共查询到20条相似文献，搜索用时 22 毫秒
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B. M. Koprov S. L. Zubkovsky V. M. Koprov M. I. Fortus T. I. Makarova 《Boundary-Layer Meteorology》1998,88(3):399-423
Surface-layer convection is investigated by analyzing multi-point measurements of temperature and velocity fluctuations at different sets of spatial points.The visual analysis of temperature and velocity fluctuations measured by sensors mounted on a mast of 36-m height clearly reveals the presence of large-scale convective cells (known as ramp structures) making large contributions to the heat transfer from the ground to lower atmosphere. The vertical temperature variability is described with the aid of empirical orthogonal functions derived from temperature covariance matrices for the heights of 1, 2, 5, 10, 18 and 36 m. Temporal-spatial correlation functions obtained allow estimates of a characteristic velocity scale, which may be interpreted as the downwind velocity of ramp structures. 相似文献
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Variability of Sub-Canopy Flow,Temperature, and Horizontal Advection in Moderately Complex Terrain 总被引：1，自引：1，他引：0
We examine the space–time structure of the wind and temperature fields, as well as that of the resulting spatial temperature
gradients and horizontal advection of sensible heat, in the sub-canopy of a forest with a dense overstorey in moderately complex
terrain. Data were collected from a sensor network consisting of ten stations and subject to orthogonal decomposition using
the multiresolution basis set and stochastic analyses including two-point correlations, dimensional structure functions, and
various other bulk measures for space and time variability. Despite some similarities, fundamental differences were found
in the space–time structure of the motions dominating the variability of the sub-canopy wind and temperature fields. The dominating
motions occupy similar spatial, but different temporal, scales. A conceptual space–time diagram was constructed based on the
stochastic analysis that includes the important end members of the spatial and temporal scales of the observed motions of
both variables. Short-lived and small-scale motions govern the variability of the wind, while the diurnal temperature oscillation
driven by the surface radiative transfer is the main determinant of the variability in the temperature signal, which occupies
much larger time scales. This scale mismatch renders Taylor’s hypothesis for sub-canopy flow invalid and aggravates the computation
of meaningful estimates of horizontal advective fluxes without dense spatial information. It may further explain the ambiguous
and inconclusive results reported in numerous energy and mass balance and advection studies evaluating the hypothesis that
accounting for budget components other than the change in storage term and the vertical turbulent flux improves the budget
closure when turbulent diffusion is suppressed in plant canopies. Estimates of spatial temperature gradients and advective
fluxes were sensitive to the network geometry and the spatial interpolation method. The assumption of linear spatial temperature
gradients was not supported by the results, and leads to increased spatial and temporal variability of inferred spatial gradients
and advection estimates. A method is proposed to estimate the appropriate minimum network size of wind and temperature sensors
suitable for an evaluation of energy and mass balances by reducing spatial and temporal variability of the spatially sampled
signals, which was estimated to be on the order of 200 m at the study site. 相似文献
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Y. S. Wang D. R. Miller D. E. Anderson R. M. Cionco J. D. Lin 《Boundary-Layer Meteorology》1992,59(1-2):125-139
Turbulent flow within and above an almond orchard was measured with three-dimensional wind sensors and fine-wire thermocouple sensors arranged in a horizontal array. The data showed organized turbulent structures as indicated by coherent asymmetric ramp patterns in the time series traces across the sensor array. Space-time correlation analysis indicated that velocity and temperature fluctuations were significantly correlated over a transverse distance more than 4m. Integral length scales of velocity and temperature fluctuations were substantially greater in unstable conditions than those in stable conditions. The coherence spectral analysis indicated that Davenport's geometric similarity hypothesis was satisfied in the lower frequency region. From the geometric similarity hypothesis, the spatial extents of large ramp structures were also estimated with the coherence functions. 相似文献
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Two-point, one-dimensional coherence in horizontally homogeneous atmospheric turbulence is studied, both by experiment and analysis. Measurements are carried out using horizontally spaced sensors with the separation perpendicular to the mean velocity. Two-dimensional spectral models and three-dimensional inertial-range spectral tensors are used in the coherence calculations. The one-dimensional coherence for both velocity and scalar fluctuations is found to roll off at a wavenumber much smaller than we would expect from the classical notion of eddy correlation. This is a consequence of the cancellation of Fourier components aliased from the direction of the sensor separation into the streamwise direction. However, the coherence for the three velocity components behaves somewhat differently, reflecting the relative orientations of the velocity component, sensor separation and the mean velocity. These features are well predicted by the calculation. The analysis is also extended to calculate the two-point scalar-vertical velocity cospectrum and the results are in good agreement with our experimental data. The ratio of two- to one-point cospectra decreases at slightly larger wavenumber than the two-point scalar coherence does. 相似文献
6.
Compared are the estimates or regional changes in temperature and precipitation on the territory of Russia for two methods of the spatial averaging of meteorological station data, one of which is adapted to the sparse observational network and takes account of the station weights proportional to the area of their influence. Considered are several variants of the zoning with the separation of the different number of regions. Formulated is a criterion of the zoning adequacy to the problem of the revelation and analysis of regional climate changes. Estimated is the representativeness of the network of observations of temperature and precipitation for separate regions. Presented are the estimates of regional trends of air temperature and precipitation for the century interval and for the recent decades obtained on the basis of the full archive of available data for the zoning attached to the administrative division of the Russian Federation into the federal districts. 相似文献
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为确保铂电阻地温传感器观测数据的准确、可靠并具有可比性,定期开展对地温传感器的检定是非常重要的。通过检定将地温传感器系统误差控制在允许范围内,并对检定结果进行不确定度评定,是考察检定结果可信程度的重要步骤。本文依据《JJG(气象)002-2015自动气象站温度传感器》和《JJF1059.1-2012测量不确定度评定与表示》的要求,设计10次重复性试验,分析检定过程中的不确定度来源,并对不同的不确定度来源进行A类和B类不确定度评定,此评定方法对自动气象站地温检定结果可信度评估具有指导意义。 相似文献
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Sea surface temperature (SST) is an important indicator of changes in the climate system and a key driver of marine ecosystems. Here we studied the strength and spatial patterns of changes in North Atlantic SST during the last three decades (1982?C2010). Regional and local patterns of change were studied using data derived from the Advanced Very High Resolution Radiometer (AVHRR) sensors. Apart from changes in mean SST, we studied changes in the seasonal cycle, in the spatial patterning of temperature anomalies and in the location of selected isotherms. We quantified the degree of nonlinearity in mean SST as an indicator of the rate at which SST trends changed during the study period. Changes in the timing and intensity of seasonal extremes were explored, and a heuristic method was used to derive the length of the period of stratification and to estimate its variation. Our results were in general coherent with the main impacts predicted by climate change projections, with greatest changes located at northern latitudes and near land. Marked variation in the spatial patterns was also found for different variables, strengthening the view that physical changes could be promoting the arrangement of novel marine biological communities. The observed changes in ocean SST highlighted the need of a more local and regional focus in future climate change studies. 相似文献
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Simultaneous temperature fluctuations have been measured along directions both parallel and orthogonal to the wind direction in the atmospheric surface layer. Ensemble-averaged temperature distributions associated with the ramp-like feature observed in instantaneous temperature traces indicate that the average duration of the ramp is approximately independent of height. Application of Davenport's geometric similarity of coherence of temperature fluctuations yields approximate estimates for the spatial extent of the structure characterized by the ramp. The longitudinal extent is approximately 12 times the vertical extent and 17 times the lateral extent. 相似文献
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Abstract During the GARP Atlantic Tropical Experiment (GA TE) in the summer of 1974, identical tethersonde packages were flown to heights of 1,000 m from two ships with a crosswind separation of approximately 4 km. The differences in the profiles and fixed level time series from the two packages are a measure of spatial variability in the tropical marine boundary layer. Correlation analysis indicate a cellular pattern in the large‐scale wind field. Similar analyses of the temperature and humidity fields give quite different results. 相似文献
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Summary Surface air temperature in central Japan was predicted from the temperature recordings from sensors in the Automated Meteorological Data Acquisition System (AMeDAS), using seven different procedures: the usual simple and universal kriging and cokriging estimators, the traditional regression analysis and the inverse distance weighted method. The cokriging estimator integrated digital elevation data as well as the air temperature readings. The performance of the procedures was evaluated and compared using cross-validation.The kriging estimator provided a better estimate than the traditional regression analysis that treated the data as spatially independent observations. The kriging estimate was also better than the inverse distance weighted method. Further improvement in the estimation accuracy was achieved by using cokriging procedures because of high correlation of air temperature with elevation. The accuracy of spatial prediction decreased due to nocturnal cooling in winter and daytime heating in summer. This decrease implies that a strong radiation balance at the surface, whether positive or negative, causes a relatively short-range variation in surface air temperature through the effects of local environments.With 8 Figures 相似文献
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中国冬季气温的年际变化 总被引：2，自引：0，他引：2
利用中国160站1951-2000年的冬季月平均气温资料，用EOF分析、小波分析和合成分析等方法对中国近50年来的冬季气温的年际变化和时空分布特征进行研究。结果表明：中国冬季气温50年来有显著的增暖趋势，在70年代后期增暖幅度开始加大，年际变化以6～9年周期为主。中国冬季气温的空间变化有很好的一致性，全国绝大部分区域呈整体变暖或变冷的趋势，并且气温变化南北有别，从南向北幅度逐渐变大。另一种模态是当东北、华北和西北地区冬季气温较高时，其它地区则偏冷；反之亦然。 相似文献
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利用1960~2006年我国地温、气温逐日4个时次[02:00(北京时间,下同)、08:00、14:00和20:00]的和中国降水台站观测资料以及NCEP/NCAR再分析资料,分析了我国春季(3~5月)和夏季(6~8月)地气温差的时空变化特征及其与夏季降水的联系。分析结果表明:我国春季地气温差主要存在着3种空间模态分布,第1模态表现出我国西部地区地气温差为正值,我国东部地区从南至北呈现出"-、+、-、+"空间分布特征;而第2模态则呈现"+、-、+"的空间分布特征;第3模态则表现出一致的空间分布特征。我国夏季地气温差同样存在着3种空间模态分布,第1模态表现出我国东部和西部地区夏季地气温差反相的空间分布特征;第2模态则呈现出"-、+、-"的空间分布特征;而第3模态则表现出"+、-、+、-"的空间分布特征。分析结果进一步表明我国春季和夏季地气温差第1模态与我国长江中下游地区夏季降水均存在正相关关系,而与华北地区出现负相关关系。而且,夏季更加显著。这主要是由于我国东部和西部热力差异增强,有利于在我国东部地区出现西北风异常,这说明东亚夏季风偏弱,不利于水汽向北输送,有利于华北地区降水偏少。并且,在我国东南部地区出现水汽辐合和上升运动,从而有利于我国长江中下游地区夏季降水偏多。 相似文献
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Measurement of the Sensible Eddy Heat Flux Based on Spatial Averaging of Continuous Ground-Based Observations 总被引：1，自引：0，他引：1
M. Mauder R. L. Desjardins E. Pattey Z. Gao R. van Haarlem 《Boundary-Layer Meteorology》2008,128(1):151-172
Using the standard eddy-covariance (EC) method to quantify mass and energy exchange at a single location usually results in
an underestimation of vertical eddy fluxes at the surface. In order to better understand the reasons for this underestimation,
an experimental set-up is presented that is based on spatial averaging of air temperature data from a network of ground-based
sensors over agricultural land. For eight days during the 34-day observational period in May and June 2007, additional contributions
to the sensible heat flux of more than 50Wm−2 were measured in the lower surface layer by applying the spatial EC method as opposed to the standard temporal EC method.
Smaller but still significant additional sensible heat fluxes were detected for four more days. The additional energy is probably
transported in organised convective structures resulting in a mean vertical wind velocity unequal to zero at the tower location.
The results show that convective transport contributes significantly to the surface energy budget for measurement heights
as low as 2–3 m. Since these structures may be quasi-stationary, they can hardly be captured by a single-location measurement.
The spatial EC set-up presented here is capable of quantifying contributions to the sensible heat flux from structures up
to the scale of our spatial sensor network, which covered an area 3.5 × 3.5 km. For future experiments aiming at closing the
energy balance, the spatial EC method should be employed to measure both the sensible and latent heat fluxes. Experimental
determination of the horizontal advection of sensible and latent heat should also be considered, since such transport must
occur due to convergence and divergence related to convection. 相似文献
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将B样条拟合算法引入到地面气温资料的质量控制当中,在分析地面气温资料空间相关性的基础上,提出一种基于空间回归的B样条拟合地面气温资料质量控制方法(SRT_BSF方法)。为了检验SRT_BSF方法的有效性及适应性,利用SRT_BSF方法对多个场景地面气温资料进行质量控制,并与反距离加权方法(IDW方法)和空间回归方法(SRT方法)进行比较分析。试验结果表明,SRT_BSF方法相对于IDW方法和SRT方法更能有效地标记出地面气温资料中的存疑数据,同时多组独立案例的分析结果说明SRT_BSF方法具有更好的稳定性和适用性。 相似文献
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This study used “factor separation” to quantify the sensitivity of simulated present and future surface temperatures and precipitation to alternative regional climate model physics components. The method enables a quantitative isolation of the effects of using each physical component as well as the combined effect of two or more components. Simulation results are presented from eight versions of the Mesoscale Modeling System Version 5 (MM5), one-way nested within one version of the Goddard Institute for Space Studies Atmosphere-Ocean Global Climate Model (GISS AOGCM). The MM5 simulations were made at 108 km grid spacing over the continental United States for five summers in the 1990s and 2050s. Results show that the choice of cumulus convection parameterization is the most important “factor” in the simulation of contemporary surface summer temperatures and precipitation over both the western and eastern USA. The choice of boundary layer scheme and radiation package also increases the range of model simulation results. Moreover, the alternative configurations give quite different results for surface temperature and precipitation in the 2050s. For example, simulated 2050s surface temperatures by the scheme with the coolest 1990s surface temperatures are comparable to 1990s temperatures produced by other schemes. The study analyzes the spatial distribution of 1990s to 2050s projected changes in the surface temperature for the eight MM5 versions. The predicted surface temperature change at a given grid point, averaged over all eight model configurations, is generally about twice the standard deviation of the eight predicted changes, indicating relative consensus among the different model projections. Factor separation analysis indicates that the choice of cumulus parameterization is the most important modeling factor amongst the three tested contributing to the computed 1990s to 2050s surface temperature change, although enhanced warming over many areas is also attributable to synergistic effects of changing all three model components. Simulated ensemble mean precipitation changes, however, are very small and generally smaller than the inter-model standard deviations. The MM5 versions therefore offer little consensus regarding 1990s to 2050s changes in precipitation rates. 相似文献
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为了解2003—2009年中国的叶面积指数(Leaf Area Index,LAI)变化特征,以及不同数据产品的差别,利用基于MODIS数据反演的3组LAI产品,比较分析了中国地区LAI的时空变化特征及其与气候因子的相关。结果表明,3组数据具有总体一致的变化特点,增长区主要位于东北大兴安岭、华北、华中和西南等地;减少区则位于四川盆地、江南以及华南东部;但在云贵川和青藏高原东南部等地有明显差异。在量值上,中科院地理所反演的LAI(LAI1)总体比NASA反演的LAI(LAI2)和北京师范大学反演的LAI(LAI3)偏小,它们在中国常绿阔叶林区的差别可达1.0以上。LAI1与同期降水和气温都有显著的相关,相关系数的空间分布一致,但LAI1的相关系数比LAI3和LAI2偏低。3组数据的差异主要与采用的遥感源数据和反演方法等不同有关。尽管不同LAI数据产品局域和量值差异对定量分析有一定影响,但是它们在时空变化及与气候条件相关等方面的一致性证明了在气候及气候变化研究中的可用性。 相似文献
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Holger Siebert Manfred Wendisch Thomas Conrath Ulrich Teichmann Jost Heintzenberg 《Boundary-Layer Meteorology》2003,106(3):461-482
A new scientific payload is introduced for fine-scale measurements of meteorological (wind vector, static air temperature, humidity, and air pressure) and microphysical (aerosol particles and cloud droplets) properties, suspended below a tethered balloon. The high resolution sensors and the tethered balloon are described. Measurements in a lifted fog layer from a first field campaign are presented.The detailed investigation of the fog/haze and the temperature inversion layer demonstrates the damping influence of the fog on temperature fluctuations, while thewind fluctuations are significantly decreased by theevolving temperature inversion, whichwas about 30 m above the fog layer.From spectral analysis the noise floors of the high-resolution sensors are determined to10-6 kg m-3 for the LWC (liquid water content) and 4 mK for the fast temperature sensor (UFT-B). The correlation betweentemperature and LWC structures in shallow haze layers is investigated. The release of latent heat and the corresponding warming in the haze of about 0.1 K could be quantified. 相似文献
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淮北地区2010年4月异常低温气候特征及成因分析 总被引：1，自引：0，他引：1
利用1961—2010年NCEP/NCAR再分析资料和4月淮北地区气温资料,用累积距平(CA)法、合成分析法对淮北地区气温的时空分布特征以及2010年4月淮北地区持续冷气候背景进行分析。文章分析了淮北地区4月冷、暖年的大气环流异常及要素场的空间分布特征。结果表明:淮北地区4月气温的年代际变化特征明显,在1990年前后发生了突变。贝加尔湖南部,100°E以东的华北地区中低层的冷空气活动与淮北地区4月气温高低存在很好的相关性,该地中低层冷空气强(弱),淮北地区4月气温低(高)。冷暖年,乌拉尔山暖脊、东亚大槽、西伯利亚高压等差异显著,说明以上是影响淮北地区4月气温异常的关键系统。另据分析,El Nino与淮北地区4月气温异常也具有很好的相关性。 相似文献