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1.
近10年夏季西北地区水汽空间分布和时间变化分析   总被引:5,自引:0,他引:5  
利用NCEP 1°×1°再分析资料对近10年(2000-2009年)夏季西北地区整层大气水汽的时空分布进行了分析。结果表明:(1)近10年西北地区夏季大气可降水量和水汽通量分布呈两头多、中间少。700~200hPa的水汽通量值要比地面至700hPa的大,在南疆盆地,地面至700hPa的水汽通量值比700~200hPa的大,水汽通量在600~450hPa之间比较丰富;(2)整层水汽通量散度辐合区对降水落区的预报具有指导意义,除甘肃河西地区外,其他地区低层(700hPa以下)和高层(700hPa以上)的水汽通量散度呈反位相分布。(3)近10年西北地区水汽输送主要来自西风带在青藏高原西侧分为南北两支所携带的水汽、孟加拉湾的水汽随西南风输送以及西风带爬上青藏高原沿高原南边输送,而造成整层水汽通量年变化的主要原因是西风带输送水汽能力的大小。(4)近10年西北地区整层水汽通量呈线性增加,整层水汽通量的年变化趋势基本上可以指示地面降水的年变化趋势。(5)西北地区近10年夏季水汽来源主要以经向输送为主,纬向水汽通量对于西北区水汽净收支起决定作用。  相似文献   

2.
1998年南海季风试验期间海 气通量的估算   总被引:2,自引:0,他引:2       下载免费PDF全文
根据1998年南海季风试验西沙海面铁塔梯度观测资料,利用总体(Bulk)系数法和多层结通量廓线法对西沙海面的海-气通量进行了估算,得出两种方法估算的潜热通量、感热通量基本一致。总体系数法估算的潜热通量比多层结通量廓线法略大1~3 W·m-2,感热通量小0~1.5 W·m-2。一般而言,季风爆发期间潜热输送逐渐增加;季风爆发前期夜间潜热通量比季风爆发后期大;季风爆发后期,白天潜热通量明显大于爆发初期和中期。感热通量季风爆发前海面向大气输送,爆发后期大气向海面输送。动量通量和摩擦速度随风速增加。  相似文献   

3.
不同下垫面湍流输送计算方法的研究   总被引:9,自引:0,他引:9       下载免费PDF全文
文章应用三种不同下垫面近地面层风速和温度梯度资料,代入风速和温度廓线公式,迭代求得感热通量及热量交换系数。确定Kh /Kw与稳定参数ξ的关系式。分别利用空气动力学方法和波文比能量平衡法计算潜热通量,并进行了比较。  相似文献   

4.
利用欧洲中期天气预报中心第五代再分析数据产品,归类分析了藏东南雅鲁藏布大峡谷地区水汽输送类别。选取大峡谷地区排龙站、墨脱站两个站点2019年涡动相关系统观测数据,分析不同水汽条件下雅鲁藏布大峡谷地区不同位置近地面水热交换通量的日变化特征。结果表明:高原季风期对应大峡谷地区水汽强输送期和温湿期,高原非季风期则相反。墨脱站、排龙站在高原季风期/非季风期典型晴天/阴天近地面潜热通量日变化对大气水汽条件较为敏感且响应一致,近地面潜热通量在强水汽条件下的日变化均强于弱水汽条件下,墨脱站特征最为显著,在高原季风期典型晴天强水汽条件下潜热通量日均值为84.05 W·m-2是弱水汽条件下的1.13倍,日变幅达345.37 W·m-2。两个站点在高原季风期/非季风期近地面感热通量对大气水汽条件响应不同。高原季风期典型晴天下,两个站点在弱水汽条件下的近地面感热通量日变化均强于强水汽条件下,海拔较高的排龙站在弱水汽条件下感热通量日均值(32.71 W·m-2)和日较差(191.10 W·m-2)是强水汽条件下的1.66倍和1.26倍。云覆盖和水汽对太阳短波辐射的削弱作用大于其自身的温室效应,墨脱站和排龙站在高原季风期/非季风期典型阴天弱水汽条件下的近地面感热通量日变化均强于强水汽条件下,排龙站在高原季风期/非季风期典型阴弱水气条件下近地面感热通量日均值为35.12 W·m-2和14.32 W·m-2分别是强水汽条件下的2.59倍和1.27倍。大峡谷地区存在水汽输送通道,大气水汽的辐射强迫对陆-气间水热交换过程存在显著影响,但近地面能量分配受地表水热属性的制约。  相似文献   

5.
使用鄱阳湖北部70 m气象塔湍流和梯度观测数据,分析了2011年6月6日夜间一次暴雨过程中近地面边界层特征.结果表明,此次过程是在高空低槽和西南急流的天气背景下,受鄱阳湖复杂地表影响产生的局地性强降水.强降水发生前受东南暖平流影响,近地面边界层中水汽累积,不稳定性增加;强降水过程中,近地层感热、潜热通量迅速增加,同时,近地面层湍流动量通量下传和水平输送增加,鄱阳湖的水汽输送加强降水强度.另外,强降水过程中,近地面湍流动能迅速增大并达到最大值,而平均动能的增大发生在强降水结束后,表明地表作用明显,近地面边界层的湍流场为暴雨提供动力条件.尺度分析表明,强降水前,中尺度动量通量占主要地位,降水过程中湍流动量通量显著加强.  相似文献   

6.
南极瑞穗站辐射平衡及湍流通量特征   总被引:3,自引:0,他引:3  
刘树华  于鹏  熊康 《气象学报》1994,52(1):68-77
本文利用南极瑞穗站1979—1980年近地面层微气象及辐射平衡等观测资料,分析了春、夏、秋和冬季辐射平衡分量的日、年变化特征,采用空气动力学方法和廓线梯度迭代法计算了不同季节的动量通量、感热通量和由能量平衡方程得到的潜热通量的日变化特征,并对计算结果进行了比较。文中还对湍流热量交换系数、湍流动量交换系数与理查孙数的日变化关系进行了讨论。  相似文献   

7.
利用NCEP 1°×1°再分析资料和国家级自动站逐时观测资料及NOAA的2.5°×2.5°每月再分析资料,对2013年8月16—17日发生在辽宁抚顺地区清原县的特大暴雨过程进行水汽特征分析。结果表明:本次暴雨为副热带高压北抬促使高空槽在中国东北地区停滞少动,使得东北冷涡持续影响辽宁地区,切变线、低空急流为此次暴雨过程的主要影响系统;辽宁抚顺清原县这次暴雨过程的底层和中层的水汽来源主要为南海和孟加拉湾以及西太平洋两条通道;暴雨发生主要时间,南海和孟加拉湾及西太平洋提供重要水汽持续输送,这为暴雨的发展提供了充足的水汽。抚顺地区清原县暴雨发生的前期和发生时均存在强烈的水汽向上输送,高湿层即比湿大值区集中在从对流层一直延伸到500 h Pa;地面水汽通量散度极值中心比降水的极值中心提前出现2 h,且二者具有一定的正相关关系。地面水汽通量散度负值中心出现后2 h内对暴雨中心位置具有一定的预报意义。  相似文献   

8.
基于2019年12月至2020年11月峨眉山站梯度塔资料、辐射观测资料和地表通量资料,采用涡动相关法对峨眉山地区近地层的地表通量和蒸散发量的变化进行分析,并估算了零平面位移、空气动力粗糙度、空气热力粗糙度、动量通量输送系数和感热通量输送系数等重要的空气动力学和热力学参数。研究表明:近地面风速呈现高层高、低层低的特征,且高层日变化较低层明显;垂直风廓线在冠层内与冠层上存在明显不同的相关关系及拐点现象,拐点以下风速随高度的增速明显比拐点以上的小;零平面位移d年平均值为10.45 m;空气动力学粗糙度Z0m和空气热力学粗糙度Z0h年均值分别为1.65 m和9.95 m;动量通量输送系数CD和感热通量输送系数CH的年平均值分别为1.58×10-2和3.79×10-3;近地层降水发生次数和降水量多寡有明显的季节变化,7月降水日和降水量都较多,近地层降水日变化明显,表现出川西盆地典型的夜雨特征;感热通量和潜热通量白天的主导地位随季节变化,夏季潜热通量占主导地位,冬季感热输送占主导地位;各天的蒸散发主要发生在08:00(北京时,下同)-17:00,在11:00-14:00达到最大值,且季节差异明显。  相似文献   

9.
利用ERA5小时再分析资料分析了1981~2019年三江源地区水汽总量和水汽通量的时空演变规律及其可能成因。结果表明:三江源地区平均水汽总量和水汽通量的空间分布总体呈东南向西北递减的态势;其中,7月水汽表现出明显的异质性,对应平均水汽总量在可可西里和黄河源区的两个高值中心,平均水汽通量则恰好是两个低值区,该月水汽输送在曲麻莱、清水河一带和久治形成两个辐合区;近39年,平均水汽总量与平均水汽通量的经向输送呈增多趋势,但夏季平均水汽通量纬向输送的显著减少导致了其年值的减少;而平均水汽总量与平均水汽通量的年内分配分别呈“单峰”型、“双峰”型分布;西风环流减弱、高原夏季风以及南海夏季风增强,有利于水汽总量的增加和经向输送,而夏季高原热力作用则对水汽经向输送起到一定的扰动作用。   相似文献   

10.
采用涡动相关方法连续观测2002年10月到2003年12月半干旱地区地气界面水汽和二氧化碳通量变化,分析水汽和二氧化碳通量的季节和日变化规律,同时比较农田和退化草地两种不同下垫面物质和能量通量交换过程的差异,得到如下一些主要结果:(1)半干旱地区湿季,相距5 km的两种不同下垫面,即使在同一天气过程控制下,不同植被下垫面的降雨分布仍不尽相同,甚至相差很大.这表明降雨空间的分布是很不均匀的,具有很强的局地特征.(2)在干季近地面层能量收支中,两种不同下垫面上的有效能量(净辐射与地表热流量之差)主要分配为感热通量,潜热通量在非生长季(干季)通常很小.在湿季(生长季),潜热通量与感热通量相当,但农田下垫面的潜热通量大于退化草原下垫面.(3)土壤的温度和湿度日变化主要集中在0~20 cm土壤层内,在湿季农田下垫面土壤的湿度有明显的跳跃,这与降雨过程有很好的相关.(4)在非生长季,两种不同下垫面地气间二氧化碳通量差别不大,都很小.白天由于光合作用,在生长季农田下垫面吸收CO2通量较退化草原大,但比湿润地区稻田下垫面小一个量级,远小于森林生态系统.  相似文献   

11.
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.  相似文献   

12.
Energy and Water Balance at Soil-Air Interface in a Sahelian Region   总被引:1,自引:0,他引:1  
l. IntroductionModel simulation of soll physical properties is very 1mportant for climate studies becauseof the role they play in different interaction processes with the atmosphere. One of the mostwidespread studies is the implementation of soil models 1n General Circulation Models(GCMs); previous studies showed, in fact, that climate simulat1ons are sensitive to theparameterization of the energy and mass fluxes at the land surface (V1terbo, l995; Beljiaars etal., l996; Dolman et al., l997…  相似文献   

13.
In order to understand the exchange and transferprocesses of water and energy in the desert soil andthe atmospheric boundary layer (ABL), we have developeda coupled model, in which a desert soil modelincluding water movement of both liquid and vapourphase, and an ABL model based on a non-local transilientturbulence closure scheme, are coupled together. Withthis model, the evolution of potential temperature andspecific humidity, the distribution of net radiationamong sensible, latent and soil heat fluxes, and thewater and heat flux profiles both in the soil and ABLhave been simulated. The HEIFE (HEIhe River Basin FieldExperiment) observational data are used to calibrate calculation of the water and heat flux both in thesoil and the ABL. The sensible and latent heatfluxes warm and moisten the bottom grid box (100m) of theABL. In this way the ABL model and the desert soil model are coupled together.The simulated results show that when the flux of watervapour in the soil is neglected, the evaporation rateand the flux profiles of specific humidity in the ABLshow great changes, hence the importance of watervapour movement in the desert soil for the calculationof specific humidity in the ABL. In the upper 5cm of thesoil, which is called an active layer, water andheat transport are more effective than in the substrate(soil below 5 cm).  相似文献   

14.
The concentration of carbon dioxide in the atmosphere acts to control the stomatal conductance of plants. There is observational and modelling evidence that an increase in the atmospheric concentration of CO2 would suppress the evapotranspiration (ET) rate over land. This process is known as CO2 physiological forcing and has been shown to induce changes in surface temperature and continental runoff. We analyse two transient climate simulations for the twenty-first century to isolate the climate response to the CO2 physiological forcing. The land surface warming associated with the decreased ET rate is accompanied by an increase in the atmospheric lapse rate, an increase in specific humidity, but a decrease in relative humidity and stratiform cloud over land. We find that the water vapour feedback more than compensates for the decrease in latent heat flux over land as far as the budget of atmospheric water vapour is concerned. There is evidence that surface snow, water vapour and cloudiness respond to the CO2 physiological forcing and all contribute to further warm the climate system. The climate response to the CO2 physiological forcing has a quite different signature to that from the CO2 radiative forcing, especially in terms of the changes in the temperature vertical profile and surface energy budget over land.  相似文献   

15.
Summary The temperature and moisture data from TIROS operational vertical sounder (TOVS) are examined to obtain humidity parameters like, mid and upper tropospheric water vapour, and scale height of water vapour. Their usefulness in characterizing the onset of south-west (SW) monsoon over India is studied. The NOAA satellite data (finished product) with a resolution of 2.5° lat/lon are used to obtain these parameters during and prior to the SW monsoon season over selected regions during 1979 to 1985. The pentad averaged values in the western Indian Ocean showed an increase in scale height of water vapour and mid-tropospheric moisture (700–500 mb) over about 8 to 10 days prior to the onset over Kerala coast. The association of the moisture flux across the Indian Ocean and the rainfall over Kerala coast has also been examined. Results showed that the gradient of middle level moisture is stronger in the case of rainfall deficit years.With 13 Figures  相似文献   

16.
河西地区非均匀下垫面的大气变性过程   总被引:14,自引:6,他引:14  
张强  胡隐樵 《高原气象》1996,15(3):282-292
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。  相似文献   

17.
沙漠土壤和大气边界层中水热交换和传输的数值模拟研究   总被引:15,自引:0,他引:15  
为了解沙漠土壤和大气边界层系统中的水分和能量的交换和传输特征,本文发展了一个一维耦合模式,其中包括一个同时考虑土壤中液态水及气态水运动的沙漠土壤模式和一个基于非局地过渡湍流闭合方案的大气边界层模式。用这一耦合模式对沙漠土壤和大气界面的水热交换及沙漠土壤和大气边界层中的水热输送过程进行了模拟,同时与HEIFE(HeiheRiverBasinFieldExperiment)沙漠站的有关资料进行了对比。模拟结果表明约65%的净辐射能以感热(50%)和潜热(15%)的形式提供大气,约35%的净辐射能以地热流量的形式进入土壤。土壤表层2cm的范围表现为水热传输的活跃层,水分和温度廓线呈现剧烈的日变化。模拟结果同时表明沙漠土壤中水分传输以气态水为主,如果忽略土壤中的气态水运动,地气界面的水汽通量计算及边界层内的湿度及水汽通量的计算会产生较大的误差  相似文献   

18.
Regional turbulent statistics over contrasting natural surfaces   总被引:1,自引:0,他引:1  
Summary Regional turbulent fluxes of momentum, sensible and latent heat collected over both agricultural and native vegetation in the south west of Australia are presented. Analysis of the energy spectrum illustrates that the most energetic eddies are between scales of 20 metres to 5 kilometres and highlights the spatial distance required to obtain representative regional fluxes. For the sensible heat flux, this distance is a function of measurement height whereas the latent flux is also influenced by surface variability. Statistics of these fluxes highlight that for the unstable surface layer, despite marked differences in the underlying vegetation and the corresponding sources of heat and moisture, heat is transported more efficiently than water vapour from the ground surface. Received October 9, 2000/Revised April 23, 2001  相似文献   

19.
Summary Water vapour flux profiles in the atmospheric boundary layer have been derived from measurements of water vapour density fluctuations by a ground-based Differential Absorption Lidar (DIAL) and of vertical wind fluctuations by a ground-based Doppler lidar. The data were collected during the field experiment LITFASS-2003 in May/June 2003 in the area of Lindenberg, Germany. The eddy-correlation method was applied, and error estimates of ±50 W/m2 for latent heat flux were found. Since the sampling error dominates the overall measurement accuracy, time intervals between 60 and 120 min were required for a reliable flux calculation, depending on wind speed. Rather large errors may occur with low wind speed because the diurnal cycle restricts the useful interval length. In the lower height range, these measurements are compared with DIAL/radar-RASS fluxes. The agreement is good when comparing covariance and error values. The lidar flux profiles are well complemented by tower measurements at 50 and 90 m above ground and by area-averaged near surface fluxes from a network of micrometeorological stations. Water vapour flux profiles in the convective boundary layer exhibit different structures mainly depending on the magnitude of the entrainment flux. In situations with dry air above the boundary layer a positive entrainment flux is observed which can even exceed the surface flux. Flux profiles which linearly increase from the surface to the top of the boundary layer are observed as well as profiles which decrease in the lower part and increase in the upper part of the boundary layer. In situations with humid air above the boundary layer the entrainment flux is about zero in the upper part of the boundary layer and the profiles in most cases show a linear decrease.  相似文献   

20.
Evapotranspiration is a source of water vapour to the atmosphere, and as a crucial indicator of landscape behaviour its accurate measurement has widespread implications. Here we investigate errors that are prevalent and systematic in the closed-path eddy-covariance measurement of latent heat flux: the attenuation of fluxes through dampened cospectral power at high frequencies. This process is especially pronounced during periods of high relative humidity through the adsorption and desorption of water vapour along the tube walls. These effects are additionally amplified during lower air temperature conditions. Here, we quantify the underestimation of evapotranspiration by a closed-path system by comparing its flux estimate to simultaneous and adjacent measurements from an open-path sensor. We apply models relating flux loss to relative humidity itself, to the lag time of the cross-correlation peak between the water vapour and vertical wind velocity signals, and to models of cospectral attenuation relative to the cospectral power of simultaneous sensible heat-flux measurements. We find that including the role of temperature in modifying the attenuation–humidity relationship is essential for unbiased flux correction, and that physically based cospectral attenuation methods are effective characterizers of closed-path instrument signal loss relative to the unattenuated flux value.  相似文献   

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