【作者】 王寅钧；

【导师】 张文建； 徐祥德；

【作者基本信息】 中国气象科学研究院 ， 大气遥感科学与技术， 2014， 博士

【摘要】 本文利用JICA项目“中日气象灾害合作研究中心”在云南大理国家气候观象台建立的边界层综合观测系统，使用EDDYPRO软件，采用涡动相关法对湍流资料进行质量控制及处理订正，将EDDYPRO与JICA项目使用的自编软件计算出的通量进行了比较，并且比较了梯度法与涡动相关法的结果。使用2008年3月~2009年2月一年的资料系统分析了近地层湍流动力特征，主要包括稳定度、湍流方差、湍流强度及湍流动能、切变项、浮力项等湍流参数，估算了陆面参数，如粗糙度、湍流输送系数。使用GPS探空数据，计算了对流边界层CBL在干季和湿季的高度，稳定边界层SBL的高度及特征。在对近地层湍流量进行诊断分析的基础上，使用NCEP、LAPS垂直速度资料，从湍流—对流运动不同尺度相互作用视角，探讨了湍流动能以及湍能方程分量与高原边界层动力、热力过程及其大尺度动力、热力结构的相关特征，发现近地层湍流动能、切变项与大尺度大气低层的垂直运动之间存在显著的相关特征。观测资料的处理与分析非常重要，有利于我们加深对边界层的理解与认识。与此同时，湍流过程的参数化问题也是当前研究的热点问题，数值模式中的湍流通量需要通过一定的参数化方法来解决，评估参数化方案的效果，找到适用于青藏高原东南缘合适的参数化方案有重要意义。本文选择青藏高原东缘大理观象台边界层通量观测系统，进一步利用了边界层观测资料，离线测试了WRF区域模式中的两种常用的近地层参数化方案(MM5相似理论非迭代方案A和ETA相似理论迭代方案B)，并将参数化方案计算结果与边界层铁塔涡动相关法的观测值进行对比分析。在离线测试两种近地层方案的基础上，将离线测试的结果作为评价WRF在线模拟青藏高原东南缘区域边界层特征效果的重要依据。在线模拟主要讨论两部分内容：1、离线测试的两种近地层方案(MM5相似理论近地层方案、ETA相似理论近地层方案)对区域通量模拟结果的影响。2、由于本文需要研究二阶矩项(湍能以及湍能方程中各分量)，所以选择了2.5级MYNN局地边界层闭合方案(3级MYNN方案目前不能与以上两种近地层方案联合使用)。以上工作得到以下几点主要结论：(1)大理的湍流强度总体较强，明显强于四川盆地温江地区，略强于青藏高原东部理塘地区。大理地区uu*、 vu*和wu*基本满足1/3方规律。大理、林芝地区浮力项、切变项大小基本相当，切变项林芝地区略小于大理地区，浮力项林芝地区略强于大理地区。大理、林芝地区的浮力项比高原当雄地区偏弱，数值总体上与平原地区大小相当；大理、林芝切变项的数值总体上与高原当雄结果更为接近，切变项总体明显大于浮力项。对于大理农田下垫面，由于农业活动引起下垫面粗糙度的季节变化还是比较明显的。夏季青藏高原东部以及周边地区动量整体输送系数C D与热量整体输送系数CH数值明显大于青藏高原中西部。(2)由于高原中部地面强热源或由地形复杂造成的下垫面强热力非均匀性，高原大尺度垂直运动与大气视热源Q1、水汽汇Q2均呈显著相关。研究可发现大理大气低层800hpaNCEP资料上升运动较强的时段，近地层湍流动能、切变项亦恰为高值时段，即湍能各分量对垂直运动的贡献特征显著，此结论揭示出热源驱动过程，高原东南缘对流运动中湍能对对流云团发生、发展的贡献。林芝近地层湍流动能、切变项与大气低层(600hPa以下)NCEP再分析资料垂直运动的相关性特征类似大理。进一步应用卫星资料等多源信息，采用LAPS模型给出林芝区域的垂直速度与近地层湍流动能、切变项有更显著的相关性，此结果印证了青藏高原地区南坡强烈的上升运动往往伴随着强的湍流动能与切变项，在大气高层(600hPa以上)两者相关性减弱，相关特征不明显，林芝两者相关系数峰值出现在600hpa~700hpa。(3)晴空少云天气条件下，大理的对流边界层CBL发展的高度可以达到2000m左右。由午时观测确定CBL顶高与感热、潜热相关性显著，CBL顶与分别湍流动能、浮力项均呈正相关（已达到信度标准），其中浮力项两者相关最为显著，而与切变项相关性相对弱些，在近地层热力湍流作用对CBL发展高度有明显影响，而机械湍流的剪切作用的影响并不确定。剪切产生的湍流主要以水平方向为主，浮力产生的湍流以垂直方向为主。高原东南缘湍能特征与CBL相关的结论进一步印证了理论上湍流贡献物理解释。(4)近地层湍流通量对于中尺度数值模拟有重要意义，湍流通量的参数化是当前大气边界层研究的热点问题之一。本文引用WRF中尺度天气预报模式中的两种常用的近地层参数化方案（MM5相似理论非迭代方案A和ETA相似理论迭代方案B），将参数化计算结果进行离线测试分析，并与大理边界层铁塔采用涡动相关法的观测值进行对比分析。计算湍流通量之前，首先确定空气动力学粗糙度。大理观测站冬半年种植蚕豆，下半年种植水稻，通过中性条件铁塔4层高度风速拟合，发现空气动力学粗糙度季节变化特征明显。将拟合的空气动力学粗糙度输入参数化方案计算通量，结果表明：对于大理农田下垫面，不同季节由于下垫面植被有明显差异，植被的稀疏对湍流通量的计算有较大影响。在不稳定条件下ETA方案低估了动量通量，MM5方案总体优于ETA方案，MM5方案误差小于ETA方案主要表现在裸土下垫面，对于有植被的下垫面，ETA方案计算动量通量的误差反而较小，青藏高原东南缘有植被下垫面的情况更为常见，故本文认为ETA方案的结果更适用于这一地区;在稳定条件下MM5方案低估了动量通量，ETA方案优于MM5方案，两种方案的误差随稳定度变化呈现相反分布的情况，两种方案的稳定度函数的形式都较适用于大理农田下垫面。ETA方案考虑了空气动力学粗糙度z0和热量粗糙度z0h的差异，热量通量交换与真实情况更为符合，感热通量计算结果在裸土或稀少植被条件下明显优于MM5相似理论方案。针对ETA方案感热通量计算结果裸土下垫面仍出现高估的现象，考虑使用(Zeng et al.,1998)提出的对于使用辐射地表温度在裸土下垫面时的订正方法。(5)在线模拟结果表明不稳定条件下MM5方案计算的动量通量和摩擦速度大于ETA方案，稳定条件下情况相反，ETA方案计算动量通量和摩擦速度结果大于MM5方案，这一结论印证了在线与离线测试上述物理量计算的结果一致。离线结果表明对于有植被的青藏高原东南缘区域模拟来说，ETA方案计算的动量通量更为准确；在线模拟结果表明1.5阶2.5级MYNN局地闭合边界层参数化方案能较好的模拟湍流动能以及湍能方程各分量的垂直廓线，另外，不稳定条件下计算摩擦速度、湍流动能、湍能耗散项模拟要强于ETA方案，参照离线测试有植被不稳定条件下两种方案计算的摩擦速度的结论，ETA方案模拟的湍流动能以及湍能方程各分量的垂直廓线更为可信。值得提出的是MM5、ETA两类近地层参数化方案的不同能显著影响湍流动能以及湍能方程各分量的垂直分布，这表明模式近地层参数化方案的选择会影响高原边界层大气动力、热力垂直结构及其湍能垂直输送特征。更多还原

【Abstract】 Making use of the boundary layer comprehensive observation system built with theJICA Project of Sino-Japan Joint Research Center of Meteorological Disaster at YunnanDali National Climatic Station, and use EDDYPRO software to complete the eddycovariance turbulence observation quality control and data correction. We compareEDDYPRO turbulent flux results with JICA fortran program results. The results of Dali dataprocessing indicate that the results of profile method and eddy covariance method areconsiderably different. We analyse the surface layer kinetic characteristic of the turbulence.The turbulence parameters including stability, turbulent variance, turbulent intensity,turbulent kinetic energy(TKE), buoyancy term, shear term and so on. We estimate landsurface parameters, such as aerodynamic roughness length(z0) and flux bulk transfercoefficients. Analysis of atmospheric boundary layer height characteristics which includestable boundary layer(SBL) and convective boundary layer(CBL) using the GPS Soundings.Based on the diagnostic analysis surface layer turbulent variables, In the viewpoint of thedifferent scales interaction between turbulence-convection motion, we discuss thecorrelation between boundary layer turbulent components and thermodynamic process inplateau, and we find that there are significant correlation between turbulent components andvertical motion.Calculation of surface layer turbulent fluxes is very important for atmospherenumerical models. How to parameterize the turbulent fluxes is one of the key researchquestions in current atmosphere boundary layer study. The paper uses two common schemes(MM5similarity non-iterative Scheme A and ETA similarity iterative Scheme B) in WeatherResearch Forecast Model(WRF) to make offline test and intercomparison of theparameterization results with PBL eddy-correlation observation. The aerodynamicroughness length(z0) obtained on Dali boundary layer is determined before calculating theturbulent fluxes. The aerodynamic roughness length(z0) by fitting four different heights wind speed from PBL tower data under neutral condition varies significantly with seasondue to the obvious changes in underlaying surface during the whole year.(horsebean inwinter half year and paddy in summer half year) Offline test results offer basis forevaluating online simulation effect. Based on the offline test two surface layer schemes,online simulation work is progressing gradually. This article mainly includes two parts, oneis the regional simulation effects of the two surface layer schemes, another is second-ordermoment term in the turbulent energy equation. Because of our interest in second-ordermoment term,1.5-order local closure model2.5level MYNN boundary layer scheme hasbeen used(3level MYNN scheme can not be combined with two surface layer schemes).The present study has mainly drawn the conclusions as follows:(1)Overall turbulent intensity in Dali cropland is larger than Sichuan basin, slightly largerthan Litang grassland. The normalized covariance of three dimensional wind speeds obeysthe power law of1/3. Buoyancy term in Dali is obviously smaller plateau Dangxiong area,and the value is close to plain area. Shear term which is considerably larger than plain areain Dali is close to plateau Dangxiong area. The aerodynamic roughness length presentsseasonal variation due to agricultural activities. The flux bulk transfer coefficients in easternTibetan Plateau is obviously larger the western area.(2)Thermal inhomogeneity of the underlying surface on the plateau results from the strongheating source or complex topography of the middle part of the plateau. Large scale verticalmotion in Tibetan Plateau is significantly correlated with apparent heat source (Q1) andmoisture sink(Q2). Meanwhile, surface TKE, buoyancy term and shear term also havenotable correlation with NCEP800hPa vertical montion in Dali. This result shows theheating source process drived by the plateau, and the turbulent contribution to the verticalmotion. The situation in Linzhi surface layer also appear the similar correlationcharacteristics bellow600hPa. The further applying of satellite data and other Multi-sourceinformation, and adopt the vertical motion data provided by LAPS model in Linzhi, we findthere exist more significant correlation between vertical motion and TKE. The resultconfirms strong vertical motion occurs with strong turbulence in the southern slopes of theTibet plateau. The correlations attenuated above600hPa in Linzhi, the coefficients ofcorrelation reach peak between600hpa~700hpa.(3)Under cloudless sky condition, CBL height in Dali can reach about2000m. There arestatistically significant correlation between CBL height and surface heat flux. Thecorrelation between CBL height and shear term is uncertain. Shear term produces thehorizontal direction turbulence, while buoyancy term produces the vertical direction turbulence. This conclusion has been confirmed by clear physical explanation.(4)Surface layer turbulent fluxes have great significance to mesoscale numerical simulation,therefore the parameterization scheme of turbulent fluxes is one of the hot spots in currentatmosphere boundary layer research. The authors of this paper use two schemes(MM5similarity non-iterative method A and ETA similarity iterative method B)in common usagein Weather Research Forecast Model(WRF) to make offline test, and compare theparameterization schemes results with PBL eddy-correlation observation. We determine themomentum roughness length(z0) before calculating turbulent fluxes. The method thatnonlinear fitting four different heights wind speed under neutral condition has been used,and fitting result suggest that the momentum roughness length(z0) appear obvious seasonalvariation due to the underlaying surface changes obviously during the whole year(winterhalf year horsebean and summer half year paddy). The turbulent fluxes result show that thevegetation sparseness degree have significant effect to turbulent fluxes calculation in Dalicropland. In general，momentum flux is estimated well for both MM5and ETA scheme. Inunstable condition, MM5scheme overestimates momentum flux，however，ETA schemeunderestimates momentum flux. In unstable condition, ETA Scheme significantlyunderestimates momentum flux in bare soil underlying surface，MM5Scheme is superior toETA Scheme. However, ETA Scheme is superior to MM5Scheme for vegetation underlyingsurface. In stable condition, MM5scheme appears more lower values while ETA schemeappears more larger values. ETA scheme takes account of the difference betweenmomentum roughness length(z0)and heat roughness length(z0h)，the exchange of heat isaccorded with actual condition better, and the heat flux result is superior to MM5schemeespecially in bare soil or sparse vegetation. Athough ETA scheme has been used to calculateheat flux, the result is still larger than the observation. In order to solve this problem，weadopt (Zeng et al.,1998) method. This method has significant effect to correct the bare soilunderlaying heat flux when the radiometric surface temperature data have been used.(5) The online results show that MM5Scheme generates larger momentum flux or frictionvelocity values in unstable condition, and ETA Scheme generates larger values in stablecondition. These results agree well with offline test. We find that the principal types ofunderlying surface is grassland and forestland in southeastern side of Tibetan Plateau byMODIS data, so we think ETA Scheme results seem more plausible and reliability. Theonline results also show that2.5level MYNN boundary layer scheme has adequateperformance to simulate TKE and turbulent terms in TKE equation. Because of the largerfriction velocity values in unstable condition calculated by MM5Scheme, larger TKE appeared in MM5Scheme relative to ETA Scheme. According to the conclusion fromoffline in unstable condition, we think TKE simulated by ETA Scheme is more reliable.更多还原