atmospheric perturbation. It was found that uncertainties in different soil layers varied due to the multiple timescales of interactions between land surface and atmospheric processes. Perturbations of the soil moisture and soil temperature at the land surface changed sensible and latent heat flux obviously, as compared to the less or indirect land surface perturbation experiment from the day-to-day forecasts. Soil state perturbations led to greater variation in surface heat fluxes that transferred to the upper troposphere, thus reflecting interactions and the response to atmospheric external forcing. Various verification scores were calculated in this study. The results indicated that taking the uncertainties of land surface processes into account in GEFS could contribute a slight improvement in forecast skill in terms of resolution and reliability, a noticeable reduction in forecast error, as well as an increase in ensemble spread in an under-dispersive system. This paper provides a preliminary evaluation of the effects of land surface processes on predictability. Further research using more complex and suitable methods is needed to fully explore our understanding in this area.
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supported by the National Natural Science Foundation of China[grant numbers 42088101 and 42130609].
文摘Land-atmosphere interaction,as one of the key processes affecting the atmosphere and climate over East Asia,has drawn increasing attention during the past few decades.However,the current level of understanding regarding the mechanisms through which land surface processes impact the East Asian climate needs to be improved.Based on existing studies,six key regions where land surface processes affect the East Asian climate are proposed in this study,which can provide a valuable reference for future research into land-atmosphere interaction in East Asia.
基金National Natural Science Foundation of China (4073094841075079)+2 种基金NMC-TIGGE Program(GYHY200706001GYHY200906007)Special Public Welfare Research Fund for Meteorological Profession of CMA (GYHY201006015)
文摘Many studies have explored the importance and influence of planetary boundary layer processes on tropical cyclones (TCs). However, few studies have focused on the influence of land surface processes on the activity of TCs. To test the effect of initial perturbations of land surface processes on TCs, a land surface process perturbation module is built in a global ensemble prediction system. Ensemble experiments for the TCs that occurred from 12 UTC 22 August to 18 UTC 24 November, 2006 show that consideration of the uncertainties within the land surface process could increase the predictability of the global ensemble prediction system. Detailed analysis on TC Xangsane (2006) indicates that the perturbation of land surface processes may increase the variation of sensible heat flux and latent heat flux. Meanwhile, the effect from land surface perturbation can be transferred to the upper atmosphere, which leads to better TC forecasts.
基金Supported by National Natural Science Fund Item,China (41005002,40875029)
文摘[Objective] The research aimed to carry out numerical simulation on impact of land-surface process in a Meiyu front rainstorm.[Method] Based on the meso-scale atmospheric non-hydrostatic model GRAPES-Meso which coupled with NOAH land-surface module,a Meiyu front rainstorm in Jianghuai basin during 6-8 July,2005 was simulated.Via sensitivity tests with and without land-surface process,the impact of land-surface process on Meiyu front rainstorm was studied.[Result] GRAPES-Meso which coupled with NOAH land-surface process could simulate daily variation characteristics of Meiyu front precipitation and atmospheric low-level southwest jet.The land-surface process could improve the simulations of precipitation initiation,intensity and distribution.The improvement of precipitation initiation simulation was especially obvious,which solved spin-up problem of model to some extent.When the land-atmosphere interaction wasn’t considered,the precipitation initiation of model was very slow.The intensity evolution of simulated precipitation was different from actual situation.Moreover,it couldn’t simulate daily variation characteristics of precipitation and southwest jet.[Conclusion] The land-surface process had important impact on Meiyu process in Jianghuai basin.
基金This work is supported jointly by the Major-Subject Program of the National Natural Science Foundation of China (Grant No.498992
文摘An analytical expression for subgrid–scale inhomogeneous runoff ratios generated by heterogeneous soil moisture content and climatic precipitation forcing is presented based on physical mechanisms for land surface hydrology and theory of statistical probability distribution. Thereby the commonly used mosaic parameterization of subgrid runoff ratio was integrated into a statistical–dynamic scheme with the bulk heterogeneity of a grid area included. Furthermore, a series of numerical experiments evaluating the reliability of the parameterization were conducted using the data generated by the emulated simulation method. All the experimental results demonstrate that the proposed scheme is feasible and practical.
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National Natural Science Foundation of China(U2243228,52121006)National Key Research and Development Programs of China(2021YFC3201100,2022YFC3205200)State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering(2022nkzd01,2021nkz490211).
文摘The Yellow River Basin faces water scarcity and ecological fragility.Changes on the land surface,characterized by large-scale soil and water conservation measures,have a significant impact on river runoff and ecological environment.However,there are still great uncertainties in the scientific understanding of the mechanisms by which multiple driver impact eco-hydrological processes due to the diversity of land surfaces and the complexity of the coupling processes.As an international scientific frontier on interdisciplinary studies in climatology,hydrology,ecology,and other related fields,it is significant to study the mechanisms and assess the impacts of land surface change on eco-hydrological risk to support ecological restoration plan and sustainable water resources utilization in the Yellow River Basin.Taking the Yellow River Basin as the study area,this study proposes several important research initiatives,focusing on addressing the ecological and water resources problems in the Loess Plateau.These initiatives include(1)to quantify the individual effect of land surface elements(e.g.,vegetation,terraces,and check dam)and reveal the nonlinear driving mechanisms of multiple drivers on eco-hydrological processes;(2)to construct a distributed eco-hydrological model that couples dynamic land surface features,and simulate eco-hydrological processes in a changing environment;(3)to improve the ecological risk assessment indicator system and methods for assessing the impacts of land surface changes on eco-hydrological synergistic functions and ecological risk;(4)to establish an ecological regulation model based on multiobjective game theory and adopt an adaptive regulation mode for ecological risk management.The research could enrich the scientific understanding and theory of eco-hydrology,and prompt disciplinary studies of ecology,hydrology,climatology,and other fields.The expected academic achievements will innovate eco-hydrological simulation and assessment techniques in a changing environment,and strongly support the implementation of the national strategy for ecological protection and high-quality development in the Yellow River Basin.
基金supported by National Natural Science Foundation of China (Grant No.40874047)supported by National Natural Science Foundation of China (Grant No.40975009)supported by the National Key Basic Research Program (Grant No. 2012CB417203)
文摘Using the Simple Biosphere Model （SiB2）, soil thermal properties （STP） were examined in a Tibetan prairie during the monsoon period to investigate ground surface temperature prediction. We improved the SiB2 model by incorporating a revised force-restore method （FRM） to take the vertical heterogeneity of soil thermal diffusivity （k） into account. The results indicate that （1） the revised FRM alleviates daytime overestimation and nighttime underestimation in modeled ground surface temperature （Tg）, and （2） its role in little rainfall events is significant because the vertical gradient of k increases with increasing surface evaporation. Since the original formula of thermal conductivity （A） in the SiB2 greatly underestimates soil thermal conductivity, we compared five Mgorithms of A involving soil moisture to investigate the cause of overestimation during the day and underestimation at night on the basis of the revised FRM. The results show that （1） the five algorithms significantly improve Tg prediction, especially in daytime, and （2） taking one of these five algorithms as an example, the simulated Tg values in the daytime are closer to the field measurements than those in the nighttime. The differences between modeled Tg and field measurements are mostly within the margin of error of -4-2 K during 3 August to 4 September 1998.
文摘城市建成区是行政区范围内具有基本完善的市政公用设施的非农业生产建设用地,它包括市区集中连片的部分以及分散在近郊区与城市有着密切联系的部分.针对利用不透水面指数和夜间灯光数据结合的方法提取城市建成区(Built-up area of urban extraction,BAUA)的结果在城市近郊工业区有缺失现象,以及市中心内部的大面积裸露土地和夜间灯光数据值较弱的地区存在大块空洞现象的问题,以2019年北京、武汉、郑州、西安4个城市建成区为研究对象,首先借助GEE(google earth engine)平台利用Weka Cobweb聚类算法以及形态学后处理,研究了基于夜间灯光数据NPP/VIIRS与Landsat-8数据计算的建筑指数和地表温度相结合的方法对城市建成区(built-up area extraction,BUAE)提取,然后利用不透水面指数和夜间灯光数据结合的方法提取城市建成区,最后对比2种方法的提取结果.研究表明:(1)在BUAE方法中加入(Landsurface temperature,LST)参数,能有效弥补市郊工业区因夜间灯光数据值损失而造成提取建成区缺失的不足.(2)BUAE方法可以一定程度上减弱提取建成区内部的大面积裸露土地和夜间灯光数据值较弱的地区存在大块空洞现象.(3)2种方法在对市郊和市中心城镇化水平差异小的特大城市北京的建成区提取轮廓基本一致,对市郊和市中心城镇化水平差异大的大城市如武汉、西安、郑州提取建成区的轮廓差异较大.相对BAUA方法,BUAE方法在北京,准确度提高了2.1%,在武汉准确度提高了13.9%,在西安准确度提高了10.6%,在郑州提高了9.7%,但BUAE的虚警率也高于BAUA的虚警率.本研究可以为建成区提取提供参考.
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.
基金supported by the National Natural Science Foundation of China(Grant Nos.42005075,41975130)Natural Science Foundation of Gansu Province(Grant No.21JR7RA047)+1 种基金Open Research Fund Program of Plateau Atmosphere and Environment Key Laboratory of Sichuan Province(Grant No.PAEKL-2022-K03)the State Key Laboratory of Cryospheric Science(Grant No.SKLCS-ZZ-2023,SKLCS-ZZ-2022).
文摘Alpine wetland is one of the typical underlying surfaces on the Qinghai–Tibet Plateau.It plays a crucial role in runoff regulation.Investigations on the mechanisms of water and heat exchanges are necessary to understand the land surface processes over the alpine wetland.This study explores the characteristics of hydro-meteorological factors with in situ observations and uses the Community Land Model 5 to identify the main factors controlling water and heat exchanges.Latent heat flux and thermal roughness length were found to be greater in the warm season(June–August)than in the cold season(December–February),with a frozen depth of 20–40 cm over the alpine wetland.The transfers of heat fluxes were mainly controlled by longwave radiation and air temperature and affected by root distribution.Air pressure and stomatal conductance were also important to latent heat flux,and soil solid water content was important to sensible heat flux.Soil temperature was dominated by longwave radiation and air temperature,with crucial surface parameters of initial soil liquid water content and total water content.The atmospheric control factors transitioned to precipitation and air temperature for soil moisture,especially at the shallow layer(5 cm).Meanwhile,the more influential surface parameters were root distribution and stomatal conductance in the warm season and initial soil liquid water content and total water content in the cold season.This work contributes to the research on the land surface processes over the alpine wetland and is helpful to wetland protection.
