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1.
通过对一次影响珠海机场航班调控和飞机起降的平流海雾过程进行天气形势、温湿条件、风廓线特征分析,结果表明:(1)850hPa以下持续暖湿平流是平流雾形成的基础;(2)近地层逆温及中低层多层逆温的温度层结和近地层的饱和湿层,以及适宜的地面风场是形成平流雾的有利条件,夜间的辐射冷却加强了贴地层大气的饱和度而形成平流雾;(3)风廓线资料分析表明边界层内东南~偏南风场保证了暖湿平流条件,而近地层偏北风干冷平流入侵并出现下沉气流、逆温层被破坏使雾趋于消散。 相似文献
2.
利用2015年7月至2016年5月寿县稻麦轮作农田区观测站地基多通道微波辐射计观测的高时间分辨率温度廓线资料,结合位温梯度法,计算了该站点的大气边界层高度,分析了边界层高度的日、月和季节演变规律。结果显示,晴朗天气情况下,边界层高度具备典型的日变化特征,随着地面温度的升高边界层高度不断增大。其最大平均值通常出现在午后,8月平均高度最高,超过1520m,1月最低,只有520m。而且边界层高度具有季节变化趋势,春季(3—5月)、夏季(6—8月)、秋季(9—11月)和冬季(12月至次年2月)平均高度分别为436m,499m,377m和322m。将边界层高度结果与FNL和ERA-Interim数据进行对比,发现在白天时间段(08:00—19:00)FNL和ERA-Interim比观测平均值分别高258m,346m,夜间时间段(19:00至次日08:00)比观测平均值分别低144m,102m。 相似文献
3.
Temperature oscillations observed in the stable boundary layer over four different underlying surfaces 
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下载免费PDF全文 《大气和海洋科学快报》2017,(3)
夜间边界层内的温度时空特征决定了边界层的稳定性。由于稳定边界层的间歇性和复杂性,模式在夜间的参数化方案还不完善,研究夜间边界层的温度变化有助于改进模式在夜间的表现。本文利用四座在不同下垫面上的气象塔的数据,研究了夜间边界层中的温度波动。研究表明,无论是海边、草原还是沙漠下垫面,夜间形成的稳定边界层中,振幅大约2摄氏度,周期在数分钟的温度波动非常频繁地出现。而在北京,由于城市下垫面较大的热容量和人为热源使得稳定边界层不容易形成,温度波动也较弱。用布朗特维萨拉频率代表的静力稳定度是影响温度脉动强弱的重要因子。 相似文献
4.
利用2007年12月的加密探空资料, 对高原东部及其下游地区的边界层结构和高原东部边界层变化对下游大气的影响进行了分析。结果表明, 冬季青藏高原东部夜间近地面逆温层可以发展到平均500 m的高度, 白天混合层可以发展到平均2000 m的高度。白天混合层内水汽和风速混合十分均匀, 在混合层发展成熟时存在十分深厚的逆湿层。冬季青藏高原下游的四川盆地, 边界层内温度日较差小, 夜间逆温层把大量地表水汽截留在近地层, 日出前近地层水汽容易达到饱和。白天, 混合层在中午发展成熟, 平均高度只有300 m。四川盆地对流层下部存在非常强的逆温层, 该逆温层是青藏高原抬升地表加热和冬季盛行西风气流形成的, 逆温层变化是青藏高原东部边界层温度日变化和局地西风变化的共同结果。逆温层显著改变大气动量、 热量和水汽的垂直分布。与对流层下部逆温相联系的中层云对辐射的影响是造成四川盆地温度日较差和混合层高度变化的原因。 相似文献
5.
在科技部公益专项"沙尘气溶胶辐射模型及气候环境生态效应研究"支持下,执行期间在二连浩特气象站用GFE(L)1型二次测风雷达和GTS1型数字式探空仪,于2006年4月24~25日对内蒙古高原半干旱荒漠化草原地区春季典型晴日边界层特征进行了加密探测。结果表明:二连浩特地区边界层的日变化大,对流边界层最大高度可以达到2000 m,超绝热层平均高度为270 m,夜间稳定边界层高度可达到900 m;白天在4000 m附近存在高空急流,最大风速达到29 m.s-1;夜间近地面层有东风急流,其高度在250 m左右,观测日低空急流最强时间是在23:00,风速达到16 m.s-1;边界层内湿度变化较大,呈现多层逆湿结构。 相似文献
6.
利用Vaisala系留探空仪系统在2008年1月乌鲁木齐探测所得资料,分析了降雪和非降雪过程中温度、湿度和风的垂直结构及其变化特征。结果表明:降雪和非降雪天,白天对流边界层特征均较明显,但在暖气团影响下,对流边界层特征消失,出现深厚平流逆温,夜间多出现贴地逆温。白天平流逆温强度较夜间逆温更强,白天逆温层出现湿中心,上部出现干中心。降雪天湿中心高度低于非降雪天。夜间近地层出现微弱的逆湿现象,上部出现干中心,降雪天近地层逆湿现象比非降雪天弱;降雪天和非降雪天近地层风向分布均较散乱,主导风向为偏北风,高空主导风向为东南风。风速多因风向改变而出现极大值或极小值,其值常以“高-低-高-低”形式出现于特定高度,风速因风向变化呈波动状随高度递增。 相似文献
7.
利用2007年12月10-24日在红原、温江和宜昌同步观测的3小时加密探空资料,分析了青藏高原东部及下游关键区大气边界层位温廓线日变化特征,以及对流边界层高度和稳定边界层高度的变化特征.分析结果表明,不同地形位温廓线具有相同的日变化特征,对流边界层在白天出现和发展,而稳定边界层在夜间出现和发展;对流边界层的发展史和发展高度与海拔高度有关,高海拔地区对流边界层的发展史较短但发展高度较高,而低海拔地区对流边界层的发展史较长但发展高度较低;稳定边界层的发展史和发展高度也与海拔高度有关,高海拔地区稳定边界层的发展史较长且发展高度较高,而低海拔地区稳定边界层的发展史较短且发展高度较低;对流边界层的最大发展高度多出现在地方时17时,而稳定边界层的最大发展高度多出现在地方时02时;红原、温江和宜昌的对流边界层高度分别可达4 930 m、1 000 m和710 m.而其稳定边界层高度分别可达1 100 m、920 m和650 m. 相似文献
8.
利用新一代大气化学在线耦合模式WRF-Chem研究城市扩张对珠三角地区春季气象条件的改变及其对地面O3浓度的影响。研究结果表明:受城市扩张的影响,珠三角城区的月平均气温上升0.35℃;城区夜间相对湿度下降幅度为4%～6%,影响程度大于白天;风速在白天和夜间都有不同程度的下降,城市月平均风速下降1.89 m/s;边界层高度在白天和夜间均升高,城市月平均边界层高度上升39.82 m。城市扩张后,城市月平均O3浓度增加0.89 ppbv,增幅大于1.5 ppbv的区域主要在佛山和东莞,白天O3浓度增幅为0.6～1.5 ppbv,夜间增幅及影响范围都大于白天,O3浓度增加区域与主要气象要素变化的区域相一致;白天14:00城区混合层内总臭氧柱浓度增加了80 ppbv;O3浓度对气象要素的敏感程度表现为:温度>边界层高度>风速>相对湿度;白天O3浓度增幅呈U型,其中14:00的O3增幅最小,为0.2 ppbv;夜间O3增幅呈倒V型,其中20:00的增幅最大(>1.5 ppbv)。 相似文献
9.
夏季金塔边界层风、温度和湿度结构特征的初步分析 总被引：10，自引：3，他引：7
利用2004年6～7月在河西走廊金塔陆-气相互作用试验的观测资料,分析了该地区夏季夜间和中午风、温、湿的垂直结构特征,结果表明：夏季夜间,当地面风较小时,金塔绿洲高空可能为偏西风气流,夜间稳定层高度大致在100～190m。夏季中午,当低空为偏东风时,风速随高度的变化比较复杂。总的来说,存在着东风急流,急流高度在1000-4000m之间,大气边界层顶盖（即逆温层底）约在3000-3600m高度,在500-800m高度以下存在绿洲内边界层;当低空为偏北风或西北风时,高空都为偏西风或西北风气流,低空风速随高度的变化比较平缓,风速有时存在极大值,大气边界层顶盖（即逆温层底）在3500m左右,在1200m以下可能存在绿洲内边界层,绿洲内边界层高度有时会很低。 相似文献
10.
本文使用了一维非定常热力方程对夜间大气边界层热力结构进行了数值模拟.结果表明:(1)当天气形势变化平稳时,平坦地区夜间边界层热力结构的变化主要受到湍流与辐射传输作用的影响.(2)由于地-气之间热量传输的相互调整作用,使低层湍流变温率与地面温度变率之间表现为有相同周期的变化. 文中通过该模式的计算结果与复杂地形的实验资料的对比,研究了平流作用对温度垂直分布的影响. 相似文献
11.
S. Khodayar N. Kalthoff M. Fiebig-Wittmaack M. Kohler 《Meteorology and Atmospheric Physics》2008,99(3-4):181-198
Summary The boundary-layer structure of the Elqui Valley is investigated, which is situated in the arid north of Chile and extends
from the Pacific Ocean in the west to the Andes in the east. The climate is dominated by the south-eastern Pacific subtropical
anticyclone and the cold Humboldt Current. This combination leads to considerable temperature and moisture gradients between
the coast and the valley and results in the evolution of sea and valley wind systems. The contribution of these mesoscale
wind systems to the heat and moisture budget of the valley atmosphere is estimated, based on radiosoundings performed near
the coast and in the valley.
Near the coast, a well-mixed cloud-topped boundary layer exists. Both, the temperature and the specific humidity do not change
considerably during the day. In the stratus layer the potential temperature increases, while the specific humidity decreases
slightly with height. The top of the thin stratus layer, about 300 m in depth, is marked by an inversion. Moderate sea breeze
winds of 3–4 m s−1 prevail in the sub-cloud and cloud layer during daytime, but no land breeze develops during the night.
The nocturnal valley atmosphere is characterized by a strong and 900 m deep stably stratified boundary layer. During the day,
no pronounced well-mixed layer with a capping inversion develops in the valley. Above a super-adiabatic surface layer of about
150 m depth, a stably stratified layer prevails throughout the day. However, heating can be observed within a layer above
the surface 800 m deep. Heat and moisture budget estimations show that sensible heat flux convergence exceeds cold air advection
in the morning, while both processes compensate each other around noon, such that the temperature evolution stagnates. In
the afternoon, cold air advection predominates and leads to net cooling of the boundary layer. Furthermore, the advection
of moist air results in the accumulation of moisture during the noon and afternoon period, while latent heat flux convergence
is of minor relevance to the moisture budget of the boundary layer.
Correspondence: Norbert Kalthoff, Institut für Meteorologie und Klimaforschung, Universit?t Karlsruhe/Forschungszentrum Karlsruhe,
Postfach 3640, 76021 Karlsruhe, Germany 相似文献
12.
The structure of nocturnal inversions in the first 300 m of the atmosphere is analyzed using observational data from the Boulder Atmospheric Observatory (BAO) from March through June 1981. The temperature profiles show more than one inversion layer 41% of the time during the observational period. The vertical distributions of wind speed and moisture also show evidence of stratification during these multiple-layer events. The relation between the radiative cooling rate in time and height, including moisture, and the vertical structure of the multiple layers is calculated. The vertical distribution of eddy kinetic energy and the turbulent vertical fluxes of heat and momentum are also calculated. Turbulent structure in the elevated inversion layers is more complicated than that in the single-layer, stable nocturnal boundary layer. The total heat budget for a multiple-layer case is calculated, and turbulent cooling is found to be negligible relative to radiative cooling and to horizontal advection and/or horizontal divergence of heat flux. 相似文献
13.
The spatial variation of the nocturnal urban boundary-layer structure is described and the time variation of the mixing height, and the nocturnal inversion top and strength after sunrise is presented for urban sites located upwind, downwind, and near the center of the heat island, and at an upwind rural site. Observations were derived from high resolution temperature profiles obtained by a helicopter during 35 intensive morning experiments in St. Louis, Missouri.The nocturnal urban boundary layer increased in depth from the upwind edge of the urban area. Far downwind, in suburban and rural areas, a remnant of the urban boundary layer existed between a stable surface-based layer and an upper inversion that resembled the upwind rural inversion.The mixing height (base of the inversion) evolved in a parabolic manner after sunrise at the urban locations. A rise in the inversion top after sunrise at the urban locations is believed to be due to low-level convergence which caused the entire inversion layer to be lifted. Due to large horizontal temperature gradients associated with the urban heat island, cold air advection tended to counteract the urban-induced lifting effect by inhibiting mixing-height growth at urban locations upwind of the heat-island center. Advection also caused the maximum height and fastest growth rate of the urban mixed layer to be shifted downwind of the urban area with time. However, mean mixing-height growth rates at various urban locations did not differ significantly. The rural mixing-height growth rate was about twice as large as urban values for up to 3 hr after sunrise. Spatial differences in the mixing height became small near the time of inversion dissipation, which appeared to occur at about the same time at all locations.On assignment from the National Oceanic and Atmospheric Administration, U.S. Department of Commerce. 相似文献
14.
Atsushi Inagaki Manabu Kanda Nurul Huda Ahmad Ayako Yagi Naoyuki Onodera Takayuki Aoki 《Boundary-Layer Meteorology》2017,163(2):161-177
Sonic anemometer measurements are analyzed from two primary field programs and 12 supplementary sites to examine the behaviour of the turbulent heat flux near the surface with high wind speeds in the nocturnal boundary layer. On average, large downward heat flux is found for high wind speeds for most of the sites where some stratification is maintained in spite of relatively intense vertical mixing. The stratification for high wind speeds is found to be dependent on wind direction, suggesting the importance of warm-air advection, even for locally homogenous sites. Warm-air advection is also inferred from a large imbalance of the heat budget of the air for strong winds. Shortcomings of our study are noted. 相似文献
15.
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
16.
A model of the evolution of the nocturnal stable boundary layer height, based on the heat conservation equation for a turbulent flow, is presented. This model is valid for nights with weak winds and little cloudiness in rural areas. The model includes an expression of vertical profile of potential temperature within the boundary layer, which is obtained using micrometeorological information from Prairie Grass, Wangara and O'Neill Projects. The expression turned out to be a second-grade polynomial of the dimensionless height of the nocturnal stable boundary layer. The resulting model is a function of the Monin–Obukhov length, the surface potential temperature of air and the roughness length. This model was satisfactorily compared with micrometeorological data. It was applied at three stations of Argentina, using surface hourly meteorological information. From the results that were obtained, the monthly average values of the stable boundary layer thickness were analysed. The maximum monthly average values occur during the cold season and the minimum ones take place during the hot season. It was observed that the monthly average thickness increases with latitude. 相似文献
17.
Soundings in the stably-stratified boundary layer were executed over the rough terrain of Northern Germany during a night with a low-level jet (LLJ) development. Vertical wind and temperature profiles were obtained at 5 m height intervals using a tethersonde transported up and down along a 300 m high radio tower by an elevator. From these profiles, turbulent fluxes of heat and momentum, coefficients of eddy diffusivity and boundary-layer parameters were estimated. The nocturnal mean state analysis agrees well with the second-order model results of Brost and Wyngaard (1978) and our own first-order numerical testing while the time histories of different profile groups are in accordance with the observations of Izumi and Barad (1963). 相似文献
18.
This paper reports on measurements of sensible and latent heat and CO2 fluxes made over an irrigated potato field, growing next to a patch of desert. The study was conducted using two eddy correlation systems. One measurement system was located within the equilibrium boundary layer 800 m downwind from the edge of the potato field. The other measurement system was mobile and was placed at various downwind positions to probe the horizontal transition of vertical scalar fluxes. Latent (LE) and sensible (H) heat fluxes, measured at 4 m above the surface, exhibited marked variations with downwind distance over the field. Only after the fetch to height ratio exceeded 75 to 1 didLE andH become invariant with downwind distance. When latent and sensible heat fluxes were measured upwind of this threshold, significant advection of humidity-deficit occurred, causing a vertical flux divergence ofH andLE.The measured fluxes of momentum, heat, and moisture were compared with predictions from a second-order closure two-dimensional atmospheric boundary layer model. There is good agreement between measurements and model predictions. A soil-plant-atmosphere model was used to examine nonlinear feedbacks between humidity-deficits, stomatal conductance and evaporation. Data interpretation with this model revealed that the advection of hot dry air did not enhance surface evaporation rates near the upwind edge of the potato field, because of negative feedbacks among stomatal conductance, humidity-deficits, andLE. This finding is consistent with results from several recent studies. 相似文献
19.
20.
An analytical framework is proposed for studying variations in the diurnal wind structure in the planetary boundary layer (PBL) and the evolution of the low-level nocturnal jet. A time-dependent eddy-diffusivity coefficient corresponding to solar input is proposed, and an appropriate coordinate transformation ensures that mixing height varies continuously with ground heat-flux changes. The solution exhibits the receding character of the daytime PBL as evening approaches, thereby dividing the PBL into two regimes — the one just above the ground, representing the nocturnal boundary layer, and the region above it. It is assumed that inertial oscillations (IO) are triggered in the upper layer at about the time of sunset when the reversal in the direction of ground heat flux is felt in the upper layer. Two approaches are adopted to determine the characteristic features of IO and the evolution of the nocturnal low-level jet. The first one is based on the physical principle that release of horizontal momentum due to deviation from the geostrophic wind gives rise to the IO. The solution captures all the characteristic features of the IO, such as phase shift and decreasing amplitude of the IO with increasing height. According to this analysis the IO is triggered at a level as soon as the top of the receding boundary layer leaves that level. The solution is discontinuous with respect to the vertical coordinate. In the second approach we solve an initial-value problem to determine the solution in the upper layer, assuming that at about the time of sunset there is a rapid collapse of the daytime PBL to the steady, nocturnal boundary layer. The assumption is based on the mixing-height profiles prepared from climatological data collected at Delhi. The solution for the nocturnal boundary-layer regime is then obtained as a boundary-value problem. The solutions so obtained are continuous throughout the domain of interest and exhibit the characteristic features of an IO. The analysis leads to the conditions under which a low-level nocturnal jet is produced and provides quantitative estimates of the parameters, such as length of night, latitude, mixing height at sunset and nocturnal mixing height, that are conducive to the generation of a jet. The nocturnal wind profile produced by this approach compares well both with typical atmospheric data observed at Delhi and with output from a mesoscale numerical model. There is still some uncertainty related to the time of initiation of the IO as a function of latitude. 相似文献