应用涡旋相关方法对戈壁地区湍流输送特征的初步研究

利用微机技术建立了一个较为廉价的近地层大气湍流数据实时采集处理系统,在1988年黑河预实验中工作良好,取得了一套较为完整的数据。对戈壁沙滩点的风、温、湿湍流脉动数据进行统计分析和涡旋相关方法处理,结果表明近地层大气的湍强特征符合一般规律。通量分析指出,戈壁地区的水汽通量在白天的绝大多数小时都呈负值(向下),而夜间为正。文中对湍流谱的特征也进行了初步分析。     

河西地区非均匀下垫面的大气变性过程

利用ＨＥＩＦＥ野外观测资料，分析了河西地区黑河流域夏半年下面动力和热力特性的不均匀 ；并以个别具有一定代表性的晴天观测资料为例，客观地分析了绿洲与沙漠或戈壁下垫面突变所产生的近地层大气变性过程；初步解释发绿洲近地层逆温和沙漠或戈壁近地层逆湿的形成机制，同时也讨论了绿洲和沙的水汽输送过程。     

敦煌绿洲-戈壁过渡带地表辐射与能量特征分析

利用"西北干旱区陆-气相互作用野外观测试验"2002年在敦煌加强期的资料, 分析了敦煌绿洲-戈壁过渡带的地表辐射和能量特征.研究表明 白天, 绿洲-戈壁过渡带的地表温度和近地层大气温度很高, 和戈壁的地表温度接近;在多数晴天夜晚, 绿洲-戈壁过渡带的地表温度和近地层大气温度要低于戈壁的值.总辐射, 反射辐射和地表长波辐射的值都很接近荒漠戈壁的值, 日积分通量分别为24.48, 6.1, 41.42 MJ*m+-2*d.绿洲-戈壁过渡带的感热、潜热和地表热通量的日积分值分别为6.58, 1.60和0.38 MJ*m+-2*d.同时, 在绿洲-戈壁过渡带有较强的水平湍流输送.     

前言

“黑河地区地气相互作用野外观溅试验研究(HEIFE)”野外观测1工作已于1992年10月15日全部结束。先后进行了“先行性试验(POP)”(1988年9月4-19日),“正常观测试验(FOP)”(1990年6月—1991年10月15日,其中日方负责的001和005微气象站和五个自动气象站延续到1992年10月15日);“先行性加强期(PIOP)”(1990年8     

绿洲周边荒漠戈壁夏末土壤-大气水分传输特征

利用“我国西北干旱区陆-气相互作用试验”2000年8-9月在甘肃敦煌地区戈壁滩上取得的野外观测资料,分析了临近绿洲的戈壁土壤湿度和温度特征以及相对应的大气湿度特征,发现土壤热量活动层约为5cm厚,比一般土壤要薄得多;临近绿洲的荒漠戈壁上,不仅近地层大气多为逆湿,而且浅层土壤有时也出现逆湿。土壤湿度日变化能清楚地被区分为湿维持、水分损失、干维持和水分补充等四个阶段。土壤湿度廓线表明：土壤水分活动层厚度约为10m;湿维持阶段的浅层土壤逆湿是土壤湿度廓线最主要的结构特征,这一土壤湿度结构预示着夜间土壤可能通过凝结吸收大气水分,它与白天的土壤水分蒸发共同构成土壤对大气水分的“呼吸”过程。土壤逆湿的形成与土壤温度状态、大气逆湿强度和大气稳定度都有关。     

北极斯瓦尔巴德地区近地层大气观测研究II.湍流场特征

利用“中国科学探险协会2002年北极科学探险考察”期间在北极朗伊尔宾地区获得的大气风温微气象脉动资料,讨论了该地区近地层湍流能谱、湍流方差、感热通量、动量通量、温度结构参数以及动量整体输送系数等的分布规律,给出了这一极端环境区夏季近地层微气象场的基本结构,分析了北极地区极昼期间陆地下垫面地-气之间能量交换,丰富了人们对该地区近地层湍流输送过程的深入理解。     

北极斯瓦尔巴德地区近地层大气观测研究Ⅱ.湍流场特征

利用"中国科学探险协会2002年北极科学探险考察"期间在北极朗伊尔宾地区获得的大气风温微气象脉动资料,讨论了该地区近地层湍流能谱、湍流方差、感热通量、动量通量、温度结构参数以及动量整体输送系数等的分布规律,给出了这一极端环境区夏季近地层微气象场的基本结构,分析了北极地区极昼期间陆地下垫面地-气之间能量交换,丰富了人们对该地区近地层湍流输送过程的深入理解.     

绿洲效应的模拟及内外因子的敏感性实验

利用一个已发展的陆面物理过程参数化方案与大气边界层数值模式耦合,模拟了半干旱区绿洲戈壁非均匀下垫面的陆面物理过程及其与大气边界层的相互作用,成功地描绘了绿洲戈壁局地气候效应,并进行了绿洲戈壁局地气候效应对于降水、绿洲水平尺度和植被结构等若干内外因子的敏感性实验.结果表明:绿洲的最小临界尺度为5～10 km之间,最大临界尺度为55～65 km之间,而最利于绿洲维持的尺度范围为20 km左右,这一结论与我国西部地区现存的绿洲尺度统计结果十分一致;绿洲植被覆盖率为0.6左右时,最利于绿洲发展.另外对植被空间分布方式和绿洲植被组成比例上也进行了数值实验,并对影响绿洲生存和持续发展的内、外因子气候效应的影响力量级进行了分级.这些结果对于深入了解绿洲气候的形成和维持机理具有重要的意义.     

甘肃省河西黑河流域沙漠、戈壁地区夏季大气浑浊度与沙尘特性分析

通过对甘肃省河西黑河流域沙漠、戈壁地区1990年夏季?ngstr?n大气浑浊度系数的计算分析，总结出了该种特殊下垫面条件下大气浊度特征。并由大气浑浊度系数及波长指数的变化，定性讨论了这一地区大气中沙尘的消光特性及其生成、消散过程。进一步应用Volz方法和Arao方法粗略地估计了这一地区大气在不同条件下的沙尘含量。     

西北干旱区绿洲—戈壁资料同化数据集的建立与分析

利用美国气象环境预报中心和美国国家大气研究中心(NCEP/NCAR)共同开发的天气研究和预报系统WRF模式3.1版本,结合地球观测系统的中分辨率成像光谱仪EOS-MODIS反演的下垫面土地利用/植被类型资料,并同化2008年夏季金塔绿洲野外观测试验所取得的气象资料,对绿洲系统陆—气水热交换过程进行模拟,最终生成金塔高分辨率资料同化再分析数据集。此数据集包括黑河流域金塔绿洲2008年6-8月逐时水平分辨率1 km的土地利用类型、19层风温湿压、4层土壤温湿度以及地表植被覆盖、辐射分量、热通量等资料。同时,利用金塔绿洲观测期内的地表气压、地面气温和相对湿度实测值对该数据集进行初步验证,并分析了绿洲—戈壁系统的"冷湿岛效应"、平均大气环流特征和空气温湿度长期变化规律。结果表明,绿洲和戈壁下垫面的热力差异明显,绿洲和戈壁平均地表温度白天和夜间分别相差21℃和3℃;10 cm土壤温度白天最大相差17℃,并且绿洲比戈壁滞后3 h达到峰值;戈壁相对湿度比绿洲平均约低11%;白天绿洲的"冷岛效应"和"湿岛效应"影响高度平均可达2000 m和1500 m;夜间绿洲的近地层500 m以下则表现出弱的"冷岛效应";夜间绿洲上空的平均垂直气流为上升气流,白天出现大范围下沉气流,平均最大下沉气流速度可达-0.3 m·s-1。     

THE CHARACTERS OF ENERGY BUDGET ON THE GOBI AND DESERT SURFACE IN HEXI REGION*

In the paper,the characters of surface energy budget on Huayin(Gobi)and the desert surface during the period from 26 June to 31 August 1990 in the HEIFE have been analyzed,then have been compared with the observed results during 4-19 September 1988 in the Pilot Observation Period of the HEIFE.The results show that the atmosphere is in superadiabatic unstable state and there is a phenomenon of inverse humidity to form negative water vapour flux.The sensible heat flux on the surface energy budget is in majority,but the latent heat flux may be neglected over the Gobi and desert surface in the cloudless daytime in the summer.     

河西戈壁（化音）小气候和热量平衡特征的初步分析

本文分析了1988年9月在甘肃省临泽县城西南侧戈壁获得的近地面层微气象观测资料。结果表明:白天晴空一般都是超绝热不稳定状态,并存在一种逆湿现象,造成向下输送的水气通量。这可能是由于戈壁地表极其干燥,没有蒸发,上层大气湿度反而比近地面层高,致使水汽从上往下输送。这时在地表面热量平衡过程中,潜热可以忽略不计,感热占绝对优势。     

Turbulence Structure In Unstable Conditions Over Various Surfaces

A comprehensive study of the turbulent structure of the atmospheric boundary layer in unstable conditions has been carried out using turbulence data obtained from the Gobi desert, grassland, suburban and urban sites based on the same instrumentation, data acquisition and data processing systems. The normalized standard deviations of u and v over the suburban and urban sites are systematically smaller than those over the Gobi desert and grassland sites. However, the normalized standard deviations of w, temperature and humidity q over the suburban and urban sites are quite close to those over the Gobi desert and grassland sites. The normalized humidity standard deviations are quite similar to those of temperature over the grassland and suburban sites. The temperature and humidity spectra are found to be independentof atmospheric stability in all frequency ranges, but spectra obtained from the Gobi desert and grassland sites reveal flatter peaks than those of the suburban and urban sites in the lower frequency range. The normalized spectral curves of temperature and humidity are independent of atmospheric stability both at high and low frequencies. The spectral characteristics of humidity over the grassland and suburban sites aresimilar to those of temperature, but the humidity spectra over the Gobi desert site are quite different from temperature spectra due to evaporation and/or large eddies in the boundary layer.     

On the Kinetic Energy Budget of the Unstable Atmospheric Surface Layer

We present a new account of the kinetic energy budget within an unstable atmospheric surface layer (ASL) beneath a convective outer layer. It is based on the structural model of turbulence introduced by McNaughton (Boundary-Layer Meteorology, 112: 199–221, 2004). In this model the turbulence is described as a self-organizing system with a highly organized structure that resists change by instability. This system is driven from above, with both the mean motion and the large-scale convective motions of the outer layer creating shear across the surface layer. The outer convective motions thus modulate the turbulence processes in the surface layer, causing variable downwards fluxes of momentum and kinetic energy. The variable components of the momentum flux sum to zero, but the associated energy divergence is cumulative, increasing both the average kinetic energy of the turbulence in the surface layer and the rate at which that energy is dissipated. The tendency of buoyancy to preferentially enhance the vertical motions is opposed by pressure reaction forces, so pressure production, which is the work done against these reaction forces, exactly equals buoyant production of kinetic energy. The pressure potential energy that is produced is then redistributed throughout the layer through many conversions, back and forth, between pressure potential and kinetic energy with zero sums. These exchanges generally increase the kinetic energy of the turbulence, the rate at which turbulence transfers momentum and the rate at which it dissipates energy, but does not alter its overall structure. In this model the velocity scale for turbulent transport processes in the surface layer is (kzɛ)^1/3 rather than the friction velocity, u_*. Here k is the von Kármán constant, z is observation height, ɛ is the dissipation rate. The model agrees very well with published experimental results, and provides the foundation for the new similarity model of the unstable ASL, replacing the older Monin–Obukhov similarity theory, whose assumptions are no longer tenable.     

边界层局地相似理论在草原下垫面的适用性检验

利用锡林浩特草原平坦下垫面塔层湍流资料,对常值通量层的高度进行了估计,检验了局地相似理论在均匀草原下垫面的适用性,对Monin-Obukhov相似理论和局地相似理论在常值通量层以上的大气边界层的适用性进行了比较。结果表明:(1)对于锡林浩特草原来说,常值通量层厚度在50m左右;(2)通过分析无量纲风速和温度梯度、无量纲风速方差、无量纲标量(温度T、水汽q、CO2浓度C)方差与稳定度z/L之间的关系,验证了局地相似理论在均匀草原下垫面70m以下大气边界层的适用性;(3)感热通量尺度与浮力长度尺度之间存在线性关系;(4)从经典Monin-Obukhov长度、局地Monin-Obukhov尺度和浮力长度尺度的对比分析来看,局地尺度更适用于50m以上的大气边界层,而浮力长度尺度不适用于50m以上的大气边界层。     

城市近地层湍流特征分析

利用中国科学院大气物理研究所在北京的325 m铁塔观测资料,本文分析了47、140和280 m三个高度的湍流统计特征.结果表明,城市近地层的湍流速度方差和湍流温度方差都较好地满足局地相似关系,140 m和280 m的湍流特征非常接近,而47 m的湍流特征与之相比表现出明显的差异,说明由于城市冠层动力和热力非均匀性的影响...     

不同下垫面上近地层湍流的多尺度属性研究

文中利用统计和多尺度分析方法分析了几种复杂下垫面情况下的风、温湍流脉动观测资料 ,结果表明 :下垫面结构的差异明显地影响湍流量 ,如 :戈壁地区的热力作用明显大于雪面和城郊面 ,表现在湍流时间尺度上也明显地大于雪面和城郊面。但复杂下垫面下的湍谱在惯性区仍满足“- 23”次律 ;多尺度方法研究湍流 ,可以更简捷地分析湍流的多尺度结构及其在湍流输送中的作用。由此可看出 ,多尺度方法是发展湍流统计理论的一种有效工具。     

Note on turbulence statistics in z-less stratification

In boundary layer meteorology, surface layer similarity theory plays a critical role in measuring and modeling biospheric fluxes. In stable boundary layer, surface layer similarity called z-less stratification has been one of main research topics for over than two decades and the issue has yet to be settled in micrometeorology. In this scientific discussion on z-less turbulence, different turbulence statistics were used inconsistently and it was argued that z-less turbulence was valid if only any turbulence statistics were constant with different atmospheric stabilities. Consequently, such inconsistently tested turbulence statistics and misconception on z-less turbulence hinder us from correctly understanding turbulence structure in the stable boundary layer. This note revisits z-less turbulence and emphasizes that different dimensionless turbulence statistics generally do not exhibit a common behavior in the limit of z-less stratification.     

ON TURBULENCE CLOSURE CONSTANTS FOR ATMOSPHERIC BOUNDARY-LAYER MODELLING: NEUTRAL STRATIFICATION

Constant sets for several turbulence closure models,based on data for the atmospheric boundary layer, areproposed. They differ from those currently used inengineering situations but are self-consistent andtuned to represent atmospheric boundary-layerturbulence. The proposed constant sets are tested in a simple,one-dimensional, neutrally-stratified planetaryboundary-layer flow over a horizontally homogeneousand aerodynamically rough flat surface. Comparisons ofmodel results with similarity theory and large-eddysimulation show promise for improving boundary-layerpredictions.