人工神经网络在感热通量计算中的应用     

储凌  张乐坚  陈渭民 《气象科技》2012,40(3):474-480

感热通量计算方法的研究是边界层研究中最重要的内容之一。基于中日JICA计划项目中青藏高原东缘四川盆地温江站的边界层铁塔观测资料初步研究了使用人工神经网络(ANN)计算边界层感热通量的方法,并将ANN和经验公式法计算得到的感热通量分别和真值作相关和误差分析。对2009年4月和5月的两个个例研究的结果表明:ANN计算结果和真值的相关性都高于经验公式法且趋势变化和真值更加吻合,ANN计算的2009年4月的感热通量与真值的均方根误差(RMSE)稍大于经验公式法,但2009年5月的RMSE明显小于经验公式法。  相似文献   

城市地表热通量遥感反演及与土地类型的关系(英文)     

刘越  后藤真太郎  庄大方  匡文慧 《地理学报(英文版)》2012,22(4):699-715

Using ASTER(Advanced Spaceborne Thermal Emission and Reflection Radiome-ter) infrared remote sensing data we inversed the parameters of urban surface heat fluxes applying the PCACA model and theoretical position algorithm,and then we analyzed the in-fluence of different land use types on the surface heat fluxes and energy balance.In this study,Kumagaya,a city in Saitama Prefecture,Japan,was selected as the experimental area.The result shows that the PCACA model is feasible for the surface heat fluxes estimation in urban areas because this model requires less parameters in the procedure of heat fluxes estimation in urban areas with complicated surface structure and can decrease the uncertainty.And we found that different land-use types have indicated the height heterogeneity on the surface heat fluxes significantly.The magnitudes of Bowen ratio in descending order are industrial,residential,transportation,institutional,dry farmland,green space,and water body.Under the same meteorological condition,there are distinct characteristics and regional differences in Bowen ratios among different surface covers,indicating higher sensible heat flux and lower latent heat flux in the urban construction land,while lower sensible heat flux and higher latent heat flux in the vegetation-covered area,the outskirt of the urban area.The increase of urban impervious surface area caused by the urban sprawl can enlarge the sensible heat flux and the Bowen ratio,so that it causes the increasing of urban surface temperature and air tem-perature,which is the mechanism of the so-called heat island effect.  相似文献   

天山北坡低山丘陵干草原生长季蒸散特征     

黄小涛  罗格平 《干旱区地理》2017,40(6):1198-1206

基于HL20波文比系统获得了天山北坡低山丘陵干草原2013-2015年的能量、气象观测数据,采用波文比-能量平衡法对其生长季（4～10月）蒸散特征进行了分析。结果表明：（1）生长季蒸散日内变化总体呈现中午最高、早晚变小和夜间蒸散微弱的特征,阴雨天蒸散日内变化相对复杂,蒸散强度通常弱于晴天;2013-2015年生长季蒸散量平均值为353.2 mm,生长季蒸散量在不同年份、不同季节和不同月份差异较大;2013-2015年生长季凝结水占降水量的比例分别为9.7%,18.8%和16.8%,日均凝结水量分别为0.177 mm,0.179 mm和0.316 mm。（2）生长季潜热和感热占据了净辐射能的主体且总体上潜热小于感热,白天潜热最大值出现之前,潜热会出现短暂小幅降低的情况。生长季感热和潜热逐日对比变化与植被长势密切相关。（3）波文比在夜间波动较大,变化复杂,白天上午波文比从负值增大到<1的正值,再到>1的正值,中午波文比为>1的正值,20：00左右波文比值开始回落。  相似文献   

宁夏一次大风扬沙天气过程机制分析     

谭志强  桑建人  纪晓玲  邵建  朱晓炜 《干旱区地理》2017,40(6):1134-1142

利用宁夏25个常规地面观测站逐时资料和欧洲中期天气预报中心（ECMWF）ERA-Interim逐6 h 0.125º×0.125º分辨率再分析资料,对宁夏2016年5月11日大风扬沙天气过程的天气形势、影响系统及其热力、动力条件和形成机制进行了分析。结果表明：（1）大风和扬沙呈现出时间位相上的不一致性,沙尘超前大风约6 h。（2）200 hPa高空急流、500 hPa锋区、700 hPa低空急流和地面冷锋是此次过程的主要影响系统。（3）大风在不同阶段对扬沙起不同作用,在初期有利于扬沙的传输,后期对扬沙起抑制作用。（4）动量下传和变压风是大风形成和发展的直接原因,感热通量通过加强地面湍流形成混合层,从而引导动量下传是其间接原因,动量下传的重要机制是对流层高层高位涡的下传,过程风力最强时位涡高值区（≥2.0 PVU）由200 hPa下传至520 hPa。（5）扬沙的产生主要是冷平流和感热通量形成的热力不稳定共同作用的结果,变压风和动量下传大风是扬沙的输送机制,次级环流缺失和冷平流中心过低（750 hPa）对沙尘输送高度的抑制作用是沙尘天气偏弱的主要原因。  相似文献   

春季亚洲中东部地表感热通量的变化特征及其与中国夏季降水的关系   总被引：3，自引：1，他引：2  

王林  刘鹏  林朝晖  秦正坤 《气候与环境研究》2011,16(3):310-321

采用1951～2000年NCEP/NCAR再分析资料中的逐月感热通量资料,分析了亚洲中东部春季近50年地表感热通量的气候分布特征,结果表明:亚洲中东部春季地表感热通量的高值区位于华北、西北和印度地区;低值区主要位于东北、江南和蒙古国北部;青藏高原、中国东部30°N附近地区和印度中部地区是感热通量年际变幅最大的区域.运用...  相似文献   

Variation of fluxes of water vapor, sensible heat and carbon dioxide above winter wheat and maize canopies     

Zhang Yongqiang Ph.D.  Shen Yanjun  Yu Qiang  Liu Changming  A. Kondoh  Tang Changyuan  Sun Hongyong  Jia Jinsheng 《地理学报(英文版)》2002,12(3):295-300

Surface energy fluxes were measured using Bowen-Ratio Energy Balance technique (BREB) and eddy correlation system at Luancheng of Hebei Province, on the North China Plain from 1999 to 2001. Average diurnal variation of surface energy fluxes and CO₂ flux for maize showed the inverse “U” type. The average peak fluxes did not appear at noon, but after noon. The average peak CO₂ flux was about 1.65 mg m^-2 s^-1. Crop water use efficiency (WUE) increased quickly in the morning, stabilized after 10:00 and decreased quickly after 15:00 with no evident peak value. The ratio of latent heat flux (λE) to net solar radiation (R_n) was always higher than 70% during winter wheat and maize seasons. The seasonal average ratio of sensible heat flux (H) divided byR _n stayed at about 15% above the field surface; the seasonal average ratio of conductive heat flux (G) divided by R_n varied between 5% and 13%, and the averageG/R> _n from the wheat canopy was evidently higher than that from the maize canopy. The evaporative fraction (EF) is correlated to the Bowen ratio in a reverse function.EF for winter wheat increased quickly during that revival stage, after the stage, it gradually stabilized to 1.0, and fluctuated around 1.0. EF for maize also fluctuated around 1.0 before the later grain filling stage, and decreased after that stage.  相似文献   

Air–Sea Flux Estimates And The 1997–1998 Enso Event     

A. Birol Kara  Peter A. Rochford  Harley E. Hurlburt 《Boundary-Layer Meteorology》2002,103(3):439-458

Bulk formulae for wind stress, sensible and latent heat flux are presented that are suitable for strong mesoscale events such as westerly wind bursts that contribute to the El Niño-Southern Oscillation (ENSO). Their exchange coefficients for heat and momentum have a simple polynomial dependence on wind speed and a linear dependence on air–sea temperature difference. The accuracy of these formulae are validated with respect to air–sea fluxes estimated using the standard algorithm adopted by the Tropical Ocean-Global AtmosphereCoupled-Ocean Atmosphere Response Experiment (TOGA COARE). The comparison ismade for observations from 96 Tropical Atmosphere Ocean (TAO) array and National Oceanographic Data Center (NODC) moorings in the equatorial and North Pacific Ocean spanning years 1990–1999. The bulk formulae are shown to have very small median root–mean-square differences with respect to the TOGA COARE estimates: 0.003 N m^-2, 1.0 W m^-2, and 10.0 W m^-2 for the wind stress, sensible heat flux, and latent heat flux, respectively.The variability of air–sea fluxes during the 1997–1998 ENSO is also examined, along with a possible relationship between air–sea fluxes and surface ocean mixed layer depth (MLD). The wind stress and latent heat flux during the 1997 El Niño are found to be greater in the warm pool of the western Pacific than in the central Pacific where the ENSO is most clearly seen. These differences disappear upon the start of La Niña. The MLD in the equatorial Pacific is found to be moderately correlated to air–sea fluxes just before the start of the 1998 La Niña and poorly correlated otherwise.  相似文献   

印度洋海气热通量交换研究   总被引：13，自引：0，他引：13  

周天军  张学洪 《大气科学》2002,26(2):161-170

基于综合海洋大气资料集(COADS)资料的研究表明,热带印度洋的海气热通量交换具有明显的区域性特征,在部分海域,如冬季热带印度洋的中东部、夏季的热带西印度洋和北印度洋,它主要表现为海洋对大气的强迫.海洋对大气的这种强迫,主要是通过潜热加热实现的.与潜热加热相比,感热加热尽管是一个小量,但感热异常与表层海温的显著相关,较之潜热明显超前.无论冬季还是夏季,热带印度洋都存在大面积海域,其SST变化难以通过海气热通量交换来解释.  相似文献   

TURBULENCE CHARACTERISTICS OF THE ATMOSPHERIC SURFACE LAYER OVER AN OPEN GRASSLAND     

刘树华  刘和平  梁福明  吴风雷  徐梅  洪钟祥  李军  刘辉志  那景阳  吴志明 《Acta Meteorologica Sinica》1997,(3)

Described in this paper is an experiment on atmosphere-surface turbulent exchange andboundary layer turbulence properties conducted in July 1994 over the Kerqin Grassland,Jilin,China.The characteristics of the turbulent spectrum,and the relationships of the standarddeviation of the turbulent velocity components and sensible heat flux with the atmospheric stabilityare studied using data from a sonic anemometer and a fast-response platinum resistancethermometer mounted on a 100 m tower.The results show that in the surface layer over a flat,uniform and open grassland,for a broad stability range(-22.12≤Z_(?)L≤17.98),the velocityspectra obey the-2/3 power law in the inertial subrange,and 1 power law at low frequencies.Under near neutral stratification,σ_u/u_*=1.20,σ_v/u_*=1.23 and σ_w/u_*=1.02.For Z_i/L≤-0.2,the standard deviations of the turbulent velocity components follow a 1/3 power law.ForZ_i/L≤-0.1,the standard deviation of the temperature fluctuations follows a-1/3 power law,and as Z_i/L≤-0.08,it exhibits nonlinear behavior.Sensible heat flux is well correlated to thestability parameter.  相似文献   

Computing energy budget within a crop canopy from Penmann’s formulae     

Mahendra Mohan  K. K. Srivastava 《Journal of Earth System Science》2001,110(2):179-184

The Lhomme’s model (1988a), that extended Penmann's formulae to a multi-layer model, is redefined as a function of micrometeorological and physiological profiles of crop canopy. The sources and sinks of sensible and latent heat fluxes are assumed to lie on a fictitious plane called zero-displacement plane. Algorithms are given to compute sensible and latent heat flux densities. Performance of the algorithms is compared with that of earlier algorithms.  相似文献