共查询到20条相似文献，搜索用时 15 毫秒
1.
利用珠海凤凰山陆气相互作用观测塔站2014年11月至2016年5月的观测数据,对比分析了干湿季森林下垫面能量通量和气象要素的变化特征,分析了在不同稳定度下3个风向范围（315°～45°、45°～135°和135°～225°）的动量和感热交换系数随冠层表面风速的变化特征,并对动量和感热交换系数进行了参数化研究。结果表明:干季感热和潜热通量值相当,湿季潜热远大于感热。干季和湿季的夜晚都出现负感热现象,感热从大气向森林输送。相对湿度的变化幅度大,与该地气象状况密切相关,相对湿度的垂直梯度夜晚较大,白天较小。干季的气温垂直梯度比湿季的明显。风速在冬季变化平缓,夏季变化剧烈,低层风速随高度变化梯度明显,高层较紊乱。各高度风向差异不大。中性和近中性状态下,在风向为315°～45°、45°～135°和135°～225°时,动量交换系数Cdn分别为0.05、0.0055和0.022,感热交换系数Chn分别为0.0055、0.003和0.004。在稳定和不稳定状态下,动量交换系数Cd、感热交换系数Ch随冠层表面风速v明显发生变化,稳定条件下,Cd、Ch随v的增大而增大;不稳定条件下,Cd、Ch随v的增大而减小。分不同风向对森林冠层Cd、Ch在稳定和不稳定条件下与v的关系进行了拟合,得到了参数化公式。 相似文献
2.
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
3.
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
4.
Direct measurements of the air–sea turbulent fluxes of momentum and heat, along with surface currents, waves and supporting
meteorological variables, were acquired during a recent field campaign. Surface currents, measured from a very high frequency
radar, were found to steer the stress away from the mean wind direction. Although this effect has been reported in a recent
scatterometer study, this is the first time it has been observed in an in situ study with co-located flux, wind and surface current measurements. Data collected during a week of stationary conditions
are used to investigate and quantify the sampling variability of the air–sea fluxes of momentum and sensible heat. 相似文献
5.
Jun A. Zhang Kristina B. Katsaros Peter G. Black Susanne Lehner Jeffrey R. French William M. Drennan 《Boundary-Layer Meteorology》2008,128(2):173-189
Boundary-layer secondary circulations or ‘roll vortices’ can have a significant influence on the turbulent exchange of momentum,
sensible heat and moisture throughout the hurricane boundary layer. In this study, analyses of data from a WP-3D aircraft
of the National Oceanic and Atmospheric Administration (NOAA) are presented. As part of the Coupled Boundary Layer Air-Sea
Transfer (CBLAST)-hurricane experiment sponsored through the Office of Naval Research and NOAA’s annual hurricane research
program, flights were conducted to investigate energy exchange across the air–sea interface. We present the first in-situ
aircraft-based observations of rolls in the hurricane boundary layer and investigate their influence on energy and momentum
exchange. The rolls detected in Hurricane Isidore (year 2002) have a characteristic wavelength of about 900 m, in good agreement
with analyses of data from a synthetic aperture radar image captured by the Canadian Space Agency’s RADARSAT satellite in
the same storm. Our analyses of the airborne data suggest that roll vortices may be a significant factor modulating the air–sea
momentum exchange. 相似文献
6.
Ekaterine Batchvarova Svan-Erik Gryning Charlotte Bay Hasager 《Boundary-Layer Meteorology》2001,99(3):489-507
Based on measurements at Sodankylä Meteorological Observatory the regional (aggregated) momentum and sensible heat fluxes are estimated for two days over a site in Finnish Lapland during late winter. The forest covers 49% of the area. The study shows that the forest dominates and controls the regional fluxes of momentum and sensible heat in different ways. The regional momentum flux is found to be 10–20% smaller than the measured momentum flux over the forest, and the regional sensible heat flux is estimated to be 30–50% of the values measured over a coniferous forest.The regional momentum flux is determined in two ways, both based on blending height theory. One is a parameterised method, the other represents a numerical solution of an aggregation model. The regional sensible heat flux is determined from the theory of mixed-layer growth. At near neutral conditions the regional momentum flux can be determined independently of the regional sensible heat flux. At unstable conditions the two models become coupled.The information that is needed by the parameterised blending height method and by the mixed-layer evolution method in order to derive the regional fluxes of momentum and sensible heat can be obtained from radiosonde profiles of wind speed and temperature. 相似文献
7.
The impact of sea waves on sensible heat and momentum fluxes is described. The approach is based on the conservation of heat and momentum in the marine atmospheric surface layer. The experimental fact that the drag coefficient above the sea increases considerably with increasing wind speed, while the exchange coefficient for sensible heat (Stanton number) remains virtually independent of wind speed, is explained by a different balance of the turbulent and the wave-induced parts in the total fluxes of momentum and sensible heat.Organised motions induced by waves support the wave-induced stress which dominates the surface momentum flux. These organised motions do not contribute to the vertical flux of heat. The heat flux above waves is determined, in part, by the influence of waves upon the turbulence diffusivity.The turbulence diffusivity is altered by waves in an indirect way. The wave-induced stress dominates the surface flux and decays rapidly with height. Therefore the turbulent stress above waves is no longer constant with height. That changes the balance of the turbulent kinetic energy and of the dissipation rate and, hence the diffusivity.The dependence of the exchange coefficient for heat on wind speed is usually parameterized in terms of a constant Stanton number. However, an increase of the exchange coefficient with wind speed is not ruled out by field measurements and could be parametrized in terms of a constant temperature roughness length. Because of the large scatter, field data do not allow us to establish the actual dependence. The exchange coefficient for sensible heat, calculated from the model, is virtually independent of wind speed in the range of 3–10 ms-1. For wind speeds above 10 ms-1 an increase of 10% is obtained, which is smaller than that following from the constant roughness length parameterization.The investigation was in part supported by the Netherlands Geosciences Foundation (GOA) with financial aid from the Netherlands Organization for Scientific Research (NWO). 相似文献
8.
With the marine ship observation data set obtained by three cruise-phases of Chinese Xi-angyanghong 5 from November 5,1992 to February 19,1993 in the TOGA-COARE IOP at 2°S,156°E.the sea surface fluxes at this point are estimated by three different bulk schemes.Firstly.aquasi-linear relation is found between the neutral drag coefficients and wind speed.Then,the sta-bility-dependent drag and heat transfer coefficients are solved in the iterative method.Based onthus-derived transfer coefficients,the momentum,sensible and latent heat fluxes are calculated.In the warm pool region,the fluxes corresponding to the westeily winds are much greater thanthose of the easterly trade winds.The magnitude of sea surface fluxes depends upon the atmo-spheric stability as well,in particular in the case of weak wind condition.The estimated sea sur-face net heat budget shows that considerable amount of heat transport from ocean to atmosphere ismainly produced by the effective longwave radiation,latent and sensible heat fluxes.Among themthe value of latent heat flux is the largest and the sensible heat flux is the smallest.Finally,an ac-curacy analysis is made by direct measurements with the eddy-correlation method on the JapaneseR/V Hakuho board at the same time.It is shown that the bulk-derived fluxes are acceptable withmuch confidence.The estimated effective longwave radiation is used to compare with those by di-rect observations on Xiangyanghong 5.This research is compared with TOGA investigation in thetropical western Pacific. 相似文献
9.
Aircraft turbulence data from the Autonomous Ocean Sampling Network project were analyzed and compared to the Coupled Ocean–Atmosphere
Response Experiment (COARE) bulk parametrization of turbulent fluxes in an ocean area near the coast of California characterized
by complex atmospheric flow. Turbulent fluxes measured at about 35 m above the sea surface using the eddy-correlation method
were lower than bulk estimates under unstable and stable atmospheric stratification for all but light winds. Neutral turbulent
transfer coefficients were used in this comparison because they remove the effects of mean atmospheric conditions and atmospheric
stability. Spectral analysis suggested that kilometre-scale longitudinal rolls affect significantly turbulence measurements
even near the sea surface, depending on sampling direction. Cross-wind sampling tended to capture all the available turbulent
energy. Vertical soundings showed low boundary-layer depths and high flux divergence near the sea surface in the case of sensible
heat flux but minimal flux divergence for the momentum flux. Cross-wind sampling and flux divergence were found to explain
most of the observed discrepancies between the measured and bulk flux estimates. At low wind speeds the drag coefficient determined
with eddy correlation and an inertial dissipation method after corrections were applied still showed high values compared
to bulk estimates. This discrepancy correlated with the dominance of sea swell, which was a usually observed condition under
low wind speeds. Under stable atmospheric conditions measured sensible heat fluxes, which usually have low values over the
ocean, were possibly affected by measurement errors and deviated significantly from bulk estimates. 相似文献
10.
Young-Hee Lee 《Boundary-Layer Meteorology》2009,132(3):383-399
Eddy-covariance data have been analyzed to investigate the influence of local stability on heat transfer within open canopies.
The flux–gradient relationship for heat is derived from the temperature variance equation, and the stability dependence of
the flux–gradient relationship is examined and discussed. The results indicate that the strong stability dependence of the
nondimensional standard deviation of temperature, and the small contributions of turbulent transport to the temperature variance,
lead to a strong stability dependence of the nondimensional temperature gradient within open canopies. Quadrant analysis and
hole size analysis were performed for momentum and heat fluxes in the subcanopy, and the results indicate that the contribution
of each quadrant to the total flux depends on both the local stability and canopy depth. The intermittency of the turbulent
flux does not show a clear dependence on local stability. As the contribution of ejections to the heat flux increases, the
vertical flux of the temperature variance changes sign from negative to positive, leading to small temperature variance transport
in unstable conditions. Multi-resolution analysis indicates that heat and momentum are transported with different dominant
time scales in very unstable conditions, suggesting a different role of local buoyancy in heat and momentum transfer. 相似文献
11.
Through the use of the hourly wind, air temperature and humidity, sea surface temperature data measured on board the observing vessel Moana Wave and buoy in the warm pool of western Pacific during the IOP of TOGA COARE, we compute the fluxes over sea surface and analyze the characteristics of the variation ofthe latent heat flux with sea surface temperature. During weak rather than strong wind periods a maximum valueof latent heat flux appears at some points of SST, which is caused mainly by the variations of wind, then by the humidity difference between air and sea and the transfer coefficient with SAT. Using correlation analysis. we also analyze the relationship between the fluxes and meteorological elements during weak wind periods. wester lywind burst periods, and convective disturbed periods etc. The main conclusions are that the latent heat flux ismainly determined by wind, sensible heat flux by the potential temperature difference between air and sea and the momentum flux by wind. The precipitation affects the sensible heat flux through the potential temperature difference and wind. 相似文献
12.
利用中国气象局成都高原气象研究所建立的5个边界层站（湄潭、巴中、什邡、曲麻莱、狮泉河）2019年的观测资料，对比分析青藏高原及周边地区近地层大气要素变化和陆—气能量交换特征及异同点，探讨其原因。结果表明：（1）青藏高原及周边地区近地层大气温度、相对湿度、风速、感热通量、潜热通量、动量通量均符合一峰一谷的常规日变化特征，气压具有双峰双谷的日变化特征。（2）高海拔台站近地层温度日变幅（12℃）高于周边低海拔地区（4～6℃），季变幅与海拔高度的关系不显著。（3）相对湿度与温度关系密切，相对湿度的垂直结构和日变化都具有明显的区域差异，其垂直梯度夜间显著高于白天，峰值出现时间随夏、秋、春、冬季呈现季节性滞后，而谷值超前。（4）风速春季较大，夏、秋季次之，冬季小，季变幅略小于日变幅；低海拔区域的风速及其日变幅均显著低于高海拔区域。（5）低海拔区域气压季变幅（>13 hPa）远高于日变幅（2.5 hPa左右），而高海拔区域气压季变幅（>3 hPa）略低于日变幅（2 hPa左右）。（6）感热通量春季大、冬季小；感热通量和动量通量在高海拔区域均较高，二者具有较一致的日、季变化特征，表明大气动... 相似文献
13.
C. Jacovides P. Kerkides G. Papaioannou F. B. Smith 《Theoretical and Applied Climatology》1992,45(2):145-154
Summary Hourly lysimetric and micrometeorological data taken over a grass surface at the Meteorological Research Unit, Cardington U.K. have been analysed. A temperature difference and measurements of wind speed at only one height, combined with an independently estimated effective roughness length allowed sensible heat and momentum fluxes determination by the profile method on an hourly basis. The estimates are compared with direct measurements of sensible heat and friction velocity obtained by the eddy correlation method. The sensible and latent heat fluxes are also modelled by the resistance method. Equations based on the Monin—Obukhov similarity theory are used to account for stability effects through various forms of parameterization Aerodynamic and surface resistances, necessary for the Penman—Monteith equation are calculated from routinely measured meteorological data. The profile method for estimation of sensible heat flux and friction velocity is found to work excellently on the discussed daytime experimental data which correspond mainly to near neutral or slightly unstable conditions.Surface latent and sensible heat fluxes can also be described very well by the resistance method. A slightly better estimate of the sensible heat flux is achieved when stability corrections are taken into account. On the contrary Penman-Monteith equation for estimating latent heat flux is insensitive to adjustments for atmospheric stability.The comparison of the various methods leads to the establishment of empirical relationships which correlate various quantities such as soil heat flux, resistances, evapotranspiration etc. to routinely measured meteorological data.With 8 Figures 相似文献
14.
Monin–Obukhov similarity functions for the structure parameters of temperature and humidity are needed to derive surface heat and water vapour fluxes from scintillometer measurements and it is often assumed that the two functions are identical in the atmospheric surface layer. Nevertheless, this assumption has not yet been verified experimentally. This study investigates the dissimilarity between the turbulent transport of sensible heat and water vapour, with a specific focus on the difference between the Monin–Obukhov similarity functions for the structure parameters. Using two datasets collected over homogeneous surfaces where the surface sources of sensible heat and water vapour are well correlated, we observe that under stable and very unstable conditions, the two functions are similar. This similarity however breaks down under weakly unstable conditions; in that regime, the absolute values of the correlations between temperature and humidity are also observed to be low, most likely due to large-scale eddies that transport unsteadiness, advection or entrainment effects from the outer layer. We analyze and demonstrate how this reduction in the correlation leads to dissimilarity between the turbulent transport of these two scalars and the corresponding Monin–Obukhov similarity functions for their structure parameters. A model to derive sensible and latent heat fluxes from structure parameters without measuring the friction velocity is tested and found to work very well under moderately to strongly unstable conditions (−z/L > 0.5). Finally, we discuss the modelling of the cross-structure parameter over wet surfaces, which is crucial for correcting water vapour effects on optical scintillometer measurements and also for obtaining surface sensible and latent heat fluxes from the two-wavelength scintillometry. 相似文献
15.
Surface turbulent flux measurements over the Loess Plateau for a semi-arid climate change study 总被引：2，自引：0，他引：2
In order to provide high quality data for climate change studies, the data quality of turbulent flux measurements at the station
of SACOL (Semi-Arid Climate & Environment Observatory of Lanzhou University), which is located on a semi-arid grassland over
the Loess Plateau in China, has been analyzed in detail. The effects of different procedures of the flux corrections on CO2, momentum, and latent and sensible heat fluxes were assessed. The result showed that coordinate rotation has a great influence
on the momentum flux but little on scalar fluxes. For coordinate rotation using the planar fit method, different regression
planes should be determined for different wind direction sectors due to the heterogeneous nature of the ground surface. Sonic
temperature correction decreased the sensible heat flux by about 9%, while WPL correction (correction for density fluctuations)
increased the latent heat flux by about 10%. WPL correction is also particularly important for CO2 fluxes. Other procedures of flux corrections, such as the time delay correction and frequency response correction, do not
significantly influence the turbulent fluxes. Furthermore, quality tests on stationarity and turbulence development conditions
were discussed. Parameterizations of integral turbulent characteristics (ITC) were tested and a specific parameterization
scheme was provided for SACOL. The ITC test on turbulence development conditions was suggested to be applied only for the
vertical velocity. The combined results of the quality tests showed that about 62%–65% of the total data were of high quality
for the latent heat flux and CO2 flux, and as much as about 76% for the sensible heat flux. For the momentum flux, however, only about 35% of the data were
of high quality. 相似文献
16.
Turbulent characteristics and bulk transfer coefficients over the desert in the HEIFE area 总被引：1，自引：0，他引：1
Ichiro Tamagawa 《Boundary-Layer Meteorology》1996,77(1):1-20
Observations of surface-layer turbulence and turbulent fluxes were made over a desert in northwestern China as a part of HEIFE (HEIhe river Field Experiment). These show that the normalized variations of the vertical wind component and of the air temperature obey Monin-Obukhov similarity well, especially in free convective conditions. However, the variations of specific humidity do not obey Monin-Obukhov similarity.Mean bulk transfer coefficients of sensible heat and momentum flux are obtained as functions of stability over a wide stability range from the observed data of turbulent fluxes and mast profiles. However, the bulk transfer coefficient for water vapor could not be obtained because of the large scatter of the data. In free convective conditions, the sensible heat flux was found to be approximately proportional to the 1.4 power of temperature difference between the surface and 20m. The bulk transfer coefficient of sensible heat is also obtained as a function of the bulk Richardson number for practical convenience. 相似文献
17.
利用船测近海层湍流热通量资料验证OAFlux数据集 总被引：1，自引：0，他引：1
美国伍兹霍尔海洋研究所(Woods Hole Oceanographic Institution,WHOI)的客观分析海气通量(Objectively Analyzed air-sea Fluxes,OAFlux)数据集中的近海层湍流热通量数据被公认为最可信,并被广泛地用于气候模式模拟结果检验。利用NOAA ETL(Environmental Technology Laboratory)两个固定观测站点的科学试验的船测通量数据库(TOGA COARE试验观测资料和KAWJEX试验观测资料),对OAFlux的热通量进行验证。结果表明:OAFlux的潜热通量普遍高于船测值,并且风速较大时,两者差异较大。风速对潜热通量的变化趋势起主导作用,海表和大气湿度差影响甚微。低风条件下,OAFlux的潜热通量和船测值差异则很小。海面湍流感热交换很弱,通量值本身依然受到风速的主导作用,但由于感热通量值与观测仪器误差十分接近,导致比较分析异常困难。分析结果表明:在上述两个观测试验期内,由于海表空气湿度和大气的湿度差变化不显著,海气相互作用的强度主要取决于海面风速的变化。 相似文献
18.
Michelle Simões Reboita Rosmeri Porfírio da Rocha Tércio Ambrizzi Ernesto Caetano 《Climate Dynamics》2010,34(6):873-889
A Regional Climate Model (RegCM3) 10-year (1990–1999) simulation over southwestern South Atlantic Ocean (SAO) is evaluated
to assess the mean climatology and the simulation errors of turbulent fluxes over the sea. Moreover, the relationship between
these fluxes and the rainfall over some cyclogenetic areas is also analyzed. The RegCM3 results are validated using some reanalyses
datasets (ERA40, R2, GPCP and WHOI). The summer and winter spatial patterns of latent and sensible heat fluxes simulated by
the RegCM3 are in agreement with the reanalyses (WHOI, R2 and ERA40). They show large latent heat fluxes exchange in the subtropical
SAO and at higher latitudes in the warm waters of Brazil Current. In particular, the magnitude of RegCM3 latent heat fluxes
is similar to the WHOI, which is probably related to two factors: (a) small specific humidity bias, and (b) the RegCM3 flux
algorithm. In contrast, the RegCM3 presents large overestimation of sensible heat flux, though it simulates well their spatial
pattern. This simulation error is associated with the RegCM3 underestimation of the 2-m air temperature. In southwestern SAO,
in three known cyclogenetic areas, the reanalyses and the RegCM3 show the existence of different physical mechanisms that
control the annual cycles of latent/sensible heating and rainfall. It is shown that over the eastern coast of Uruguay (35°–43°S)
and the southeastern coast of Argentina (44°–52°S) the sea-air moisture and heat exchange play an important role to control
the annual cycle of precipitation. This does not happen on the south/southeastern coast of Brazil. 相似文献
19.
Impact of Sea-Spray on the Atmospheric Surface Layer 总被引：1，自引：0，他引：1
The feedback effects of sea-spray on the heat and momentum fluxes under equilibrium conditions associated with winds of tropical
cyclones are investigated using a one-dimensional coupled sea-spray and atmospheric surface-layer (ASL) model. This model
is capable of simulating the microphysical aspects of the evaporation of saline water droplets of various sizes and their
dynamic and thermal interaction with the turbulence mixing that is simulated by the Mellor–Yamada 1.5-order closure scheme.
Sea-spray droplet generation is described by a state-of-the-art parametrization that predicts the size spectrum of sea-spray
droplets for a given surface forcing. The results from a series of simulations indicate the way in which evaporating droplets
of various sizes modify the turbulence mixing near the surface, which in turn affects further droplet evaporation. All these
results are direct consequences of the effects of sea-spray on the balance of turbulent kinetic energy in the spray-filled
surface layer. In particular, the overall impact of sea-spray droplets on the mean wind depends on the wind speed at the level
of sea-spray generation. When the wind speed is below 40 m s−1, the droplets are small in size and tend to evaporate substantially and thus cool the spray-filled layer, while for wind
speeds above 50 m s−1, the size of the droplets is so large that they do not have enough time to evaporate much before falling back into the sea.
The sensible heat carried by the droplets is released to the ambient air, increasing the buoyancy of the surface layer and
enhancing the turbulent mixing. The suspension of sea-spray droplets reduces the buoyancy and makes the surface layer more
stable, decreasing the friction velocity and the downward turbulent mixing of momentum. The results from the numerical experiments
also suggest that, in order not to violate the constant flux assumption critical to the Monin–Obukhov similarity theory, a
displacement equal to the mean wave height should be included in the logarithmic profiles of the wind and thermal fields. 相似文献
20.
Different flux estimation techniques are compared here in order to evaluate air–sea exchange measurement methods used on moving
platforms. Techniques using power spectra and cospectra to estimate fluxes are presented and applied to measurements of wind
speed and sensible heat, latent heat and CO2 fluxes. Momentum and scalar fluxes are calculated from the dissipation technique utilizing the inertial subrange of the power
spectra and from estimation of the cospectral amplitude, and both flux estimates are compared to covariance derived fluxes.
It is shown how even data having a poor signal-to-noise ratio can be used for flux estimations. 相似文献