Showing papers on "Sea breeze published in 1991"

A numerical investigation of the influence of large-scale winds on sea-breeze- and inland-breeze-type circulations

Abstract: A two-dimensional mesoscale model is used to study the influence of large-scale background winds on sea-breeze- and inland- (vegetation) breeze-type circulations. It is found that the intensity (vertical velocity) of the sea breeze is at its maximum when the Propagation speed of the sea-breeze front is canceled out by the background wind speed. Using the gravity current theory, we get a fair prediction of this optimum background wind value. The intensity and extent of the inland breeze, forming between a forecast and an adjacent crop area, do not vary over a large range of values for the large-scale wind. The location of the ascending branch of the inland breeze is stationary with respect to the interface between the two vegetation types. It is suggested that it is not friction drag but rather turbulent mixing that leads to a moon horizontally uniform boundary layer and which is responsible for the different behavior of the inland breeze, i.e., a weak and nonpropagating circulation.

A Numerical Study on Sea/Land Breezes as a Gravity Current: Kelvin–Helmholtz Billows and Inland Penetration of the Sea-Breeze Front

Abstract: A two-dimensional, nonhydrostatic, compressible, and dry numerical model was developed. By using high spatial resolution and an appropriate turbulence model, fine structure and dynamics of the sea-breeze head were investigated. Kelvin–Helmholtz (KH) instability was found to occur in the foremost part of the head. Consequently KH billows were generated there and grew in amplitude while travelling backward relative to the advancing front along the “zero-velocity boundary.” The KH billows entrained the upper air into the sea breeze. The resultant turbulent mixing and wave perturbations induced a top friction force acting on the sea-breeze head. Structure of the KH billow and the wavelike motion induced by it near the ground were also investigated and compared with the results obtained in laboratory density currents, linear theories, and observations. The KH instability (KHI) did not occur at all stages of the sea breeze, and this resulted in a diurnal variation of the fine structure and dynamics of ...

A Two-Dimensional Numerical Investigation of the interaction between Sea Breezes and Deep Convection over the Florida Peninsula

Abstract: The Colorado State University Regional Atmospheric Modeling System is used to investigate the interaction between sea breezes and deep convection over the Florida peninsula, and it is shown that this model can simulate the broad features of the three characteristic types of convection systems classified by Blanchard and Lopez (1985). In sensitivity tests performed for a variety of wind and thermodynamic profiles and for different soil-moisture contents, it was found that increases in the low-level temperature and in moisture content speeded up the development of convection. It was found that the dry-soil simulation produced rapidly developing sea breezes that moved inland quickly, while the moist soil case produced a much more slowly developing sea breeze. The total rainfall over the peninsula for the dry-soil case was greater than for the moist soil; it is suggested that the enhanced surface heat fluxes for the dry soil case create stronger low-level convergence over the peninsula (than in the moist-soil case) to force the convection.

The Effects of Width of Landmasses on the Development of Sea Breezes

Abstract: A two-dimensional hydrostatic model has been employed to simulate sea-breeze circulations introduced by different-sized landmasses. The following influences on the sea breeze are examined. 1) environmental thermal stratification, 2) synoptic flow, and 3) latitude. In the simulation of a strip of land with a width of 150 km, the maximum sea-breeze convergence is much better developed than for other widths. This maximum computed upward velocity occurred when two sea-breeze cells from the two sides of the land merge together in the late afternoon. For the experiments presented here, the sea breeze reached the strongest vertical velocity (1.7 m s−1) when the environmental vertical gradient of potential temperature is 2.5°C km−1 with a land width of 150 km. With a very stable static stability, the sea breeze is not well developed. When the sea breeze occurs at 20°N, its intensity is the strongest, presumably because the solar insulation is greatest at this latitude for the separate simulations. At 60°...

Observational Evaluation of the Snow Breeze

Abstract: An observational evaluation of the daytime thermally induced flow between the snow and snow-free areas (termed snow breeze) has been carded out Aircraft measurements within the lower atmosphere made in the winter of 1988 reveal large temperature reductions over the snow cover relative to the bare ground implying the potential for snow-breeze generation The aircraft flights were generally made under unfavorable synoptic conditions although in one particular case with a moderate synoptic flow, a snow breeze was clearly identified A less distinctive snow breeze was indicated in a second case Observed features and a scaling analysis of relevance to snow breezes are presented

Main features of the sea-breeze in Barcelona

Abstract: From a data set of sea-breeze observations corresponding to cases of no synoptic-scale flow in Barcelona during the period 1970–89, some features of this wind have been deduced. Maximum velocities of between 6–14 m/s generally occur during 12–16 SLT. Diurnal evolution gives a clockwise rotation of sea breeze so that this wind blows roughly parallel to the shoreline in late afternoon. The rate of the change of direction is in agreement with numerical results from a simple nonlinear sea breeze model.

A study of nonhydrostatic effects in idealized sea breeze systems

Abstract: Nonhydrostatic effects in two-dimensional mesoscale sea breeze systems are investigated by numerical simulations. It is shown that nonhydrostatic effects are directly contributed by the vertical gradients of the vertical velocity variance as well as by the vertical accelerations. It is also shown that a K-type turbulence closure is not suitable in a nonhydrostatic primitive equation model, and a higher-order closure scheme should therefore be used. Results from hydrostatic and fully-nonhydrostatic models are compared for various surface and atmospheric background conditions, such as scale and strength of surface heating, geostrophic wind, stability, surface roughness contrast, Coriolis effect, etc. It is found that for strongly developed sea breeze cases, vertical gradients of vertical velocity variance contribute most to nonhydrostatic forcing in the lower layers, and that the resultant nonhydrostatic pressure gradient acts against the hydrostatic pressure gradient, so that nonhydrostatic simulations produce weaker systems than hydrostatic ones. For weak sea breeze systems, the difference between the two models tends to be small.

Interaction of the sea breeze with a river breeze in an area of complex coastal heating

Abstract: 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.

A Numerical Study of Mesoscale Eddy Development over the Santa Barbara Channel

Abstract: The development of the “midchannel eddy” over the Santa Barbara Channel represents a mesoscale response of the large-scale airflow to the combination of the diurnal heating cycle over land surfaces, the curvature of the coastline, and the orientation of major ridges with respect to the coastline. In this paper we analyze and discuss the results of a numerical simulation of mesoscale airflow over the Santa Barbara Channel and adjacent land areas on 23–24 September 1985, with emphasis upon nocturnal mesoscale eddy development. Simulated winds are compared with SCCCAMP 1985 wind observations. Both simulation and observations indicate inception of a midchannel eddy in the vicinity of Santa Barbara during the late evening of 23 September, followed by westward and southward expansion of the eddy. Our analyses indicate that simulated midchannel eddy development is associated with the following sequence of events: 1) offshore-directed flow develops over coastal ridges in the early evening, associated wit...

Airborne observations of thermal mesoscale circulations in the coastal marine boundary layer

Abstract: Airborne observations of thermal mesoscale circulations in the coastal marine boundary layer

Characteristics of Ozone Episodes during SCCCAMP 1985

Abstract: Extensive meteorological and air chemistry measurements were obtained along the Ventura and Santa Barbara county coastal areas in California during four 2–3 day case studies conducted during the September–October 1985 South-Central Coast Cooperative Aerometric Monitoring Program (SCCCAMP 1985). An overview of the characteristics of ozone episodes during these four case studies is given, showing that the episodes are associated with warm, high pressure systems with light winds. In the absence of easterly winds, the observed ozone in the region is primarily due to local sources. At other times, easterly wind components transport ozone and its precursors from large source regions to the east (i.e., Los Angeles County). This transport sometimes occurs in inland valleys at elevations up to 600 m, and sometimes occurs over the ocean near the surface. Local sea breezes, mesoscale eddies, and terrain-generated winds often cause complex flow patterns and recirculation of pollutants.

Wind-augmented transport and dilution in shallow-water flows

Abstract: This paper focuses attention on the joint dependence of the horizontal dilution rates upon the strength of the wind-augmented current and upon the vertical rise (or sinking) velocity of the particles. In strong wind the greatly enhanced mixing counterbalances the onshore drift and explains why shoreline pollution is not significantly correlated to the onshore wind

A Study on the Air Pollution Potential in the Central Part of Korea

Abstract: Air pollution potentials of the 7 cities in the central part of Korea were obtained with the mean wind speed within the mixed layer and the mixed layer height calculated by the Jump Model. Seasonal variation of the afternoon mixed layer height in Seoul area shows that low in winter and high in summer. Annual mean of the morning air pollution potential was lowest in Incheon and highest in Wonju. On the other hand annual mean of the afternoon air pollution potential was lowest in Incheon and highest in Chuncheon. Relatively low air pollution potential in Incheon can be explained as high mixed layer height and the effect of sea breeze.

Simulation of Shear Dispersion of an Effluent Plume caused by Wind Stress on the Sea Surface

Abstract: This paper is based on experience gained during the quality control of several site specific models of effluent dispersion in coastal areas in the UK and Eire, which has shown the perceived importance of wind effects when estimating shoreline concentration levels. The paper examines the relative importance of wind shear in this problem, proposes a form for the induced current profile, discusses the failings of the models often applied to coastal outfalls and suggests an outline methodology for a particle tracking model which would include explicitly the effects of wind and tidal shear currents.

Numerical simulation of sea breeze in south Andamans

Abstract: The air flow over the south Andaman island is simulated using a three dimensional numerical meso-scale model. Port Blair observations are used as initial data. The surface orography, soil moisture soil albedo variations and vegetations effects are included in the model. The combined effect of these factors on the development of sea/land breeze circulations is obtained quantitatively. The model simulated results are compared with the available observations. The principal results obtained are : (1) The meso-scale circulations induced by the differential heating of the island were intensified by topography. (2) The ground vegetative cover trans- port higher amount of turbulent heat fluxes: to the atmosphere and the meso-circulations appeared with higher intensities. (3) If we Include the lateral variations of flux with topographic and coastal asymmetries the induced meso-scale circulations appeared with different intensities along meridional direction and the inland penetration distances varied in y direction. The maximum Inland penetration of sea breeze was seen, where the inland was widest and terrain height was maximum. Stronger sea breeze was simulated over the central/northern parts of the island.

The Sea Breeze on the Pacific Side of the Shimokita Peninsula

Abstract: The Yamase wind is a cold north-easterly wind that causes summertime low temperatures in North Honshu. Because of its low elevation, the Yamase wind is affected by the mountain ranges. According to Ojika (1974), Kudo (1981) and Bokura (1990), small scale topographic features, such as the Shimokita hills (500m above sea level), are also affect the Yamase wind. However, local climate data did not show the topographic effect at the Shimokita Hills in 1987 (Kanno et al., 1989). Because the sea breeze on the Pacific side of North Honshu also causes low temperatures (Asai, 1952; Shitara, 1952, 1964), the east-west temperature contrast between the small-scale mountains may be result from not only the Yamase wind but also the sea breeze. However, the sea breeze on the Pacific side of North Honshu has not been examined since Shitara's studies in 1952 and 1964, and its vertical structure is still unknown. We here report on the results of our investigation of the sea breeze.A captive balloon observation was done on July 25 in 1989 at Tomari (Fig. 1). The Ogasawara anticyclone strongly spread (Fig. 2) and the Yamase wind did not blow on the observation day (Fig. 3). A distinct sea breeze (about 20°C) was found under about 200m elevation in the afternoon (Fig. 4). The vertical profiles of wind direction, wind speed, mixing ratio and equivalent potential temperature show that a return flow is formed in the sea breeze and the water vapor under about 100m is relatively small (Fig. 5). The temperature data of AMeDAS stations indicate that this sea breeze is restricted in the Pacific side of the Shimokita Peninsula (Fig. 6).The sea breeze observed in this work is characterized by lower elevation and higher temperature than the Yamase wind. Since the stratus and the fog were not found in the sea breeze, the sea breeze may form only by cooling from the sea surface. This process is different from the formation of the Yamase wind which results from the heating of air from the sea surface and cooling by the long wave radiation at the upper part of the stratus. Further analyses about the frequency and distribution of the sea breeze will be made in the future.