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In this study radar, surface observations and numericalsimulations are used to examine the inland penetrationand intensity of the sea breeze during various large-scaleflow regimes along the curved coastline of the Carolinas,U.S.A. The results clearly indicate that the flow directionrelative to the curved coastline has a significant effecton the sea-breeze evolution.Overall, during northerly flow regimes alongthe curved North Carolina coast, observationsand numerical simulations show that the sea-breezefront has a tendency to remain close to the south-facingcoast. During these same flow regimes the frontmoves further inland relative to the east-facingcoast. The sea-breeze front during westerly flowcases progressed further inland relative to the southcoast and less so from the east-facing coastline.South-westerly flow allows the sea breeze to moveinland from both coastlines but the coastal shapeinfluence makes the inland penetration less fromthe easterly facing beaches. During periods of lightonshore flow (south-east), the sea breeze movesconsiderable distances inland but is not discernableuntil later in the afternoon. The simulations indicatedthat the sea-breeze intensity is greatest (least) when thelarge-scale flow direction has an offshore (onshore)component. Model results indicate the existence of astrong front well inland in the late afternoon duringlight onshore flow. Also noted was that the simulatedsea-breeze front develops earlier in the afternoon duringoffshore regimes and later in the day as the large-scaleflow becomes more onshore. It is concluded that thecoastline shape and coast-relative flow direction areimportant factors in determining how the sea-breezecirculation evolves spatially. 相似文献
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Interaction between local and regional pollution during Escompte 2001: impact on surface ozone concentrations (IOP2a and 2b) 总被引：2，自引：0，他引：2
Escompte, a European programme which took place in the Marseille region in June–July 2001, has been designed as an exhaustive database to be used for the development and validation of air pollution models. The air quality Mesoscale NonHydrostatic Chemistry model (Meso-NH-C) is used to simulate 2 days of an Intensive Observation Period (IOP) documented during the Escompte campaign, June 23 and 24, 2001. We first study the synoptic and local meteorological situation on June 23 and 24, using surface and aircraft measurements. Then, we focus on the pollution episode of June 24. This study emphasizes the deep impact of synoptic and local dynamics on observed ozone concentrations. It is shown that ozone levels are due both to regional and local factors, with highlights of the importance of ozone layering. More generally this confirms, even in an otherwise predominant local sea-breeze regime, the need to consider larger scale regional pollutant transport. 相似文献
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2016年6月5日海南出现了一个弱风垂直切变背景下的EF2级致灾龙卷。利用海口多普勒天气雷达观测资料、10 min间隔的地面自动气象站观测资料以及风廓线资料,研究了该龙卷风暴的结构、龙卷风暴与龙卷形成的可能物理过程。初始风暴在文昌附近向西传播,而同时海口风暴亦由海风锋触发并向东移动,两风暴下沉气流导致的出流相遇在海风锋辐合线上,触发了龙卷母云体。龙卷初始涡旋在低层两风暴出流相遇的切变辐合线上形成,当初始涡旋与其上方深厚且强烈的上升气流叠置时,拉伸作用加强了垂直涡度,使得龙卷形成。深厚的强上升气流有3个来源:对流风暴的出流边界相遇形成的辐合抬升,环境正浮力造成的对流单体内强上升气流,还可能与中高层强中气旋强迫的扰动低压有关。龙卷形成过程中,中高层强中气旋位于6—9 km高空并向上发展,龙卷初始涡旋先于龙卷母云体出现且比一般微气旋尺度大,伸展至更高的高度,属于非典型中气旋龙卷（或非典型超级单体龙卷）。此次热带强龙卷出现在弱的大尺度系统强迫的天气背景下,水平风垂直切变弱,海风锋、出流边界等边界层β中尺度辐合线边界在龙卷形成过程中可能起决定性作用。 相似文献
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In the present study, we examine the dynamics of a sea-breeze front and the urban heat island interacting with the heavily
urbanized city of Athens. For this reason, simulations were performed with a modified version of the PSU/NCAR Mesoscale Model
(MM5), whereby urban features are considered, and the model results were compared with surface routine meteorological data.
An unrealistic run was also performed, where the city of Athens was replaced by dry cropland and pasture surface, as in the
surrounding area. A delay in the sea-breeze front was found during daytime, together with frictional retardation concerning
its penetration, as well as inland displacement of the heat island as the air moved over the city of Athens. During nighttime,
the wind speed increased over the lower atmosphere in the city centre due to the enhanced urban heat island. 相似文献
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We examine the mesoscale structure of the atmospheric boundary layer (ABL), low-level circulation, and trade wind convection
over the sub-tropical island of Puerto Rico in mid-summer. Shallow afternoon thunderstorms are frequently seen over the western
plains of the island. Observational data include automatic weather station measurements, radiosonde profiles, infrared satellite
images, and mesoscale reanalysis data with a focus on the summer of 2006. Satellite microwave radar data (TRMM and CloudSat)
indicate that island clouds typically extend just above the −20°C level during afternoon hours with reflectivity values reaching
50 dBz. A singular value decomposition of 3-hourly high resolution satellite rainfall maps reveals an island mode. From this
a composite is constructed for a group of ten cases. With a Froude number ≈1 the trade winds pass over the mountains and standing
vortices and gravity waves are trapped in the meandering wake. The Weather and Research Forecasting (WRF) model at 1-km resolution
with 51 vertical layers is used to simulate the short-lived thunderstorms for two cases: 27 June and 20 July 2006. The model
correctly locates the convective cells that develop between 1400 and 1700 LST. The shallow afternoon thunderstorms are triggered
by surface heat fluxes, confluent sea breezes and a mountain wake. Recommendations for enhanced observations are given. 相似文献
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A numerical mesoscale model is used to make a high-resolutionsimulation of the marine boundary layer in the Persian Gulf, duringconditions of offshore flow from Saudi Arabia. A marine internal boundary layer(MIBL) and a sea-breeze circulation (SBC) are found to co-exist. The sea breeze develops in the mid-afternoon, at which time its frontis displaced several tens of kilometres offshore. Between the coastand the sea-breeze system, the MIBL that occurs is consistent with a picture described in the existing literature. However, the MIBL isperturbed by the SBC, the boundary layer deepening significantly seaward of the sea-breeze front. Our analysis suggests that thisstrong, localized deepening is not a direct consequence offrontal uplift, but rather that the immediate cause is the retardation of theprevailing, low-level offshore windby the SBC. The simulated boundary-layer development can be accounted for by using a simple 1D Lagrangian model of growth driven by the surface heatflux. This model is obtained as a straightforward modification ofan established MIBL analytic growth model. 相似文献
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V. Puygrenier F. Lohou B. Campistron F. Saïd G. Pigeon B. Bnech D. Sera 《Atmospheric Research》2005,74(1-4):329-353
Surface and remote-sensing instruments deployed during ESCOMPTE experiment over the Marseille area, along the Mediterranean coast, were used to investigate the fine structure of the atmospheric boundary layer (ABL) during sea-breeze circulation in relation to pollutant transport and diffusion. Six sea-breeze events are analyzed with a particular focus on 25 June 2001.Advection of cool and humid marine air over land has a profound influence on the daytime ABL characteristics. This impact decreases rapidly with the inland distance from the sea. Nearby the coast (3 km inland), the mixing height Zi rises up to 750 m and falls down after 15:00 (UT) when the breeze flow reaches its maximum intensity. A more classical evolution of the ABL is observed at only 11-km inland where Zi culminates in the morning and stabilizes in the afternoon at about 1000 m height.Fine inspection of the data revealed an oscillation of the sea-breeze with a period about 2 h 47 min. This feature, clearly discernable for 3 days at least, is present in several atmospheric variables such as wind, temperature, not only at the ground but also aloft in the ABL as observed by sodar/RASS and UHF wind profilers. In particular, the mixing height Zi deduced from UHF profilers observations is affected also by the same periodicity. This pulsated sea-breeze is observed principally above Marseille and, at the northern and eastern shores of the Berre pond.In summary, the periodic intrusion over land of cool marine air modifies the structure of the ABL in the vicinity of the coast from the point of view of stability, turbulent motions and pollutants concentration. An explanation of the source of this pulsated sea-breeze is suggested. 相似文献
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渤海湾地区碰撞型海风锋天气过程的资料诊断分析 总被引：2，自引：0，他引：2
利用多普勒雷达资料和地面自动站以及再分析资料对近年来7次典型的渤海湾地区碰撞型海风锋天气过程进行了分析。资料分析显示对流系统正面碰撞海风锋时(偏东西向碰撞)得到显著发展,而追赶碰撞海风锋时(偏南北向)则没有明显加强。海风锋移动沿途近地面出现明显的降温和风切变可以帮助判断海风锋的移动位置。高层稳定的偏西风有利于引导对流系统与西进海风锋发生正面碰撞。而低层的风场辐合则有利于碰撞过程中对流运动的发生,同时副高西北侧的水汽输送为降水的形成提供了有利条件。渤海湾地区地形的热力效应形成的低层偏中性层结有利于对流运动的发生,另外,在高空偏西风环境下地形可能对与海风锋碰撞的对流系统的触发或加强有促进作用。 相似文献
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