Showing papers on "Sea breeze published in 1995"

Simulated Urban Climate Response to Modifications in Surface Albedo and Vegetative Cover

Abstract: Three-dimensional meteorological simulations have been conducted to investigate the potential impact of urban surface characteristic modifications on local climate. Results for a base case simulation for the Los Angeles basin are compared to results from cases in which urban albedo or vegetative cover are increased. The methodology for determining the distribution and magnitude of these simulated surface modifications is presented. Increasing albedo over downtown Los Angeles by 0.14 and over the entire basin by an average of 0.08 decreased peak summertime temperatures by as much as 1.5°C. This level of albedo augmentation also lowered boundary layer heights by more than 50 m and reduced the magnitude and penetration of the sea breeze. A second simulation, in which vegetative cover was increased, showed qualitatively similar impacts. The results from these simulations indicate a potential to reduce urban energy demand and atmospheric pollution by 5%–10% through application of reasonable surface mo...

Convection Initiation Associated with a Sea-Breeze Front, a Gust Front, and Their Collision

Abstract: The initiation of convection associated with a sea-breeze front, a gust front, and their collision is analyzed using data collected in east-central Florida during the Convection and Precipitation/Electrification project. In conjunction with satellite, surface, and rawinsonde information, dual-Doppler radar-derived winds are used to determine the three-dimensional kinematic factors critical to storm development. The gust front, which emanated from storms on the western half of the peninsula, propagated more rapidly and was deeper than the sea-breeze front, which originated from the east coast and was characterized by a distinctly scalloped appearance. Convection associated with the sea-breeze front appeared to develop preferentially at the vertices of this scalloped pattern where there were enhanced regions of convergence and upward motion. On the gust front, a Helmholtz shearing instability produced an organized configuration of convergence and updraft maxima along its length. However, these were...

Observations of the Sea-Breeze Front during CaPE. Part II: Dual-Doppler and Aircraft Analysis

Abstract: The three-dimensional kinematic structures of offshore and onshore flow sea-breeze fronts observed during the CaPE experiment are shown using high resolution dual-Doppler and aircraft data. The fronts interact with horizontal convective rolls (HCRs) that develop within the convective boundary layer. Nearly perpendicular intersections between the HCRs and sea-breeze front were observed during the offshore flow case. Close to the front, the HCR axes were tilted upward and lifted by the frontal updrafts. Consequently, a deeper updraft was created at the intersection points, providing additional impetus for cloud development. Furthermore, clouds forming at periodic intervals along the NCRs intensified as they propagated over the front. During the onshore flow case, the HCR orientation was nearly parallel to the front. Extended sections of the front “merged” with the HCRs. This process strengthened the front and is explained as the merger of like-sign vortices associated with both the front and HCRs. ...

Airborne Bacteria in the Atmospheric Surface Layer: Temporal Distribution above a Grass Seed Field.

Abstract: Temporal airborne bacterial concentrations and meteorological conditions were measured above a grass seed field in the Willamette River Valley, near Corvallis, Oreg., in the summer of 1993. The concentration of airborne bacteria had a maximum of 1,368.5 CFU/m(sup3), with a coefficient of variation of 90.5% and a mean of 121.3 CFU/m(sup3). The lowest concentration of bacteria occurred during the predawn hours, with an average of 32.2 CFU/m(sup3), while sunrise and early evening hours had the highest averages (164.7 and 158.1 CFU/m(sup3), respectively). The concentrations of bacteria in the atmosphere varied greatly, with a maximum difference between two 2-min samples of 1,995 CFU/m(sup3). The concentrations of bacteria in the atmosphere could be divided into five time periods during the day that were thought to be related to the local diurnal sea breeze and Pacific Coast monsoon weather conditions as follows: (i) the nighttime minimum concentration, i.e., 2300 to 0600 h; (ii) the sunrise peak concentration, i.e., 0600 to 0800 h; (iii) the midday accumulating concentration, i.e., 0800 to 1515 h; (iv) the late-afternoon sea breeze trough concentration, i.e., 1515 to 1700 h; and (v) the evening decrease to the nighttime minimum concentration, i.e., 1700 to 2300 h. The sunrise peak concentration (period ii) is thought to be a relatively general phenomenon dependent on ground heating by the sun, while the afternoon trough concentration is thought to be a relatively local phenomenon dependent on the afternoon sea breeze. Meteorological conditions are thought to be an important regulating influence on airborne bacterial concentrations in the outdoor atmosphere in the Willamette River Valley.

The Amazon River Plume during AMASSEDS: Subtidal current variability and the importance of wind forcing

Abstract: Current variability over the north Brazilian shelf, particularly within the Amazon Plume, is characterized using observations from a moored array deployed about 300 km north of the Amazon River mouth from February to June 1990 as part of A Multidisciplinary Amazon Shelf SEDiment Study (AMASSEDS). The moored array consisted of a transect perpendicular to the coast with inner shelf (18 m depth) and midshelf (65 m) moorings and a third mooring near the shelf break, in 100 m of water. To our knowledge, the AMASSEDS moored array includes the first long-term (2 months) moored observations made within the Amazon Plume. The current variability is dominated by two components, semidiurnal cross-shelf currents with peak velocities of 50 to 200 cm/s and vertically sheared subtidal (timescales days to weeks) along-shelf currents. This study focuses on the subtidal flow within the Amazon Plume which is strong and variable with along-shelf currents ranging from −50 cm/s to over 150 cm/s. The variability in the along-shelf current within the plume is wind driven. The relatively weak (<0.5 dyn/cm2) along-shelf wind stresses in this region drive strong along-shelf current variability because the Amazon Plume is thin and the interfacial drag is weak. However, in the absence of an along-shelf wind stress the plume flow is northwestward at 40 to 80 cm/s, indicating that direct wind forcing does not account for the mean northwestward flow of the Amazon Plume. In the cross-plume direction there is a tendency for the onshore wind stress due to the persistent trade winds to balance the typically offshore buoyancy force and the Coriolis force associated with the wind-driven along-shelf flow. Thus the wind stress is a key factor influencing variability in both the flow and cross-shelf structure of the Amazon Plume in the vicinity of the moored array.

A complete sea-breeze circulation cell derived from aircraft observations

Abstract: Using an instrumented aircraft, a complete sea-breeze circulation cell was sampled from its offshore end to the sea-breeze front over land and up to a height of approximately 1000 m AMSL Many of its typical features can be resolved in detail mainly by cross-sectional analysis These are: the diverging onshore flow in the lower layers over the sea the convergence over land at the seabreeze front and the connected cross-frontal circulation, a distinct return flow in the upper layers, the propagation of the seaward end of the cell over water, as well as the propagation of the front over land, the baroclinicity as a driving mechanism of the cell and also budget and frontogenesis terms

Sea Breezes Shallow and Deep on the California Coast

Abstract: Analyses of Doppler lidar data reveal sea breezes occurring on two different depth and time scales at Monterey Bay, California, on a day with offshore gradient flow indicated before sunrise and after sunset. The lidar data used in this study consist of vertical cross sections and profiles of the westerly, onshore wind component u. In the morning after 0900 PST a shallow sea breeze formed, which reached a depth of 300 m by noon. Starting in early afternoon a deeper sea-breeze layer formed in the lowest kilometer, and by late afternoon the shallow sea breeze blended into the deeper sea breeze and was no longer evident. Maximum speeds of 6 m s−1 in the shallow sea breeze occurred at the surface, whereas those in the deep sea breeze (also 6 m s−1) were about 300 m above the surface. It is hypothesized that the shallow sea breeze is a local phenomenon responding to a more local temperature contrast between the sea and the region between the ocean and the mountain ranges. The deeper sea breeze, on the ...

The Cape Canaveral Sea and River Breezes: Kinematic Structure and Convective Initiation

Abstract: This study examines complex flow patterns associated with the Cape Canaveral sea breeze and sea-breeze front using dual-Doppler radar, sounding, and surface data collected on 26 July 1991 during the Convection and Precipitation/Electrification Experiment. This case focuses on (a) the structure of the sea breeze, an associated trailing convergence line, river-induced convergence zones, and thunderstorm outflow boundaries, and (b) the development of convection where these features interacted. Variations in the direction of the sea breeze in the vicinity of irregular coastlines, such as Cape Canaveral, can lead to persistent zones of convergence within the sea-breeze air. The findings show that these zones of convergence, in turn, can locally increase the depth of the sea-breeze air and create circulations at the top of the sea breeze, which can support the development of convection. The observational study is the first to document the development and evolution of the trailing convergence line over ...

A first numerical simulation of the development and structure of the sea breeze on the Island of Mallorca

Abstract: A numerical study of the development and structure of the sea breeze in Mallorca is presented using a meso- numerical model. The model includes a detailed representation of the soil and vegetation processes. The study covers a diurnal cycle. The results show that the model reproduces the main known features of the circulation and new ones appear, which seem to have an appreciable effect on the circulation during the decay of the sea breeze. The orography and soil dryness have been identified as the main factors determining the structure of the breeze. Three more experiments have been performed in order to isolate the effect of each factor.

The Australian nocturnal jet and diurnal variations of boundary‐layer winds over Mt. Isa in North‐eastern Australia

Abstract: An analysis of radiosonde data shows the nocturnal boundary-layer jet over Australia to be continental in scale. the detailed temporal development of the jet is described using two years of boundary-layer wind-profiler data from Mt. Isa in north-eastern Australia. A distinct isallobaric wind is found, which has a spectral peak near the inertial period. This is associated with the diurnal pressure-oscillation and developments in the heat low over central and western Australia. However, it is not important for the development of the nocturnal jet. the nocturnal jet begins as a shallow disturbance and grows through the night. Most of the year the wind maximum is at about 500 m above the ground and has a well-defined jet-profile. In the summer-monsoon season the vertical extent of the wind maximum increases, but has weaker vertical shear. the jet results from an inertial response, but is affected by other processes. the amplitude of the jet is less than would be expected from a straightforward response to the daytime ageostrophic flow and there is super-inertial rotation and damping of the wind vector late in the night.

A study of sea and land breezes in an archipelago on the west coast of Sweden

Abstract: This paper reports analyses of recordings made on three tower masts in order to study the dynamics of sea and land breezes as well as the development of these systems in an archipelago along the west coast of Sweden. Intensive studies have focused on the duration and strength of sea and land breezes and the development of small-scale systems controlled by the irregular coastline in the study area. The internal dynamics of the land breeze and the occurrence of temperature variations in the coastal area are discussed as well as the interrelationship between these factors. The studies show that the sea and land breezes are well developed when the synoptic-scale pressure gradient is relatively weak. However, a division into smaller systems has been observed, i.e. small islands outside the coastline develop their own wind systems. In the archipelago, a primary sea breeze with no interaction with the main coastline develops during the first hours after sunrise. The primary sea breeze continues to act until a stronger sea breeze, developed in interaction with the main coastline, begins to blow. This phenomenon was not observed for the land breeze. Here, no general land breeze develops, instead a breeze was recorded which always blew towards the coastline.

General aspects of land and sea breezes in Osaka Bay and surrounding area

Abstract: The general aspects of land and sea breezes in the Osaka Bay area and its environment are revealed from an analysis of the wind data obtained by the AMeDAS. The study area consists of a complex land-sea configuration and a complex topography which includes plains, hilly terrain, and mountainous regions. The land and sea breezes are classified into five types according to the behavior of the sea breeze at several locations in the study area. The most frequently occurring type is characterized in the following. Along the southern coast of Osaka Bay, the sea breeze from Osaka Bay changes with time into that from the Kii Channel. At the same time, along the coast of the Seto Inland Sea the sea breeze contains a predominant easterly component. For this type, several interesting features are further elucidated: (1) the simultaneous onset of the coastal sea breeze and the valley or upslope wind in the mountainous region is clearly seen, especially in the eastern Chugoku area, (2) the meeting of the southerly sea breeze from the Seto Inland Sea and the northerly breeze from the Sea of Japan occurs around the region of the mountain ridges in eastern Chugoku, (3) the alternation of converging sea breezes from surrounding seas forms a uniform southerly sea breeze from the Kii Channel at Awaji Island, (4) the southerly sea breeze continues until the late afternoon in the coastal area of the Kii Channel and Osaka Bay. Other types are discussed and compared with the above type for the mature stage of the sea breeze. The relationships between the occurrence of the land and sea breeze and general meteorological conditions are also analyzed.

Sea breeze effects on large-scale atmospheric flow

Abstract: Sea and land breeze circulations (SBC) are quasi-regular diurnal mesoscale flow patterns driven by the temperature contrast between land and sea. The systematic convergences of momentum, potential temperature and moisture fluxes caused by SBC over a 250 km wide coastal zone were estimated from linear theory and from high-resolution mesoscale model simulations in a typical subtropical case. Sensitivity of this SBC forcing on the larger-scale flow was charted by varying parameters. It appears that kinematic forcing (sea breeze drag) is negligible in the 250 km scale, which is the typical horizontal resolution in general circulation models (GCM). In contrast, the thermodynamic forcing (convergence of mesoscale heat and moisture fluxes) is strong. It tends to cool and dry the coastal zone near the surface and to warm and moisten the air higher up in the daytime. This vertical structure is insensitive to parameter variations but its amplitude scales linearly with the driving temperature contrast and with cosine of latitude. The forcing effect is relatively insensitive to the sloping of the coast (i.e. to simultaneous upslope and downslope winds), but large-scale wind across the coast reduces it. The major SBC effect on the larger-scale flow is thus enhanced upward scalar mixing in the coastal boundary layer. This could be parameterized into GCMs either directly as extra terms, or indirectly by increasing the vertical mixing coefficients for scalars over the coastal gridsquares during conditions favorable for sea breeze.

Flow and transport modeling in the sea-breeze part II: Flow model application and pollutant transport

Abstract: A modifiedE-∈ non-hydrostatic model with non-equilibrium level 2.5 closure was applied to the flow and pollutant dynamics in the sea-breeze. The model predicts key observed characteristics of the sea-breeze, such as midday slowing of inland penetration, fast and deep inland penetration in late afternoon, and detachment of the sea-breeze from the feeding flow in early evening. In late evening when the turbulent mixing over the land subsides due to the surface cooling, a frontal density current is formed and the predicted structure is in good agreement with observations and laboratory experiments of density currents. Turbulent mixing over the land is a key parameter that controls midday slowing and late afternoon frontal development.

An assessment of boundary-layer air mass characteristics associated with topographically-induced local wind systems

Abstract: Measured and derived meteorological parameters are used to examine the changes in air mass associated with local winds of differing origin. Research conducted explores the usefulness of wet bulb potential temperature, equivalent potential temperature, virtual potential temperature and relative humidity as indicators of air mass change during sea breeze, foehn wind and nocturnal drainage flow events. The complex interactions between these different topographically-induced wind systems in South Canterbury, New Zealand, provide an environment in which marked changes in air mass characteristics are common. Results demonstrate that under a considerable range of boundary-layer conditions, measured wet bulb potential temperature when used in conjunction with windspeed and direction enables quick and accurate determination of air mass origin. Relative humidity was also found to respond closely to changes in local air mass type, but its dependence on air temperature makes it a less reliable indicator.

Onshore flow in an urban area: Microclimatic effects

Abstract: Afternoon field observations contrasting waterfront and inland environmental conditions during summer, onshore flows from a cool water surface were conducted in residential areas of Victoria, British Columbia, Canada. The waterfront, under the direct influence of the onshore flow, had lower air temperature, vapour pressure, sky and ground radiant temperatures and a higher wind speed than did inland sites. Areas under the influence of the onshore flow would have a cooler environment for people and plants, lower interior building temperatures, and less evaporation demand.

Interaction of a cold front with a sea-breeze front Observations

Abstract: On 9 May 1989, during the field experiment FRONTEX, a synoptic-scale cold front was observed which moved from the North Sea to Northern Germany and interacted with a sea-breeze front. The modification of the cold front is documented by satellite images and measurements over the sea, at the coast and further inland. The synoptic-scale front was characterized by weak frontal gradients over the sea. It was aligned approximately parallel to the coast as was approximately the wind ahead of it. While the synoptic-scale front approached the coast during the forenoon hours, a strong temperature contrast developed between sea and land due to solar heating of the land surface. This led to the formation of a sea-breeze front associated with a stronger temperature gradient than the synoptic-scale front. At about noon, when the synoptic-scale front almost reached the coast, the sea-breeze front began to move inland. The onshore wind behind the sea-breeze front and ahead of the synoptic-scale front was so large that the wind field at the synoptic-scale front changed from confluence to difluence. This process was supported by a shallow inversion ahead of the synoptic-scale front which confined the vertical depth of the sea-breeze. The former sea-breeze front overtook the main frontal characteristics, continued its inland propagation and was the only frontal event observed over the land. As a result of the interaction, the synoptic-scale front was significantly intensified in the boundary layer. DOI: 10.1034/j.1600-0870.1995.t01-2-00001.x

Synoptic and mesoscale influences on refraction during SHAREM 110

Abstract: : Highly variable refractive conditions over the Persian Gulf and Gulf of Oman are studied during the SHAREM 110. Data collected during SHAREM 110, conducted in February 1995, included the Naval Operational Regional Atmospheric Prediction System (NORAPS), a large data base of upper air profiles, shipboard surface weather observations, and satellite imagery. Four different meteorological regimes occurred; pre-Shamal or Kaus, Shamal, Northeast Monsoon, and a short Shamal event. In addition to discussing the effects of synoptic meteorology on refraction during these periods, topography is also found to be a major factor in influencing refractive variability. The land/sea breeze was also found to be very important in modifying the low level refractive structure, especially in the Gulf of Oman.

Description of the Martian polar cap breeze

Abstract: The surface temperature of the Martian polar caps is about 148 K (frost point temperature of CO2 at a surface pressure of about 6 hPa), with the “desert” (frost-free) areas adjacent to the polar caps having much greater surface temperatures The existence of this steep meridional gradient of temperature between the polar caps and the adjacent “desert” areas may produce in the atmosphere a baroclinic instability which generates an atmospheric circulation system similar in some aspects to the terrestrial sea breeze We have called this circulation system the Martian polar cap breeze