【作者】 张杰；

【导师】 黄建平； 张强；

【作者基本信息】 兰州大学 ， 应用气象学， 2009， 博士

【摘要】 地球生物圈活动和人类活动不仅直接改变陆地land use和land cover,而且调节着地表与大气之间的物质、能量、水分的交换。由于考虑生物圈的调节作用,陆面过程的研究已经从最初的物理过程研究拓展到生物圈化学过程的研究。要客观评价陆地生物圈对气候变化的脆弱性和适应性,就有必要系统地认识清楚生物圈、人类活动及其与气候系统之间的相互关系,这就需要一个具有完善的陆面过程模式的气候模式。陆面过程模式的发展寄希望于发展完善的陆面过程参数化方案。国际上曾开展过超过50多个陆面过程试验,从局地的土壤—植被—大气相互作用的综合观测入手,借助卫星遥感资料和数值模式由点及面地分析,研究了陆面过程特征及其参数化,探索提出用于大气数值模式的陆面过程参数化方案。由于复杂、非均匀下垫面和稀疏植被特征存在,我国相继开展的一些较有影响的陆面过程观测试验结果并未被目前国际上流行的陆面过程模式或卫星遥感反演方法所采纳。因为遥感可以获得连续、真实的植被活动信息,针对我国稀疏植被特征,发展一套完善的遥感参数化方案对陆面过程模式的改进有重要意义。本研究针对我国典型的稀疏植被半干旱地区,结合黄土高原定西试验站的观测资料、卫星遥感资料,对半干旱区的陆面过程参数进行研究,建立了针对稀疏植被区的卫星遥感参数化方案和模型。陆面过程参数化目的是获取准确的能量参数如净辐射量、感热通量、土壤热通量和潜热通量,水分参数如蒸散发量,物质参数如NPP等,这些参数的参数化前提就是获得高精度的反照率、表面温度、空气温度、以及空气动力学阻抗及其相关联的动力学粗糙度特征,本研究根据遥感参数化的思路,进行观测分析和参数化研究。本研究在系统分析陆面过程参数化中存在的问题以及各参数的参数化思路基础上,首次对影响感热通量变化的重要参数粗糙度长度进行参数化,同时对适于半干旱稀疏植被区的Choud-1空气动力学阻抗方法进行了遥感反演;采用二向反射模型对遥感几何效应问题进行研究,实现了反照率的反演;在空气温度的估算上,首次提出了采用高垂直分辨率和光谱分辨率的遥感资料结合反演边界层廓线的方法得到表层空气温度的思路;在水分特征的研究中除了蒸散发量的反演,首次提出了遥感反演叶水势的方法,为微观用水特征的认识提供了参考,另外,在地表温度的反演基础上,采用能量和物质平衡算法实现了陆面各能量通量和Npp的反演,将参数化方案应用到黄土高原对其陆面过程特征进行了详细研究。并得出以下几点结论:(1)本研究首次提出了稀疏植被粗糙度参数化方案,替代了以前的经验关系,有助于提高对稀疏植被粗糙度的认识。得出:稀疏植被区的粗糙度对植被区域植株的密度、覆盖度、风速等的响应很敏感。在风速一定的情况下,随着植株数量的增加,粗糙度有增加的趋势;单位面积植株越稠密,叶面积越大,粗糙度越高。根据动力学模型的模拟结果建立了粗糙度与LAI和风速的关系,实现了粗糙度的遥感参数化。(2)在粗糙度参数化的基础上,基于Choudh-1计算空气动力学阻抗的方法,结合冠-气温度差关系,实现了空气动力学阻抗的遥感参数化。(3)反照率和表面温度是陆面过程的两个重要参数。考虑稀疏植被对光学特性的影响,采用二向反射模型反演反照率,进而对几何效应进行了订正,得到反照率的反演误差大部分在5%左右。采用温度—比辐射率分离方法得到表面温度的反演误差大部分在±1.8℃范围内。(4)空气温度一直是遥感参数化方面比较困难、反演误差较大的参数,很多研究直接用观测资料替代。本研究采用边界层温度廓线的遥感反演方法得到地表层空气温度,提高了对空气温度的遥感估算精度,考虑到北方地区大气中气溶胶含量较高,对红外遥感大气温度廓线的方法进行了气溶胶订正研究,订正后可提高反演精度0.38K。(5)基于上述几个参数的参数化,根据能量平衡原理、物质平衡原理,建立了能量、碳以及其它陆面过程参数化的陆面过程参数化模型,模型应用到黄土高原地区得到效果较好。由于降水分布的时间差异,产生了土壤湿度空间分布与植被覆盖度分布的不一致性,使得区域反照率、能量通量和蒸散发量呈现出3种分布模态。(6)水分参数除了蒸散发量外,叶水势被认为是反映植被水分特征的重要参数,本研究在粗糙度、空气动力学阻抗以及反照率、温度参数化的基础上,采用能量平衡理论方法,提出了叶水势的遥感参数化方案,实现了对微观用水特征认识,该模型对植被水分胁迫的监测有一定指导意义。更多还原

【Abstract】 It is found that biosphere activity and human activity change not only land use and land cover, but also the matter, energy and water exchange. Because of biosphere system considered, land process researches have been developed from physical process to biosphere chemical process. As the main body of land process, biosphere activity and the relations between atmosphere and human activity are needed to resolve so as to evaluate biosphere frangibility and adaptability, all these need to developing a perfect land process model for climate model.Developping a good land processing model relays on developping a perfect parameterizing project. To these days, there are more than 50 land process experiments, all these experiments paying attentions to integrate observation of the interaction between land, vegetation and atmosphere, and analyzing land process character and parameterize relation from stations to wide range by using satellite and numerical model. On the basis of above means, the land process parameterize project is developed for atmospheric numerical model. Due to complex, heterogeneous surface, and sparse vegetation, some land process experiments results have never been used by land process model and satellite retrieval method. Because continuum and real vegetation activity information can be obtained from remote sensing, the perfect land process parameterizing project for improving land process model is important aiming at sparse vegetation.The research do some experiments, by combining experiment over Dingxi station in loess plateau, with remote sensing data, the parameterize researches in heterogeneous are done, and the parameterize model for remote sensing are built. The intention of land process parameterizing is obtaining land energy, water and matter, the energy parameters are net radiance, sensible heat flux, soil heat flux and latent heat flux, water parameter is evaportranspiration, matter parameter is Npp. The prime of these parameterizing is obtaining albedo, surface and air temperature, and aerodynamic resistance and aerodynamic roughness length. According to the parameter idea, paramterizing research is performed, the aerodynamic roughness length is parameterized for the first time.BRDF model is used for geometry revising of albedo retrieval. On the air temperature parameterizing, high vertical resolution and high spectrum resolution data was used for atmospheric profile retrieved so as to obtain surface air temperature for the first time.Except for evapor-transpiration, leaf water potential is parameterized for the first time for evaluating water status.In addition, on the basis of surface temperature retrieval and energy balance and matter balance theory, land energy flux and NPP is retrieved, the parameterizeing projects were used over loess plateau, and some interesting conclusions were drawn.a. Aerodynamic roughness length project over sparse vegetation region is put forward in the research, the project replace the experience relation performed former, and help to realize roughness length over sparse vegetation. Aerodynamic roughness length is sensible to vegetation density, land cover and wind speed. Under the condition of wind speed, with increasing of vegetation amount, zero displacement height and aerodynamic roughness are increased. Under the condition of vegetation amounts, with amounts increasing, zero displacement height and aerodynamic roughness are also increased.b. On the basis of aerodynamic roughness length, aerodynamic resistance is parameterized by using Choudh-1 arithmetic, according to canopy-air temperature difference.c. Albedo and surface temperature are two important parameters. Consider the effect of sparse vegetation on multi reflecting, BRDF model was used for retrieval albedo, so as to correct geometry domino effect, and the retrieval error is about 5% for many cases. TISIE algorithm is used for retrieval surface temperature, and the retrieval error is about±1.8℃for many cases.d. Air temperature is the complex parameter with large retrieval error, and which is replaced by observed value at weather stations.The research also retrieval boundary layer temperature and surface air temperature so as to get spatial temperature. And aerosol effect on atmospheric temperature structure within boundary layer and infrared remote sensing was considered. The retrieval error was improved about 0.38K after aerosol effect was considered.e. On the basis of above parameters parameterizing and energy balance theory, matter balance theory, the model including energy, C and land process parameterize is built, the model is used in loess plateau, testing results show that the model have good effect. There are inconsistent distributing between soil humidity and vegetation fraction due to regional precipitation difference, which results three distributing modes about albedo, energy flux and evaportranspiration.f. Except evapor-transpiration, leaf water potential is deemed to another moisture parameter.On the basis of roughness length, aerodynamic resistance, albedo and temperature parameterizing, and energy balance theory, leaf water potential model is put forward, the method is realized on microcosmic water usage, and it also connected microcosmic water with macroscopical water usage. The method also has application value, which can be used for water inspecting.更多还原