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1.
Observational results of the structure of the sea breeze over the urban and suburban areas of Tokyo for four summer days are presented.On two of these days, the inland penetration of the sea breeze front could be clearly traced. In one case, the sea breeze was first observed along the shores of Tokyo Bay around 0900 JST, and propagated in three hours through the Tokyo City area, the width of which is about 20 km. It then advanced inland at a rate of 16 km h–1. Prior to the arrival of the sea breeze at the suburban site, the mixing height had remained at about 600 m for four hours. With the arrival of the sea breeze front, accompanied by an abrupt change in wind speed and direction, the mixing height increased sharply to 1700 m. It is suggested that this behavior and the structure of the front are intensified due to the urban effect, or the difference in the thermal characteristics between the urban and rural areas.On the days without a sea breeze front, the land breeze system during the early morning was less intense, allowing the sea breeze to develop simultaneously with the inland valley wind and easily form a large-scale local wind system during the morning hours. In both cases, the vertical motion accompanying the local wind system works as a feedback mechanism to control the local winds by modifying the thermal and pressure fields.  相似文献   

2.
The inland and offshore propagation speeds of a sea breeze circulation cell are simulated using a three-dimensional hydrostatic model within a terrain-following coordinate system. The model includes a third-order semi-Lagrangian advection scheme, which compares well in a one-dimensional stand-alone test with the more complex Bott and Smolarkiewicz advection schemes. Two turbulence schemes are available: a local scheme by Louis (1979) and a modified non-local scheme based on Zhang and Anthes (1982). Both compare well with higher-order closure schemes using the Wangara data set for Day 33–34 (Clark et al., 1971).Two-dimensional cross-sections derived from airborne sea breeze measurements (Finkele et al. 1995) constitute the basis for comparison with two-dimensional numerical model results. The offshore sea breeze propagation speed is defined as the speed at which the seaward extent of the sea breeze grows offshore. On a study day, the offshore sea breeze propagation speed, from both measurements and model, is -3.4 m s-1. The measured inland propagation speed of the sea breeze decreased somewhat during the day. The model results show a fairly uniform inland propagation speed of 1.6 m s-1 which corresponds to the average measured value. The offshore sea breeze propagation speed is about twice the inland propagation speed for this particular case study, from both the model and measurements.The influence of the offshore geostrophic wind on the sea breeze evolution, offshore extent and inland penetration are investigated. For moderate offshore geostrophic winds (-5.0 m s-1), the offshore and inland propagation speeds are non-uniform. The offshore extent in moderate geostrophic wind conditions is similar to the offshore extent in light wind conditions (-2.5 m s-1). The inland extent is greater in light offshore geostrophic winds than in moderate ones. This suggests that the offshore extent of the sea breeze is less sensitive to the offshore geostrophic wind than its inland extent. However, these results hold only if it is possible to define an inland propagation speed. For stronger offshore geostrophic winds (-7.5 m s-1), the sea breeze is completely offshore and the inland propagation speed is ill-defined.  相似文献   

3.
The characteristics of the sea breeze in the Attica region of Greece, in which Athens is located, have been studied for occasions of weak synoptic-scale pressure gradient. The analysis is based on synoptic observations from six meteorological stations, three on the coast and three inland. The three inland stations and one of the coastal stations lie almost in a straight line at different distances from the coast. For each meteorological station, the basic characteristics of the sea breeze were determined, i.e.,
  1. The mean number of sea-breeze days for each calendar month.
  2. The monthly mean wind speed for each synoptic hour.
  3. The times of onset and cessation of the sea breeze.
  4. The monthly vector mean wind, and its constancy ‘Constancy’ is defined as 100{itV{inr}/V{ins}}, where {itV{inr}} is the magnitude of the vector mean wind, and {itV{ins}} is the scalar mean wind speed. See Brooks and Carruthers (1953). (In this paper, the factor 100 is not used.) for each synoptic hour.
  5. For days on which there was a sea breeze at Helliniko (the coastal reference station), the percentage number of days on which there was also a sea breeze at the given station.
An attempt was also made to determine further characteristics, such as the inland penetration of the sea breeze, its depth, the spatial and temporal variation of wind speed and direction, and the existence of the return flow. Finally, the properties of the land breeze are briefly outlined.  相似文献   

4.
The daytime boundary-layer heating process and the air-land heat budget were investigated over the coastal sea-breeze region by means of observations over the Sendai plain in Japan during the summer. In this area, the onset of the sea breeze begins at the coast around 0900 LST, intruding about 35 km inland by late afternoon. The cold sea breeze creates a temperature difference of over 10°C between the coastal and inland areas in the afternoon. On the other hand, warm air advection due to the combination of the counter-sea breeze and land-to-sea synoptic wind occurs in the layer above the cold sea breeze in the coastal region. Owing to this local warm air advection, there is no significant difference in the daytime heating rate over the entire atmospheric boundary layer between the coastal and inland areas. The sensible heat flux from the land surface gradually decreases as distance from the coastline increases, being mainly attributed to the cold sea breeze. The daytime mean cold air advection due to the sea breeze is estimated asQ adv local =–29 W m–2 averaged over the sea breeze region (035 km from the coastline). This value is 17% of the surface sensible heat fluxH over the same region. The results of a two-dimensional numerical model show that the value ofQ adv local /H is strongly affected by the upper-level synoptic wind direction. The absolute value ofQ adv local /H becomes smaller when the synoptic wind has the opposite direction of the sea breeze. This condition occurred during the observations used in the present study.  相似文献   

5.
The sea-land breeze circulation （SLBC） occurs regularly at coastal locations and influences the local weather and climate significantly. In this study, based on the observed surface wind in 9 conventional meteorological stations of Hainan Island, the frequency of sea-land breeze （SLB） is studied to depict the diurnal and seasonal variations. The statistics indicated that there is a monthly average of 12.2 SLB days and an occurrence frequency of about 40%, with the maximum frequency （49%） in summer and the minimum frequency （29%） in autumn. SLB frequencies （41%） are comparable in winter and spring. A higher frequency of SLB is present in the southern and central mountains due to the enhancement effect of the mountain-valley breeze. Due to the synoptic wind the number of SLB days in the northern hilly area is less than in other areas. Moreover, the WRF model, adopted to simulate the SLBC over the island for all seasons, performs reasonably well reproducing the phenomenon, evolution and mechanism of SLBC. Chiefly affected by the difference of temperature between sea and land, the SLBC varies in coverage and intensity with the seasons and reaches the greatest intensity in summer. The typical depth is about 2.5 km for sea breeze circulation and about 1.5 km for land breeze circulation. A strong convergence zone with severe ascending motion appears on the line parallel to the major axis of the island, penetrating 60 to 100 km inland. This type of weak sea breeze convergence zone in winter is north-south oriented. The features of SLBC in spring are similar both to that in summer with southerly wind and to that in winter with easterly wind. The coverage and intensity of SLBC in autumn is the weakest and confined to the southwest edge of the central mountainous area. The land breeze is inherently very weak and easily affected by the topography and weather. The coverage and intensity of the land breeze convergence line is significantly less than those of the sea breeze. The orographic forcing of the cen  相似文献   

6.
Summary  According to past experience, the nearly stagnant conditions caused by the presumed equilibrium between the Saronikos Gulf sea breeze and an opposing synoptic flow is identified as the principal mechanism leading to high pollution episodes in Athens during the summer. However, previous experimental work has not examined in detail the interaction of the sea breeze flow with the opposing background flow. In this context, recent experimental work covering the basic key-locations of the Athens Basin focused on the inland propagation of the southerly sea breeze from the coast to the northern part of the basin mainly under moderate northerly background wind. During this campaign, a network of four meteorological stations established along the Athens Basin and a high range acoustic sounder at the centre of Athens operated over a two months time period in the summer of 1993. In addition, tethered balloon flights in the centre of Athens and on a sea vessel about 15 km offshore were employed during an experimental day with moderate opposing background wind. The results from this experimental campaign include the documentation of the sea breeze delay and its intensity as a function of a sea breeze index and features of the vertical structure of the sea breeze over land as well as over sea. Received March 20, 1998 Revised October 12, 1998  相似文献   

7.
一次冷锋过境后的海风三维结构数值模拟   总被引：2，自引：1，他引：1       下载免费PDF全文
为研究大尺度系统风对海风的影响以及海风三维结构特征,利用山东省123个地面自动站资料、青岛地区三十多个内陆及沿海、海岛观测站以及奥帆赛场3个浮标站资料,对2006年8月21日青岛一次海风个例进行了分析,并利用美国俄克拉荷马大学风暴分析预测中心开发的ARPS(the Advanced Regional Prediction System)模式,对海风过程进行了数值模拟研究。结果发现:在较强的离岸风背景下,当内陆气温高于海面气温2℃左右时,海风也可以发生。海风首先在海岸线附近的海上开始,发展的同时向内陆及远海地区推进。海风低层环流很浅,主要位于500 m以下。在较强的偏北离岸风下,海风向内陆推进的距离很短。偏北的大尺度系统风由于渤海冷下垫面的影响,不利于青岛海风的维持。海风开始时,在1500～2500 m高度处同时有反环流出现,但直到傍晚前后,海风的垂直环流圈才发展得比较清晰,其高度也更接近地面。海风消亡后,高层的垂直环流圈及反环流维持3 h左右才逐渐消亡。  相似文献   

8.
To examine the correlation between the sizes of sea breeze fronts and pollutants under the influence of synoptic fields, a numerical simulation was conducted in the southeast coastal area of the Korean Peninsula, where relatively high concentrations of pollutants occur because of the presence of various kinds of industrial developments. Sea breeze and sea breeze front days during the period 2005-09 were identified using wind profiler data and, according to the results, the number of days were 72 and 53, respectively. When synoptic forcing was weak, sea breeze fronts moved fast both in horizontal fields and in terms of wind velocity, while in the case of strong synoptic forcing, sea breeze fronts remained at the coast or moved slowly due to strong opposing flows. In this case, the sea breeze front development function and horizontal potential temperature difference were larger than with weak synoptic forcing. The ozone concentration that moves together with sea breeze fronts was also formed along the frontal surfaces. Ozone advection and diffusion in the case of strong synoptic forcing was suppressed at the frontal surface and the concentration gradient was large. The vertical distribution of ozone was very low due to the Thermal Internal Boundary Layer (TIBL) being low.  相似文献   

9.
海南岛海风演变特征的观测分析   总被引：4，自引：1，他引：3  
王静  苗峻峰  冯文 《气象科学》2016,36(2):244-255
本文利用2012年海南岛19个常规气象站、5个海岛站的逐时资料以及海口站的探空资料,对海南岛海风的时空演变特征及在不同天气条件下海风发展的特征进行了统计分析,结果表明:2012年全年海南岛的海风多发生于春、秋季,频率分别为40%和33%,冬季最少(约为19%),尤其是一月,大部分站点均不足10%。夏季海风出现时刻较早;南部沿海海风结束时间晚于北部沿海;冬季海风开始得较晚,南部海风结束时间早于北部沿海。海风平均持续时间约为10 h。沿海站的海风风速主要集中在3~6 m·s~(-1),且最大风速值出现在春季,除琼山、海口站外,最大海风强度多出现于春夏季。内陆站中部山区附近海风出现频率较高、开始时刻较早、持续时间较长、强度也较大。海风向内陆的传播距离至少为70 km;海风易发生在阴天,其次为多云天气,少云日的海风最少。  相似文献   

10.
利用葫芦岛观测站1980—2009年观测资料,分析了葫芦岛沿岸海陆风风速的季节特征和日变化规律,以及海陆风环流对沿岸环境的影响。结论如下:1)葫芦岛站点在冬季出现海陆风日数最多,其他依次为秋季、夏季和春季。陆风风速从春季到冬季呈现递减趋势;海风在春季最大,其次为秋季的,冬季的最小。总体上,海陆风日中海风要强于陆风。2)对海陆风风速椭圆拟合结果表明,海陆风在10:32由陆风转化为海风,海风在16:32达到最大,在21:42由海风转化为陆风,陆风在04:32达到最大。3)由于海风的存在,沿岸地带在春夏两季日最高气温在12时出现,秋冬季的在13时出现。4)能见度日变化在四季中表现一致,早晨能见度转好的时刻比最低气温出现时刻滞后约2 h,在海风维持较长时间后空气绝对湿度增加导致能见度开始转差。5)冬季静止型海陆风日比例最高,再循环型海陆风日在秋季出现最多,而夏季通风型海陆风日出现最多。  相似文献   

11.
Meteorological measurements were carried out at North Chennai semi rural area during pre-monsoon period as a part of an air quality study program. Analysis of the data showed the effects of coastal terrain namely the land-sea breeze circulation, temperature cooling during the sea breeze, difference in onset times at these sites etc. Sea breeze onset was observed with a sharp turning of the wind from westerly to south easterly associated with rise in wind speed. Advection speed of the front was about 2.0 m s− 1. A simple mesoscale meteorological model (MAM-I) developed at Kalpakkam for coastal atmospheric dispersion estimation was used to simulate the observed characteristics. All the major features observed could be simulated by the model while significant difference was noticed in sea breeze frontal movement. MAM results were also inter-compared with MM5. There were no significant differences in the estimate of mean parameters by both the models. It is concluded that the simple model, which takes less run time in a desktop PC, is adequate enough for practical application of providing wind field for plume dispersion models at coastal sites.  相似文献   

12.
In-situ sodar and lidar measurements were coupled with numerical simulations for studying a sea-breeze event in a flat coastal area of the North Sea. The study’s aims included the recognition of the dynamics of a sea-breeze structure, and its effects on the lower troposphere stratification and the three-dimensional (3D) pollutant distribution. A sea breeze was observed with ground-based remote sensing instruments and analysed by means of numerical simulations using the 3D non-hydrostatic atmospheric model Meso-NH. The vertical structure of the lower troposphere was experimentally determined from the lidar and sodar measurements, while numerical simulations focused on the propagation of the sea breeze inland. The sea-breeze front, the headwind, the thermal internal boundary layer, the gravity current and the sea-breeze circulation were observed and analysed. The development of a late stratification was also observed by the lidar and simulated by the model, suggesting the formation of a stable multilayered structure. The transport of passive tracers inside the sea breeze and their redistribution above the gravity current was simulated too. Numerical modelling showed that local pollutants may travel backward to the sea above the gravity current at relatively low speed due to the shearing between the landward gravity current and the seaward synoptic wind. Such dynamic conditions may enhance an accumulation of pollutants above coastal industrial areas.  相似文献   

13.
Two-dimensional mesoscale model results support the claim of evening sea-breeze activity at Daly Waters, 280 km inland from the coast in northern Australia, the site of the Koorin boundary-layer experiment. The sea breeze occurs in conditions of strong onshore and alongshore geostrophic winds, not normally associated with such activity. It manifests itself at Daly Waters and in the model as a cooling in a layer 500–1000 m deep, as an associated surface pressure jump, as strong backing of the wind and, when an offshore low-level wind is present, as a collapse in the inland nocturnal jet.Both observational analysis and model results illustrate the rotational aspects of the deeply penetrating sea breeze; in our analysis this is represented in terms of a surge vector — the vector difference between the post- and pre-frontal low-level winds.There is further evidence to support earlier work that the sea breeze during the afternoon and well into the night — at least for these low-latitude experiments — behaves in many ways as an atmospheric gravity current, and that inland penetrations up to 500 km occur.  相似文献   

14.
An investigation of the long-term variability of wind profiles for wind energy applications is presented. The observations consists of wind measurements obtained from a ground-based wind lidar at heights between 100 and 600 m, in combination with measurements from tall meteorological towers at a flat rural coastal site in western Denmark and at an inland suburban area near Hamburg in Germany. Simulations with the weather research and forecasting numerical model were carried out in both forecast and analysis configurations. The scatter between measured and modelled wind speeds expressed by the root-mean-square error was about 10 % lower for the analysis compared to the forecast simulations. At the rural coastal site, the observed mean wind speeds above 60 m were underestimated by both the analysis and forecast model runs. For the inland suburban area, the mean wind speed is overestimated by both types of the simulations below 500 m. When studying the wind-speed variability with the Weibull distribution, the shape parameter was always underestimated by the forecast compared to both analysis simulations and measurements. At the rural coastal site although the measured and modelled Weibull distributions are different their variances are nearly the same. It is suggested to use the shape parameter for climatological mesoscale model evaluation. Based on the new measurements, a parametrization of the shape parameter for practical applications is suggested.  相似文献   

15.
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   

16.
梁钊明  高守亭  王东海  王彦 《大气科学》2013,37(5):1013-1024
海风锋与沿海强对流天气密切相关,而城市化发展对沿海地区下垫面的改变会对海风锋特征产生影响。鉴于此,本文利用耦合了新一代城市物理方案UCP-BEM(Urban Canopy Parameterization-Building Energy Model)的WRF(Weather Research and Forecasting)模式开展数值试验分析了城市下垫面对渤海湾海风锋特征的影响。结果显示:城市下垫面高粗糙度对低层海风风速的明显削弱造成海风锋往内陆推进距离稍减,低层辐合和上升运动减弱;城市下垫面较大的向上感热通量和较小的向上水汽通量以及高粗糙度对海风的削弱的共同作用造成冷湿海风对低层大气的降温和增湿幅度减弱;高粗糙度的城市下垫面对海风环流的摩擦力效应使得海风得到抬升,这导致了冷湿海风对低层大气的降温和增湿的垂直范围得到提升;受这些结果影响,海风锋背后低层有效位能减小,但垂直分布范围扩大,从而造成对流抑制高值区抬升,同时海风锋背后的静力不稳定区变厚,其上面的动力不稳定区则变薄,但不稳定区总厚度基本不变。  相似文献   

17.
A high-resolution mesoscale numerical model (MM5) has been used to study the coastal atmospheric circulation of the central west coast of India, and Goa in particular. The model is employed with three nested domains. The innermost domain of 3 km mesh covers Goa and the surrounding region. Simulations have been carried out for three different seasons—northeast (NE) monsoon, transition period and southwest (SW) monsoon with appropriate physics options to understand the coastal wind system. The simulated wind speed and direction match well with the observations. The model winds show the presence of a sea breeze during the NE monsoon season and transition period, and its absence during the SW monsoon season. In the winter period, the synoptic flow is northeasterly (offshore) and it weakens the sea breeze (onshore flow) resulting in less diurnal variation, while during the transition period, the synoptic flow is onshore and it intensifies the sea breeze. During the northeast monsoon at an altitude of above 750 m, the wind direction reverses, and this is the upper return current, indicating the vertical extent of the sea breeze. A well-developed land sea breeze circulation occurs during the transition period, with vertical extension of 300 and 1,100 m, respectively.  相似文献   

18.
In this paper,a simulation study is made on the sea breeze process over southwestern Bohai Gulf byuse of the Pielke mesoscale meteorological model.The simulated results show that when a south wind of 8m/s blows over the top of the model,a strong wind zone of 15—25 km wide with a maximum speed more than14 m/s,which is close and nearly parallel to the south shore,will appear at 160 m above the sea surface.When a strong sea breeze penetrates inland,there often appears a thermal internal boundary layer(TIBL)near shore.The inversion above the TIBL can damp the vertical dispersion of atmospheric pollution.Besides,it is also found that,for a three-dimensional sea/land breeze circulation,if the divergence centre inthe return flow departs vertically far from the correspondent convergence centre in the sea breeze,a centre ofstrong descending movement will be formed at the middle and upper levels of the return flow.The resultsin this paper is also applicable to the Laizhou Bay.  相似文献   

19.
Summary The aim of this study is the evaluation of the sea breeze speed on the basis of its energy. Energetics of the sea breeze can be studied by means of the available potential energy (APE). Part of this energy is transformed into the kinetic energy of the sea breeze. Some similarity exists between the large scale processes of the circulation and the small coastal air circulation due to the fact that both circulations are triggered by the same physics, i.e., solenoidal activity of the baroclinic atmosphere. To evaluate the sea breeze speed, APE was calculated by use of the Lorenz’s equation (1955), and which is possible if the coastal circulation is considered to be a closed system in a hydrostatic equilibrium. For calculations and verifications hourly sea-surface temperatures, near-ground air temperatures and wind speed measurements, as well as the radio-sounding measurements at 12 UTC were used at the Zadar station (ϕ = 44° 08′ N, λ = 15° 13′ E), which is situated in the central part of the eastern Adriatic coast. Two days with an undisturbed sea breeze circulation were extracted using the methods for minimizing other atmospheric influences. Calculated hourly near ground sea breeze speeds obtained in this way were higher than the measured ones. With the assumption that some of the APE is transformed into the kinetic energy it is possible to obtain characteristic speed of the developed sea breeze with small discrepancies to the near-ground measurements. If 6.6% of the mean daily near ground APE was taken to be transformed to the mean daily kinetic sea breeze energy on the 29th and 4.2% on the 30th September 2002, the best agreement was obtained with the mean daily measured near ground sea breeze speed. This range of values can be attributed to inability to extract precise values for the lapse-rate needed in the APE sea breeze calculations. Results show similarities to the general circulation of the atmosphere, since about 10% of the APE is transformed to the kinetic energy of the sea breeze. On the other hand calculated wind speed at the lower branch of the borderline coastal circulation was not dependent on the integral value of the APE over the land, but on its value at the near-ground level.  相似文献   

20.
Meteorological observation by a helicopter was carried out to investigate the structure of sea breezes over the coastal area of Tosa Bay in Shikoku island, Japan. Several groups of wave trains were found over the sea during a flight made on 25 November 1992. Not only the terrain barrier but the remaining cold air pools formed in valleys hindered further advance of the sea breeze inland, so that the presence of such wave trains may appear to be due to the effect of the secondary flow which supplies moister and cooler air from behind the sea breeze front.  相似文献   

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