共查询到20条相似文献，搜索用时 31 毫秒
1.
根据2017、2019年7月塔克拉玛干沙漠腹地GPS探空和地面观测数据,利用位温廓线法等方法,对比分析了沙漠腹地夏季晴天和沙尘暴天气大气边界层结构变化特征。结果表明：晴天和沙尘暴天气大气边界层结构特征显著不同。晴天大气边界层各气象要素垂直分布较为均一,白天对流边界层深厚,高度接近5 km,夜间稳定边界层一般在500 m左右。沙尘暴天气边界层内位温和比湿垂直变化较小,风速较大,可达24.0 m/s,其白天对流边界层在1.5 km左右,夜间稳定边界层在1 km左右。晴天辐射强烈,地表升温迅速,湍流旺盛,是形成晴天深厚对流边界层的主要因素。大尺度天气系统冷平流的动力条件,以及云和沙尘减弱了到达地表的辐射强度是形成沙尘暴天气独特的大气边界层结构的主要因素。 相似文献
2.
利用一次冷空气过程的14组GPS探空数据,采用位温梯度法确定了冷空气过境前后大气边界层高度,并分析了冷空气过程对大气边界层结构的影响。结果表明：冷锋过境加大了海洋大气边界层的静力不稳定度,使边界层内对流活动增强,且锋面过后距离锋面越近的区域边界层的静力不稳定度越大;冷锋过境使边界层的平均高度升高,边界层顶处逆温梯度增大。结合ERA-Interim再分析资料,分析认为大气边界层高度与静力稳定度（海气温差）存在显著的正相关关系（相关系数达0.73）,海气温差越大,大气边界层高度越高。 相似文献
3.
A Study of the Atmospheric Boundary Layer Structure During a Clear Day in the Arid Region of Northwest China 
下载免费PDF全文
下载免费PDF全文 The local climate and atmospheric circulation pattern exert a clear influence on the atmospheric boundary layer （ABL） formation and development in Northwest China. In this paper, we use field observational data to analyze the distribution and characteristics of the ABL in the extremely arid desert in Dunhuang, Northwest China. These data show that the daytime convective boundary layer and night time stable boundary layer in this area extend to higher altitudes than in other areas. In the night time, the stable boundary layer exceeds 900 m in altitude and can sometimes peak at 1750 m, above which the residual layer may reach up to about 4000 m. The daytime convective boundary layer develops rapidly after entering the residual layer, and exceeds 4000 m in thickness. The results show that the deep convective boundary layer in the daytime is a pre-requisite for maintaining the deep residual mixed layer in the night time. Meanwhile, the deep residual mixed layer in the night time provides favorable thermal conditions for the development of the convective boundary layer in the daytime. The prolonged periods of clear weather that often occurs in this area allow the cumulative effect of the atmospheric residual layer to develop fully, which creates thermal conditions beneficial for the growth of the daytime convective boundary layer. At the same time, the land surface process and atmospheric motion within the surface layer in this area also provide helpful support for forming the particular structure of the thermal ABL. High surface temperature is clearly the powerful external thermal forcing for the deep convective boundary layer. Strong sensible heat flux in the surface layer provides the required energy. Highly convective atmosphere and strong turbulence provide the necessary dynamic conditions, and the accumulative effect of the residual layer provides a favorable thermal environment. 相似文献
4.
5.
利用宜昌2007年12月10-25日的加密观测资料,分析了两次低值系统经过宜昌时大气边界层的温湿风廓线结构及其日变化特征。结果表明：位温廓线具有明显的日变化特征,对流边界层在白天出现和发展,其高度可达600m,而稳定边界层在夜间出现和发展,其高度可达300m,降水会抑制对流边界层和稳定边界层的发展;湿度廓线结构及其日变化与对流边界层的发展有关,总体上湿度随高度减小,贴近地面的薄层湿度随高度减小较快,而混合层内湿度随高度变化较小,出现降水时,近地层的湿度有明显增加,大气边界层内湿度随高度快速平稳减小;风速廓线结构比较复杂,总体上风速随高度增大,在大气边界层低层有时会出现一个风速极大值,风速廓线没有明显的日变化特征,大气边界层内风向变化较大,但以偏东风为主。 相似文献
6.
大气边界层高度是天气、气候、大气环境研究中的一个重要参数,目前尚缺少基于激光雷达探测系统反演全天边界层高度的有效方法。文中利用北京朝阳站、大兴站的激光云高仪数据,首先评估了梯度法、标准偏差法、曲线拟合法和小波协方差法反演边界层高度的适用性和局限性,发现梯度法容易受环境噪声的影响,曲线拟合法稳定性较好,但在夜间弱湍流条件下会将残留层高度误判为夜间边界层高度。提出两步曲线拟合法,将一天中边界层结构划分为白天的对流边界层、夜间的残留层和稳定边界层,通过用不同的理想曲线对其进行两步拟合,获取全天边界层高度的变化。将两步曲线拟合法的反演结果与基于L波段探空雷达的位温梯度法的探测结果进行比较发现:两者相关系数为0.91,证明了两步曲线拟合法的可行性以及激光云高仪探测边界层高度的应用潜力。采用该方法反演2017年5—6月朝阳站与大兴站边界层高度,对比发现:城区特殊的下垫面性质使朝阳站日间对流边界层发展更早,边界层高度更高,全天朝阳站边界层高度的变化在308—1391 m,大兴站在197—1302 m。 相似文献
7.
David Melecio-Vázquez Prathap Ramamurthy Mark Arend Jorge E. González-Cruz 《Boundary-Layer Meteorology》2018,169(1):151-161
We use various temperature profilers located in and around New York City to observe the structure and evolution of the thermal boundary layer. The primary focus is to highlight the spatial variability of potential-temperature profiles due to heterogeneous surface forcing in an urban environment during different flow conditions. Overall, the observations during the summer period reveal the presence of thermal internal boundary layers due to the interaction between the marine atmospheric boundary layer and the convective urban environment. The summer daytime potential-temperature profiles within the city indicate a superadiabatic layer is present near the surface beneath a mildly stable layer. Large spatial variability in the near-surface (0–300 m) potential temperature is detected, with the thermal profile in the lower atmosphere uniquely determined by the underlying surface forcing and the distance from the coast. The summer and winter average night-time potential-temperature profiles show that the atmosphere is still convective near the surface. The seasonal averages of mixing ratio show large variability in the vertical direction. 相似文献
8.
Analytical solutions of convective waves in the convective boundary layer (CBL) were obtained with two-layer linearized atmospheric
equations including Rayleigh friction, which represents the turbulent viscosity in the lower CBL. The analytical model shows
that the interaction between the convection in the lower layer and gravity waves in the upper layer is one of the causes for
the formation of convective bands. The flow and temperature fields obtained by the analytical model present the main characteristics
of convective bands found in field observations. We have also investigated the influences of atmospheric conditions on the
characteristics of the bands. Results accord with previous knowledge about these phenomena. 相似文献
9.
Study on Physical Mechanism of Influence on Atmospheric Boundary Layer Depth in the Arid Regions of Northwest China 总被引：1，自引：0，他引：1 下载免费PDF全文
下载免费PDF全文 Using the sounding data of wind, temperature, and humidity in the boundary layer and micrometeorological data on the earth's surface observed in the same period in Dunhuang arid region of Northwest China,this paper researches characteristics of potential temperature, wind, and humidity profiles, confirms the structure and depth of thermodynamic boundary layer in Dunhuang region, and analyzses the relationship of depth of thermodynamic boundary layer with surface radiation, buoyancy flux as well as wind speed and
wind direction shear in the boundary layer. The results show that the maximum depth of diurnal convective boundary layer is basically above 2000 m during the observational period, many times even in excess of 3000 m and sometimes up to 4000 m; the depth of nocturnal stable boundary layer basically maintains within a range of 1000-1500 m. As a whole, the depth of atmospheric boundary layer is obviously bigger than those results observed in other regions before. By analyzing, a preliminary judgement is that the depth
of atmospheric thermodynamic boundary layer in Dunhuang region may relate to local especial radiation characteristics, surface properties (soil moisture content and heat capacity) as well as wind velocity shear of boundary layer, and these properties have formed strong buoyancy flux and dynamic forcing in a local region which are fundamental causes for producing a super deep atmospheric boundary layer. 相似文献
10.
大气对流边界层中的涡漩结构 总被引：4，自引：1，他引：4
大气边界层中存在尺度从几百米到几十公里的大涡漩运动。它们在边界层中动量、热量、水汽等垂直输送中起重要作用。作者从边界层中对流和上部稳定层中波动相互作用的观点，发展得出大涡结构的对流波动理论。根据此理论，大涡的波谱构成主要由上、下层大气中风向、风速、层结以及两层之间的温度跃变等因素决定。本文根据卫星云图和天气资料分析了一次冷空气爆发流经暖洋面上形成云街、对流单体以及它们之间的相互演化的过程，并用对流波动理论，依据各阶段的大气条件计算出它们的波数构成，并得出了垂直速度、辐合带、界面扰动的分布，解释了云街、对流单体的形成、结构及相互转化的原因 相似文献
11.
Zbigniew Sorbjan 《Boundary-Layer Meteorology》2007,123(3):365-383
We examine daily (morning–afternoon) transitions in the atmospheric boundary layer based on large-eddy simulations. Under
consideration are the effects of the stratification at the top of the mixed layer and of the wind shear. The results describe
the transitory behaviour of temperature and wind velocity, their second moments, the boundary-layer height Z
m
(defined by the maximum of the potential temperature gradient) and its standard deviation σ
m
, the mixed-layer height z
i
(defined by the minimum of the potential temperature flux), entrainment velocity W
e, and the entrainment flux H
i
. The entrainment flux and the entrainment velocity are found to lag slightly in time with respect to the surface temperature
flux. The simulations imply that the atmospheric values of velocity variances, measured at various instants during the daytime,
and normalized in terms of the actual convective scale w*, are not expected to collapse to a single curve, but to produce a significant scatter of observational points. The measured
values of the temperature variance, normalized in terms of the actual convective scale Θ*, are expected to form a single curve in the mixed layer, and to exhibit a considerable scatter in the interfacial layer. 相似文献
12.
The temperature structure parameter at Delhi has been determined from intensity information of sodar observations for a period of one year at a height of 200 m in the planetary boundary layer applying the moisture correction due to Wesely. It is found that mean monthly values of the temperature structure parameter for stable and unstable conditions are quite different during the monsoon months (July to October) but are rather similar during the other months.The refractive index structure parameter values have been calculated for the dry atmosphere (optical) as well as by applying the moisture correction (radio) due to the Sirkis and Ottersten et al. models. It is found that the dry atmospheric values of the parameter are generally lower than the humidity-corrected values. The sodar-measured values of the parameter under dry atmospheric conditions have been examined in relation to the Hufnagel and Tsvang models. 相似文献
13.
Large vortices with scales ranging from hundreds meters to tens of kilometers are generallyfound in the atmospheric convective boundary layer(CBL).These vortices play important roles in the vertical transport of momentum,heat,water vaporand other tracers in the boundary layer.On the basis of the view of interaction between theconvection in CBL and the gravity waves in the upper stable layer the authors developed aconvection-wave theory on the formation of large vortices.According to the theory thewavenumber spectrum of the large vortices mainly depends on the atmospheric conditions in bothof the upper and lower layers,such as wind speed,wind direction shear,stratification as well astemperature jump.In the present paper satellite image and weather data in a case of cold air outbreak over warmocean are analyzed to study every stage of the convective processes,such as cloud street,convective cell as well as their transformation.According to the theory the wavenumbercompositions for cloud street and convective cell are calculated,respectively,on the basis of theatmospheric conditions at every stage.The distributions of vertical motions,convergent band anddisturbed interface are obtained and compared with the cloud patterns in the convective processes.Thus the study seems to offer a likely explanation for the origin of large vortices in CBL. 相似文献
14.
Large vortices with scales ranging from hundreds meters to tens of kilometers are generally found in the atmospheric convective boundary layer(CBL).These vortices play important roles in the vertical transport of momentum,heat,water vapor and other tracers in the boundary layer.On the basis of the view of interaction between the convection in CBL and the gravity waves in the upper stable layer the authors developed a convection-wave theory on the formation of large vortices.According to the theory the wavenumber spectrum of the large vortices mainly depends on the atmospheric conditions in both of the upper and lower layers,such as wind speed,wind direction shear,stratification as well as temperature jump.In the present paper satellite image and weather data in a case of cold air outbreak over warm ocean are analyzed to study every stage of the convective processes,such as cloud street,convective cell as well as their transformation.According to the theory the wavenumber compositions for cloud street and convective cell are calculated,respectively,on the basis of the atmospheric conditions at every stage.The distributions of vertical motions,convergent band and disturbed interface are obtained and compared with the cloud patterns in the convective processes.Thus the study seems to offer a likely explanation for the origin of large vortices in CBL. 相似文献
15.
本文采用二阶闭合的湍流边界层模式,进行一系列数值试验以模拟边界层中连续线源的扩散状况。试验表明:无论在稳定的或不稳定的边界层中,高源的扩散能力都低于低源;在稳定层中,粗糙地表上的大气扩散能力高于光滑表面;在相同风速和地表净辐射情况下,粗糙表面上的大气扩散能力反而低于光滑表面;对流边界层中存在反梯度输送,因而K理论的应用受到限制。试验还表明,修正的Kazanski-Monin参数可能比Monin-Obukhov长度更能反映大气的扩散能力。 相似文献
16.
Zbigniew Sorbjan 《Boundary-Layer Meteorology》1989,47(1-4):195-203
A model for the temperature spectrum in the convective boundary layer is presented. The model is developed by using local similarity parameterization of the mixed layer. The model is compared with an idealized temperature spectrum obtained during the Minnesota experiment and exhibits behavior very similar to that observed in the atmosphere. 相似文献
17.
Although the residual layer has already been noted in the classical diurnal cycle of the atmospheric boundary layer,its effect on the development of the convective boundary layer has not been well studied. In this study, based on 3-hourly20 th century reanalysis data, the residual layer is considered as a common layer capping the convective boundary layer. It is identified daily by investigating the development of the convective boundary layer. The region of interest is bounded by(30°–60° N, 80°–120° E), where a residual layer deeper than 2000 m has been reported using radiosondes. The lapse rate and wind shear within the residual layer are compared with the surface sensible heat flux by investigating their climatological means, interannual variations and daily variations. The lapse rate of the residual layer and the convective boundary layer depth correspond well in their seasonal variations and climatological mean patterns. On the interannual scale, the correlation coefficient between their regional averaged(40°–50°N, 90°–110° E) variations is higher than that between the surface sensible heat flux and convective boundary layer depth. On the daily scale, the correlation between the lapse rate and the convective boundary layer depth in most months is still statistically significant during 1970–2012. Therefore, we suggest that the existence of a deep neutral residual layer is crucial to the formation of a deep convective boundary layer near the Mongolian regions. 相似文献
18.
Gerard Kiely John D. Albertson Marc B. Parlance William E. Eichinger 《Boundary-Layer Meteorology》1996,77(3-4):267-284
The flux of sensible heat from the land surface is related to the average rate of dissipation of temperature fluctuations in the atmospheric surface layer through the temperature variance budget equation. In many cases it is desirable to estimate the heat flux from measurement or inference of the dissipation rate. Here we study how the dissipation rate scales with atmospheric stability, using three inertial range methods to calculate the dissipation rate: power spectra, second order structure functions, and third order structure functions. Experimental data are analyzed from a pair of field experiments, during which turbulent fluctuations of velocity and temperature were measured over a broad range of neutral and unstable atmospheric flows. It is shown that the temperature dissipation rate scales with a single convective power law continuously from near-neutral to strongly unstable stratification. The dissipation scaling is found to nearly match production in the near-neutral region, but to be consistently lower than production in the more convective regimes. The convective scaling is shown to offer a simplified means of computing sensible heat flux from the dissipation rate of temperature variance.Also at Johns Hopkins University, Baltimore, MarylandAlso at Los Alamos National Laboratory, Los Alamos, New Mexico. 相似文献
19.
Remote Sensing Methods to Investigate Boundary-layer Structures relevant to Air Pollution in Cities 总被引：2，自引：0，他引：2
Simultaneous surface-based remote sensing with optical (Ceilometer) and acoustic (Sodar) methods allows the diurnal variation of the structure of the atmospheric boundary layer to be deduced with high temporal resolution. Primarily the convective boundary layer, the nocturnal stable surface layer, and the residual layer can be identified from the measured vertical profiles of aerosol concentration and thermal fluctuations. The ability of the two remote sensing techniques is shown in different examples from two different locations and two seasons. The impact on urban air quality assessment is addressed. 相似文献
20.
盛夏渤海湾大气边界层辐合线触发对流风暴对比分析 总被引：2，自引：2，他引：0
本文对渤海湾2008—2009年,由大气边界层辐合线引起的对流风暴进行了分析。结果表明,在高温、高湿不稳定大气层结环境条件下：（1）单一的海风锋在其端点可产生对流性降水。（2）海风锋与弱冷锋相遇,或者两条海风锋相交,或者雷暴单体的出流边界与海风锋相遇均会产生强对流风暴。（3）渤海湾边界层辐合线触发对流风暴大多发生在每年7 8月,且在副热带高压控制渤海湾后东退的过程中,此时大气层结处在高温、高湿不稳定状态。辐合线触发的对流风暴是沿辐合线移动,移动方向取决于辐合线两侧的主导风向。（4）边界层辐合线触发对流风暴,具有突发性强,持续时间短等特点,分析渤海湾边界层辐合线的移动与演变能提高强对流风暴的临近预报、预警,减少突发性天气引起的灾害。 相似文献