玉米冠层辐射传输参数优化对陆气通量模拟的影响

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蔡福, 明惠青, 纪瑞鹏, 冯锐, 米娜, 赵先丽, 张玉书. 玉米冠层辐射传输参数优化对陆气通量模拟的影响. 地球科学进展, 2014, 29(5): 598-607[Cai Fu, Ming Huiqing, Ji Ruipeng, Feng Rui, Mi Na, Zhao XianLi, Zhang Yushu. Effects of Maize Canopy Radiative Transfer Parameters Optimization on Simulating Land-Atmosphere Flux Exchanges. Advances in Earth Science, 2014, 29(5): 598-607] 复制到剪切板

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玉米冠层辐射传输参数优化对陆气通量模拟的影响

蔡福¹, 明惠青², 纪瑞鹏¹, 冯锐¹, 米娜¹, 赵先丽¹, 张玉书¹

1.中国气象局沈阳大气环境研究所,辽宁沈阳 110166

2.辽宁省气象服务中心,辽宁沈阳 110166

张玉书(1963-),女,辽宁黑山人,正研级高级工程师,主要从事应用气象、3S技术应用研究. E-mail:yushuzhang@126.com

蔡福(1980-)，男，辽宁海城人，副研究员，主要从事应用气象、陆面过程及模型模拟研究. E-mail:caifu_80@163.com

基金:国家自然科学基金项目“东北春玉米根系吸水过程的控制机制及其参数方案改进对陆—气通量模拟的影响”(编号：41305058)资助;

摘要

设置合理的冠层辐射传输参数有利于地表能量过程的真实表达,将对改善陆面过程模型模拟精度起到重要作用。基于2008年和2012年锦州农田生态系统的通量、气象及生物因子连续观测,分析了玉米农田叶面积指数、植被覆盖度、平均叶倾角、叶片反射率和透射率动态变化规律及各因子间的关系,对CoLM模型辐射传输参数进行优化,并对模型优化效果进行定量评价。结果表明：叶面积指数与植被覆盖度和平均叶倾角分别呈幂函数和二次函数关系；平均叶倾角的参数优化对模型模拟几乎没有影响；叶片反射率和透射率优化后,冠层反照率模拟精度明显提高；净辐射、感热模拟值对实测值解释能力分别提高0.6%和4.0%,Nash-Sutcliffes系数增大0.008和0.028,相对均方差(RRMSE)减小0.068和0.050；潜热模拟精度改善程度小于感热,地表热通量未表现出改善。

关键词: 玉米农田生态系统; 辐射传输过程; 参数改进; CoLM模型; 陆面过程模拟

中图分类号:P935.1 文献标志码:A 文章编号:1001-8166(2014)05-0598-10

Effects of Maize Canopy Radiative Transfer Parameters Optimization on Simulating Land-Atmosphere Flux Exchanges

Cai Fu¹, Ming Huiqing², Ji Ruipeng¹, Feng Rui¹, Mi Na¹, Zhao XianLi¹, Zhang Yushu¹

1.Institute of Atmospheric Environment, China Meteorological Administration, Shenyang 110166,China

2.Liaoning Province Meteorological Service Center, Shenyang 110166,China )

Fund:

Abstract

A reasonable canopy radiative transfer parameters setting will play an important role in improving the simulation performance of land surface process model. This research was to investigate and assess the effects of optimized radiative transfer parameters in CoLM model on simulating land-atmosphere flux exchanges. Firstly, based on continuous observations of land-atmosphere flux exchanges, meteorological and biological elements from 2008 and 2012 at Jinzhou agricultural ecosystem research station, dynamic rules of maize field Leaf Area Index(LAI), fraction of vegetation coverage(Fveg), Mean Leaf Angle(MLA), leaf reflectivity and transmissivity and their inter relationships were analyzed. Secondly, radiative transfer parameters in CoLM model were optimized with above the rules and relationships. Lastly, the effects of parameters optimization were quantificationally assessed with the criteria including Nash Sutcliffe(NS) and Relative Root Mean Square Error(RRMSE). The results showed that LAI had power and quadratic relationships withFveg and MLA, respectively. Model simulation precision was hardly any affected with optimization of MLA. On the contrary, with leaf reflectivity and transmissivity optimized, canopy albedo simulation precision was obviously increased, which improved the simulation performance of CoLM for net radiation and sensible heat flux with the explanatory ability of simulations to observations increased 0.6 and 4.0 percent, NS increasing 0.008 and 0.028 as well asRRMSE decreasing 0.068 and 0.050, respectively. However, simulation performance of latent heat flux improved lesser than sensible heat flux. Soil heat flux simulation was hardly improved.

Keyword: Maize agroecosystem; Radiative transfer process; Improving parameters; CoLM model; Land surface processes simulating.

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1 引言

植被在陆面过程中扮演着重要角色,它的存在及季节变化通过影响地—气系统的能量、物质和动量交换对陆面过程乃至区域气候产生重要影响^{[ 1~ 3]}。植被冠层内辐射传输过程直接影响地表反照率的模拟。地表反照率是计算地表辐射平衡的重要参数,通过直接控制太阳辐射在地表和大气之间的分配影响植物光合、呼吸等多种生物化学过程^{[ 4]},其估算精度直接影响地气热量交换和地表温度计算的准确性^{[ 5]},从而影响陆面过程或气候模式模拟的准确性。相对于裸土,植被下垫面地表反照率影响因子较多且机制复杂,很多研究集中在下垫面性质变化相对较小的多年生常绿或落叶森林^{[ 6]},而一年生如草地、农田等植被反照率研究相对较少^{[ 7, 8]}。张果等^{[ 9]}、蔡福等^{[ 10]}研究发现,叶面积指数(LAI)和植被覆盖度(F_veg)对植被反照率影响明显。随着第三代陆面过程模型如美国国家大气研究中心的陆面过程模型(NCAR LSM)、简单生物圈模型第二版(SiB2)^{[ 11]}、SiB3^{[ 12, 13]}、通用陆面过程模型CLM3^{[ 14]}、CoLM^{[ 15, 16]}等的不断涌现,植被的生理生化甚至是各类化学元素(C,N)的循环过程被考虑得更为精细,模型模拟精度得到显著提升。众多模型中,戴永久等^{[ 15]}发展的CoLM是国际上最为先进的模型之一,结合了公认较好的LSM,BATS,IAP94 3个模式的特点^{[ 17]},广泛应用于气候模式^{[ 18]}。辛羽飞等^{[ 19]}、王澄海等^{[ 20]}、罗斯琼等^{[ 21]}、宋耀明等^{[ 22]}和肖瑶等^{[ 23]}研究证明该模型对不同下垫面类型的地表能量平衡及陆气通量的日、季变化都能实现较好的模拟。CoLM模型计算植被冠层反照率采用二流辐射传输方案^{[ 24]},决定冠层结构和性质且影响辐射传输的关键参数除了LAI和F_veg以外,还有叶片反射率、透射率及叶片倾角,它们在现有辐射传输方案中被赋为定值,这种赋值方式是否合理,模型对它们的改变是否敏感以及更为真实的赋值能否提高模型模拟精度,关于此类问题的研究鲜有报道。玉米农田因其冠层高度、LAI和F_veg等下垫面结构和状态随生育期的较大变化使辐射、水分、热量的分配和传输等一系列物理过程不断变化,加之分布广泛,可对局地大气环流和区域气候产生影响,在陆面过程研究中是非常重要的植被类型^{[ 25]},对其开展陆面过程及模型参数研究不但有助于深入理解陆气相互作用规律,还将为进一步加深农业生产对气候变化响应规律的认识提供参考^{[ 26, 27]}。目前, 利用CoLM模型对玉米农田进行陆面过程模拟以及利用二流辐射传输方案对玉米冠层辐射传输过程进行模拟的研究都很少,因此,很有必要通过连续实测资料对模型参数进行验证和优化。

综上所述,本研究拟利用锦州农田生态系统野外观测站连续观测的玉米叶片反射率、透射率、叶片倾角等植被冠层参数对CoLM模型中辐射传输参数进行优化,定量评价参数优化对玉米农田水热通量模拟的影响,以期为陆面过程模型植被冠层参数方案的完善提供参考,也为开展玉米农田下垫面陆气相互作用规律研究提供依据。

2 资料和方法

2.1 研究地点

锦州农田生态系统野外观测站位于东北玉米带(41°49´N,121°12´E,海拔17 m),属典型温带季风型气候区,1971—2000年30年年平均气温9.5 ℃,1月平均气温-8.0 ℃,7月平均气温24.4 ℃,年降水量565.9 mm,玉米生育期为5~9月,土壤为典型棕壤。该站建有涡度相关观测系统和气象梯度观测系统,可实现不同高度各类气象要素和地表通量的观测^{25, 28]}。

2.2 资料来源

于2012年4月10日、4月30日、5月10日、5月20日在研究地点进行玉米分期播种,从出苗开始,每隔10天利用LAI2200冠层分析仪进行LAI和平均叶倾角的测定,利用冠层照相机进行F_veg的测定,利用FieldSpec®ProJR分光光谱分析仪进行叶片反射率和透射率测定,考虑到人为和采样误差,对异常数据进行剔除。

利用2008年气象梯度观测系统测得的气温、比湿、降水、风速、太阳总辐射、向下长波辐射、气压等气象要素以及LAI和F_veg对CoLM模型进行驱动。通量观测系统测得的感热通量、潜热通量以及净辐射、土壤热通量资料用于模拟结果验证,上述资料均为通过湿度修正、高频衰减修正和WPL校正等质量控制后的30 mins平均值^{[ 28, 29]}。2008年逐日LAI由王玲等^{[ 30]}所建立的相对积温方法利用玉米各生育期LAI实测数据和日平均气温资料求得^{[ 31]},利用2012年测得的LAI和F_veg所建立的关系和所求得的2008年逐日LAI可计算得到该年逐日F_veg值。

2.3 试验设计

本研究设计3次试验,即原模型引入逐日LAI和F_veg进行模拟的对照试验,把在对照试验基础上引入动态平均叶倾角进行模拟定义为改进试验1,在对照试验基础上优化叶片反射率和透射率进行模拟定义为改进试验2。利用2008年全年资料对模型进行连续10次起转(spin-up)独立离线(off-line)数值模拟,确保各种陆面参量趋于稳定,考虑玉米生育期在5~9月,因此本研究只针对该时段第10次模拟结果进行模型模拟精度比较。

2.4 模型介绍

CoLM 模型精细地考虑了陆面的生态、水文等过程, 对土壤—植被—积雪—大气之间能量与水分的传输进行了合理的描述,包括一层可以实现光合作用的植被和一个底部达到3.43 m深的10层不均匀的垂直土壤及5层积雪。计算叶面温度和气孔阻抗采用双大叶模型；在解决植被反照率产生的奇异点中采用二流近似, 并且在计算辐射时区分了植被的阴、阳面；计算叶面温度采用新迭代算法；计算叶面截留水量时对对流降水和大尺度降水分开处理；考虑了冠层下的湍流传输；土壤水、热传导过程考虑了土壤基岩厚度；考虑了地表径流和次地表径流；考虑了土壤中植物根的分布和水压对植被抽吸土壤水的影响。

模型中冠层辐射传输基本方程为:

I↑和 I↓分别是向上和向下的辐射通量, K=G(μ)/μ为冠层消光系数, μ为太阳天顶角的余弦值, 为μ的均值, 为叶片散射率, 和分别为叶片反射率和透射率, β和 β₀分别为散射与直射辐射参数, L为叶面积指数, S为茎面积指数。 G(μ)=ϕ₁+ϕ₂ μ,当时, , , 为叶角分布与球型分布的偏离指数,当为+1时代表叶片水平,-1时叶片垂直, , 为平均叶倾角。由辐射基本方程可以看出,叶片反射率和透射率直接影响向上和向下辐射通量的比例,进而影响辐射平衡;而平均叶倾角通过影响G函数来影响冠层消光系数,进而对辐射平衡加以调控。它们在辐射传输过程中所起的作用到底有多大,辐射传输对其是否敏感,将通过以下研究进行深入探讨。

2.5 模型模拟精度验证方法

为更直观比较模型对各输出变量的模拟精度,引入相对均方差(RRMSE)^{[ 32]}和模型效率系数(Nash-Sutcliffe,NS)^{[ 25]}作为判断指标。其中,RRMSE代表模拟与观测间的相对偏差；NS用于评价模型的效果,从负无穷大到1,当模拟与观测之间的方差超过观测方差,则NS<0;当模拟与观测之间方差趋近于0,即NS趋近于1,说明模型很好地模拟了观测值的变化。表达式分别为：

, ,

式中, m为模拟值, o为实测值, 为 o均值, n为样本数。

3 结果

3.1 LAI与F_veg的关系

蔡福等^{[ 10]}(2011c)研究表明LAI与F_veg在玉米拔节前呈对数关系,拔节后呈指数关系,但由于采用样本数较少,所确定的关系不确定性很大,本研究在2008年观测资料基础上在2012年又开展了一些针对性观测,累计样本数26个,以期更为准确地表达二者关系。由图1可见,指数、对数和幂函数3种关系都达到显著性水平(P<0.05),但LAI与F_veg为幂函数关系时拟合相关系数最大,达到极显著水平(P<0.001)。通过确立二者关系,代入逐日LAI可实现F_veg的动态模拟。

CoLM原模型中玉米平均叶倾角被设定为69.5°,通过观测发现(图2),随着玉米生育期的变化平均叶倾角介于30°~85°间变化,与LAI呈二次曲线关系,表达式为：

A_ML=-2.5795I_LA²+5.227I_LA+45.205, n=132, R²=0.3225, P<0.0001 (1)

式中：A_ML为平均叶倾角,I_LA为LAI。平均叶倾角最大值出现在LAI为3前后,利用与LAI的二次曲线关系,可实现平均叶倾角的动态模拟。

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	图1 LAI与F_veg的关系Fig.1 Relationship between leaf area index and fraction of vegetation coverage

3.2 平均叶倾角与LAI的关系

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	图2 平均叶倾角与LAI的关系Fig.2 Relationship between mean leaf angle and leaf area index

3.3 叶片反射率和透射率

图3给出了可见光和近红外波段玉米不同生育阶段上层和下层叶片反射率和透射率的动态变化情况。由图3a可见,可见光波段叶片反射率随着生育进程呈增大趋势,变化范围一般介于0.06~0.09之间,下层叶片反射率略大于上层,这种差异随叶龄增大而增大。玉米叶片反射率在生育后期偏大主要是由于叶片的枯黄和死亡所致,大部分生育时期都明显小于模型设定值0.11。就透射率而言,玉米成熟前上层叶片透射率大于下层,在玉米生长前期(拔节前)和后期(成熟后)这种差异相对较大。玉米成熟后,下层叶片透射率反而大于上层,原因是此时下层叶片已完全干枯,基本无叶绿素,对光的吸收很小,使大部分光线透射。从整个生育期来看,在叶片枯黄前叶片透射率变化趋势不明显,与模型设定值0.07相比明显偏小。近红外波段(图3b),上下层叶片反射率和透射率差异很小,几乎不随发育期变化而变化,变化范围在0.3~0.4之间,与模型设定反射率0.58和透射率0.25相差较大。

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	图3 不同波段玉米叶片反射率和透射率与模型值对比((a)可见光；(b)近红外)Fig.3 Comparison of leaf reflectivity and transmissivity in different wave-bands between observed and model values: (a)visible light; (b)near-infrared rays

3.4 辐射传输参数改进对陆气通量模拟的影响

利用2008年梯度观测资料并引入逐日LAI和F_veg对CoLM模型进行驱动,模拟结果作为对照；在此基础上利用平均叶倾角与LAI的二次曲线关系(1)式,实现平均叶倾角的动态参数化,模拟结果定义为改进1；在对照基础上利用实测叶片反射率和透射率替换原模型设定值,模拟结果定义为改进2。考虑到影响叶片反射率和透射率的因素的复杂性,这里对玉米生育期内实测值求平均,具体赋值见表1。

3.4.1 辐射传输参数改进对冠层反照率模拟的影响

图4为改进和对照试验模拟的冠层反照率与实测值各月日动态对比情况。5月大部分时段植被覆盖度很小,下垫面以裸土为主,CoLM模型对裸土反照率设定为常数,且没有进行考虑太阳高度的日动态处理,在此基础上进行的叶片倾角、反射率和透射率的改进还没有得到体现,因此改进效果不明显。从6月开始,随着冠层覆盖度逐渐增大,冠层参数对辐射传输的作用增大,通过比较发现,平均叶倾

表1 反射率与透射率优化前后对比 Table1 Comparison of leaf reflectivity and transmissivity between before and after parameters optimization

角的改善对反照率改进作用不明显,分析原因认为：从图２可知,当LAI大于2时,平均叶倾角与原模型值差异在10°以内,这种较小范围内的变化可能不足以影响辐射传输过程；而当LAI小于2时,玉米冠层植被覆盖度仅约为0.5,土壤对辐射传输过程影响还很大,虽然此时平均叶倾角与模型值有较大差异,但由于冠层在辐射传输过程中的作用很小,导致平均叶倾角较大幅度优化对辐射过程改进仍不明显。相比之下,反射率和透射率的改进对冠层反照率模拟改善作用更为明显,尤其在7,8月,参数改进已使反照率模拟值十分接近实测值,9月由于玉米植株开始进入成熟,上下层叶片枯黄进度不同,增大了模型对活叶与死叶判断的不确定性,因此导致冠层反照率模拟误差较7,8 月偏大,但参数改进的作用仍很明显,与对照相比模拟精度有了很大提升。

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	图4 冠层反照率对照和改进试验模拟值与实测值各月平均日动态对比Obs.实测；ref.对照；imp1.改进1；imp2.改进2(下同)Fig.4 Comparison of diurnal dynamics of monthly mean albedo between observed and simulated values from controlled and improved testsObs.observation;ref,reference;imp1.firstly improved;imp2.secondly improved(the same below)

3.4.2 辐射传输参数改进对辐射模拟的影响

从反照率模拟精度比较中发现,平均叶倾角优化对反照率模拟几乎没有改善作用,因此在以下分析中对改进1试验结果不做比较。从各月净辐射平均日变化模拟值与实测值对比情况看(图5),除5月外,其他各月改进2模拟值较对照都不同程度有所改善,7,8月改进更为明显。总体上看,生长季内净辐射与

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	图5 各月净辐射(Nr)平均日变化模拟精度比较Fig.5 Comparison of diurnal dynamics of monthly mean net radiation between observed and simulated values from controlled and improved tests

反照率改进情况相对应。从生长季内拟合精度来看(图6),参数改进后拟合相关系数大于对照,拟合趋势系数更接近1,模拟值对实测值的解释能力提高0.6%,表明叶片反射率和透射率的优化对辐射传输过程起到明显的改进作用。

从感热月平均日动态模拟值与实测值比较情况看(图7a),由于5,6月净辐射在参数优化后模拟精度改善不明显,导致感热的模拟几乎没有得到改进,而7,8月模拟精度提高明显。9月在参数优化后感热模拟误差反而增大,分析其原因认为,原模型净辐射模拟值较实测值低估的情况下感热却有所高估,参数优化后净辐射模拟值大于原模型且更接近于实测值,而潜热和土壤热通量在该月模拟精度都几乎没有改善,使净辐射增大的部分反映在感热的增大上,这与原本原模型中感热的高估叠加,使感热高估幅度进一步增大,进而导致模型优化后误差增大。究其最终原因,还是原模型在9月对感热高估所致,而感热的高估则主要由潜热的明显低估所造成,潜热的低估则由土壤湿度的不真实模拟引起^{[ 29, 33]}。从潜热模拟情况看(图7b),参数优化的改进作用非常有限,尤其对9月原模型较大的模拟误差没有丝毫的改善,表明辐射参数优化对潜热模拟影响较小。对于土壤热通量的模拟(图7c),参数优化几乎没有改进作用。

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	图6 生长季净辐射模拟值对实测值拟合精度的比较Fig.6 Comparison of the fitting precision of simulation for observation of net radiation in growing season between controlled and improved tests

3.4.3 辐射传输参数改进对热通量模拟的影响

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	图7 各月平均日变化模拟值与实测值的比较(a)感热(H); (b)潜热(LE); (c)土壤热通量(G)Fig.7 Comparison of diurnal dynamics of monthly mean between observed and simulated values from controlled and improved tests(a)Sensible; (b)Latent; (c)Soil heat fluxes

图8

生长季感热(H)、潜热(LE)模拟值对实测值拟合精度的比较

Fig.8

Comparison of the fitting precision of simulation for observation of sensible and latent heat fluxes in growing season between controlled and improved tests

从整个生长季情况来看(图8),参数优化后,感热模拟值对实测值的拟和相关系数有所增大,解释能力提高约4%,且拟和趋势系数更接近1。潜热模拟值对实测值的拟合趋势系数更接近1,但拟合相关系数略有减小,模拟改进情况不明显。土壤热通量模拟值对实测值的拟合精度没有改善。

3.5 模型模拟精度定量比较

利用NS和RRMSE２种判断模型精度的指标对模型参数优化后的改进作用进行评价,净辐射的NS提高约0.008,RRMSE减小0.068,在原模型对其有较高模拟精度的前提下,参数优化能进一步降低误差,表明参数优化作用十分明显。感热的NS提高0.028,RRMSE减小0.050。潜热NS提高0.013,RRMSE减小0.007。进一步证明感热模拟精度提高更为明显。

表2 模型模拟精度比较 Table 2 Comparisons of simulation accuracy between original and modified models

4 结论和讨论

通过对玉米整个发育期LAI、植被覆盖度、平均叶倾角、叶片反射率和透射率等与辐射传输有关参数的动态观测,分析各参数动态变化规律并确立参数间关系,对CoLM模型相应参数进行优化,通过比较模拟值与实测值拟合相关系数、相对均方差(RRMSE)和模型效率系数(NS)等指标对参数优化后模型模拟精度进行评价,得出以下几点结论：

①玉米农田LAI与植被覆盖度呈幂函数关系,与平均叶倾角呈二次函数关系。②CoLM模型中玉米农田平均叶倾角、叶片反射率和透射率等参数设置与实际情况差异较大,各参数比实测值不同程度偏大。③平均叶倾角在模型中为不敏感参数,其参数优化对模型模拟几乎没有影响。④叶片反射率和透射率在辐射传输过程中起到重要作用,在模型中对其优化可明显提高冠层反照率的模拟精度,进而使净辐射模拟得到改善,模拟值对实测值解释能力提高0.6%,NS增大0.008,RRMSE减小了0.068。⑤叶片反射率和透射率的参数优化也使模型对陆气通量交换过程的模拟得到一定改善,其中感热模拟精度提高较为明显,模拟值对实测值的解释能力提高约4%,NS提高0.028,RRMSE减小了0.050；潜热NS提高0.013,RRMSE减小0.007,较感热改善程度偏小；模型对地表热通量模拟未因参数优化而得到改善。

通过以上研究结论可以证明,植被叶片反射率和透射率是辐射传输中重要参数,模型中对它们的优化可改善能量通量的模拟,进而实现了对陆气相互作用过程更为真实的描述,与各类复杂的参数化方案改进相比,这类参数的优化简单而且效果明显。房云龙等^{[ 34]}、蔡福等^{[ 25, 26]}研究发现,参数方案改进后反而出现某些参量模拟精度下降的现象,而当某些参数或参量优化后会使参数化方案改进的效果更加明显,说明合理的参数化方案只有在更为真实的参数设置前提下才能更好的发挥作用,因此,改善现有模型中一些不合理参数的设置是开展参数化方案研究的重要前提,对改进陆面过程模型模拟能力非常重要。

The authors have declared that no competing interests exist.

参考文献

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2006

0.0

1.005

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Modeling of impacts of vegetation coverage change on land surface conditions

利用NCAR最新的公用陆面模式CLM3.0,通过数值模拟初步研究了植被叶面积指数(LAI,leaf area index)异常变化对陆面状况的可能影响,结果表明,植被LAI的异常变化能够引起地表能量平衡、地表水循环等陆面状况的异常.(1)植被LAI的异常变化主要影响太阳辐射在植被与地表之间的分配,以及地表的感热、潜热通量.植被LAI增大,能够引起植被吸收的太阳辐射增加,而到达土壤表面的太阳辐射减小,并导致植被的蒸发、蒸腾潜热通量增加,造成地表的蒸发潜热和感热通量不同程度的减小.(2)植被LAI增大时,植被对降水的拦截和植被叶面的蒸发增大,植被的蒸腾作用也明显增强;植被LAI增加会使得热带地区各个季节的土壤表面蒸发、地表径流减小,而土壤湿度有所增加;LAI增加造成中高纬度地区土壤蒸发的减少主要出现在夏季;LAI增加还能够引起中高纬地区冬、春积雪深度不同程度的增加,造成春末、夏初地表径流的增加.(3)植被LAI增加能够使得叶面和土壤温度有所下降,但植被LAI的变化对叶面、土壤温度的影响相对较小.

... 1 引言植被在陆面过程中扮演着重要角色,它的存在及季节变化通过影响地—气系统的能量、物质和动量交换对陆面过程乃至区域气候产生重要影响^[1~3] ...

2007

0.0

2013

0.0

1.388

. 2013, 28(8):875-889

The observation and calculation method of soil heat flux and its impact on the energy balance closure

State Key Laboratory of Remote Sensing Science,School of Geography,Beijing Normal University,Beijing 100875, China

The soil heat flux is an important component of the surface energy balance equation,and the observation and calculation method of soil heat flux is of great significance. The surface soil heat flux was calculated and analyzed using the observation and calculation methods,including PlateCal,TDEC,HM,TCAV,ITCC based on the meteorological data of Guantao site in 2010. With the comparison of the results derived from these five methods,the optimal method is selected and used to obtain the land surface heat fluxes of Guantao site during 20082010,and the diurnal and seasonal variation characteristics are analyzed. The main conclusions are: ①PlateCal and TDEC are the optimal observation and calculation methods for obtaining land surface soil heat flux,respectively; while the results of HM,TCAV,and ITCC method are not satisfied. ②The PlateCal and TDEC methods are both sensitive to the surface soil temperature,however,the HM method is not sensitive to the surface soil temperature,and all the observation and calculation methods are sensitive to soil moisture. ③The surface soil heat flux showed a typical diurnal variations during winter wheat,corn and bare soil,and the seasonal variation is consistent with the trend of net radiation. ④When the soil heat storage was considered,the monthly surface energy balance closure ratio in 2010 could increase 4%~11%,and the annual energy balance closure ratio increased 3%~5% in the year of 20082010 at Guantao site.

土壤热通量是地表能量平衡的重要分量，对其测算方法的研究对理解能量平衡过程具有十分重要的意义。利用2010年馆陶站土壤热通量等相关观测数据对多种测算土壤热通量的方法：实测土壤热通量和热储存量的结合方法（PlateCal）、热传导方程校正法（TDEC）、谐波分析法（HM）、平均土壤热电偶法（TCAV）、耦合热传导—对流法（ITCC）获取的地表土壤热通量进行了对比分析，并且采用最优方法计算馆陶站2008—2010年的地表土壤热通量，分析了该站土壤热通量日、季节变化特征。主要结论如下：①PlateCal和TDEC法分别为获取土壤热通量的最优观测与计算方法，而HM，TCAV和ITCC法计算结果均不理想；②PlateCal与TDEC法对地表土壤温度均不敏感，而HM法对地表土壤温度则比较敏感，各种地表土壤热通量的观测与计算方法均对土壤湿度敏感；③馆陶站冬小麦、玉米覆盖地表及地表裸露时期的地表土壤热通量均呈现典型的日、季节变化特征，与净辐射变化趋势一致；④考虑热储存后，可将馆陶站2010年各月地表能量闭合率提高4%～11%，对2008—2010年的年能量平衡闭合率提高3%~5%。地表土壤热通量；土壤热流板；地表能量平衡闭合率

2002

3.634

0.0

. 2002, 55:451-477 DOI:10.1023/A:1020780211008

Modeling carbon dynamics of boreal forest ecosystems using the Canadian land surface scheme

1.University of Alberta 2.Meteorological Service of Canada 3.University of British Columbia

The ecosystem carbon (C) and nitrogen (N) simulations recently implemented in the Canadian Land Surface Scheme (CLASS) are presented. The main calculations include plant photosynthesis, autotrophic respiration, root N uptake, litterfall, plant growth, and soil heterotrophic respiration. Model experiments are made on two boreal forest ecosystems, deciduous (aspen) and conifers (black spruce). Simulated plant, soil, and ecosystem CO₂ exchanges are analysed on half-hourly, daily, and annual time scales and compared with tower eddy correlation flux measurements and estimates from various authors. Modeled daily ecosystem CO₂ exchange explained86% and 54%, respectively, of the observed variance of eddy correlationflux at the aspen site and at the black spruce site. Annual results show that the aspen ecosystem was simulated as a C sink in both 1994 (+164 g Cm^–2) and 1996 (+142 g C m^–2), and the black spruce ecosystem wassimulated as a C sink in 1994 (+39 g C m^–2) and 1995 (+25 g Cm^–2), but as a C source in 1996 (–27 g C m^–2).

... 地表反照率是计算地表辐射平衡的重要参数,通过直接控制太阳辐射在地表和大气之间的分配影响植物光合、呼吸等多种生物化学过程^[4],其估算精度直接影响地气热量交换和地表温度计算的准确性^[5],从而影响陆面过程或气候模式模拟的准确性 ...

2001

0.799

0.363

. 2001, 59(5):533-548

Sensitivity tests of interaction between land surface physical process and atmospheric boundary layer

文中建立了一个研究陆面物理过程与大气边界层相互作用的模式.模拟了草原下垫面的土壤环境物理、地面热量通量、蒸发、蒸散及大气边界层结构特征.并对主要的环境物理参数进行了敏感性实验.结果表明,本模式能合理地模拟地表热量平衡、土壤体积含水量、植被蒸发阻抗、地表水汽通量日变化和湍流交换系数、湍流动能、位温和比湿廓线等.该模式还可进一步应用于研究城市陆面物理过程与大气边界层相互作用机制,及与中尺度大气模式耦合用于区域气候的研究.

2005

3.982

0.0

... 相对于裸土,植被下垫面地表反照率影响因子较多且机制复杂,很多研究集中在下垫面性质变化相对较小的多年生常绿或落叶森林^[6],而一年生如草地、农田等植被反照率研究相对较少^[7,8] ...

2004

2.59

0.0

. 2004, 49:106-112 DOI:10.1007/s00484-004-0216-4

Crop growth and development effects on surface albedo for maize and cowpea fields in Ghana, West Africa

1.Centre for Development Research (ZEF) University of Bonn Walter-Flex-Strasse 3 53113 Bonn Germany 2.Tu Delft CiTG Stevinweg 1 2628 CN Delft The Netherlands

The albedo () of vegetated land surfaces is a key regulatory factor in atmospheric circulation and plays an important role in mechanistic accounting of many ecological processes. This paper examines the influence of the phenological stages of maize (Zea mays) and cowpea (Vigna unguiculata) fields on observed albedo at a tropical site in Ghana. The crops were studied for the first and second planting dates in the year 2002. Crop management was similar for both seasons and measurements were taken from 10 m×10-m plots within crop fields. Four phenological stages were distinguished: (1) emergence, (2) vegetative, (3) flowering, and (4) maturity. measured from two reference surfaces, short grass and bare soil, were used to study the change over the growing seasons. Surface was measured and simulated at sun angles of 15, 30, 45, 60, and 75°. Leaf area index (LAI) and crop height (CH) were also monitored. Generally, increases from emergence to maturity for both planting dates in the maize field but slightly decreases after flowering in the cowpea field. For maize, the correlation coefficient (R) between and LAI equals 0.970, and the R between and CH equals 0.969. Similarly, for cowpea these Rs are 0.988 and 0.943, respectively. A modified albedo model adequately predicted the observed s with an overall R>0.860. The relative difference in surface with respect to the values measured from the two reference surfaces is discussed. Data presented are expected to be a valuable input in agricultural water management, crop production models, eco-hydrological models and in the study of climate effects of agricultural production, and for the parameterization of land-surface schemes in regional weather and climate models.

2009

0.0

1.742

. 2009, 20(12):2 847-2 852

Characteristics and numerical simulation of surface albedo in temperate desert steppe in Inner Mongolia

1State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China|2Chinese Academy of Meteorological Sciences, Beijing 100081, China|3Graduate University of Chinese Academy of Sciences, Beijing 100049, China

Based on the meteorological and biological observation data from the temperate desert steppe ecosystem research station in Sunitezuoqi of Inner Mongolia during growth season (from May 1st to October 15th, 2008), the diurnal and seasonal characteristics of surface albedo in the steppe were analyzed, with related model constructed. In the steppe, the diurnal variation of surface albedo was mainly affected by solar altitude, being higher just after sunrise and before sunset and lower in midday. During growth season, the surface albedo was from 0.20 to 0.34, with an average of 0.25, and was higher in May, decreased in June, kept relatively stable from July to September, and increased in October. This seasonal variation was related to the phenology of canopy leaf, and affected by precipitation process. Soil water content (SWC) and leaf area index (LAI) were the key factors affecting the surface albedo. A model for the surface albedo responding to SWC and LAI was developed, which showed a good performance in consistent between simulated and observed surface albedo.

基于内蒙古苏尼特左旗温带荒漠草原生态系统野外观测站2008年生长季(5月1日—10月15日)的气象和生物要素观测资料，分析了地表反射率日、季动态，并构建了温带荒漠草原地表反射率模型.结果表明：研究区地表反射率日变化主要受太阳高度角影响，呈早晚高、中午低的U形曲线特征；生长季地表反射率在0.20～0.34，平均为0.25，以5月较高、6月下降、7—9月相对稳定、10月增大；研究区地表反射率的季节动态与冠层叶片的物候变化有关，同时受降水过程的影响；土壤含水量和叶面积指数是影响该区地表反射率的关键因子；反映土壤含水量和叶面积指数共同作用的地表反射率模型的模拟值与野外实测值具有较好的一致性.

2010

0.0

... 张果等^[9]、蔡福等^[10]研究发现,叶面积指数(LAI)和植被覆盖度(F_veg)对植被反照率影响明显 ...

2011

0.0

2.407

. 2011, 26(10):1 775-1 788 DOI:10.11849/zrzyxb.2011.10.014

Dynamic parameterization scheme of surface albedo: A case study on maize field

1. Chinese Academy of Meteorological Sciences, Beijing 100081,China; 2. Nanjing University of Information Science and Technology, Nanjing 210044, China; 3. Institute of Atmospheric Environment, China Meteorological Administration, Shenyang 110016,China; 4. Liaoning Province Meteorological Science and Technology Service Center, Shenyang 110016, China

Using continuous flux data, meteorological data and biological data from 2006 to 2008 from Jinzhou agricultural ecosystem research station, dynamic parameterization scheme of surface albedo(α) was investigated. The results show that α has logarithm, logarithm or linear, exponential or linear relationships with solar altitude(h_θ), surface soil water contents(SWC) and leaf area index(LAI), respectively. The model founded considering respectively logarithm and linear relationship between α and h_θ and SWC is better than those considering other relationships and is able to simulate diurnal pattern of α with smaller error in most of the non-growing season except early spring. In the growing season, the simulation precision of the α parametric model founded with statistical regression method considering respectively logarithm, linear and exponential relationships between α and h_θ, SWC and LAI play an important role in α which is higher than those considering other relationships. For the limitation of data, the model underestimates evidently α in most of the period especially in vegetative growth phase of maize. As vegetation coverage (FVEG) introduced and used to bestow weighing to soil and vegetation, the model whose simulation error decreases significantly in total growing season especially in vegetative growth phase is able to reflect seasonal variation of α and has dynamic simulation ability, which changes an untrue hypothesis that vegetation α is only constant in many land surface models and makes the model universal-adapted to simulate dynamic α in different phases of maize field. By this study, land surface process model will be offered dynamic parameter of vegetation α and then whose simulation accuracy will be improved.

利用2006—2008年锦州玉米农田生态系统野外观测站的通量、气象及生物因子观测资料研究了地表反照率(α)的动态参数化方案。结果表明:α与太阳高度角(h_θ)呈对数关系,与表层土壤湿度(SWC)呈对数或线性关系,与叶面积指数(LAI)呈指数或线性关系。非生长季,h_θ与SWC为α的主要影响因子,与α分别呈对数和线性关系时α的模拟精度明显好于其他关系,除初春外,大部时段的α模拟误差都较小。生长季,α主要受h_θ、SWC和LAI的影响。采用α分别与h_θ、SWC和LAI呈对数、线性和指数关系时α的模拟精度较高,受资料限制,大部分时段的α被明显低估,玉米营养生长阶段的模拟精度更差。引入植被覆盖度(F_veg)对裸土和植被分别赋权重所建立的α动态参数化模型,在生长季内α的模拟误差明显减小,营养生长时段α的模拟精度显著提高。该研究将为陆面过程模型提供动态的植被反照率参数,从而可提高模拟的准确性。

... 张果等^[9]、蔡福等^[10]研究发现,叶面积指数(LAI)和植被覆盖度(F_veg)对植被反照率影响明显 ...

... 1 LAI与F_veg的关系蔡福等^[10](2011c)研究表明LAI与F_veg在玉米拔节前呈对数关系,拔节后呈指数关系,但由于采用样本数较少,所确定的关系不确定性很大,本研究在2008年观测资料基础上在2012年又开展了一些针对性观测,累计样本数26个,以期更为准确地表达二者关系 ...

1996

4.362

0.0

... 随着第三代陆面过程模型如美国国家大气研究中心的陆面过程模型(NCAR LSM)、简单生物圈模型第二版(SiB2)^[11]、SiB3^[12,13]、通用陆面过程模型CLM3^[14]、CoLM^[15,16]等的不断涌现,植被的生理生化甚至是各类化学元素(C,N)的循环过程被考虑得更为精细,模型模拟精度得到显著提升 ...

2003

6.91

0.0

2011

0.0

2004

0.0

2007

0.0

... 众多模型中,戴永久等^[15]发展的CoLM是国际上最为先进的模型之一,结合了公认较好的LSM,BATS,IAP94 3个模式的特点^[17],广泛应用于气候模式^[18] ...

2010

0.0

1.388

. 2010, 25(1):1-6

Recent progress on the Earth system dynamicalmodel and its numerical simulations

Institute of Atmospheric Physics, Chinese Academy of Sciences

This paper briefly describes the initiative of the earth system dynamic model, recent international and domestic progress on the model development and its numerical simulations. As the mathematical representation of the integrated evolution of coupled climate, ecosystem and environmental system, earth system dynamical model can be applied for the longterm simulation in order for the understanding and prediction of climate and environmental change from global to regional scale, hence for the disaster prevention and mitigation, and the planning for sustainable development. At present, there is no practical earth system model available for the real applications, and it will take about two to three years′ efforts in order to have such an integrated model system.

概述地球系统动力学模式的由来及国内外目前的研究和模拟进展。地球系统动力学模式是描述全球气候以及生态和环境系统的整体耦合演变的数学表达。利用他作大规模数值模拟，以便认识和预测全球和区域的气候和生态环境变化，有效应对防灾减灾和规划可持续发展等。目前国内外尚未完全研制出可供实用的地球系统模式，还须二三年时间。

2010

0.0

1.241

... 众多模型中,戴永久等^[15]发展的CoLM是国际上最为先进的模型之一,结合了公认较好的LSM,BATS,IAP94 3个模式的特点^[17],广泛应用于气候模式^[18] ...

2005

0.0

. 2005, 82(34):225-243 DOI:10.1007/s00704-005-0132-5

The coupling of the Common Land Model (CLM0) to a Regional Climate Model(RegCM

1.School of Earth and Atmospheric Sciences, Georgia Institute of Technology Atlanta GA USA 2.Department of Environmental Science, Policy and Management University of California Berkeley CA USA 3.Physics of Weather and Climate Group International Centre for Theoretical Physics Trieste Italy

We replace the existing land surface parameterization scheme, the Biosphere-Atmosphere Transfer Scheme (BATS), in a regional climate model (RegCM) with the newly developed Common Land Model (CLM0). The main improvements of CLM0 include a detailed 10-layer soil model, the distinction between soil ice and water phases, a linked photosynthesis-stomatal conductance model, a multilayer snow model, and an improved runoff parameterization. We compare the performance of CLM0 and BATS as coupled to the RegCM in a one year simulation over East Asia. We find that the RegCM/CLM0 improves the winter cold bias present in the RegCM/BATS simulation. With respect to the surface energy balance, lower CLM0 albedos allow the absorption of more solar radiation at the surface. CLM0 tends to simulate higher sensible heat and lower latent heat fluxes than its BATS counterpart. The surface water balance also changes considerably between the two land surface schemes. Compared to BATS, CLM0 precipitation is reduced overall and surface runoff is increased, thereby allowing less water to enter the soil column. Evapotranspiration is lower in CLM0 due to lower ground evaporation, which leads to a wetter surface soil in CLM0 in spite of less precipitation input. However, transpiration is greater in CLM0 than BATS, which has an overall effect of less surface storage during the summertime. Comparison with station observations indicates that CLM0 tends to improve the simulation of root zone soil water content compared to BATS. Another pronounced difference between the two schemes is that CLM0 produces lower snow amounts than BATS because of different snow models and warmer CLM0 temperatures. In this case, BATS snow cover amounts are more in line with observations. Overall, except for the snow amounts, CLM0 appears to improve the RegCM simulation of the surface energy and water budgets compared to BATS.

... 众多模型中,戴永久等^[15]发展的CoLM是国际上最为先进的模型之一,结合了公认较好的LSM,BATS,IAP94 3个模式的特点^[17],广泛应用于气候模式^[18] ...

2006

0.0

1.688

. 2006, 25(4):567-574

The application of CoLM to arid region of Northwest China and Qinghai-Xizang Plateau

运用CoLM(CLM3.0)模式对典型干旱区(张掖站)和青藏高原区(安多站、MS3478站)进行了off-line验证试验,检验了CoLM模式在典型干旱区和青藏高原区的性能.结果表明: CoLM模式对典型干旱区绿洲灌溉农业的陆面过程模拟较好,土壤各层温度的日变化趋势和季节变化趋势都能较准确地模拟出来,模拟的地表温度与观测值相关系数为0.885,均方差为0.873;模拟的5 cm土壤温度值与实测值的相关系数为0.944,均方差为0.891.在高原地区能量平衡分量的模拟中,净辐射、感热模拟效果较好,潜热分量模拟值偏大,故将CoLM模式用于高原地区还有待进一步改进.

... 辛羽飞等^[19]、王澄海等^[20]、罗斯琼等^[21]、宋耀明等^[22]和肖瑶等^[23]研究证明该模型对不同下垫面类型的地表能量平衡及陆气通量的日、季变化都能实现较好的模拟 ...

2007

0.0

1.301

. 2007, 29(1):73-81

Simulation of the land surface processes in the Western Tibetan Plateau in summer

Key Laboratory of Western China’s Environmental Systems, College of Atmospheric Sciences, Lanzhou University, Lanzhou Gansu 730000, China

The observational data from 1 May to 18 September 1998 collected by Automatic Weather Station installed in Shiquanhe of the Western Tibetan Plateau are analyzed.The land surface processes on the Tibetan Plateau are simulated by an improved land surface model(Common Land Model),which can present the surface thermal condition tendency under observation data forcing.In the Western Tibetan Plateau,the sensible heat flux dominates the heat energy balance in summer,followed by the latent heat fluxes.But during the rain season,the latent heat flux can not be ignored.Phase change of surface soil water takes place often,resulting in soil absorbing and releasing latent heat frequently.Moreover,surface-released effective thermal fluxes(sensible and latent heat) follow the change in precipitation,freezing and thawing,and so does their Bowen ratio.As a result,the situation of atmosphere heating and transportation of atmospheric vapor will be affected.In return,the changed atmosphere will affect the soil water content due to the variation of land surface evapotranspiration and soil water containing capacity.

利用1998年5月1日至9月18日狮泉河自动气象站(AWS)的观测资料作为强迫场,运用改进的陆面过程模式CoLM(Common Land Model),对青藏高原西部的陆面特征进行了模拟研究.结果表明,该模式能够较好地模拟出高原地区的陆面特征.在高原西部地表能量平衡过程中,感热通量占主要地位,潜热通量较小,但在高原西部的湿季,潜热通量也是不可忽略的.在5月及6月初表层土壤频繁的发生水分相变,使土壤在相变过程中不断地吸收和释放潜热.降水及土壤表层频繁的冻结-消融使地表有效通量(感热+潜热)发生变化.有效辐射中的感热、潜热的分配,即Bowen会发生变化,进一步影响到对大气的加热及大气水汽输送情况,大气状况的改变又反过来影响地表蒸散及土壤持水能力,使土壤水分状态和含量发生变化.

2007

0.0

1.688

2008

0.0

1.688

2011

0.0

0.736

2010

0.799

0.363

... CoLM模型计算植被冠层反照率采用二流辐射传输方案^[24],决定冠层结构和性质且影响辐射传输的关键参数除了LAI和F_veg以外,还有叶片反射率、透射率及叶片倾角,它们在现有辐射传输方案中被赋为定值,这种赋值方式是否合理,模型对它们的改变是否敏感以及更为真实的赋值能否提高模型模拟精度,关于此类问题的研究鲜有报道 ...

2012

0.799

0.363

... 玉米农田因其冠层高度、LAI和F_veg等下垫面结构和状态随生育期的较大变化使辐射、水分、热量的分配和传输等一系列物理过程不断变化,加之分布广泛,可对局地大气环流和区域气候产生影响,在陆面过程研究中是非常重要的植被类型^[25],对其开展陆面过程及模型参数研究不但有助于深入理解陆气相互作用规律,还将为进一步加深农业生产对气候变化响应规律的认识提供参考^[26,27] ...

... 该站建有涡度相关观测系统和气象梯度观测系统,可实现不同高度各类气象要素和地表通量的观测^25,28] ...

... 5 模型模拟精度验证方法为更直观比较模型对各输出变量的模拟精度,引入相对均方差(RRMSE)^[32]和模型效率系数(Nash-Sutcliffe,NS)^[25]作为判断指标 ...

... 房云龙等^[34]、蔡福等^[25,26]研究发现,参数方案改进后反而出现某些参量模拟精度下降的现象,而当某些参数或参量优化后会使参数化方案改进的效果更加明显,说明合理的参数化方案只有在更为真实的参数设置前提下才能更好的发挥作用,因此,改善现有模型中一些不合理参数的设置是开展参数化方案研究的重要前提,对改进陆面过程模型模拟能力非常重要 ...

2013

0.0

1.742

. 2013, 24(8):2 265-2 273

Effects of dynamic aerodynamic parameters on simulating land-atmosphere flux exchanges over rainfed maize agroecosystem: A case study of BATS1e model

(1Institute of Atmospheric Environment, China Meteorological Administration, Shenyang 110016, China;  2 Liaoning Province Meteorological Service Center, Shenyang 110016, China;  3Chinese Academy of Meteorological Sciences, Beijing 100081, China)

Based on the continuous observations on the land-atmosphere flux exchange and the meteorological and biological elements in a maize field at the Jinzhou Agricultural Ecosystem Research Station in Liaoning Province of Northeast China from 2006 to 2008, and by using the dynamic roughness (z₀) and zerodisplacement (d) parameterization scheme considering the effects of leaf area index, canopy height and wind speed at different developmental stages of maize, the BATS1e model was modified, and applied to investigate the effects of dynamic aerodynamic parameters on the flux exchange between maize agroecosystem and atmosphere. Compared with the original model, the drag coefficient (C_D) simulated by the modified model increased, and its diurnal variation was more obvious with increasing vegetation coverage, which was more accordant with practical circumstances. The simulation accuracies of sensible heat (H), latent heat (λ_E) and soil heat flux were improved in varying degree, and the NashSutcliffes (NSs) were increased by 0.0569, 0.0194 and 0.0384, with the improvement quantities in the growth season being 0.9%, 1.1% and 1.2% of global radiation, respectively. The dynamic parameterizations of z₀ and d played a more remarkable role to increase the simulation accuracies of H and λ_E with the actual observation of soil water content introduced into the improved model. This research proved that more reasonable dynamic aerodynamic parameterizations could fulfill an obvious function to improve the land surface processes simulation.

基于2006—2008年锦州玉米农田生态系统的通量、气象及生物因子连续观测,利用所建立的考虑玉米不同发育期叶面积指数、冠层高度和风速的地表粗糙度(z₀)和零平面位移(d)动态参数化方案对BATS1e陆面模型进行改进，研究空气动力学参数变化对玉米田陆-气通量模拟的影响.结果表明: 改进后的拖曳系数(C_D)随植被覆盖度增大而增大,更符合实际;感热、潜热和土壤热通量的模拟精度均有不同程度改进,效率系数分别提高0.0569、0.0194和0.0384,生长季累计改进量分别占总辐射的0.9%、1.1%和1.2%;当输入真实的表层土壤湿度后,z₀和d动态参数化对感热和潜热的改进作用更大.合理的动态空气动力学参数化方案对陆面过程模拟具有明显改善作用.

2013

0.0

. 2013, 33(17):5 339-5 352 DOI:10.5846/stxb201205230768

Dynamics of aerodynamic parameters over a rainfed maize agroecosystem and their relationships with controlling factors

Based on continuous observation data of 16 m gradient weather observation tower from 2006 to 2008 at Jinzhou agricultural ecosystem research station, dynamic characteristics of aerodynamic parameters roughness (z₀) and zero-plane displacement(d) over a rainfed maize agroecosystem and their relationships with controlling factors during growing seasons are analyzed. The results showed that d appears about 10 days after jointing when plant height (h) is about 1.40 m and increases from 0.80-1.00 m to 1.00-1.40 m after tasseling stage. z₀ is smaller than 0.20 m before tasseling stage and comes to the maximum about 0.4m before and after milk stage. d/h and z₀/h are 0.40-0.54 and 0.10-0.14, and are decreasing and increasing with LAI, respectively, before h comes to the maximum. Before d appears, negative exponent and positive linear relationships between z₀ and wind speed at 2 m (u₂), z₀ and LAI or h are found. Yet, after d appears, relationship between u₂ and z₀+d is more notable than those between u₂ and z₀ or d. At the same time, positive exponent relationships between z₀ or d and LAI or h respectively are found. LAI and h influence more to z₀ than to d and z₀+d with greater role for the latter. Those relationships are more conspicuous from d appearing to h coming to the maximum. These research conclusions will play an important reference role for setting up aerodynamic parameterization and improving land surface process model.

对锦州玉米农田生态系统生长季内的粗糙度(z₀)和零平面位移(d)动态特征及其与风速、株高(h)和叶面积指数(LAI)的关系分析表明:零平面位移(d)在玉米拔节后10d左右,株高约1.40m时开始出现,在抽雄前为0.80-1.00m,抽雄后为1.00-1.40m;z₀在抽雄前小于0.20m,乳熟前后达到最大,约为0.40m。d/h和z₀/h分别为0.40-0.54和0.10-0.14,在h达到最大值前,分别随LAI增大而减小和增大。d出现前,z₀与风速呈负指数关系,与LAI和h都呈线性关系。d出现后,风速与z₀、d之和的关系比与各自的关系更显著;d与LAI、h都呈显著指数正相关关系,LAI、h对z₀的影响大于d和z₀+d,且h的作用大于LAI。d出现至h达到最大期间,上述各种关系最为显著。研究结果可为建立空气动力学参数的动态参数化方案及改进陆面过程模型提供依据。

2007

1.355

0.0

. 2007, 31(6):1 132-1 144

Latent and sensible heat fluxes and energy balance in a maize agroecosystem

1Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China;2 Graduate University of Chinese Academy of Sciences, Beijing 100049, China

Aims Agroecosystems are influenced strongly by human activity and climate change. In order to scientifically manage
agroecosystems under climate change, it is important to understand water exchange and energy transfer between agroecosystems
and the atmosphere. We analyze latent and sensible heat fluxes of a maize agroecosystem as a case study.
Methods Latent and sensible heat fluxes were measured in a maize agroecosystem using a 3.5 m eddy covariance tower from
June 2004 to December 2005 at the Jinzhou maize agricultural ecosystem field observation station (Liaoning Province, China).
Meteorological factors were recorded using sensors at 2.3 and 4.1 m using a micrometeorological tower. 
Important findings Diurnal and annual variations of latent heat fluxes and sensible heat fluxes had the same characteristics
as net radiation and could be expressed as hyperbola curves. Their peak values appeared at 12∶00-13∶00. The maximum latent
heat flux was about 655 w•m^-2 (at 13∶00 July 8, 2004), and the maximum sensible heat flux was 369 w•m^-2 (at 13∶00 May 31,
2004). The intensities of latent heat fluxes and sensible heat fluxes had close relationships with environmental factors.
Latent heat flux was negatively correlated with atmospheric pressure, and sensible heat flux was positively correlated with
air temperature. Fluxes of latent and sensible heat were very sensitive to precipitation. Latent heat flux was greatly
affected by the intensity and timing of precipitation, regardless of seasonal and daily changes. Energy of the maize
agroecosystem was unbalanced with the loss of about 15.5%, possibly because of lack of knowledge of 0-5 cm soil heat reserve
and canopy heat reserve. The energy balance had obvious differences between cloudy and rainy days, with the loss of energy
much less on rainy than cloudy days, especially with a surplus of energy on rainy days in August.

基于锦州农田生态系统野外观测站玉米农田涡度相关系统近2年的水热通量观测数据，分析了玉米农田水热通量的日际、年际变化特征及其能量
平衡状况。结果表明： 1）玉米农田水热通量日变化与年变化均呈单峰型二次曲线，峰值出现在12∶00～13∶00左右，与净辐射的日变化、年
变化同步，潜热通量最大可达到655 w•m^－2（出现在2004年7月8日1 3∶00），显热通量最大值大约为369 w•m^－2（出现在2004年5月31日13∶
00）。2）玉米农田水热通量强度与局地的环境条件密切相关：显热通量与大气压的年变化呈负相关，潜热通量与气温年变化呈正相关。水热通
量受降水的影响较大，对降水的反应较敏感。其中，潜热通量(LE)不仅与降水的强度有关，而且随着降水的季节分布的不同而出现不同的响应
，即使同样量级的降水在夜间与白天对LE的影响也是不同的。3）玉米农田通量观测呈现能量不闭合现象，主要原因可能是未包含0～5 cm土壤
热储量与冠层热储量，造成大约15.5%的能量损失。

... 该站建有涡度相关观测系统和气象梯度观测系统,可实现不同高度各类气象要素和地表通量的观测^25,28] ...

... 通量观测系统测得的感热通量、潜热通量以及净辐射、土壤热通量资料用于模拟结果验证,上述资料均为通过湿度修正、高频衰减修正和WPL校正等质量控制后的30 mins平均值^[28,29] ...

2011

0.0

1.388

. 2011, 26(3):300-310

Sensitivity of land surfaces model to dynamic parameters of land surface

1.Chinese Academy of Meteorological Sciences, Beijing100081,China;  2. Nanjing University of Information Science and Technology, Nanjing210044, China；3.Institute of Atmospheric Environment, China Meteorological Administration，Shenyang110016，China； 4.Liaoning Province Meteorological Science and Technology Service Center, Shenyang110016,China

Using continuous flux data, meteorological data and biological data in 2006(from June 1 to August 9) from Jinzhou agricultural ecosystem research station, based on BATS1e model, the sensitivity of land surface model to dynamic assignment of roughness(Z₀), leaf area index(LAI) and fractional vegetation coverage (FVEG) and albedo(α) were investigated. The results show that dynamic assignment of Z₀has effect on simulating surface soil temperature(SST) and sensible heat flux (SH) especially on the time when maize field surface covered changes from bare soil to vegetation. Dynamic LAI plays important role in improving the simulation of SST, net absorbed solar energy flux(Frs), SH and surface soil water content(SWC), at the same time affects simulation of latent heat flux (LE). Dynamic FVEG affects obviously simulations of all abovementioned variables and shows greater sensitivity when they are smaller. Also, dynamical change of α can affect simulations of SST, LE and SH, especially for the latter. Furthermore, the interactions among different dynamic parameters are ignored by the model. The improvement of single land surface parameter might be helpful for simulating one or multivariate but not for all variables. In short, it is necessary to set up a parameterization scheme with the interactions of different land surface parameters.

利用2006年锦州玉米农田生态系统野外观测站动态连续的通量、气象及生物因子观测数据，分析了BATS1e陆面模型对动态的粗糙度（Z₀）、叶面积指数（LAI）、植被覆盖度（FVEG）及反照率（α）变化的敏感性。结果表明：Z₀的动态变化对表层土壤温度（SST）和感热（SH）的模拟有一定影响，主要发生在玉米农田从裸土向有植被覆盖转变这一阶段。LAI的动态赋值可以改善SST、净入射短波辐射（frs）、SH和SWC的模拟效果，对潜热（LE）的模拟也有一定影响。动态FVEG对上述各变量的模拟影响最为明显，当FVEG较小时敏感性最大。α的动态赋值可影响SST、SH和LE的模拟，其中SH反应最为敏感。各动态参数越接近模型设定值，模拟结果受影响越小；各参数间关系密切，单一参数的改进可提高某些变量的模拟精度，但不一定改善所有变量的模拟效果。

... 究其最终原因,还是原模型在9月对感热高估所致,而感热的高估则主要由潜热的明显低估所造成,潜热的低估则由土壤湿度的不真实模拟引起^[29,33] ...

2004

0.0

0.3741

. 2004, 26(3):303-311

A universal growth model for maize leaf area index

建立了1个模拟叶面积指数动态变化的扩充的Logistic模型,利用禹城、沈阳的玉米叶面积指数(LAI)实测资料进行了拟合,结果表明,此模式是模拟叶面积指数随地理位置、品种、播期、密度变化的统一模型,对叶面积指数与积温间关系的分析,综合了不同地理位置、不同品种、不同播期、不同密度的叶面积指数资料,得到1条相对叶面积指数变化曲线,可反映特定区域作物叶面积指数的动态变化,也可用于区域作物产量模拟和遥感估产的研究.

... 2008年逐日LAI由王玲等^[30]所建立的相对积温方法利用玉米各生育期LAI实测数据和日平均气温资料求得^[31],利用2012年测得的LAI和F_veg所建立的关系和所求得的2008年逐日LAI可计算得到该年逐日F_veg值 ...

2011

0.0

1.729

. 2011, 30(3):494-501

Dynamic characteristics of land surface parameters of rainfed maize fields in Northeast China

1Chinese Academy of Meteorological Sciences, Beijing 100081, China|2Nanjing University of Information Science and Technology, Nanjing 210044, China|3Institute of Atmospheric Environment, China Meteorological Administration, Shenyang 110016, China|4Liaoning Province Meteorological Science and Technology Service Center, Shenyang 110016, China

By using the continuous flux data, meteorological data, and biological data from Jinzhou agricultural ecosystem research station in 2006, the dynamic characteristics of maize plant height (H), leaf area index (LAI), surface soil water content (SWC), roughness (Z₀), and albedo as well as their relationships were investigated, aimed to provide references for setting up dynamic parameterization schemes on maize field surface. The H and LAI were estimated with relative accumulated temperature method, and the Z₀ was calculated with wind profile equation under neutral condition. The H increased linearly and slowly before jointing stage, and came quickly to the peak value until milk stage. The change of LAI, which emerged the maximum equal to about 4 at jointing-heading stage and reduced to 1.5 in harvesting time, showed an asymmetrical n-type pattern in the growth period. The SWC was the minimum (12%-20%) in winter and the maximum (30%-36%) in summer, while the surface albedo was greater (0.2-0.3) in cold season (from November to next March), the greatest (0.5-0.7) when ground surface was covered by snow, and the smallest (0.1-0.2) in warm season (from June to September). Albedo was significantly positively correlated to LAI during the growth season. Its monthly mean diurnal pattern showed a U-shape distribution, and was affected by the LAI, canopy color and roughness. At the daytime, albedo was in the order of June < September < August < July. In no-freezing period, the albedo had a significant negative correlation with SWC, but this correlation became weaker with increasing LAI. The Z₀ had positive exponential correlations with H and LAI.

利用2006年锦州玉米农田生态系统野外观测站动态连续的通量、气象及生物因子观测数据对玉米植株高度、叶面积指数（LAI）、粗糙度（Z₀）、表层土壤湿度（SWC）、反照率的动态变化及其相互关系进行分析，旨在为建立玉米农田下垫面动态参数方案提供参考。动态LAI和株高采用相对积温方法求得，Z₀通过中性条件下风速廓线方程求得。研究表明：玉米株高增长速度以拔节期为转折点先慢后快，到乳熟期达到最大；LAI呈不对称“n”型分布，最大值出现在抽雄至乳熟期，约为4；SWC冬季最小，为12%～20%，夏季最大，为30%～36%。反照率在冷季（11-翌年3月）最大，为0.2～0.3，积雪覆盖时为0.5～0.7；暖季（6-9月）最小，为0.1～0.2。生长季内反照率与LAI呈显著正相关，其月均值日变化呈U型分布，受LAI、冠层颜色及粗糙度等因素影响，白天反照率6月<9月<8月<7月。在非结冻期反照率与SWC呈极显著负相关，但随着LAI增大，该关系逐渐减弱。Z₀与株高和LAI呈指数正相关。

2009

0.0

2.123

. 2009, 31(9):1 599-1 606

A comparative study on estimation models for field evapotranspiration

Crop evapotranspiration (ET) is an important component of simulation models many practical applications related to the efficient management of crop water supply. Also, the accurate evaluation of evapotranspiration is key to the soil water content. In our study, a spring maize ecosystem located in Jinzhou Station of Agricultural Ecosystem Research (41o 49' N, 121o 12' E) is taken as an example, observational data are generated by using eddy correlation (EC) method, in order to compare the methods for estimating crop ET, including Hargreaves model, Priestley-Taylor model, FAO-Penman-Monteith model, Bowen ratio method, aerodynamics method and process-based physio-ecological model. The data from weather station with the time step of 1 day are used in the Hargreaves model, Priestley-Taylor model and FAO-Penman-Monteith model to calculate daily ET, while vertical gradient data with the time step of 30 minutes are used in the Bowen ratio method and aerodynamics method to calculate daily ET-Performance analyses of these methods show that the modeling results of Hargreaves model, Priestley-Taylor model and FAO-Penman-Monteith model have the same changing trends the observational data, but these models overestimate the crop ET by 20-26%. Among the three methods, Priestley-Taylor model is the best in performance, since it can explain 74% of the variations in daily ET of this maize field. Therefore, Priestley-Taylor model can be applied in the ET calculation with the simple input and can retrieve relatively accurate results. The process-based physio-ecological model is proved to be the optimal model in simulating the crop ET. It can obtain all kinds of simulation results besides ET and be used in mechanism and process analysis between atmosphere and terrestrial ecosystems. Meanwhile, this model considers several physical processes and parameters which made it difficult to apply under some conditions. The results indicate that the Bowen ratio method can provide accurate measurement of crop ET when is correctly installed and β value is below 0.4. It is also suggested that observation height and height differences can affect the performance of aerodynamics method greatly. At last, a majority of the site are not ideal conditions, so it can not fully meet the basic assumption of eddy covariance technique for the flux measurement, and result in some uncertainties in the flux measurement. It is made clear that the differences between the observational data and the modeling results are conditional, but not absolute.

模拟蒸散的物理过程，计算农田蒸散量是进行生态系统水资源评价和管理的重要手段，同时也是气象部门进行土壤湿度预报的首要条件。本研究以玉米农田为研究对象，基于涡度相关法观测的蒸散实测资料，比较分析了基于常规气象数据的蒸散模型（Hargreaves法、Priestley-Taylor法、FAO-Penman-Monteith法）和基于气象梯度数据的蒸散模型（波文比法、梯度法、生态系统过程模型模拟）的模拟精度。结果表明：①Hargreaves法、Priestley-Taylor法和FAO-Penman-Monteith法日蒸散的模拟结果较为一致，总体上高估20%~26%，其中Priestley-Taylor法模拟结果最优；②生态系统过程模型模拟的农田日蒸散精度较高，但模型中涉及的物理过程和参数较多，在实际应用中难于获取；③波文比法在波文比小于0.4且仪器精度较高时可以得到较准确的估算值。研究同时还指出，仪器的安装高度及高差设计对梯度法估算蒸散十分重要。

... 5 模型模拟精度验证方法为更直观比较模型对各输出变量的模拟精度,引入相对均方差(RRMSE)^[32]和模型效率系数(Nash-Sutcliffe,NS)^[25]作为判断指标 ...

2012

0.0

1.388

. 2012, 27(6):678-685

Sensitivity and parameters optimization method of soil parameters to soil moisture in common land model

1. School of Resource and Environmental Science，Wuhan University，Wuhan430079, China; 2. Cold and Arid Regions Environmental and Engineering Research Institute，Chinese Academy of Sciences，Lanzhou730000, China

The sensitivity analysis of soil moisture to soil texture (sand and clay) was studied by using the common land model and meteorological forcing data from January 1, 2008 to September 31, 2009 at the Arou Observation Station in Heihe river basin. The SCEUA algorithm was utilized to optimize the soil texture and soil hydraulic parameters separately and the impact of the result of soil moisture with different strategies was analyzed. The result shows that surface moisture is quite sensitive to soil texture, the sensitivity coefficients are larger than 0.45, and the sand percentage is more significant to the soil moisture; SCE-UA algorithm is used to optimize the soil texture or soil hydraulic parameters which can effectively improve the accuracy of soil moisture simulation. However, optimizing soil hydraulic parameters will likely lead to the apperance of the phenomenon of equifinality for different parameters, while optimizingsoil texture can constrain the range of soil hydraulic parameters and make them more reasonable.

利用2008年1月1日至2009年9月31日黑河流域阿柔冻融观测站的气象和土壤水分数据，采用基于方差的多参数敏感性分析方法研究通用陆面模型（Common Land Model，CoLM）模拟的土壤水分对土壤质地（砂土和黏土）的敏感性，进而采用SCE-UA参数优化算法分别优化土壤质地和土壤水力参数，分析不同优化策略对土壤水分模拟结果的影响。研究结果表明，浅层土壤水分对土壤质地较为敏感，敏感性系数达到了0.45以上，并且砂土含量对土壤水分的影响更为显著；利用SCE-UA算法优化土壤质地或土壤水力参数都可以有效地提高土壤水分的模拟精度，优化土壤水力参数易产生“异参同效”现象，而优化土壤质地能够使土壤水力参数的取值范围更加合理。

... 究其最终原因,还是原模型在9月对感热高估所致,而感热的高估则主要由潜热的明显低估所造成,潜热的低估则由土壤湿度的不真实模拟引起^[29,33] ...

2010

0.0

1.948

. 2010, 34(2):290-306 DOI:10.3878/j.issn.1006-9895.2010.02.05

The optimization of parameters of land surface model in arid region and the simulation of land-atmosphere interaction

Using the observed data at Dunhuang Gobi site in Northwest China, the optimum values of surface albedo, roughness length and soil thermal properties for the arid region required by the Common Land Model (CoLM) are obtained. In order to understand land－atmosphere interaction and the sensitivity of simulation outputs to different settings of the important parameters, two control tests and three sensitive tests with different combinations of the three parameters are carried out by using the forcing data collected at the same Dunhuang Gobi site from May 2000 to July 2004. The results from the control tests indicate that the CoLM with the optimum values of the parameters, here called Optimized CoLM, can simulate the land surface processes reasonably. By comparison with the observed data, it is shown that the simulations from Optimized CoLM are much more precise than those from the original CoLM, which uses default values of the parameters. The results from the sensitive tests demonstrate that: (1) Surface albedo has great influence on the ground surface temperature (TGS) all year round, especially in spring and summer; (2) the roughness length and the soil thermal properties can also affect the TGS in spring－summer and autumn－winter, respectively; (3) as to the sensible heat flux (SHF), it is more sensitive to the surface albedo and the roughness length in the summer half-year than in the winter half-year, and less sensitive to the soil thermal properties; (4) when computing the TGS, the net radiation and the SHF in the original CoLM, it is found that there exist error counteractions, which will conceal the simulation error. The reason for the phenomenon is that each default parameter will add some positive or negative errors to the simulation results, but these errors will be offset reciprocally, which make the total simulation error mitigate eventually.Analyses of the surface heat balance show that: The SHF is the major component and the latent heat flux is so small that it can be omitted; the daily-mean SHF is upward from the ground surface to atmosphere all year round, especially in summer. The big portion of net radiation returns to atmosphere in the form of SHF and the rest becomes the ground heat flux and is stored in the soil in summer, which will be released to atmosphere again in the form of SHF in winter. The soil as a heat reservoir is a heat sink in summer and a heat source in winter.

依据干旱区陆地下垫面观测结果, 对陆面过程模式Common Land Model (CoLM) 中反照率、粗糙度长度和土壤热力性质3个方面的参数进行了优化, 并按照不同的参数组合形式设计了为加深理解干旱区地气相互作用的控制试验和研究重要参数影响的敏感性试验, 对敦煌戈壁2000年5月～2004年7月的陆面过程进行了离线 (off-line) 数值模拟分析。控制试验结果表明: 优化参数的模式在干旱区得到了更好的模拟性能, 对地表和深层土壤温度、净短波辐射、净长波辐射以及感热通量的模拟能力较原模式有了明显的提高。敏感性试验的结果表明: 地表温度在全年对反照率都比较敏感, 春季和夏季更为显著; 粗糙度长度和土壤热力性质分别在春夏和秋冬对地表温度有较大影响; 感热通量对反照率和粗糙度长度在夏半年比较敏感, 而土壤热力性质对感热通量的影响并不明显。对敏感性试验的结果进一步分析发现: 原模式在计算地表温度、净辐射和感热通量的过程中存在不同形式的误差抵消的现象, 这就会掩盖模式的模拟误差, 优化参数的模式可以更好的反映干旱区地气相互作用的物理过程。针对模式输出的感热通量和地表热通量的分析发现: 感热通量的季节变化明显, 全年都有由地表向上的感热通量输送, 夏季尤为显著; 相对于感热通量而言, 潜热通量量级很小可以忽略不计。夏季, 净辐射的能量大部分以感热通量的形式返回大气, 其余的能量以地表热通量的形式进入土壤并贮存, 夏季土壤为热汇; 冬季, 夏季贮存的能量又由土壤返回大气, 此时土壤为热源。