Scintillometer-Based Turbulent Fluxes of Sensible and Latent Heat Over a Heterogeneous Land Surface – A Contribution to Litfass-2003     

W. M. L. Meijninger  F. Beyrich  A. Lüdi  W. Kohsiek  H. A. R. De. Bruin 《Boundary-Layer Meteorology》2006,121(1):89-110

The performance of a combined large aperture scintillometer (LAS) and a millimetre wave scintillometer (MWS) for estimating surface fluxes of sensible and latent heat over natural landscape is investigated, using data gathered during LITFASS-2003. For this purpose the LAS–MWS system was installed in a moderate heterogeneous landscape over a path length of 4.7 km with an effective beam height of 43 m. The derived surface fluxes have been compared with aggregated eddy-covariance (EC) measurements. The fluxes of sensible and latent heat from the LAS–MWS combination, as well as sensible heat fluxes of the single LAS, agreed fairly well with the EC-based fluxes, considering the uncertainties of the similarity stability functions and observed energy imbalance.  相似文献   

A history and state-of-the-art of accommodation coefficients     

E.J. Davis   《Atmospheric Research》2006,82(3-4):561

This paper reviews theory and measurements of transport processes between small particles and the surrounding gas. Evaporation and condensation coefficients and gas uptake coefficients are of particular interest. There has long been a great difference in coefficients reported by different experimentalists, and much of this disagreement is considered in this overview. A brief review of the kinetic theory of gases is provided to describe molecular transport to or from a surface when the mean free path of molecules, ℓ, is large compared with the particle dimensions, that is, when the Knudsen number is large. For a sphere of radius a the Knudsen number, Kn = ℓ / a. The condition Kn >> 1 is called the free molecule regime, and for Kn << 1 continuum theory applies. It is shown that accommodation coefficients cannot be determined by experiments operating in the continuum regime. At intermediate Knudsen numbers (the Knudsen regime) transport theory is more difficult, but results based on solution of the Boltzmann equation describing the evolution of the molecular velocity distribution are reviewed. With the advent of high-speed computers transport theory has been supplemented by molecular dynamics calculations, and these calculations are often at odds with experimental measurements of accommodation coefficients. Examples are provided.Experimental methods surveyed include Knudsen cell methods, jet tensimetry, electrodynamic levitation experiments, expansion cloud chamber measurements, and vibrating orifice aerosol generator (VOAG) techniques. VOAG measurements are particularly useful for studying processes over small times, and theory and results related to VOAG experiments are presented. More recent experimental measurements of condensation coefficients involving the use of molecular beams are reported. There is a growing body of evidence that accommodation coefficients are of order unity in many cases, but coefficients smaller than 0.01 are still reported, particularly for uptake coefficients.  相似文献   

What limits evaporation from Mediterranean oak woodlands – The supply of moisture in the soil,physiological control by plants or the demand by the atmosphere?     

Dennis D. Baldocchi  Liukang Xu 《Advances in water resources》2007

The prediction of evaporation from Mediterranean woodland ecosystems is complicated by an array of climate, soil and plant factors. To provide a mechanistic and process-oriented understanding, we evaluate theoretical and experimental information on water loss of Mediterranean oaks at three scales, the leaf, tree and woodland. We use this knowledge to address: what limits evaporation from Mediterranean oak woodlands – the supply of moisture in the soil, physiological control by plants or the demand by the atmosphere?  相似文献   

斯洛伐克西喀尔巴阡山脉Gemerská Poloma滑石-菱镁矿矿床中镁的交代作用     

Martin RADVANEC  Peter KODRA  Walter PROCHASKA 《岩石学报》2004,20(4)

Gemerská Poloma矿床是个重要的滑石矿床(储量20万吨),位于西喀尔巴阡山脉Germeric地区。部分滑石化的镁质碳酸盐体赋存在早古生代火山沉积杂岩体中(黑色片岩,变质泥岩),在Variscan变质作用(M1)过程中受到了绿泥石-黑云母带区域变质相的改造。这种原岩是石灰岩的矿体由白色-灰白或者灰色-黑色的菱镁矿与白云石1组成,被次生的白云石2和滑石脉切割。本次研究考察了两次变质事件(M1和M2)的几个连续的矿物组合,最早的组合包括铁白云石,镁菱铁矿与菱铁矿,(并与黑电气石,铁绿泥石,磷灰石,与伊利石-白云母伴生),它们以微小残留物形式产出在菱镁矿和白云石1中,其形成可能早于M1变质作用高峰期。M1变质事件的高峰期以富铁金云母,镁绿泥石1,镁电气石(黑电气石的边缘)和石英的组合为代表。在M1退变质作用过程中,发生了镁交代作用,开始是白云石1结晶,接下来形成菱镁矿,最后是以铁菱镁矿沿裂隙的形成而终。根据碳酸盐地质测温原理,M1变质事件的高峰期温度为460~490℃,变质矿物组合特征也支持这一测温结果。滑石,白云石2,与镁绿泥石2沿着镁碳酸盐岩石裂隙的发育,主要受到M2变质事件的影响,这个变质事件与较年青的Alpine造山事件有关。 菱镁矿流体包裹体的研究表明,成矿流体具有复杂的组成,可能以MgCl2组分为主,主要来  相似文献   

蜜蜂舐水对蒸发量的影响及对策     

张宏建  张宏伟  董美琴  徐晓凤 《内蒙古气象》2009,(2):37-38

蜜蜂采舐蒸发水量,一直不被人们注意,但通过对养蜂人走访调查,并与历年同期蒸发记录对比分析,排除大风等天气现象对蒸发量的影响后,发现蜜蜂舐水干扰后的蒸发结果异常,及时采取措施合理阻断蜜蜂舐水,尽量减少对蒸发的影响。  相似文献   

储油罐气态污染物计算方法的选择及污染控制   总被引：3，自引：0，他引：3       下载免费PDF全文

洪冰 《气象与环境学报》2008,24(3):59-62

储罐无组织排放的定量估算是石化企业污染源核查的重要项目。通过对比分析美国国家环保局(EPA)、美国石油学会(API)及中国石油化工(CPCC)系统经验公式等3种常用定量方法的应用情况,选择储罐区预测大气污染物的最佳方法,进而确定对储油罐的油品蒸发损耗量。结果表明:采用浮顶罐可减少小呼吸损耗,设置油气回收设施可减少大呼吸损耗,EPA公式较适合轻质油品,CPCC公式较适合拱顶罐,并提出减少油品损耗量的防治措施。  相似文献   

Estimating Potential Evaporation over a Hill     

E. M. Blyth 《Boundary-Layer Meteorology》1999,92(2):185-193

A simple analytical model of the effect of a hill on potential evaporation (i.e., evaporation from well-watered vegetation) is presented. It is shown to reproduce the results from a two-dimensional non-linear numerical model. The analytical model is used to demonstrate the sensitivity of the changes in evaporation to surface resistance, aerodynamic resistance, temperature, slope and sun angle. Methods used by MORECS (Meteorological Office Regional Evaporation Calculation System) to estimate the potential evaporation at high elevations, and by Numerical Weather Prediction models to represent sub-grid scale hills, take account of the change in altitude but neglect the slope effects. A slope of 20 degrees, which is typical of upland terrain in the U.K., increases the potential evaporation by about 5%.  相似文献   

Large-scale desiccation of the Aral Sea due to over-exploitation after 1960     

Behzod GAYBULLAEV  Su-Chin CHEN 《山地科学学报》2012,9(4):538-546

The Aral Sea was one of the largest lakes in the world before it started to shrink in the 1960s due to water withdrawal for agricultural irrigation.Precipitation decreased from 9.4 km3 in 1960 to 3.2 km3 in 2009,and annual river inflow into the Aral Sea decreased from 31.5 km3 in 1998 to 5.2 km3 in 2009.Comparison on the hydrological data of the Aral Sea between 1960 and 2009 showed the evaporation,water surface area,and water volume decreased by 90%,80%,and 88%,respectively.This study employs the observed values of water volume,precipitation,runoff,evaporation,and salinity to estimate water volume and salinity from 1960 to 2009,and the efficiency coefficients for predicted water volume and salinity are 0.975 and 0.974,respectively.Regression equations calculated from the observed data are used to predict precipitation,runoff,evaporation,and salinity from 2010 to 2021,and the results are then applied in the estimation of water volume and salinity.Our estimates suggest that salinity will increase to around 200 g/L and water volume will decrease to around 83 km3 in 2021.  相似文献   

一次黑潮海洋锋强迫下的蒸发波导突变性与非均匀性的观测与模拟研究     

丁菊丽  梁志超  费建芳  吕庆平  赵小峰 《气象学报》2021,79(6):1049-1062

蒸发波导是影响海上雷达系统探测性能的主导机制,海表温度（SST）锋带来的蒸发波导非均匀性和突变性具有重要的研究价值。2018年春季航次“海气相互作用观测试验”,曾两次穿越黑潮海域获取了珍贵的观测资料。在此基础上,结合欧洲中期天气预报中心（ECMWF）再分析资料（ERA-Interim）和HYSPLIT（Hybrid Single Particle Lagrangian Integrated Trajectories）气块轨迹溯源,分离出两个重要的走航观测时段。S1段（持续约21 h）气流从暖海水区吹向冷海水区,以稳定层结为主,其间因黑潮海洋锋的存在,气流由黑潮主体的暖水区吹向大陆冷海区时,形成具有强逆温层的海洋边界层,并伴随海雾的生成,导致此处蒸发波导高度突降为0。此后为持续近66 h的S2段,气流由冷海水区吹向暖海水区,以近中性弱不稳定层结为主,蒸发波导高度基本维持在12 m高度。数值模拟结果表明,模拟时段内的黑潮海洋锋区,蒸发波导高度突变性和非均匀性始终存在,且伴随暖海水吹向冷海水的锋区突变性更强。黑潮海洋锋对蒸发波导的这种天气尺度强迫作用的加强与层结稳定度的突变和海雾的生成有关。   相似文献   

罗布泊罗北西3号断陷带固体钾盐矿地质特征及成因分析          下载免费PDF全文

李博昀  张凡凯  邓宇飞  于咏梅  董连兵  李文学  王凌芬  马宝成 《盐湖研究》2022,30(3):63-71

经遥感解译及地表调查,在罗布泊新庆台地罗北西3号断陷带内存在固体钾盐矿化带。为初步查明该断陷带钾盐矿化带的矿体赋存特征、矿物组分、矿石类型及矿体规模,开展了系统的坑探揭露、刻槽取样、盐矿鉴定、X射线衍射及化学分析测试等工作。经勘查,钾盐矿层赋存于洼地内第四系全新统化学沉积层中,呈似层状分布。面积约30 km²,矿层厚0.30～2.73 m,平均1.02 m。经X射线衍射及盐矿鉴定,矿石中含钾矿物以杂卤石为主,钾盐镁矾次之,局部见含光卤石,矿石中KCl含量在2.07%～8.44%,平均含量在3.55%。通过本次研究,确认该区存在一低品位固体钾盐矿床,初步查明了矿床地质特征,其成因为台地内的局部洼地汇水经蒸发作用沉积形成,为进一步的勘查及开发提供了地质依据。  相似文献