Showing papers on "Sea breeze published in 1994"

Sea Breeze and Local Winds

Abstract: Foreword Preface 1. The sea breeze 2. Formation of the sea breeze 3. Sea-breeze fronts 4. Sea-breeze forecasting 5. Other local winds 6. Air quality 7. Sea breeze interactions 8. Life and the sea breeze 9. Sports 10. Technology: field measurements of the sea-breeze 11. Laboratory measurements 12. Theoretical models References Index.

Determining the power-law wind-profile exponent under near-neutral stability conditions at sea

Abstract: On the basis of 30 samples from near-simultaneous overwater measurements by pairs of anemometers located at different heights in the Gulf of Mexico and off the Chesapeake Bay, Virginia, the mean and standard deviation for the exponent of the power-law wind profile over the ocean under near-neutral atmospheric stability conditions were determined to be 0.11 ± 0.03. Because this mean value is obtained from both deep and shallow water environments, it is recommended for use at sea to adjust the wind speed measurements at different heights to the standard height of 10 m above the mean sea surface. An example to apply this P value to estimate the momentum flux or wind stress is provided.

Air Pollutant Transport in a Coastal Environment. Part I: Two-Dimensional Simulations of Sea-Breeze and Mountain Effects

Abstract: Over the southern California coastal region, observations of the vertical distributions of pollutants show that maximum concentrations can occur within temperature inversion layers well above the surface. A mesoscale model is used to study the dynamical phenomena that cause such layers, including sea breezes and mountain flows, and to study the characteristics of air pollutant transport in a coastal environment capped by a temperature inversion. The mathematical and physical structure of the model is described. Two-dimensional simulations corresponding to four configurations of coastal plains and mountains are discussed. The simulations reveal that pollutant transport over a coastal plain is strongly influenced by the topographic configuration, including the height of coastal mountains and their distance from the coastline. Sea breezes induced by land-sea thermal contrasts, as well as upslope winds induced along mountain flanks, both create vertical transport that can lead to the formation of elevated pollution layers. The sea-breeze circulation generates pollution layers by undercutting the mixed layer and lofting pollutants into the stable layer. Heating of mountain slopes acts to vent pollutants above the mountain ridge during the day; during the evening, pollutants can be injected directly into the inversion layer from the decaying upslope flows. In a land-sea configuration with mountains close to the coastline, the sea breeze and heated-mountain flow are strongly coupled. In the afternoon, this interaction can produce upslope flow from which polluted air is detrained into the inversion layer as a return circulation. When the mountains lie farther inland, however, pollutants may be trapped aloft when the mixed layer stabilizes in the late afternoon. As the nocturnal boundary layer forms over the coast in the evening, polluted mixed-layer air is effectively left behind in the inversion layer. In the Los Angeles Basin, the formation mechanism for elevated polluted layers is most similar to our cases with inland mountains.

Observations of the Sea-Breeze Front during CaPE. Part I: Single-Doppler, Satellite, and Cloud Photogrammetry Analysis

Abstract: An analysis of two sea-breeze events on 6 August (an onshore flow event) and 12 August (an offshore flow event) 1991 is presented using single-Doppler observations, satellite images, and cloud pictures collected during the Convection and Precipitation/Electrification (CaPE) Experiment. Documentation of the alongfrontal variability at the leading edge of the sea-breeze circulation is presented for the first time. The horizontal structure of the front was strongly modulated by the near-perpendicular intersections of horizontal convective rolls developing in the ambient air out ahead of the sea breeze on 12 August. These intersection points also appeared to be preferred locations for cloud development along the front. Horizontal convective rolls were also documented on 6 August; however, their orientation was nearly parallel to the sea-breeze front. As a result, extended sections of these rolls appeared to have merged with the front as it propagated inland rather than having distinct intersection po...

Observations of Fluxes and Inland Breezes over a Heterogeneous Surface

Abstract: Repeated aircraft runs at about 33 m over heterogeneous terrain are analyzed to study the spatial variability of the mesoscale flow and turbulent fluxes. An irrigated area, about 12 km across, generates a relatively cool moist inland breeze. As this air flows out over the warmer, drier surrounding land surface, an internal boundary layer develops within the inland breeze, which then terminates at a well-defined inland breeze front located about 1½ km downstream from the change of surface conditions. This front is defined by horizontal convergence, rising motion, and sharp spatial change of moisture, carbon dioxide, and ozone. Both a scale analysis and the observations suggest that the overall vertical motion associated with the inland breeze is weak. However, the observations indicate that this vertical motion and attendant vertical transport are important in the immediate vicinity of the front, and the inland breeze does lead to significant modification of the turbulent flux. In the inland breez...

Observations of sea breeze events in Rome and the surrounding area by a network of Doppler sodars

Abstract: 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.

Development and structure of a maritime continent thunderstorm

Abstract: The evaluation of a maritime continent thunderstorm complex (Hector) occurring over Bathurst and Melville Islands north of Darwin, Australia (12° S, 131° E) is investigated primarily using Doppler radar data. Thunderstorm formation follows the development of sea breeze circulations and a period of shallow non-precipitating convection. Evidence exists for initiation of long-lived and organised convection on the sea breeze fronts, although short-lived, scattered convection is apparent earlier in the day. Merging of the convective systems is observed in regions of enhanced low-level convergence related to sea breeze circulations. The merged convective complex is initially aligned in an almost east-west direction consistent with the low-level forcing. The merged complex results in rapid vertical development with updraughts reaching 40 m s− and echo tops reaching 20 km height. Maximum precipitation production occurs during this merger phase. On the perimeter of the merged convective complex, evidence exists for front-to-rear updraughts sloped over lower-level downdraughts with rear-to-front relative flow and forward propagating cold pools. The mature phase is dominated by this convection and the complex re-orientates in the prevailing easterly vertical shear to an approximate north-south direction, then moves westward off the islands with the classic multicellular squall-like structure. The one-dimensional cloud model of Ferrier and Houze (1989) used with a four class ice formulation reproduced the cloud top height, updraught structure and echo profile very well. To test the importance of ice physics upon thunderstorm development, several sensitivity tests were made removing the effects of the ice phase. All of these model clouds reached nearly 20 km, although simulations without the effects of ice had updraughts reduced from about 40 m s−1 to 30 m s−1. The simulated convection was more sensitive to changes in environmental conditions and parameterised cloud dynamics. The strong intensity of the convection was largely accounted for by increasing equivalent potential temperatures due to diurnal heating of the surface layer. The vertical velocity and radar structure of the island thunderstorm has more similarity with continental rather than oceanic convection. Maximum vertical velocities, in particular are almost an order of magnitude greater than typical of oceanic convection. With the intense updraughts, even in the low shear environment, there is evidence for mesoscale circulations within the convection.

The Amazon river breeze and the local boundary layer: II. Linear analysis and modelling

Abstract: Observed boundary-layer circulations close to the confluence of the Negro and Solimoes 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.

Thermal effect of the sea breeze on the structure of the boundary layer and the heat budget over land

Abstract: 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 (0∼35 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

Vertical layering of photochemical ozone during land-sea breeze transport

Abstract: Recent theoretical and experimental studies have shown how local wind fields, such as the land-sea breeze circulation in coastal areas, influence the transport of oxidant precursors and the residence time and re-entry of photochemical compounds. Simple models usually do not take into account the vertical layering of pollutants, assuming a uniform concentration distribution within the boundary layer during transport processes. The present study reports the results of a monitoring survey conducted in an industrial coastal area to assess the time evolution of the vertical layering of ozone subject to land-sea breeze circulation in the boundary layer.

Mixed-layer heat advection and entrainment during the sea breeze

Abstract: A model is developed to simulate the potential temperature and the height of the mixed layer under advection conditions. It includes analytic expressions for the effects of mixed-layer conditions upwind of the interface between two different surfaces on the development of the mixed layer downwind from the interface. Model performance is evaluated against tethersonde data obtained on two summer days during sea breeze flow in Vancouver, Canada. It is found that the mixed-layer height and temperature over the ocean has a small but noticeable effect on the development of the mixed layer observed 10 km inland from the coast. For these two clear days, the subsidence velocity at the inversion base capping the mixed layer is estimated to be about 30 mm s−1 from late morning to late afternoon. When the effects of subsidence are included in the model, the mixed-layer height is considerably underpredicted, while the prediction for the mean potential temperature in the mixed layer is considerably improved. Good predictions for both height and temperature can be obtained when values for the heat entrainment ratio,c, 0.44 and 0.68 for these two days respectively for the period from 1000 to 1300 LAT, were used. These values are estimated using an equation including the additional effects on heat entrainment due to the mechanical mixing caused by wind shear at the top of the mixed layer and surface friction. The contribution of wind shear to entrainment was equal to, or greater than, that from buoyant convection resulting from the surface heat flux. Strong wind shear occurred near the top of the mixed layer between the lower level inland flow and the return flow aloft in the sea breeze circulation.

Preliminary Sea Breeze Studies over Bathurst and Melville Islands, Northern Australia, as part of the Island Thunderstorm Experiment (ITEX)

Abstract: The “maritime continent” area to the north of Australia is one of three major global centres of tropical convective activity and has a fundamental role in the general circulation of the atmosphere. Tropical convection within this region is dominated by island thunderstorm activity which is strongly diurnally modulated, is deep and is geographically fixed. The storms over Bathurst and Melville Islands (11.5°S, 131°E) are representative of island thunderstorms that occur throughout the maritime continent and are believed to be primarily a response to sea breeze convergence. In this paper, we produce an indicative climatology of the Melville and Bathurst Island sea breeze (obtained during a three week period of the 1988 transition season), and we examine the surface patterns of island-scale convergence and divergence, especially in relation to the diurnal modulation of island thunderstorm activity. These observations are placed in the context of the broadscale environment and the relevant surface energy balance and radiation regimes.

Sea breezes and advective effects in southwest James Bay

Abstract: Observations from a transect extending 100 km inland during the Northern Wetlands Study (NOWES) in 1990 show that the sea breeze develops on approximately 25% of days during summer and may penetrate up to 100 km inland on occasions. The sea breeze exhibits a marked diurnal clockwise rotation as a result of the Coriolis effect along the unobstructed coastline. The marine advective effect is shown to depend on gradient wind direction. With northwesterly upper level flow the sea breeze tends to be northeasterly in direction and is associated with decreased temperatures and vapor pressure deficits (VPD). With southwesterly upper level flow the sea breeze tends to have a southeasterly direction and less effect on temperatures and VPD. This is attributed to shorter residence times of air parcels over water. For two cases, Colorado State University mesoscale model simulations show good agreement with surface wind observations and suggest that under northwesterly gradient flow, Bowen ratios are increased in the onshore flow along western James Bay, while during southwesterly gradient flow these effects are negligible. These results have implications for the interpretation of local climate, ecology, and hydrology as well as land-based and airborne turbulent flux measurements made during NOWES.

Sea breeze activity at an Inland station Kharagpur (India): a case study

Abstract: Surfaces fluxes, turbulent kinetic energy and Flux Richardson number are calculated for three typical sea breeze days characterizing three types of sea breeze onset at an inland station Kharagpur (22°21′ N, 87°19′ E), 80 km inland, one of the sites for MONTBLEX (MONsoon Trough Boundary Layer EXperiment), in India. The sea breeze onset is associated with a decrease in momentum and heat fluxes and an increase in moisture flux. The turbulent kinetic energy shows quite a significant value even in the late afternoon. The surface layer becomes nearly stable even before sunset, due to the passage of the sea breeze.

An Analytical Model of the Diurnal Oscillation of the Inversion Base Due to the Sea Breeze

Abstract: The diurnal oscillation of the height of the inversion due to the sea breeze is studied analytically by use of a linear model. The base of the inversion over the sea moved downward during daytime and upward during nighttime. Over the land the diurnal movement of the inversion base is opposite to that over the sea. The change in the height of the inversion base reached about 250 m. An increase in the mean height of the inversion's base and the stability of the inversion results in a smaller diurnal oscillation. The amplitude of this oscillation is almost independent of the latitude and of the diffusion above the boundary layer. Weak gradient wind blowing in the inland direction increases the amplitude of the oscillation, while stronger gradient wind decreases the amplitude of the oscillation due to a decrease in the intensity of the sea breeze.

Evidence of sea-breeze flow at the top of Hymettos mountain

Abstract: Results from an observational study of a sea-breeze flow at the top of a steep mountain are presented and discussed. Measurements of the profiles of temperature, humidity, wind speed and direction from a tethered balloon are given together with the hourly variations of the same parameters at surface level, The thermal structure of the atmospheric boundary layer (ABL) along with the profiles of the temperature structure parameter (C2 T) and the vertical wind component variance (σ2 w) obtained by acoustic sounder at the mountain top are also included. An attentive examination of the collected data indicates the presence of sea-breeze flows on top of the 1000 m height mountain. This is of importance, especially in cases like Athens, where the understanding of the wind flow is necessary for the study of the air pollution problem

Observation and Simulation of Urban-Topography Barrier Effects on Boundary Layer Structure Using the Three-Dimensional TVM/URBMET Model

Abstract: Urban areas affect prevailing mesoscale and synoptic flow patterns due to a variety of physical processes, including urban heat island induced accelerations, surface roughness induced decelerations, and building barrier effects. Analysis of data collected over New York City (NYC) has shown that the city is capable of significantly altering the speed and/or direction of movement of thunderstorm cells, sea breeze fronts, and synoptic fronts. Analyses of the above effects, plus additional analysis (during periods without such features) of surface flow patterns, surface convergence fields, tetroon vertical velocities, and double theodolite velocity fields all point to the urban barrier effect as the most significant factor altering mesoscale flow over NYC (Bornstein and LeRoy1).

Wave trains over the sea due to sea breezes

Abstract: 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.

Sea Breeze in Summer, Along the West Coast of Portugal

Abstract: Along the west coast of Portugal, in a narrow strip of 20 to 35 Km, more than 70% of the portuguese population is concentrated, and more than 90% of air pollutants in Portugal are released in this region. The atmospheric circulations detailed study as well as the thermal structure in the lower troposphere are very important because they are determinant factors in the air pollutants transport and dispersion conditions. During the dry period, since middle May to middle October, it is frequent the formation of a thermal low pressure over the central region of the Iberian peninsula; in association with this low pressure, a persistent ridge over the north of the peninsula is connected with the Azores anticiclone. Under these conditions, along the west coast of Portugal, especially during the months since June to September, the sea breeze regime is a direct consequence of the differential heating of the surface air, which reaches more than 20 o C between the land and the sea, in the horizontal scale along the coastal strip.

Wind Flow and Photochemical Smog in Thessaloniki: Model Results Compared with Observations

Abstract: The EUMAC Zooming Model is applied to simulate wind flow and pollutant transport and transformation in the Greater Thessaloniki Area (GTA). The simulation results agree fairly well with observations during the Thessaloniki ‘81 Field Measurement Campaign. Both the calculation and the observation show that the ozone levels in the GTA are decisively affected by the sea breeze circulation and the nighttime inversion.

Wind flow in the Fraser Valley as measured by a pulsed CO{sub 2} Doppler lidar

Abstract: The Vancouver, British Columbia metropolitan area, with a population close to 1.5 million people, experiences high levels of tropospheric ozone during the summer months. The transport of pollution, including tropospheric ozone, in the Vancouver area, is influenced by a local land/sea breeze circulation, the valley flows associated with the Lower Fraser River Valley to the east of the city, and the complex terrain to the north and northeast of the city. In July and August of 1993, an experiment was conducted in the Vancouver area to assess the distribution and transport of tropospheric ozone. Wind flow and aerosol measurements were obtained with a pulsed CO(sub 2) Doppler lidar and wind fields and their interactions with the complex terrain were mapped. The combination of Doppler lidar measurements of wind velocity and backscattered signal intensity, obtained simultaneously, will help identify wind flow patterns that enhanced the transport of urban pollution from the city of Vancouver to the Lower Fraser River Valley, and the possible recirculation of these pollutants back into Vancouver.

중규모 국지 순환에서 대기 오염 물질의 확산에 관한 연구

Abstract: Dispersion characteristics of air pollutants in the mountainous coastal area are investigated in considering with the mesoscale local circulations using a two dimensional numerical model with two kinds of topograpy of 500m and 300m. In the model, land-sea breezes and mountain-valley wind are mainly considered under the condition of the absence of large scale prevailing flow in the circulation analysis, and the pollutants dispersion is traced by the Lagrangian methods. According to the results, the wind velocity is affected by topography and is stronger in the case of 500m height mountain than that of 300m, the pollutants that source is near the coast transported over the mountain and dispersed to behind inland area. It is classified that the topography change control affects the wind velocity and the circulations. The pollutants that source is different transported and concentrated to behind inland and/or diffused to the sea area by the combination of the wind system with topographic changes. The results can be applied to the air pollution control with the arrangement design of industrial area and the planning of coastal developments.

On the Characteristic of Wind over Pusan Coastal Area, Korea

Abstract: We have Studied the characteristics of wind over Pusan coastal area in order to precisely predict surface wind having an important effect on oil spill fate using the data on surface observation of Pusan, Kimhae and Gadeogdo island which are collected during the 3 years from 1988 to 1990. We also investigated the correlation of the surface wind between Pusan, Kimhae and Gadeogdo island. In both Pusan areas and Kimhae, the land and sea breeze occurs during. the whole season except for winter. The occurrence frequency of land and sea breeze is significantly high from April to August. The correlation of surface wind between Pusan, Kimhae and Gadeogdo island surface wind is high in the daytime. The occurrence frequency of sea breeze in the Kimhae areas is higher than that in Pusan on the basis of the present criteria. For monthly occurrence, Pusan has the highest occurrence frequency of the sea breeze in August and Kimhae has in May. Key Words : land and sea breeze, surface wind

해풍이 부산 지역의 대기 오염 농도에 미치는 영향

Abstract: 【Air pollution characteristics and the influence of sea breeze on air pollution concentration were studied using the data measured at 7 air quality continuous monitoring stations in Pusan, 1993. Maximum air pollution concentration in Pusan was Gamjeondong for $SO_2$ , Sinpyeongdong for TSP, Daeyeondong for $O_3 , Kwangbokdong for $NO_2$ , Beomcheondong for CO and all substances were under annual ambient air quality standards. Increased rate of concentration for sea breeze was 24.4% for 502, 31.5% for TSP, 8.0% fort $O_3 , 26.7% for $NO_2$ , 15.7% for CO. Frequencies distribution of $SO_2$ , TSP, $O_3$ , $NO_2$ , and CO concentration for sea breeze moved toward high concentration class. Key Words : sea breeze, sea breezing day, air pollution concentration, ambient air quality standards】

Influence of the Sea Breeze on the Air Pollution over the Attica Peninsula

Abstract: In the frame of the APSIS project simulations of the dispersion of air pollutants over the Attica Peninsula are carried out for May 25, 1990. This day is characterized by clear sky conditions and a general flow from Northwest. Such conditions support the development of a sea breeze around the Peninsula, which is especially pronounced in the basin of Athens and the neighbouring coastal zone. The flow and turbulence fields are simulated with the the non hydrostatic model KAMM (Adrian and Fiedler, 1991). Based on these fields the dispersion of the air pollutants are calculated with the DRAIS model (Nester and Fiedler, 1992). The simpler chemical mechanism RADM1 was selected because only measurements of NO, NO 2, SO 2,CO and O 3 are available, which are well predicted by the RADM1 mechanism.

Dispersion Modelling and Observations from Elevated Sources in Coastal Terrain

Abstract: This study is focussed on the Central Coast region of New South Wales, on the east coast of Australia, where Pacific Power Inc. operates three power stations, situated on small lakes within a few kilometres of the coast. One of the objectives of the study was to assess the suitability and value of our modelling system to the air quality assessment needs of Pacific Power in the region, including the evaluation of green-fields sites for future power stations. The dispersion of plumes from all power stations throughout the year is not only influenced by the terrain blocking and channeling of the synoptic winds, but also by mesoscale wind systems such as sea breezes and drainage flows. Our Lagrangian Atmospheric Dispersion Model (LADM) predicts winds and turbulence and uses these to simulate the transport and diffusion of emissions from discrete sources, for impact distances ranging from hundreds of metres to a few hundred kilometres. In this paper we compare LADM results to available observations in the far field.

Synoptic-scale influence on the Monterey Bay sea-breeze

Abstract: : The diurnal fluctuations of the surface ambient wind associated with the sea-breeze are analyzed for the period May 01 through September 30, 1993 from a single station, Monterey airport, located on the southern Monterey Bay coast Data analyzed included time series of wind speed, wind direction, clouds, precipitation and locally generated 3 hourly surface pressure analyses of California and the Pacific northwest The characteristics of the sea-breeze circulation under varying synoptic-scale patterns are evaluated to determine the modifying roles of boundary layer stability, surface inversion strength, and low-level cloud amount on the resultant time of onset and peak intensity of the Monterey Bay sea-breeze The primary modifying factor under all synoptic-scale pressure patterns was the boundary layer depth and stability with the differential heating taking longer to destabilize the boundary layer during the Trough regime