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The Observed and Simulated Major Summer Climate Features in Northwest China and Their Sensitivity to land surface processes

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Journal of Meteorological Research 2014年第5期28卷 836-848页

作者：李倩薛永康 Center for Monsoon System Research Institute of Atmospheric PhysicsChinese Academy of Sciences Department of Geography University of CaliforniaLos AngelesCA 90095-1524USA Department of Atmospheric and Oceanic Sciences University of CaliforniaLos AngelesCA 90095-1524USA

Northwest China （NWC） is a typical arid and semi-arid region. In this study, the main summer climate features over NWC are presented and the performance of an atmospheric general circulation model （NCEP GCM/SSiB） over this region is evaluated. Satellite-derived vegetation products are applied in the model. Based on comparison with observational data and Reanalysis II data, the model generally captures major features of the NWC summer energy balance and circulation. These features include： a high surface tem- perature center dominating the planetary boundary layer; widespread descending motion; an anticyclone （cyclone） located in the lower and middle （upper） troposphere, covering most parts of central NWC; and the precipitation located mainly in the high elevation areas surrounding NWC. The sensitivity of the summer energy balance and circulation over NWC and surrounding regions to land surface processes is assessed with specified land cover change. In the sensitivity experiment, the degradation over most parts of NWC, except the Taklimakan desert, decreases the surface-absorbed radiation and leads to weaker surface thermal effects. In northern Xinjiang and surrounding regions, less latent heating causes stronger anomalous lower-level anticyclonic circulation and upper-level cyclonic circulation, leading to less summer precipitation and higher surface temperature. Meanwhile, the dry conditions in the Hexi Corridor produce less change in the latent heat flux. The circulation change to the north of this area plays a domi- nant role in indirectly changing lower-level cyclonic conditions, producing more convergence, weaker vertical descending motion, and thus an increase in the precipitation over this region.

关键词： Northwest China (NWC) arid and semi-arid regions atmospheric general circulation model land cover change land surface processes

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Offline experiment of land surface processes in Qinghai-Xizang Plateau

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Science China Earth Sciences 2004年第Z1期47卷 115-121页

作者： ZHANG Yanwu, LU Shihua, FENG Qi, HUANG Jing & HU ZeyongCold and Arid Regions Environmental and Engineering Institute, Chinese Academy of Sciences, Lanzhou 730000, China Resource Environment College, Lanzhou University, Lanzhou 730000, China

The observational data of Beiluhe test of the Qinghai-Xizang railway in June 2002 are used as forcing field of the surface model to study the simulation performance in Qinghai-Xizang Plateau. The simulation result shows that the model (NCAR/LSM) can present the surface character tendency reasonably under observation forcing. In NCAR/LSM, the descriptions of the surface vegetation type in Qinghai-Xizang Plateau have much difference to what is actually happening. According to the actual characteristic of the surface, we define the grassland vegetation coverage rate is 0.6, and the vegetation canopy is 0.15 m, and the displacement height is 0.10 m. Compared the results with the old model's parameter in experiment, we find that the simulation air (2 m) temperature and the ground temperature are close to those of the observation, and the simulation temperature of peak value is better, and the simulation flux of the ground is sure to be improved too. So, if the surface and vegetation parameters are revised in LSM model, the simulation capability of the land surface process model can be improved effectively in Qinghai-Xizang Plateau.

关键词： Qinghai-Xizang Plateau land surface processes NCAR/LSM.

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Regional climate dynamical downscaling over the Tibetan Plateau——From quarter-degree to kilometer-scale

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Science China Earth Sciences 2022年第12期65卷 2237-2247页

作者： Yanhong GAO Jianwei XU Meng ZHANG Zhaoyang LIU Jingyu DAN Institute of Atmospheric Sciences&Department of Atmospheric and Oceanic Sciences Fudan UniversityShanghai 200438China Shanghai Frontiers Science Center of Atmosphere-Ocean Interaction Shanghai 200438China Natiobal Observations and Research Station for Wetland Ecosystems of the Yangtze Estuary Shanghai 200438China College of Resource and Environment Hunan University of Art and SciencesChangde 415000China

The Tibetan Plateau(TP)possesses the largest cryosphere in the world outside of the Arctic and Antarctic,and is the source of nine major rivers in *** surface environment of the TP has undergone significant changes against the background of global *** is projected that the continuation of climate change in the future will result in most of the glaciers and frozen soil disappearing by the end of this century,and freshwater resources will be greatly reduced,on which 22%of the world’s population *** environmental changes are of great concern to global society given the influences of the TP on the climate at the global ***,great uncertainties exist in global climate simulations over the TP,which affects our ability to properly understand the associated water security *** on atmospheric dynamics and physical processes,dynamical downscaling can characterize surface conditions more accurately than global simulations,and better simulate and predict regional or local weather and climate *** advances in supercomputing,the grid spacing of dynamical downscaling simulations has been continuously increasing,marching the technique into the kilometer-scale *** this paper,the origin and development of dynamical downscaling in the TP region from the quarter-degree to kilometer scale is firstly introduced,including an assessment of the advantages and disadvantages of dynamical downscaling at the kilometer scale over the ***,the main land surface factors affecting the performance of dynamical downscaling over the TP are described,as well as a brief introduction to a land surface model with specific plateau ***,it has emerged that perfecting the land surface model and improving the performance of land-atmosphere interaction are the most effective ways to advance the performance of dynamic downscaling in this ***,the challenges and some recommended future research directions are discussed and

关键词： Tibetan Plateau Climate dynamical downscaling land surface processes

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The Sensitivity of Ground surface Temperature Prediction to Soil Thermal Properties Using the Simple Biosphere Model(SiB2)

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Advances in Atmospheric Sciences 2012年第3期29卷 623-634页

作者：张晓惠高志球魏东平 College of Earth Science Graduate University of Chinese Academy of Sciences Key Laboratory of Computational Geodynamics Chinese Academy of Sciences State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry Institute of Atmospheric PhysicsChinese Academy of Sciences College of Applied Meteorology Nanjing University of Information Science and Technology

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.

关键词： land surface processes SiB2 sensitivity ground surface temperature soil thermal diffusivity soil thermal conductivity

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The Effects of land surface Process Perturbations in a Global Ensemble Forecast System

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Advances in Atmospheric Sciences 2016年第10期33卷 1199-1208页

作者： Guo DENG Yuejian ZHU Jiandong GONG Dehui CHEN Richard WOBUS Zhe ZHANG National Meteorological Center China Meteorological Administration Environmental Modeling Center National Centers for Environmental Prediction5830 University Research Court Institute of Atmospheric Physics Chinese Academy of Sciences

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.

关键词： perturbation land surface processes GEFS ensemble transform with rescaling

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The Characteristics and Controlling Factors of Water and Heat Exchanges over the Alpine Wetland in the East of the Qinghai–Tibet Plateau

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Advances in Atmospheric Sciences 2023年第2期40卷 201-210页

作者： Jinlei CHEN Yuan YUAN Xianyu YANG Zuoliang WANG Shichang KANG Jun WEN State Key Laboratory of Cryosphere Sciences Northwest Institute of Eco-Environment and ResourcesChinese Academy of SciencesLanzhou 730000China Plateau Atmosphere and Environment Key Laboratory of Sichuan Province Chengdu University of Information TechnologyChengdu 610225China Key Laboratory of land surface processes and Climate Change Northwest Institute of Eco-Environment and ResourcesChinese Academy of SciencesLanzhou 730000China College of Atmospheric Science Lanzhou UniversityLanzhou 730000China

Alpine wetland is one of the typical underlying surfaces on the Qinghai–Tibet *** plays a crucial role in runoff *** on the mechanisms of water and heat exchanges are necessary to understand the land surface processes over the alpine *** 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 *** 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 *** transfers of heat fluxes were mainly controlled by longwave radiation and air temperature and affected by root *** pressure and stomatal conductance were also important to latent heat flux,and soil solid water content was important to sensible heat *** temperature was dominated by longwave radiation and air temperature,with crucial surface parameters of initial soil liquid water content and total water *** 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 *** work contributes to the research on the land surface processes over the alpine wetland and is helpful to wetland protection.

关键词： alpine wetland Qinghai-Tibet Plateau land surface processes atmospheric factor surface parameter

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