Improving and validating land surface models based on integrated observations in deserts is one of the challenges in land modeling. Particularly, key parameters and parameterization schemes in desert regions need to b...Improving and validating land surface models based on integrated observations in deserts is one of the challenges in land modeling. Particularly, key parameters and parameterization schemes in desert regions need to be evaluated in-situ to improve the models. In this study, we calibrated the land-surface key parameters and evaluated several formulations or schemes for thermal roughness length （z 0h ） in the common land model （CoLM）. Our parameter calibration and scheme evaluation were based on the observed data during a torrid summer （29 July to 11 September 2009） over the Taklimakan Desert hinterland. First, the importance of the key parameters in the experiment was evaluated based on their physics principles and the significance of these key parameters were further validated using sensitivity test. Second, difference schemes （or physics-based formulas） of z 0h were adopted to simulate the variations of energy-related variables （e.g., sensible heat flux and surface skin temperature） and the simulated variations were then compared with the observed data. Third, the z 0h scheme that performed best （i.e., Y07） was then selected to replace the defaulted one （i.e., Z98）; the revised scheme and the superiority of Y07 over Z98 was further demonstrated by comparing the simulated results with the observed data. Admittedly, the revised model did a relatively poor job of simulating the diurnal variations of surface soil heat flux, and nighttime soil temperature was also underestimated, calling for further improvement of the model for desert regions.展开更多
模式评估是模式发展中不可或缺的重要一环。本文利用最新版陆面模式评估软件—ILAMB(International Land Model Benchmarking)对通用陆面模式(The Common Land Model,CoLM)进行客观评估,并与NCAR陆面模式CLM5(Community Land Model vers...模式评估是模式发展中不可或缺的重要一环。本文利用最新版陆面模式评估软件—ILAMB(International Land Model Benchmarking)对通用陆面模式(The Common Land Model,CoLM)进行客观评估,并与NCAR陆面模式CLM5(Community Land Model version 5)结果进行比较。作为一个陆面模式评估软件,ILAMB能对参与评估的模式变量自动生成诊断图形并对模式性能进行评分。评估结果表明,CoLM总体性能良好,模拟结果与基准数据较为接近。与CLM5相比,CoLM在总初级生产力及水文方面的表现略微逊色,在辐射方面则表现相当,对部分变量如地表向上长波辐射、地表净辐射等的模拟甚至优于CLM5。通过对比CRUNCEPv7和GSWP3v1两种强迫资料发现,它们在气候平均态上具有一定的差异,模式在GSWP3v1强迫下的表现相对较好。CoLM和CLM5在CRUCNEPv7强迫下模拟的潜热通量在亚马逊平原、亚洲东部和南部地区以及北美东部一带正偏差显著,而在GSWP3v1强迫下的模拟则有明显改善。这两个模式对感热通量的模拟在非洲北部、亚洲中部一带均明显偏高。在辐射方面,CoLM模拟的地表向上短波辐射在全球以偏高为主,这在一定程度上造成了地表净辐射的模拟偏低。各组试验模拟的地表向上长波辐射得分相差不大,但在具体的空间分布上有一定的差别。展开更多
A terrestrial biogeochemical model （CASACNP） was coupled to a land surface model （the Common Land Model,CoLM） to simulate the dynamics of carbon substrate in soil and its limitation on soil respiration.The combine...A terrestrial biogeochemical model （CASACNP） was coupled to a land surface model （the Common Land Model,CoLM） to simulate the dynamics of carbon substrate in soil and its limitation on soil respiration.The combined model,CoLM CASACNP,was able to predict long-term carbon sources and sinks that CoLM alone could not.The coupled model was tested using measurements of belowground respiration and surface fluxes from two forest ecosystems.The combined model simulated reasonably well the diurnal and seasonal variations of net ecosystem carbon exchange,as well as seasonal variation in the soil respiration rate of both the forest sites chosen for this study.However,the agreement between model simulations and actual measurements was poorer under dry conditions.The model should be tested against more measurements before being applied globally to investigate the feedbacks between the carbon cycle and climate change.展开更多
利用公共陆面模式Co LM(community land model),检验其在西北干旱区敦煌戈壁陆面过程特征的模拟能力。通过2008年敦煌夏季典型晴天观测资料驱动模式,对模式在敦煌戈壁地区的适应性进行研究,通过和该站点同期实测资料对比发现:公共陆面模...利用公共陆面模式Co LM(community land model),检验其在西北干旱区敦煌戈壁陆面过程特征的模拟能力。通过2008年敦煌夏季典型晴天观测资料驱动模式,对模式在敦煌戈壁地区的适应性进行研究,通过和该站点同期实测资料对比发现:公共陆面模式(Co LM)基本能较好地模拟极端干旱区,如对敦煌戈壁下垫面的地表能量通量,及对于物理量的日变化趋势模拟得均比较准确,与观测值的相关系数较高。不足之处是对于感热的模拟,白天的模拟峰值偏大,而在夜间负感热的峰值也存在偏大现象。利用辐射资料计算出该下垫面反照率为0.25,修改模式中反照率的设定后,从模拟结果来看Co LM的模拟能力有一定改进。展开更多
利用陆面过程模式Common Land Model(CoLM),选取青藏高原上3个不同下垫面观测站(藏东南站、纳木错站和珠峰站)的观测资料,对这3个野外观测站进行了单点数值模拟试验。根据3个测站的试验数据,对模式中土壤孔隙度和饱和导水率进行了优化,...利用陆面过程模式Common Land Model(CoLM),选取青藏高原上3个不同下垫面观测站(藏东南站、纳木错站和珠峰站)的观测资料,对这3个野外观测站进行了单点数值模拟试验。根据3个测站的试验数据,对模式中土壤孔隙度和饱和导水率进行了优化,针对青藏高原地区土壤层薄的特点,对模式中土壤分层方案进行了调整。结果表明,调整分层方案后的CoLM模式对3个测站土壤湿度的模拟性能较原分层方案有明显提高,平均偏差均减小0.014以上。但是与观测值相比,藏东南站土壤湿度的模拟整体偏低,纳木错站和珠峰站则整体偏高。对土壤温度而言,3个测站模拟与观测的相关系数都达到了0.9以上,珠峰站偏差较大,调整分层方案后模拟的偏差有一定的改进。模式较好地模拟了3个测站的净辐射、感热通量和潜热通量的日变化和季节变化情况,调整分层方案后潜热通量的改进最为明显。展开更多
数据质量问题和模式参数化方案的非完备性是陆面模拟中不确定性的主要来源。本文将高斯误差传播原理(Gaussian Error Propagation,GEP)应用于通用陆面模式(the Common Land Model,CoLM),研究关键的植被和土壤属性参数随机误差在模式中...数据质量问题和模式参数化方案的非完备性是陆面模拟中不确定性的主要来源。本文将高斯误差传播原理(Gaussian Error Propagation,GEP)应用于通用陆面模式(the Common Land Model,CoLM),研究关键的植被和土壤属性参数随机误差在模式中的传播,确定由此类误差导致的CoLM模拟的不确定性。结果表明:(1)基于本研究给定的土壤和植被参数的不确定性,CoLM模拟的表层土壤温度、土壤湿度和植被蒸散通量(植冠蒸腾+地表蒸发)的相对误差分别为0.11%、34.07%和5.58%;砂土和稀疏森林上模拟效果最差。土壤参数随机误差对CoLM模拟的影响高于植被参数,而土壤水文参数(孔隙率、饱和基质势、气孔尺寸分布指数和饱和导水率)对各模拟量不确定性的贡献率均远大于热力参数(饱和反照率和热容)。对于本研究涉及的所有模拟变量而言,最关键的参数均是气孔尺寸分布指数b,这可能与描述基质势与体积水含量关系的函数有关,其次重要的是砂土的孔隙度和粘土的饱和导水率。混交森林上的根深分布和苔原上的动力学粗糙度对蒸散通量贡献显著。本身相对误差大的经验参数对CoLM模拟不确定性的贡献不一定多。(2)干燥条件下(表层液态水饱和度小于0.1)土壤温度的不确定性大;相变发生时刻附近(表层土壤温度在0℃附近且表层液态水含量大于0)土壤湿度不确定性显著;蒸散通量的不确定性随本身绝对值的增大而增大,在相对温暖干燥环境中(表层土壤温度高于280K且表层液态水饱和度小于0.3)其不确定性最高。研究证实,GEP能够辨识CoLM中需优先提高观测精度的关键参数和关键参数化过程,对陆面模拟的参数选定、不确定性评估和模式完善具有重要意义。展开更多
The method to estimate NSSR （net surface shortwave radiation） from LST （land surface temperature） in regional scale is discussed. First, an elliptical model between the time series of normalized LST and NSSR was d...The method to estimate NSSR （net surface shortwave radiation） from LST （land surface temperature） in regional scale is discussed. First, an elliptical model between the time series of normalized LST and NSSR was developed using the daily evolution of LST and NSSR. Second, time series of LST and NSSR were simulated by common land model （CoLM） and were proved to be of high accuracy. On the basis of these, a non-linear least square ellipse fitting using the genetic algorithm method was used to fit the normalized LST and NSSR. Finally, LST was inverted using MODIS （moderate resolution imaging spectroradiometer） data with the split-window algorithm, and the regional NSSR was then estimated with LST and an elliptical model. The validation result shows that the derived average NSSR of 50×50 pixels of MODIS data was quite close to the observed data, and the distribution was reasonable, which indicates that the proposed method was capable of estimating NSSR on a regional scale.展开更多
基金jointly funded by the National Natural Science Foundation of China(GrantNo40775019)Desert Meteorology Science Foundation of China(Grant NoSqj2009012)Project of Key Laboratory of Oasis Ecology(Xinjiang University)Ministry of Education(Grant NoXJDX0206-2009-08)
文摘Improving and validating land surface models based on integrated observations in deserts is one of the challenges in land modeling. Particularly, key parameters and parameterization schemes in desert regions need to be evaluated in-situ to improve the models. In this study, we calibrated the land-surface key parameters and evaluated several formulations or schemes for thermal roughness length （z 0h ） in the common land model （CoLM）. Our parameter calibration and scheme evaluation were based on the observed data during a torrid summer （29 July to 11 September 2009） over the Taklimakan Desert hinterland. First, the importance of the key parameters in the experiment was evaluated based on their physics principles and the significance of these key parameters were further validated using sensitivity test. Second, difference schemes （or physics-based formulas） of z 0h were adopted to simulate the variations of energy-related variables （e.g., sensible heat flux and surface skin temperature） and the simulated variations were then compared with the observed data. Third, the z 0h scheme that performed best （i.e., Y07） was then selected to replace the defaulted one （i.e., Z98）; the revised scheme and the superiority of Y07 over Z98 was further demonstrated by comparing the simulated results with the observed data. Admittedly, the revised model did a relatively poor job of simulating the diurnal variations of surface soil heat flux, and nighttime soil temperature was also underestimated, calling for further improvement of the model for desert regions.
文摘模式评估是模式发展中不可或缺的重要一环。本文利用最新版陆面模式评估软件—ILAMB(International Land Model Benchmarking)对通用陆面模式(The Common Land Model,CoLM)进行客观评估,并与NCAR陆面模式CLM5(Community Land Model version 5)结果进行比较。作为一个陆面模式评估软件,ILAMB能对参与评估的模式变量自动生成诊断图形并对模式性能进行评分。评估结果表明,CoLM总体性能良好,模拟结果与基准数据较为接近。与CLM5相比,CoLM在总初级生产力及水文方面的表现略微逊色,在辐射方面则表现相当,对部分变量如地表向上长波辐射、地表净辐射等的模拟甚至优于CLM5。通过对比CRUNCEPv7和GSWP3v1两种强迫资料发现,它们在气候平均态上具有一定的差异,模式在GSWP3v1强迫下的表现相对较好。CoLM和CLM5在CRUCNEPv7强迫下模拟的潜热通量在亚马逊平原、亚洲东部和南部地区以及北美东部一带正偏差显著,而在GSWP3v1强迫下的模拟则有明显改善。这两个模式对感热通量的模拟在非洲北部、亚洲中部一带均明显偏高。在辐射方面,CoLM模拟的地表向上短波辐射在全球以偏高为主,这在一定程度上造成了地表净辐射的模拟偏低。各组试验模拟的地表向上长波辐射得分相差不大,但在具体的空间分布上有一定的差别。
基金supported by R & D Special Fund for Nonprofit Industry (Meteorology,GYHY200706025),the U.S. Department of Energy,Office of Science,Biological and Environmental ResearchOak Ridge National Laboratory is managed by UT-Battelle,LLC for the U.S. Department of Energy under Contract No. DE-AC05-00OR22725
文摘A terrestrial biogeochemical model （CASACNP） was coupled to a land surface model （the Common Land Model,CoLM） to simulate the dynamics of carbon substrate in soil and its limitation on soil respiration.The combined model,CoLM CASACNP,was able to predict long-term carbon sources and sinks that CoLM alone could not.The coupled model was tested using measurements of belowground respiration and surface fluxes from two forest ecosystems.The combined model simulated reasonably well the diurnal and seasonal variations of net ecosystem carbon exchange,as well as seasonal variation in the soil respiration rate of both the forest sites chosen for this study.However,the agreement between model simulations and actual measurements was poorer under dry conditions.The model should be tested against more measurements before being applied globally to investigate the feedbacks between the carbon cycle and climate change.
文摘利用陆面过程模式Common Land Model(CoLM),选取青藏高原上3个不同下垫面观测站(藏东南站、纳木错站和珠峰站)的观测资料,对这3个野外观测站进行了单点数值模拟试验。根据3个测站的试验数据,对模式中土壤孔隙度和饱和导水率进行了优化,针对青藏高原地区土壤层薄的特点,对模式中土壤分层方案进行了调整。结果表明,调整分层方案后的CoLM模式对3个测站土壤湿度的模拟性能较原分层方案有明显提高,平均偏差均减小0.014以上。但是与观测值相比,藏东南站土壤湿度的模拟整体偏低,纳木错站和珠峰站则整体偏高。对土壤温度而言,3个测站模拟与观测的相关系数都达到了0.9以上,珠峰站偏差较大,调整分层方案后模拟的偏差有一定的改进。模式较好地模拟了3个测站的净辐射、感热通量和潜热通量的日变化和季节变化情况,调整分层方案后潜热通量的改进最为明显。
文摘数据质量问题和模式参数化方案的非完备性是陆面模拟中不确定性的主要来源。本文将高斯误差传播原理(Gaussian Error Propagation,GEP)应用于通用陆面模式(the Common Land Model,CoLM),研究关键的植被和土壤属性参数随机误差在模式中的传播,确定由此类误差导致的CoLM模拟的不确定性。结果表明:(1)基于本研究给定的土壤和植被参数的不确定性,CoLM模拟的表层土壤温度、土壤湿度和植被蒸散通量(植冠蒸腾+地表蒸发)的相对误差分别为0.11%、34.07%和5.58%;砂土和稀疏森林上模拟效果最差。土壤参数随机误差对CoLM模拟的影响高于植被参数,而土壤水文参数(孔隙率、饱和基质势、气孔尺寸分布指数和饱和导水率)对各模拟量不确定性的贡献率均远大于热力参数(饱和反照率和热容)。对于本研究涉及的所有模拟变量而言,最关键的参数均是气孔尺寸分布指数b,这可能与描述基质势与体积水含量关系的函数有关,其次重要的是砂土的孔隙度和粘土的饱和导水率。混交森林上的根深分布和苔原上的动力学粗糙度对蒸散通量贡献显著。本身相对误差大的经验参数对CoLM模拟不确定性的贡献不一定多。(2)干燥条件下(表层液态水饱和度小于0.1)土壤温度的不确定性大;相变发生时刻附近(表层土壤温度在0℃附近且表层液态水含量大于0)土壤湿度不确定性显著;蒸散通量的不确定性随本身绝对值的增大而增大,在相对温暖干燥环境中(表层土壤温度高于280K且表层液态水饱和度小于0.3)其不确定性最高。研究证实,GEP能够辨识CoLM中需优先提高观测精度的关键参数和关键参数化过程,对陆面模拟的参数选定、不确定性评估和模式完善具有重要意义。
基金Supported by the Knowledge Innovation Programs of Chinese Academy of Sciences (XMXX280722)China International Science and Technology Cooperation Project (0819)+1 种基金National Program on Key Basic Research Project (2010CB428800)Wong K C Education Foundation, Hong Kong
文摘The method to estimate NSSR （net surface shortwave radiation） from LST （land surface temperature） in regional scale is discussed. First, an elliptical model between the time series of normalized LST and NSSR was developed using the daily evolution of LST and NSSR. Second, time series of LST and NSSR were simulated by common land model （CoLM） and were proved to be of high accuracy. On the basis of these, a non-linear least square ellipse fitting using the genetic algorithm method was used to fit the normalized LST and NSSR. Finally, LST was inverted using MODIS （moderate resolution imaging spectroradiometer） data with the split-window algorithm, and the regional NSSR was then estimated with LST and an elliptical model. The validation result shows that the derived average NSSR of 50×50 pixels of MODIS data was quite close to the observed data, and the distribution was reasonable, which indicates that the proposed method was capable of estimating NSSR on a regional scale.
