Testing and Improving the Performance of the Common Land Model:A Case Study for the Gobi Landscape

Land surface processes take place on the interface between the earth and atmosphere, exerting significant influences on the weather and climate. Correct modeling of these processes is important to numerical weather forecast and climate prediction. In order to obtain a more thorough understanding of the land surface processes over the Gobi landscape, we evaluated the performance of the Common Land Model(Co LM) at Dunhuang station in Gansu Province of China to determine whether the model formulation, driven by observational data, is capable of simulating surface fluxes over the underlying desert surface. In comparison with the enhanced observation data collected at Dunhuang station over the period 22–28 August 2008, the results showed that the surface albedo simulated by Co LM was larger than that in the observation, and the simulated surface temperature was lower than the observed. After the measured values were used to correct the surface albedo, the solar radiation absorbed by the ground surface was more consistent with the measurements. A new empirical relationship of the surface thermal exchange coefficient rah was used to modify the thermal aerodynamic impedance. The simulated soil surface temperature became significantly closer to the observed value, and the simulated surface sensible heat as well as net radiative fluxes were also improved.     

基于陆面模式基准平台ILAMB对陆面模式CoLM的评估

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。     

Coupling a Terrestrial Biogeochemical Model to the Common Land Model

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.     

通用陆面模式对土壤质地和亮度的敏感性分析

使用前苏联Valdai 1966～1971年的气象观测资料,研究了通用陆面模式(Common Land Model,CoLM)模拟的水分循环和地表通量在12种土壤质地和8种土壤亮度条件下的差异。结果表明,在相同的气象条件下,模拟的热通量对土壤质地和亮度都比较敏感,而地表水文过程只对土壤质地敏感。土壤亮度相同时,相对砂性土壤,粘土含量高的土壤保水性强,土壤湿度、地表蒸发和径流量都比较大（月均最大差值：土壤湿度约为5 kg·m-2,地表蒸发和径流量约为年降水量的7%和1.2 %）,相应地在热通量分配上存在明显差异（月均最大差值为8 W·m-2）;土壤质地相同,亮度由亮变暗时,潜热通量变化很小,地表温度略有升高,而感热通量和净辐射增加显著（月均最大差值为7 W·m-2）。土壤质地和亮度对模拟的影响主要存在于降水少、植被覆盖度低的3～5月。     

Coupling the Common Land Model to ECHAM5 Atmospheric General Circulation Model

The ECHAM5 model is coupled with the widely used Common Land Model(CoLM). ECHAM5 is a state-of-theart atmospheric general circulation model incorporated into the integrated weather and climate model of the Chinese Academy of Meteorological Sciences(CAMS-CSM). Land surface schemes in ECHAM5 are simple and do not provide an adequate representation of the vegetation canopy and snow/frozen soil processes. Two AMIP(Atmospheric Model Intercomparison Project)-type experiments using ECHAM5 and ECHAM5-CoLM are run over 30 yr and the results are compared with reanalysis and observational data. It is found that the pattern of land surface temperature simulated by ECHAM5-CoLM is significantly improved relative to ECHAM5. Specifically, the cold bias over Eurasia is removed and the root-mean-square error is reduced in most regions. The seasonal variation in the zonal mean land surface temperature and the in situ soil temperature at 20-and 80-cm depths are both better simulated by ECHAM5-CoLM. ECHAM5-CoLM produces a more reasonable spatial pattern in the soil moisture content, whereas ECHAM5 predicts much drier soils. The seasonal cycle of soil moisture content from ECHAM5-CoLM is a better match to the observational data in six specific regions. ECHAM5-CoLM reproduces the observed spatial patterns of both sensible and latent heat fluxes. The strong positive bias in precipitation over land is reduced in ECHAM5-CoLM, especially over the southern Tibetan Plateau and middle–lower reaches of the Yangtze River during the summer monsoon rainy season.     

陆面模式中土壤和植被经验参数随机误差的传播研究

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280 K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。     

Preliminary Assessment of the Common Land Model Coupled with the IAP Dynamic Global Vegetation Model

The Common Land Model（CoLM） was coupled with the IAP Dynamic Global Vegetation Model（IAPDGVM）, and the performance of this combined CoLMIAP model was evaluated. Offline simulations using both the original Common Land Model（CoLM-LPJ） and CoLM-IAP were conducted. The CoLM-IAP coupled model showed a significant improvement over CoLMLPJ, as the deciduous tree distribution decreased over temperate and boreal regions, while the distribution of evergreen trees increased over the tropics. Some biases in CoLM-LPJ were preserved, including the overestimation of evergreen trees in tropical savanna, the underestimation of boreal evergreen trees, and the absence of boreal shrubs. However, most of these biases did not exist in a further coupled simulation of IAP-DGVM with the Community Land Model（CLM）, for which the parameters of IAP-DGVM were optimized. This implies that further improvement is needed to deal with the differences between CoLM and CLM in parameterizations of landbased physical and biochemical processes.     

CoLM模式地表温度变分同化研究

本文采用变分方法对通用陆面模式 (CoLM) 中的地表温度进行同化.同化伴随约束条件采用CoLM模式中的地表及植被能量平衡方程,调节因子采用裸土及植被蒸发比.采用美国通量网 (AmeriFlux) 中的Bonville站数据对同化方法进行了单点验证,验证结果表明同化后地表温度以及蒸散结果更加接近于实测值.选取中国华北地区对同化方法进行区域验证,结果显示每天仅采用白天一次观测值对地表温度进行同化的方法是有效的.通过对同化前后地表温度误差直方图比较可以发现,在有MODIS观测值的区域,同化后白天地表温度误差大大降低,同时,同化后地表蒸散空间分布图也发生了变化.单点验证以及区域验证结果都表明了变分同化方法是可靠的.变分同化方法可以改进陆面模式模拟结果,对于地表过程研究中的植被生态、水文等研究具有重要意义,同时,陆面模式可以与数值预报模式进行耦合,改进数值预报结果.     

基于FLUXNET数据集对陆面模式CoLM能量通量的单点评估

模式评估是模式发展中的重要一环。本文利用来自FLUXNET2015数据集的30个站点的涡动相关系统观测数据,重点关注能量通量,对通用陆面模式（Common Land Model version 2014,CoLM2014）在不同典型下垫面的模拟能力进行评估。结果表明,模式总体上能抓住感热、潜热和净辐射通量在日、季节和年平均等不同时间尺度上的变化特征,对感热、潜热和净辐射通量都有较好的模拟能力,净辐射的模拟效果最好,潜热通量次之。季节变化模拟中,感热、潜热通量在夏季不同植被型下站点的空间离散程度大于冬季,不同站点间模拟效果相差较大,净辐射多站点标准差变化幅度要小于感热、潜热,不同站点间模拟效果偏差较小。CoLM在常绿针叶林、稀树林地、草地、农田模拟感热、潜热通量的效果相对较好,在永久湿地、落叶阔叶林下模拟感热通量较差。本研究对CoLM2014在未来的改进和发展中提供了有用的参考。     

复杂陆面模式与中期数值天气预报模式的耦合

将复杂陆面模式(CLM3)耦合到中期数值预报模式YHMPT106中,替换原来的简单3层陆面过程参数化方案.对比分析表明,较为复杂的陆面过程模式CLM3与中期预报业务模式YHMPT106的耦合是成功的,耦合模式可稳定运行,其预报效果也好.这个试验亦为将来气候预测模式中使用精细的大气环流模式提供了有用的经验.     

Land use and local climate: A case study near Santa Cruz, Bolivia

Summary The Tierras Bajas regions of eastern Santa Cruz, Bolivia have undergone among the most rapid rates of concentrated deforestation during the 1980s and 1990s. We investigate the sensitivity of local climate to these land cover changes as observed from Landsat images acquired between 1975 and 1999. The Simple Biosphere model (SiB2) is used to assess the effects of both morphological and physiological changes in vegetation and the implications for fluxes of water, energy and carbon between the vegetation and the atmosphere during the rainy season.Conversion from tropical forest to cropland implicates morphological changes in vegetation as the primary drivers for a daily maximum warming of about 2°C and a slight nighttime cooling, suggesting that clearing of tropical forests for agricultural use may increase the diurnal temperature range, mainly by increasing the maximum temperature. On the other hand, the conversion of wooded grassland to cropland resulted in a similar daily warming and drying but exclusively due to vegetation physiological activity.The area-averaged monthly mean response for each conversion type resulted in a warming of about 0.6°C for the conversion of broadleaf evergreen and 1.2°C for conversion of wooded grassland. These temperature differences represent an augmentation in the local heat source associated with a reduction in evapotranspiration due to land cover conversion and do not reflect variations forced by changes in atmospheric circulation.When averaged over the entire domain, the effect of landscape conversion results in a reduction of the latent heat flux and an increase in sensible heat flux, producing a large-scale apparent heat source of 0.5°C during January. This warming is in line with an increasing trend observed in monthly mean temperature in Santa Cruz, Bolivia during the same period.     

Use of adjoint sensitivity analysis to diagnose the CMC global analysis performance: A case study

Abstract

The sensitivity of forecast errors to initial conditions obtained from the adjoint of a numerical weather prediction model provides new insights into the analysis errors responsible for poor short‐range to mediumrange forecasts. In recent years, we have developed a sensitivity analysis system based on the tangent linear and adjoint of the Global Environmental Multiscale model, in which an iterative procedure minimizing the shortrange forecast errors leads to the so‐called key analysis errors. These errors are dominated by a small number of atmospheric structures, those growing the most rapidly. The algorithm has proven very useful in understanding improvements to the three‐dimensional variational data assimilation (3D‐Var) system implemented in the Canadian Meteorological Centre operational suite in December 2001. The main difference between the old and the new 3D‐Var systems is the assimilation of temperature and surface pressure from surface and upper air stations as opposed to geopotential heights, additional Tiros Operational Vertical Sounder channels, new sources of observations such as temperature observations from aircraft, and wind and temperature from dropsondes.

In this paper, we examine key analysis errors of the old 3D‐Var analysis, which led to a very poor 3‐day forecast of a severe winter storm that struck eastern Canada on 10 February 2001. In this case, the same 3‐day forecast from the new 3D‐Var analysis is much better. We compare the difference between the two 3D‐Var analyses and the key analysis errors. We find that the main key analysis errors, in terms of potential vorticity, is located along the west shore of southern California and is characterized by a strong baroclinic structure that has its maximum amplitude in the upper part of the troposphere. The difference between the two analyses is three times more energetic than the key analysis errors and its structure is much more barotropic in the troposphere. However, we show that the large improvement in the new 3D‐Var analysis stems mainly from the reduction of the analysis errors that project onto the key analysis structures.     

通用陆面模式CLM在东亚不同典型下垫面的验证试验

利用野外观测资料,考察了通用陆面过程模式(CLM)对东亚地区3种典型下垫面(高原稀疏植被下垫面、森林、水田)的模拟能力.验证结果表明,在高原稀疏植被下垫面,CLM模拟的地表气温跟实测较为接近,同时CLM还可以较好地模拟出土壤温度随时间和深度的变化特征,但模式模拟的地面温度的幅值跟观测相比显著偏小;对于能量通量而言,除感热通量外,CLM所模拟出的其它能量通量的变化均与观测实况比较一致.对于淮河流域的森林下垫面,CLM所模拟出陆气间的各能量通量均与实测较为接近,尤以夏季(8月份)的模拟性能最好.对于水田下垫面,CLM模式较好地模拟出了各能量通量的主要变化特征及其季节差异,如水田的净辐射以及潜热通量夏季最大,而感热通量则是秋季最大等.     

陆面过程模型CoLM与区域气候模式RegCM3的耦合及初步评估

陆面过程通过影响陆面和大气之间物质（如,水分）和能量的交换影响气候, 其参数化方案对数值天气预报、全球及区域气候模拟有重要影响。本研究利用对生物物理、生物化学过程考虑更全面的陆面模式Common Land Model(CoLM) 替代区域气候模式RegCM3原有的陆面模式BATS, 发展了耦合区域气候模式C－RegCM3; 将其应用于东亚地区典型洪涝年份夏季气候模拟以进行评估, 结果表明新耦合的模式C－RegCM3能合理模拟大尺度环流场、近地表气温和降水的分布特征, 对西北半干旱地区降水模拟比RegCM3有所改进。通过利用区域气候模式C－RegCM3及RegCM3对地表能量和水文过程模拟结果的比较, 发现在半干旱、半湿润过渡区C－RegCM3模拟的潜热增大、感热减小; 模拟的地表吸收太阳辐射差异较明显的地区位于模式模拟的主要雨区; C-RegCM3在上述过渡区模拟的夏季地表土壤湿度比RegCM3偏干, 这与它在过渡区降水模拟偏少、蒸散发模拟偏大相对应, 体现了该模式在半干旱、半湿润过渡带模拟出比RegCM3更明显的局地土壤湿度－降水－蒸散发之间的正反馈作用。     

陆面过程模式BCC_AVIM中地表覆盖数据现状

地表覆盖是陆面和气候模式中的一个重要基础数据。以陆面过程模式BCC_AVIM为例,介绍模式中的地表覆盖数据变量、数据分辨率、不同类型数据的来源,重点比较分类方法差异巨大且类型众多的植被覆盖。综述比较了国际和国内常用的几套全球地表覆盖数据的来源、分类系统和分类方法以及空间分辨率,根据陆面过程模式的地表覆盖数据需求,确定不同全球土地覆盖数据在模式中的应用方法,讨论分析了全球地表覆盖产品在模式应用中存在的差距,提出不同遥感数据产品之间一致性较差的可能解决方案,探讨遥感数据产品在模式中应用的可能方式,以期更好地发挥全球地表覆盖数据产品的作用。     

一个简单的陆面过程模式

本模式为针对大气环流模式所发展的一个简单的陆面过程模式，它包含:（1）地表温度计算，（2）冠层叶面贮水量和土壤湿度计算，（3）陆面与大气之间的水分和能量交换。对于表面温度和含水量的计算，采用的是联立求解计算方案，即耦合计算。植被冠层叶面的辐射特性和冠层形态对冠层中的辐射交换的影响得到有效和尽可能简单的模拟。另外，植被的气孔阻抗、表面与大气之间的水热交换通量和土壤中的水热输导作了较为细致的描写。利用此模式开展了对两个不同覆盖类型的陆面过程的模拟，模拟和观测的表面通量、温度和湿度较为相近。     

Climate change and the world predicament: A case study for interdisciplinary research

The relationship between climatic change and issues of population, food, resources, environment and the human condition i.e., the world predicament, are explored. It is concluded that society is dangerously vulnerable to natural climatic variability at times of depleted food reserves (such as now) and that massive use of technologies (especially energy) to improve the human condition could well cause significant climatic change as early as the year 2000. Therefore, these problems cannot be addressed in the sole context of disciplinary research, and the obstacles and opportunities for interdisciplinary research at academic institutions are explored. Criteria for interdisciplinary research quality review are suggested, and contrasted to traditional peer review processes.The National Center for Atmospheric Research is sponsored by the National Science Foundation.     

Integrating agriculture and climate change mitigation at landscape scale: Implications from an Australian case study

Rural and regional hinterlands provide the ecosystem service needs for increasingly urbanised communities across the globe. These inter-related ecosystem services provide key opportunities in securing climate change mitigation and adaptation. Their integrated management in the face of climate change, however, can be confounded by fragmentation within the complex institutional arrangements concerned with natural resource management. This suggests the need for a more systemic approach to continuous improvement in the integrated and adaptive governance of natural resources.This paper explores the theoretical foundations for integrated natural resource management and reviews positive systemic improvements that have been emerging in the Australian context. In setting clear theoretical foundations, the paper explores both functional and structural aspects of natural resource governance systems. Functional considerations include issues of connectivity, knowledge use and capacity within the natural resource decision making environment. Structural considerations refer to the institutions and processes that undertake planning through to implementation, monitoring and evaluation.From this foundation, we review the last decade of emerging initiatives in governance regarding the integration of agriculture and forests across the entire Australian landscape. This includes the shift towards more devolved regional approaches to integrated natural resource management and recent progress towards the use of terrestrial carbon at landscape scale to assist in climate change mitigation and adaptation. These developments, however, have also been tempered by a significant raft of new landscape-scale regulations that have tended to be based on a more centralist philosophy that landowners should be providing ecosystem services for the wider public good without substantive reward.Given this background, we explore a case study of efforts taken to integrate the management of landscape-scale agro-ecological services in the Wet Tropics of tropical Queensland. This is being achieved primarily through the integration of regional natural resource management planning and the development of aggregated terrestrial carbon offset products at a whole of landscape scale via the Degree Celsius initiative. Finally, the paper teases out the barriers and opportunities being experienced, leading to discussion about the global implications for managing climate change, income generation and poverty reduction.     

A New Approach for Parameter Optimization in Land Surface Model

In this study,a new parameter optimization method was used to investigate the expansion of conditional nonlinear optimal perturbation (CNOP) in a land surface model (LSM) using long-term enhanced field observations at Tongyu station in Jilin Province,China,combined with a sophisticated LSM (common land model,CoLM).Tongyu station is a reference site of the international Coordinated Energy and Water Cycle Observations Project (CEOP) that has studied semiarid regions that have undergone desertification,salination,and degradation since late 1960s.In this study,three key land-surface parameters,namely,soil color,proportion of sand or clay in soil,and leaf-area index were chosen as parameters to be optimized.Our study comprised three experiments:First,a single-parameter optimization was performed,while the second and third experiments performed triple-and six-parameter optimizations,respectively.Notable improvements in simulating sensible heat flux (SH),latent heat flux (LH),soil temperature (TS),and moisture (MS) at shallow layers were achieved using the optimized parameters.The multiple-parameter optimization experiments performed better than the single-parameter experminent.All results demonstrate that the CNOP method can be used to optimize expanded parameters in an LSM.Moreover,clear mathematical meaning,simple design structure,and rapid computability give this method great potential for further application to parameter optimization in LSMs.     

东疆黑戈壁陆面过程参数及陆面模式离线模拟

新疆东部黑戈壁气候恶劣、人迹罕至,是具有黑色砾石下垫面的生态脆弱区。利用东疆哈密戈壁陆气相互作用站2018年全年观测资料,给出该戈壁地表动力学与热力学粗糙度、比辐射率和地表反照率等陆面过程特征参数,并将这些参数代入Noah模式对该戈壁热通量、地表温度及土壤温湿度进行模拟。结果表明：（1）东疆黑戈壁下垫面动力学粗糙度为1.13×10-3 m,热力学粗糙度为0.32×10-3 m,比辐射率为0.905。（2）地表反照率日变化呈早晚高,中午低的“U”型曲线。12月因地面积雪,反照率最高,年内极大值出现在12月8日,为0.79,年均反照率为0.29。地表反照率关于太阳高度角的参数化方案为：α=0.78-0.47×(1-e^((-h)/1.12)),地表反照率关于5 cm土壤湿度的参数化方案为α=0.28-0.136w_s。（3）将改进后的陆面过程参数带入Noah模式,大大提高了模式在戈壁区域的模拟能力。