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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 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   

4.
Observed boundary-layer circulations close to the confluence of the Negro and Solimões rivers near Manaus in the Brazilian equatorial Amazon forest were presented in Part I. These are shown through linear analysis and second-order turbulence modelling to be aspects of a river breeze superimposed on the basic flow. Linear analysis is presented to estimate the spatial structure and intensity of a breeze induced by a river with width and thermal contrast similar to that observed in the central Amazon. It is found that observed thermal contrasts are sufficient to produce a river breeze that can be perceived more than 20 km inland daily. A one-dimensional second-order closure model is used to show that observed nocturnal low-level wind maxima and diurnal surface wind rotation are aspects of a river breeze interacting with the seasonally-varying mean flow. At night, partial decoupling of the surface from the lower atmosphere allows the land breeze to be expressed as a low-level wind maximum. During the day, convective mixing communicates upper level winds to the surface during rapid morning boundary-layer growth. Rotation of the surface wind follows as the river breeze circulation is then superimposed.  相似文献   

5.
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   

6.
香港地区海陆风的显式模拟研究   总被引：2，自引：2，他引：2  
利用MM5模式对香港地区的海陆风进行了显式数值研究,模拟的风向、风速和温度与站点的观测值比较一致,较详细地分析了海陆风的日变化规律和三维结构特征,结果显示香港地区海风分布复杂,主要受偏西、偏南和偏东海风气流的影响,形成多个辐合带,海风锋最远可以深入内陆约90 km;陆风较简单,主要是偏北气流,陆风的风速和强度都比海风要弱,与山谷风、城市热岛环流等形成弱的辐合。香港是一个海岸曲折、多丘陵的地区,其中75%的面积是山区,为了研究这些丘陵地形对香港地区海陆风的影响,设计了保留海陆分布,去掉丘陵地形的敏感性试验,结果表明,由于丘陵地形的存在,在白天地形的热力作用是主要的,增强了海风的强度;而晚上动力阻挡作用比较明显,减弱了陆风的强度。  相似文献   

7.
湛江东海岛二月海陆风环流特征研究   总被引：1，自引：0，他引：1  
徐峰  王晶  张羽  张书文  黄克鑫 《气象科学》2012,32(4):423-429
利用2011年2月湛江东海岛风廓线雷达资料,系统分析了湛江东海岛2月平均风场特征及海陆风特征,结果表明:2月湛江东海岛150 m高度处以东偏北出现频率最大,在E、ENE和NE三个方位的风向出现频率之和为66.6%,偏西七个方位的风向出现频率之和仅为1%。以SSW方位为界,偏东风与偏西风的出现频率差异明显。各整点的月平均风速1:00—15:00变化较小,均在1 m/s左右波动;15:00—20:00风速及风速波动都较大,最大值出现在16:00时,为2.1 m/s。2011年2月中只有2日与14日两日符合海陆风日条件,两日共同海风时段为13:00—20:00,持续7 h;陆风时段为2:00—7:00,持续5 h。海风平均风速为2.1 m/s,陆风平均风速为0.8 m/s,海风平均风速明显大于陆风风速。海风与陆风环流垂直高度相差甚小,约1.2 km,风速随高度变化趋势均为先增后减;海风最大风速出现在750 m高度处,陆风出现在500 m高度处,500～750 m高度区间海风环流强度明显强于陆风环流。2 km之上为均匀一致的系统性西风环流。  相似文献   

8.
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   

9.
Sea-breeze dynamics in the Marseille area, in the south of France, is investigated in the framework of the ESCOMPTE experiment conducted during summer 2001 in order to evaluate the role of thermal circulations on pollutant transport and ventilation. Under particular attention in this paper is the sea-breeze channelling by the broad Rhône valley and the narrow Durance valley, both oriented nearly-north–south, i.e., perpendicular to the coastline, and its possible impact on the sea-breeze penetration, intensity and depth, which are key information for air pollution issues. One situation of slight synoptic pressure gradient leading to a northerly flow in the Rhône valley (25 June 2001) and one situation of a weak onshore prevailing synoptic wind (26 June 2001) are compared. The impact of the Rhône and Durance valleys on the sea-breeze dynamics on these two typical days is generalized to the whole ESCOMPTE observing period.The present study shows by combining simple scaling analysis with wind data from meteorological surface stations and Doppler lidars that (i) the Durance valley always affects the sea breeze by accelerating the flow. A consequence is that the Durance valley contributes to weaken the temperature gradient along the valley and thus the sea-breeze circulation. In some cases, the acceleration of the channelled flow in the Durance valley suppresses the sea-breeze flow by temperature gradient inhibition; (ii) the Rhône valley does not generally affect the sea breeze significantly. However, if the sea breeze is combined with an onshore flow, it leads to further penetration inland and intensification of the low-level southerly flow. In this situation, lateral constriction may accelerate the sea breeze. Simple scaling analysis suggests that Saint Paul (44.35°N, about 100 km from the coastline) is the lower limit where sea breeze can be affected by the Rhône valley. These conclusions have implications in air quality topics as channelled sea breeze may advect far inland pollutants which may be incorporated into long-range transport, particularly in the Durance valley.  相似文献   

10.
A three-dimensional finite-element mesoscale model is used to study the interaction of two different but related mesoscale phenomena in an area having a complex pattern of surface heating. The model simulations have been compared with temperature and wind fields observed on a typical fall day during the Kennedy Space Center Atmospheric Boundary Layer Experiment on the east coast of Florida.Numerical results and observations both show that the meso- scale flow field is significantly modified from the conventional coastal-flow patterns by the smaller meso- scale irregular geographic features in this area. A local river breeze is observed to develop around the Indian River almost the same time as the Atlantic sea breeze. A comparison of the sea and the river breezes shows a large difference in their horizontal circulations but only slight differences in their vertical scales. The sea breeze intensifies more rapidly than the river breeze, so that a lag of 1 to 1.5 h exists between their most developed stages. The river breeze is relatively stationary, whereas the sea breeze propagates inland, with an eventual merger of the two circulations occurring about 6–8 h after their onset.Different synoptic wind regimes create different flow structures. Well-defined sea- and river-breeze circulations become established under calm, weak offshore, and weak alongshore synoptic-wind conditions. Maximum vertical velocities occur in the sea-breeze front (river-breeze front) in the cases of calm (offshore winds). The sea breeze and the river breeze are weaker when the synoptic winds are stronger.Finally, the results from numerical experiments designed to isolate the rivers' effect indicate that the convergence in the sea-breeze front is suppressed when it passes over the cooler surface of the rivers.Journal Paper No. J-14150 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa, Project No. 2779  相似文献   

11.
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   

12.
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13.
In the period June–July 1992, four Doppler sodars were operated simultaneously in Rome and the surrounding area. The data have been used to investigate the contributions from sea breeze events to the local low-level circulation. Three days in which synoptic-scale pressure gradients were weak have been selected. A number of characteristics of the sea breeze are examined including the onset and cessation of the phenomenon, the behavior of the wind speed, and the depth of the density flow. The time propagation of the events and the influence of orography are obtained from a comparison between the data at different sites. The low-level circulation in the early morning is associated with the land breeze and appears to be enhanced by a mountain wind from the surrounding hills. The observed behavior of the vertical velocity field associated with the sea breeze is consistent with model predictions.  相似文献   

14.
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   

15.
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   

16.
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   

17.
Tower measurements for the sea breeze front in the surface layer were carried out over the Kochi plain about 2 km inland from Tosa Bay in Shikoku, Japan during the period from August 1986 to October 1987. The study shows that the penetration time of the sea breeze has an annual variation, which is around 0830 JST in summer and 12 JST in winter, and that the width of the sea breeze front depends on the ratio of the sea breeze speed and the opposing flow speed. Moreover, the frontal width also shows a seasonal variation.The characteristics of the vertical winds (w) found just before and just after the passage of the sea breeze front lead to remarkable downdrafts and updrafts, respectively, with relatively large vertical velocities. Such behaviour ofw is shown to be consistent with the flow relative to the head of the front as reviewed by Simpson (1987), influencing the magnitude of the turbulence scale and the turbulent energy dissipation near the ground surface.  相似文献   

18.
Using data from automatic surface weather stations,buoys,lidar and Doppler,the diurnal variation and the three-dimensional structure of the sea breezes near the sailing sites of the Good Luck Beijing— 2006 Qingdao International Regatta from 18 to 31 August 2006 are analyzed.Results show that excluding rainy days and days affected by typhoon,the sea breezes occur nearly every day during this period.When Qingdao is located at the edge of the subtropical high at 500 hPa,the sea breeze is usually stronger,aroun...  相似文献   

19.
Although the sea breeze at Venice and on her hinterland is influenced by orography - mainly the Alps — to the north and the Po Valley to the west, the search for a correlation between the frequency of development of the sea breeze and the daily global solar radiation seems to be desirable, and may be useful for the management of emissions from the industrial area near Venice. Three different cases are examined: (i) the sea breeze occuring in the absence of any appreciable gradient wind; (ii) the sea breeze superimposed on a prevailing wind; (iii) the sea breeze not developing at all. The frequency distributions of these cases related to the global solar radiation at Venice are discussed.  相似文献   

20.
A two-dimensional prognostic numerical model has been used to study a lake breeze event reported by Keen and Lyons (1978). Model predictions showed fair to good agreement with the observations. For the mature lake breeze, the model predicted inflow at the coast within about 1.5 m s–1 of the observed value, lake breeze depth within 50–90 m of the observed, and inland penetration within about 6 km of the observed. The top of the thermal internal boundary layer (TIBL) was associated with a minimum in the predicted turbulent kinetic energy profile. This may be of consequence for attempts to evaluate pollutant dispersion using numerical models.Predicted lake breeze characteristics showed little sensitivity to temperature of the water surface, except when the water surface temperature was increased to a value exceeding the inland maximum temperature. The most sensitive lake breeze characteristic was the TIBL, which grew more slowly with inland distance and persisted for a greater distance inland as the lake surface became colder.  相似文献   

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