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1.
Summary The Bowen Ratio-Energy Balance (BREB) and the aerodynamic method were used to estimate turbulent fluxes of sensible and latent
heat flux over an irrigated agricultural area (IAA) and over two dry agricultural areas (DAA1 and DAA2). These turbulent fluxes
were analysed and particular attention paid to two specific areas. First, a quantitative analysis of sensible and latent heat
fluxes obtained by the BREB method was carried out, taking into account different soil type, vegetation and surface conditions.
The results showed that in IAA latent heat flux was higher than sensible heat flux, except in summer months, while in DAA1
and DAA2, sensible heat flux was higher except in the months when the vegetation was at the stage of maximum development.
Second, sensible and latent heat fluxes estimates from the BREB method were compared with those obtained from the aerodynamic
method. In this comparison factors such as soil type, soil vegetation cover, homogeneity or inhomogeneity of terrain and mesoscale
effects such as orography and wind patterns were taken into account. The results show that in conditions of light wind, the
two methods only concur if the condition of horizontal homogeniety is fulfilled. The influence of inhomogeneity seems to decrease
and agreement between methods improves, if the wind is stronger and the effects of meso and synoptic scales are predominant.
Received May 18, 1999/Revised March 15, 2000 相似文献
2.
利用2005年7月盘锦芦苇湿地生长旺季的小气候梯度系统30 min观测资料和开放式涡动相关系统10Hz原始观测资料,比较并分析了廓线法、波文比能量平衡法与涡动相关法计算的芦苇湿地生态系统水热通量。结果表明:廓线法与波文比能量平衡法计算的芦苇湿地生态系统水热通量与涡动相关法得到的芦苇湿地生态系统水热通量具有较好的相关性,但是涡动相关法存在能量不平衡。分析盘锦芦苇湿地生态系统水热通量的日变化发现,能量平衡各分量基本上以正午为中心,呈倒“U”型分布。用波文比法计算得到的芦苇湿地生态系统日感热通量最大值为164.25 W.m-2,日潜热通量最大值为294.18 W.m-2。降雨之后,芦苇湿地生态系统水热通量都有所增加,尤其是潜热通量增加显著,且峰值出现时间提前。 相似文献
3.
There is not much information in the literature about the energy partitioning and micrometeorological features of sunn hemp. Therefore, in this study, the variations in the energy-balance components and plant characteristics such as aerodynamic and surface conductance, crop coefficient, albedo, short- and long wave down- and upward radiation have been measured and estimated for the time period from August to October 2004 over an irrigated sand field at the Arid Land Research Center in Tottori, Japan. The Bowen ratio energy-balance method was used to calculate the partitioning of heat fluxes of sunn hemp. The Bowen ratio values at the first growing stages in August were found to be higher than the Bowen ratio values at the latest growing stages in September and October because of the heavy rain and high soil-water content. The daytime averaged Bowen ratio was 0.19. During the measurement period, the daytime average net radiation, and soil, latent and sensible heat fluxes were approximately 231, 28, 164, and 39 W m–2, respectively. The net radiation and soil heat flux showed decreasing trends from the beginning to the end of the experiment period due to the atmospheric and crop growth conditions. The daytime averages of aerodynamic and surface conductance for sunn hemp were around 31 and 17 mm s–1, respectively. Also, the daytime average albedo of sunn hemp was around 19%. Finally, the high precipitation amount due to typhoons, high soil-water content, low available energy and low vapor-pressure deficit lead to decreasing trend of the energy fluxes during the generative phase of sunn hemp. 相似文献
4.
Summary Energy balance components over a grassland surface were compared to those obtained above an adjacent, uniform Scots pine plantation during a five-day period of fine, sunny, spring weather. Soils were judged to contain ample water. Shortwave and total radiation flux densities were measured at both sites with pyranometers and total pyrradiometers. Soil heat flux densities were measured with heat flux plates at both sites, and additional storage changes were estimated for air and canopy at the forest site. The forest gained more shortwave energy than the grassland during daytime because of its lower albedo, but it lost more longwave radiation at night. The turbulent fluxes of sensible and latent energy were evaluated with the Bowen ratio energy balance (BREB) method at both sites. Temperature and humidity gradients were measured with fixed psychrometers at the grassland site, and with interchanging psychrometers at the forest site. Mean daily evapotranspiration (ET) averaged 2.26 mm over the five days for the Scots pine, or only 57 percent of the 3.94 mm measured at the grassland site. The mean Bowen ratios were 2.6 and 0.8, respectively.An error analysis was carried out for the BREB estimates of latent heat flux at the two sites. For a given error in latent heat flux and at a specified Bowen ratio the demands on accuracy of dry- and wet-bulb temperature gradients above the rough forest canopy was found to be 10 times higher than above the smoother grassland. If additionally the observed differences in transpiration rates between the two sites were taken into account, the precision for temperature gradient measurements above the slowly transpiring forest becomes fortyfold greater than required above the rapidly transpiring grass. At present, BREB precision requirements for gradients above rougher, drier canopies appear achievable only through use of specialized instrumentation, such as measurement systems that incorporate interchangeable psychrometers into their design.With 9 Figures 相似文献
5.
利用变分法计算西北典型干旱区地表通量的研究 总被引：6，自引：0，他引：6
利用2000年5～6月在敦煌进行的陆面过程野外观测试验加强期的观测资料,采用变分法计算了西北干旱区荒漠戈壁的地表感热通量和潜热通量,并与Bowen比能量平衡方法(简称BREB法)的结果进行了对比.结果表明:变分法由于同时应用了地表能量平衡方程和相似性廓线方程,充分利用了边界层观测资料的信息,避免了BREB法中出现在Bowen比接近于-1时产生的计算不稳定和虚假的峰值,使计算的通量结果更趋合理和稳定.同时也计算了动量和感热的总体输送系数,与已有结果比较表明也具有合理性. 相似文献
6.
The sensible heat loss from a stand of winter wheat was calculated from radiometric measurements of crop surface temperature, measurements of air temperature, and an atmospheric resistance to momentum transfer; corresponding latent heat flux was obtained through the energy balance equation. These estimates of sensible and latent heat were compared with fluxes from the Bowen Ratio method. When radiative temperature was derived using a measured canopy emissivity of 0.98, calculations of sensible heat flux were systematically 50–100 W m-2 less than Bowen Ratio values. The two techniques agreed more closely when an apparent emissivity of 0.96 was used with an apparent reflectivity of 0.03. The mean difference between the estimates of latent heat flux was then -16 ± 32 W m-2.The surface temperature method showed less systematic error in comparison with the Bowen Ratio values than did estimates using the aerodynamic method.On leave from: University of Nottingham, School of Agriculture, Loughborough LE12 5RD. 相似文献
7.
Simultaneous energy balance observations at a rural and a suburban site in Vancouver, B.C. during the summer of 1983 are presented. The study is a follow-up to that conducted in 1980. Many of the 1980 results were unexpected and the present study seeks to assess their representativeness. The net radiant, turbulent sensible, and rural soil heat flux densities were measured directly. The suburban heat storage was parameterized and the turbulent latent heat flux densities were resolved as residuals in the energy balances. The 1983 average diurnal energy partitioning for both sites was typical of those quoted in the literature, suggesting that the 1980 results represent an extreme case. Suburban-rural differences showed the suburban area to have a 4% increase in net radiation, a 51% increase in turbulent sensible heat, and a 46% decrease in turbulent latent heat flux density. The values of the average daytime Bowen ratio were 0.46 and 1.28 for the rural and suburban areas, respectively. The sensible heat flux density exhibited relatively large values in the late afternoon and remained directed upward on many summer evenings. Large day-to-day variability in the relative magnitude of the suburban turbulent fluxes may have been due to synoptic influences. In this environment, the turbulent surface and mixed layers are closely coupled because of the low aerodynamic resistance over the rough surface. 相似文献
8.
内蒙古半干旱草原能量物质交换的微气象方法估算 总被引：15，自引：1，他引：14
根据1998年5～8月和1999年8月在中国科学院内蒙古草原生态系统定位试验站进行微气象观测的资料,作者分析了该地区能量平衡及其各分量的基本特征.结果表明:(1)净辐射通量的转化形式有明显的季节性变化,5～6月份,净辐射能大部分用于感热交换,而后期则多用于潜热交换,5～8月份的日波文比值分别为1.26,1.42,0 41和0.20.(2)观测期间,波文比的日变化特征表现为,早晚变化大不稳定,而白天则相对稳定.(3)用涡度相关方法观测的感热和潜热通量之和与同期的净辐射相比较,前者的结果偏小1 5%左右,两种方法观测到的潜热通量的差异达平均35%左右.(4)半干旱草原CO2通量有明显的日变化,在生长旺期,白天CO2通量强度可达到1.5 mg s-1m-2以上,但在生长后期,1998年和1999年8月份的白天CO2通量强度分别为0.38 mg s-1m-2和0.2 mg s-1m-2左右;其差异与草地土壤水分和植物长势有关. 相似文献
9.
Denny P. Alappattu D. Bala Subrahamanyam P. K. Kunhikrishnan Radhika Ramachandran K. M. Somayaji R. Venkatesh G. S. Bhat A. Bhagavath Singh 《Boundary-Layer Meteorology》2008,126(2):297-309
We report the spatio-temporal variability of surface-layer turbulent fluxes of heat, moisture and momentum over the Bay of
Bengal (BoB) and the Arabian Sea (AS) during the Integrated Campaign for Aerosols, gases Radiation Budget (ICARB) field experiment.
The meteorological component of ICARB conducted during March – May 2006 onboard the oceanic research vessel Sagar Kanya forms
the database for the present study. The bulk transfer coefficients and the surface-layer fluxes are estimated using a modified
bulk aerodynamic method, and then the spatio-temporal variability of these air-sea interface fluxes is discussed in detail.
It is observed that the sensible and latent heat fluxes over the AS are marginally higher than those over the BoB, which we
attribute to differences in the prevailing meteorological conditions over the two oceanic regions. The values of the wind
stress, sensible and latent heat fluxes are compared with those obtained for the Indian Ocean Experiment (INDOEX) period.
The variation of drag coefficient (C
D
), exchange coefficients of sensible heat and moisture (C
H
= C
E
) and neutral drag coefficient (C
DN
) with wind speed is also discussed.
相似文献
10.
Estimating heat fluxes by merging profile formulae and the energy budget with a variational technique 总被引：6，自引：0，他引：6
A variational technique (VT) is applied to estimate surface sensible and latent heat fluxes based on observations of air temperature, wind speed, and humidity, respectively, at three heights (1 m, 4 m, and 10 m), and the surface energy and radiation budgets by the surface energy and radiation system (SERBS). The method fully uses all information provided by the measurements of air temperature, wind, and humidity profiles, the surface energy budget, and the similarity profile formulae as well. Data collected at Feixi experiment station installed by the China Heavy Rain Experiment and Study (HeRES) Program are used to test the method. Results show that the proposed technique can overcome the well-known unstablility problem that occurs when the Bowen method becomes singular; in comparison with the profile method, it reduces both the sensitivities of latent heat fluxes to observational errors in humidity and those of sensible heat fluxes to observational errors in temperature, while the estimated heat fluxes approximately satisfy the surface energy budget. Therefore, the variational technique is more reliable and stable than the two conventional methods in estimating surface sensible and latent heat fluxes. 相似文献
11.
Radiometric surface temperatures, derived from measurements by the AVHRR instrument aboard the NOAA-9 and the NOAA-11 polar orbiting satellites, were used in combination with wind velocity and temperature profiles measured by radiosondes, to calculate surface fluxes of sensible heat. The measurements were made during FIFE, the First ISLSCP (International Satellite Land Surface Climatology Project) Field Experiment, in a hilly tall grass prairie area of northeastern Kansas. The method of calculation was based on turbulent similarity formulations for the atmospheric boundary layer. Good agreement (r = 0.7) was obtained with reference values of sensible heat flux, taken as arithmetic means of measurements with the Bowen ratio method at six ground stations. The values of evaporation (latent heat fluxes), derived from these sensible heat fluxes by means of the energy budget, were also in good agreement (r = 0.94) with the corresponding reference values from the ground stations. 相似文献
12.
Summary Strong stable layers are a common occurrence during western Colorado's winter. Analysis of radiosonde observations indicate wintertime boundary layer heights are near 500 m. The terrain in this region consists of mountains that rise approximately 1500–2000 m above the ground to the east, providing an effective blocking barrier. An experiment is described to observe upwelling and downwelling, longwave and shortwave radiative fluxes at two sites in western Colorado during January and February 1992, for combinations of clear, cloudy, snow covered, and bare ground periods. Analysis of the observations and the surface energy budget for typical Bowen ratios provides a better understanding of the role of radiation in maintaining and destroying stable layers.During the day, the surface received a net gain of energy from radiation, while at night there was a net loss. Over snow, the 24-hour net radiative flux was small and either positive or negative. Over bare soil, the 24-hour net radiative flux was positive but still small. There is little difference in the net radiative flux between clear and cloudy days; the reduction of the incident solar flux by clouds is nearly compensated by the hindering of the longwave cooling. The cumulative effects of the 24-hour net radiative flux were negative over snow early in the experiment. The 24-hour values shifted to near zero as the snow albedo decreased and were positive for bare ground.If the daytime net radiative flux is partitioned into sensible and latent heat flux using typical Bowen ratios, the daytime sensible heat available for destroying boundary layers is small for the low solar angles of the winter season. With a Bowen ratio of 0.5, the daytime sensible heat flux available is only 0.3 to 1.2 MJ m–2 over a snow surface and 1.4 to 2.3 MJ m–2 over soil. These heat fluxes will not build a deep enough boundary layer to break a typical wintertime inversion. The 24-hour sensible heat flux was negative at both sites for the entire experiment with this Bowen ratio.The radiation observations and the use of typical Bowen ratios lead to the conclusion that the net radiation will sustain or strengthen a stable atmosphere in the winter season in western Colorado. Analysis of the radiosonde observations confirm this result as the boundary layer depths were less than 500 m early in the experiment and grew to only 700 m later in the experiment.With 12 Figures 相似文献
13.
L. W. Gay R. Vogt Ch. Bernhofer J. H. Blanford 《Theoretical and Applied Climatology》1996,53(1-3):33-48
Summary The surface energy exchange of 12m high Scots pine plantation at Hartheim, Germany, was measured with a variety of methods during a 11-day period of fine weather in mid-May 1992. Net radiation and rate of thermal storage were measured with conventional net radiometers, soil heat flux discs and temperature-based storage models. The turbulent fluxes discussed in this report were obtained with an interchanging Bowen ratio energy budget system (BREB, at 14 m), two one-propeller eddy correlation systems (OPEC systems 1 and 2 at 17m), a 1-dimensional sonic eddy correlation system (SEC system 3) at 15 m, all on one low tower, and a 3-dimensional sonic eddy correlation system (SEC system 22) at 22 m on the high tower that was about 46 m distant. All systems measured sensible and latent heat (H and LE) directly, except for OPEC systems 1 and 2 which estimated LE as a residual term in the surface energy balance. Closure of turbulent fluxes from the two SEC systems was around 80% for daytime and 30% for night, with closure of 1-dimensional SEC system 3 exceeding that of 3-dimensional SEC system 22. The night measurements of turbulent fluxes contained considerable uncertainty, especially with the BREB system where measured gradients often yielded erroneous fluxes due to problems inherent in the method (i.e., computational instability as Bowen's ratio approaches –1). Also, both eddy correlation system designs (OPEC and SEC) appeared to underestimate |H| during stable conditions at night. In addition, both sonic systems (1- and 3-dimensional) underestimated |LE| during stable conditions. The underestimate of |H| at night generated residual estimates of OPEC LE containing a phantom dew error that erroneously decreased daily LE totals by about 10 percent. These special night problems are circumvented here by comparing results for daytime periods only, rather than for full days. To summarize, turbulent fluxes on the low tower from OPEC system 2 and the adjacent SEC system 3 were in reasonable agreement, while the BREB system appeared to overestimate H and underestimate LE; H and LE measured by SEC system 22 on the high tower were lower than from OPEC and SEC3 on the low tower. The turbulent flux measurements tended to converge, but the data exhibit unexplained differences between days, between systems, and between locations.With 7 Figures 相似文献
14.
The Signature of Sea Spray in the Hexos Turbulent Heat Flux Data 总被引：7，自引：0，他引：7
The role of sea spray intransferring heat and moisture across the air-sea interface has remained elusive. Some studies have reported that sea spray does not affect the turbulent air-sea heat fluxes for 10-m wind speeds up to at least 25 m s-1, while others have reported important spray contributions for wind speeds as low as 12 m s-1. One goal of the HEXOS (Humidity Exchange over the Sea) program was to quantify spray's contribution to the turbulent air-sea heat fluxes, but original analyses of the HEXOS flux data found the spray signal to be too small to be reliably identified amid the scatter in the data. We look at the HEXOS data again in the context of the TOGA-COARE bulk flux algorithm and a sophisticated microphysical spray model. This combination of quality data andstate-of-the-art modelling reveals a distinct spray signature in virtually all HEXOS turbulent heat flux data collected in winds of 15 m s-1 and higher. Spray effects are most evident in the latent heat flux data, where spray contributes roughly 10% of the total turbulent flux in winds of 10 m s-1 and between 10 and 40% in winds of 15–18 m s-1. The spray contribution to the total sensible heat flux is also at least 10% in winds above 15 m s-1. These results lead to a new, unified parameterization for the turbulent air-sea heat fluxes that should be especially useful in high winds because it acknowledges both the interfacial and spray routes by which the sea exchanges heat and moisture with the atmosphere. 相似文献
15.
半干旱区不同下垫面近地层湍流通量特征分析 总被引：11，自引：3，他引：8
本文分析了2003～2005年半干旱区退化草地和农田下垫面近地层湍流通量日、季、年的变化特征, 探讨了不同年份的气候背景和下垫面土地覆被对地气交换过程的影响。结果表明: 半干旱区退化草地和农田近地层湍流通量具有明显的日变化、季变化周期; 地气间通量交换年际间的差异主要受当年的气候背景影响, 尤其是降水的影响; 同时还受到下垫面覆被的影响。潜热通量和感热通量的能量分配比率呈反位相变化, 且农田和退化草地的变化趋势相似, 在夏季潜热通量所占比例均超过感热通量; 两种下垫面的波恩比月均值变化趋势十分相似, 量级接近, 夏季低, 春、秋季高; 夏季退化草地和农田下垫面波恩比均小于或等于1。 相似文献
16.
Some evaluations of drag and bulk transfer coefficients over water bodies of different sizes 总被引：1，自引：0，他引：1
B. B. Hicks 《Boundary-Layer Meteorology》1972,3(2):201-213
Three recent experiments allow evaluation of the bulk transfer coefficients for momentum, water vapour and sensible heat over water bodies of different sizes. As part of a study of evaporation rates from a swamp, measurements of latent and sensible heat fluxes were made over Lake Wyangan in southern N.S.W., Australia. This lake is of several kilometers diameter. In a later experiment, Reynolds stress and sensible heat transfer were measured from a natural-gas platform standing in Bass Strait, south of mainland Australia. The most recent experiment involved the direct measurement of each of these turbulent fluxes from a fixed tower erected in Lake Michigan, U.S.A.Perhaps the most important of the results is the finding that drag coefficients measured over Bass Strait are not significantly different from those over Lake Michigan, despite the obvious differences in depth, fetch, and hence surface wave structure. At both locations, drag coefficients are found to increase slightly with increasing wind speed, while at low wind speeds they are not significantly different from those corresponding to aerodynamic smoothness.Near-neutral bulk transfer coefficients for sensible heat and for water vapour are found to be similar. An average value of about 1.4 × 10–3 is obtained.It is emphasized that stability effects should be considered in any discussion of drag coefficients or bulk transfer coefficients. Large errors can result if near-neutrality is incorrectly assumed. 相似文献
17.
18.
利用第三次青藏高原大气科学观测试验数据,对高原不同地区感热、潜热交换等湍流输送特征进行了分析,并进一步对比研究了其与气象环境因子的相关关系。结果表明:（1）高原各站之间感热和潜热的差异性较大,但大多在雨季潜热会大于感热。干燥的狮泉河站属于高寒荒漠地区,降水极少,全年感热都远大于潜热,波文比年平均值可达到20.0;湿润的比如站和嘉黎站潜热在4～10月均显著大于感热,波文比在4～10月的数值范围在0.27～0.88。（2）高原感热和潜热通量的季节变化与高原季风所处的地理位置有密切关系,高原中部的感热通量在3～5月达到最大值,而高原西部则在4～6月最大,可能与高原季风的活动有关。（3）通过与气象要素的相关分析表明,高原西部狮泉河站感热与地气温差的正相关关系最为显著,全年的相关系数可以达到0.905,在4个季节相关系数也均大于0.79,这可能与下垫面是裸地有关;高原中部安多站和那曲站感热与风速的正相关在夏季最为显著,比如站感热与风速的正相关在冬季最为明显,而狮泉河站感热与风速在春、夏季均有着十分显著的正相关。 相似文献
19.
沙漠地区沙尘天气近地层湍流输送特征分析 总被引：12，自引：3，他引：12
利用1996－04－20－50－10在内蒙古自治区吉兰泰气象站以及1997－04－05－27在内蒙古自治区阿拉善右旗气象站观测到的风，温，湿廓线资料，应用空气动力学方法，计算了每天各观测时次的流动量通量，湍流感热通量和湍流潜热通量，并且比较分析了荒漠下垫面不同沙尘天气状况下的湍流动量通量，感热通量和潜热通量的日变化。结果表明，在沙漠地区春季无降水天气状况下，晴空条件下，白天热力湍流基于动力湍流，在近地层最重要的物质交换是湍流感热交换，浮尘天气条件下，近地层湍流输送较晴空天气条件下弱；扬沙天气条件下，近地层湍流感热交换和湍流动力量流感热通量的峰值大于交换，并且湍流动量通量的峰值较晴空峰值大将近一个量级，湍流感热通量的峰值大于浮尘天气峰值，但小于晴空条件下峰值，沙尘暴天气条件下，湍流动量通量和感热通量一样都是最重要的湍流交换，湍流交换强于扬沙天气，强的感热对沙漠地局地性沙尘暴的产生和加强起着重要作用。 相似文献
20.
农田蒸散量计算方法的比较研究 总被引：9，自引：1，他引：8
根据观测资料,采用波文比法、廓线梯度法和综合阻地等分别计算了农田植被层上的蒸散量,并对比分析了不同方法之间的相对误差和相关程度。结果表明,用波文比法计算的潜热通量存在系统性偏小的现象,而工法和综合阻抗法的计算结果比较一致。文中还讨论了不同方法的优缺点和产生误差的可能原因。 相似文献