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利用1998—2016年NCEP/DOE逐日的日平均地面感热通量和地面潜热通量、MICAPS历史天气图资料、青藏高原低涡切变线年鉴,对高原低涡涡源区与高原地面加热特征进行统计分析,对比研究了移出青藏高原的高原涡(移出涡)、未移出青藏高原的高原涡(未移出涡)的涡源与高原地面加热的季节变化特征,及移出涡、未移出涡涡源区的地面加热特征及高原地面加热与低涡生成的相关性。结果表明,高原涡、未移出涡、移出涡的涡源分布季节变化特征相似,由冬到春到夏,初生区域逐渐扩大,由夏到秋到冬正好相反,不同的是移出涡涡源区明显比高原涡、未移出涡小,初生中心位置的季节变化也不同;高原地面感热、地面潜热、地面热源分布的季节变化特征相似,由冬到春到夏经历了明显增强的过程,由夏到秋到冬经历了减弱的过程,不同的是热源的快速增强、减弱程度及其发生季节差异大,地面潜热由春到夏增强特别明显,这与移出涡生成个数的明显增加相一致;未移出涡、移出涡春、夏、秋季主要涡源区所处的地面热源值域不同,移出涡夏季的值比未移出涡高,移出涡生成对高原区域地面热源依赖要比未移出涡强一些;夏季移出涡、未移出涡的涡源区都处在与高原地面热源正相关区内,它们与地面潜热的显著正相关区比高原地面感热的大,尤其是移出涡,高原地面潜热在高原涡生成中有重要作用,对移出涡生成影响更大。 相似文献
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1971-2012年青藏高原春季风速的年际变化及对气候变暖的响应 总被引：2，自引：0，他引：2
利用青藏高原73个气象台站的观测资料和日本气象厅JRA-55再分析资料,通过引入年际增量和动能收支方程,分析了1971-2012年高原春季风速的年际变化特征及其对气候变暖的响应。结果表明,在气候变暖的背景下高原风速呈减弱的趋势,随着变暖趋缓风速的变化也趋于平稳。春季高原风速与气温的线性趋势是相反的,但在年际尺度上二者表现出同位相的变化,当青藏高原、中南半岛和印度半岛的地面气温偏高,北亚和东亚地区的地面气温偏低时,有利于高原地面风速增大,反之风速减小。20世纪末青藏高原及其周边地区的升温速率表现为北快南缓,高原南、北侧气温差异减小,而东、西向的气温差异增大,风速趋于减弱;21世纪初高原中部及其南侧地区以升温为主,高原东北侧和东亚地区以降温为主,南、北向气温差异较小,高原风速的变化也趋于平缓,东、西向气温差异有减小的趋势,对应高原东部风速有所增大。青藏高原及其邻近地区的热力差异及其变化速率的不均衡改变了对流层大气的斜压性,进而通过两种途径影响青藏高原的风速,一方面是近地面层气压梯度力的直接作用,另一方面是高层动能向低层的输送。此外,还指出JRA-55再分析风速资料比ERA-Interim和NCEP/NCAR资料在青藏高原的适用性更强。 相似文献
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利用“绿洲系统能量与水分循环过程观测与数值研究”的观测资料和酒泉站的地面和探空气象资料,计算了酒泉绿洲夏季大气边界层的加热（冷却）率,分析了酒泉绿洲近地面层和行星边界层的大气加热（冷却）率逐日变化,研究了不同典型天气下大气加热（冷却）率的变化特征。结果表明,酒泉绿洲近地面层和行星边界层内,大气加热（冷却）率具有明显的逐日变化特征;近地面层和行星边界层及整个大气层白天的大气加热率和夜晚的大气冷却率基本相当,大气能量基本守恒;日照时数、云量和特殊天气过程（如冷空气活动、沙尘天气和降水等）对大气加热（冷却）率有很大影响。 相似文献
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青藏高原近地面层特征的初步分析 总被引：1，自引：0，他引：1
利用西藏日喀则、那曲１９９３年７月至１９９４年４月近地面层梯度观测资料，采用近地面层相似理论方法，计算了预测期间地面粗糙度、平均曳力系数、平均动量通量、平均感热通量和平均湍流系数，讨论了它们与稳定度的关系，给出了日变化个例。 相似文献
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一次对流系统引起奥帆赛场风速突然减小的多普勒雷达特征 总被引：1，自引：1，他引：0
根据青岛黄岛新一代天气雷达和浮标站等观测资料,对2006年8月青岛国际帆船赛期间一次赛场风速突然减小的多普勒雷达特征进行了分析,以探讨雷达产品对地面风变化的指示意义.结果发现,对流系统周围的环境风场存在较强的风垂直切变,在对流系统移动和发展过程中,风切变层的高度发生了变化.当赛场附近近地面风切变层高度降低、切变层风速减小时,赛场附近风速也减小;切变层升高后,赛场附近的风速又重新增大,表明近地面风切变层的高度和切变层风速的大小对地面风速有影响.新一代天气雷达VAD风廓线产品可以较好地反映出雷达站附近风切变层以及风速的垂直变化,对地面风速的变化有指示意义. 相似文献
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利用2006年5～6月和2007年5～6月中国科学院HEST大气科学实验在珠峰绒布寺河谷野外观测期间获得的观测资料,分析了珠峰地区河谷近地层风向、风速、温度、湿度和CO2的日变化特征,讨论了珠峰北坡冰川风和山谷风的特点以及高原地表辐射、地表反照率和近地层湍流通量的变化特征.结果表明:在复杂地形和特殊下垫面影响下,珠峰绒布河谷地区近地面层各个气象要素和湍流通量日变化特征显著,并且明显存在冰川风和山谷风复合的局地环流,冰川风对该地区地气间物质能量交换起着重要作用. 相似文献
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夏季高原天气系统生命史短,空间尺度小,天气变化剧烈,气压系统又与风场不完全适应,因此,只有500mb和近地面层分析流线图较能正确地反映高原的天气实际情况。1979年5月—8月高原西部新增加了高空地面资料,这就有可能更进一步了解和掌握高原夏季风环流的发生演变特点及天气气候规律。我们分析了1979年5—8月高原地区的逐日流线图,发现它有几种固定的流场型式,有一定的天气区与之配合。现将分型原则及结果介绍如下。 相似文献
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The effects of variations in sea-surface temperature on the surface fluxes of the marine atmospheric boundary layer have been investigated. The boundary model developed by Brown and Brown and Liu has been used to estimate these effects for near neutral conditions. Data taken on September 1, 1978, during the JASIN experiment have been used to corroborate the results obtained with Brown's model. Some speculations on secondary effects of the sea-surface temperature are given. 相似文献
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分析了2000年7月21日～8月10日在内蒙古奈曼流动沙丘下垫面取得的近地面层湍流及辐射观测资料,讨论了无量纲湍流方差与稳定度参数z/L的关系,发现无量纲速度分量方差及无量纲温度、湿度脉动方差在不稳定层结下,均满足莫宁-奥布霍夫相似理论;同时还讨论近地面层能量的收支.发现流动沙丘下垫面感热通量与地表热通量最大值分别为170 W m-2及100 W m-2;潜热通量通常小于50 W m-2;流动沙丘净辐射最大值为400 W m-2左右.(Hs+Hl),与(Rn-G)的比值在晴天白天平均值为0.78左右,流动沙丘下垫面近地面层能量不平衡现象存在,其原因有待进一步研究. 相似文献
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Specification of the eddy exchange coefficients is perhaps one of the most difficult problems in the numerical modeling of the planetary boundary layer. These coefficients have been computed from finite-difference analogs to analytical expressions associated with surface boundary-layer similarity theory, which is based on observations in an equilibrium surface layer. This procedure leads to erroneous results in the region above the surface layer and in a non-equilibrium surface layer. In addition, differencing problems arise in regions of small vertical wind shear. A new turbulence transport model has been obtained through the closure procedures for the transport equations of the Reynolds stress and the turbulent length scale. The new approach could be used to calculate Reynolds stresses and eddy exchange coefficients throughout a non-neutral planetary boundary layer under non-equilibrium conditions. 相似文献
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An acoustic Doppler sounder has been used to document the behaviour of the stable atmospheric boundary layer during the “Coast” experiment, in April-May, 1983, on a homogeneous terrain near the Dutch coast. It has been shown that kaimal's model of the spectrum of velocity in the stable surface layer can be applied and that surface-layer parameterization can be used in the whole stable surface layer. Velocity spectra have been computed between .0005 c.p.s. and .1 c.p.s. and for the stability range for z/L between 0 and 10. It is to be noted that the information has been obtained using only sodar data. 相似文献
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Summary A spectral analysis of the domain averaged height field at 1000 hPa surface over the Sahara using ECMWF data reveals a major oscillation of about five days. A composite analysis technique has then been developed which permits to emphasize the major characteristics of the evolution of the thermal low over the Sahara during a five day period in the summer season. This analysis shows that the composite structure of the termal field reveals a well mixed layer with an almost constant potential temperature and specific humidity from the surface up to about 650 hPa.The computation of the vertical velocity and the horizontal divergence reveals a presence of a two cell vertical circulation over the thermal low region. Although the heat low over the Saharan desert appears as a shallow low pressure area confined into the mixed layer, the entire troposphere seems to be dynamically active.In the surface layer, the response of the height field to the temperature field has a lag time of about one day.Adjustment of the theoretical net radiative heating rate have been applied assuming dust to have an effect on both shortwave and longwave irradiances. The results compare reasonably well with measurements obtained from the literature, and provide an improvement for the surface heat fluxes as compared to those deduced from conventional radiative transfer model.The thermodynamic budget over the desert region reveals that the contribution of the advective terms is to stabilize the mixed layer by removing the excess of heat from the surface layer. Furthermore, the destabilization of the mixed layer seems to result from a thermal unbalance between the net radiative heating and the convergence of the eddy sensible heat flux during the formative stage of the thermal low.Downward motion developing above the mixed layer during the occurrence of the heat low seems to be responsible for the cooling of the surface layer and a decrease of the surface temperature, which marks the decaying phase of the thermal wave.A qualitative inference of the top of the dust layer from the large scale variables has been attempted, and a simple scheme for the parameterization of the net solar radiation as a function of the large scale apparent heating is proposed. The results appear to be a reasonable approach for the definition of the net radiative heating.The moisture budget reveals that water vapor is supplied to the domain via horizontal advection from the region of the West African monsoon. Furthermore, its vertical distribution appears to be controlled by the complex vertical eddy motions in the dry thermals which develop over the warm Saharan desert during the afternoon hours.With 27 Figures 相似文献
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A. Lapworth 《Boundary-Layer Meteorology》2006,119(3):501-526
Six years of observations from a surface instrument site have been analysed to determine timings and factors influencing developmental changes in the near-surface wind and turbulent heat fluxes during the morning heating of the atmospheric boundary layer. A simple relationship has been found between near-surface wind speed and screen temperature, together with a predictive equation for the morning transition air temperature. Profile measurements from a probe mounted on a tethered balloon have beenused to supplement the surface data and study the processes underlying these surface relationships. The results have confirmed earlier work and have shown that both before and immediately after morning transition, almost all heating in the surface layer is due to turbulent diffusion from above. In order to explain the mechanisms involved in the relationships, a simple finite difference model has been run and validated against the profile data. The model predictions are compared with observations during both the morning and evening and the differences related to the different temperature profiles. Numerical forecasting rules for the surface wind speed and transition temperature are derived from the results. 相似文献
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组合法确定近地面层湍流通量和通用函数 总被引：17，自引：3，他引：17
本文发展了确定近地面层湍流通量的组合法,得到了它们的一般表达式。并用这种方法确定近地面层MO相似性函数。利用ITCE的观测资料作为实例计算,结果表明这种方法是可行的。 相似文献
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THE COMBINATORY METHOD FOR DETERMINATION OF THE TURBULENT FLUXES AND UNIVERSAL FUNCTIONS IN THE SURFACE LAYER* 
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下载免费PDF全文 A combinatory method of determining the turbulent fluxes in the surface layer has been developed and their general representations have been thus obtained.The universal functions of the (M-O) similarity in the surface layer can be determined by the method.The results calculated by using the ITCE's data indicate that the method is feasible. 相似文献