Showing papers on "Sea breeze published in 1984"

Mesoscale Vortices over the Great Lakes in Wintertime

Abstract: The occasional occurrence of wintertime mesoscale lake vortices is documented. The vortices are readily discernible in satellite imagery, in which they take one of three forms: a miniature comma cloud, a swirl of cloud bands (resembling a miniature tropical storm) or a swirl of cloud streets. Despite their impressive appearance in satellite imagery, these vortices are usually relatively mild in comparison with other lake-effect storms and produce only gusty winds and brief snow squalls as they move onshore. The vortices are accompanied by a slightly lowered surface pressure and a weak cyclonic low-level wind circulation. Fourteen vortices were detected over the Great Lakes in the years 1978–82; they occurred under conditions of relatively weak surface pressure gradient, with a ridge of high pressure usually found over or west of the region. Convergence was generally detected in the surface winds prior to vortex development, apparently related to land breeze circulations. Comparisons are made betw...

Area-average rainfall variations on sea-breeze days in South Florida

Abstract: Summer convective regimes over south Florida can be broadly, classified as either sea breeze or disturbed. Sea-breeze circulations develop on one or both coasts on most days with relatively little high cloudiness during the morning hours. The sea breeze strongly modulates the development of deep convection and produces a sharp midafternoon peak in rainfall. Disturbed days, which are characterized by extensive high cloudiness near sunrise, also have a rainfall maximum during the afternoon. Relationships between rainfall and thermodynamic and kinematic variables on disturbed and sca-breeze days have some significant differences. Comparison of rainfall records from the south Florida peninsula with observations from the Florida Keys, where sea-breeze circulations are relatively weak, indicates that the sea breeze accounts for about 35-40% of south Florida peninsula rainfall during the summer months. Area-averaged rainfall and the time variations of peninsula-scale surface divergence and hourly rainfa...

Sulfate accumulation in a sea breeze/land breeze circulation system

Abstract: An atmospheric tracer study using SF_6 was conducted on July 22, 1977, to examine the origin of the high particulate sulfate concentrations observed in coastal Los Angeles County. It was found that the sea breeze/land breeze circulation system in the Los Angeles Basin both increases the retention time for sulfate formation in the marine environment and causes individual air parcels to make multiple passes over large coastal emissions sources. Day-old sulfur oxides emissions advected out to sea by the land breeze at night were estimated to be the largest single contributor to 24-hour average sulfate air quality over land the next day. In contrast, 24-hour average SO_2 concentrations were dominated by fresh emissions from nearby sources. The overall rate of SO_2 transformation to form particulate sulfur oxides along some trajectories that spent a considerable time over the ocean at night probably exceeds the rate that can be explained by known photochemical processes acting during the daylight portion of these trajectories. This suggests that appreciable aerosol formation may occur in a polluted marine environment at night.

Sea‐breeze‐like winds across the north wall of the Gulf Stream: An analytical model

Abstract: Sea-breeze-like winds have been observed on the warmer side of the Gulf Stream when synopticscale winds blow from cool shelf water toward a warm water surface (Sweet et al., 1981). It is shown that a simple, thermally driven analytical model can explain satisfactorily the increase in wind speed from the cold to the warmer water side as resulting from horizontal temperature gradient across the Gulf Stream.

Doppler Radar Observation of a Land-Breeze Cold Front

Abstract: During the early morning hours of Ii January 1981, a very narrow, intense band of snow which had formed along the leading edge of a land-breeze cold front was viewed by CP-4 radar near Muskegon, Michigan. The front formed well inland and moved through the area from the northeast shortly after dawn. The driving force for the land breeze was the large temperature contrast that existed between radiationally-cooled air over the Northern Highlands of Lower Michigan, and the relatively warm, lake-modified air near the shore of Lake Michigan. The possibility that the observed snowband was associated with a mesoscale feature other than the land breeze is investigated. An analysis of minimum temperatures in the Great Lakes Region for 11 January 1981 shows that a strong temperature gradient existed over western Lower Michigan.This gradient reached a maximum value well inland rather than at the lake shore. Radar observations show the band to be over 80 km long and only 4 km wide, oriented roughly parallel t...

Numerical Simulation of the Transport of Chemically Reactive Species under Land- and Sea-Breeze Circulations

Abstract: The characteristics of the transport of chemically reactive species under land- and sea-breeze (LSB) circulations are investigated using a detailed transport/chemistry model, which includes 84 gas-phase and 10 heterogeneous chemical reactions. Model applications are presented which use flow fields derived from a modified version of the Asai and Mitsumoto model and eddy diffusivity profiles predicted by the boundary-layer model of Yamada and Mellor as inputs. The effects of nonprecipitating clouds associated with the LSB circulation on the calculated concentration fields are also studied. Mass transports by updrafts and counterflows associated with the LSB circulation and diurnally varying eddy diffusion processes show transitions between double and single maxima within a 24-hour cycle. The vertical profiles of some secondary pollutants such as O3 generally agree with field observations. Clouds are also shown to affect the predicted distributions of both the soluble and less soluble species by red...

The Use of Land and Sea Based Wind Data in a Simple Circulation Model

Abstract: The use of land based wind data in nearshore oceanographic work is common, but these winds do not accurately reflect coastal oceanic winds. Ocean winds are often underestimated by a factor of 2 and directional differences are also observed. Wind time series from land and sea regimes in the South Atlantic Bight (SAB) were applied to a reduced form of the momentum equation to estimate the alongshore current. Currents were closely approximated by ocean wind stress, but were consistently underestimated by land data. Further statistical analyses verified this discrepancy in speed and also indicated significant differences between ocean and speed-adjusted land winds. The bottom frictional coefficient required to balance alongshore momentum was unrealistically small when land based wind data were used as input.

The Coriolis Force in Relation to the Sea and Land Breezes—A Historical Note

Abstract: The deflecting effect of the earth's rotation on winds has been known since the writings of Hadley in 1735, and observations of the clockwise diurnal directional turning of the sea and land breezes in the Northern Hemisphere have been published in quantity since 1801. But, the first reference associating the turning with the earth rotation through the latter's deflecting effect appears to have been made by the Austrian meteorologist and climatologist von Hann in 1901. Jeffreys' (1922) conclusion that the earth's rotation is not relevant to the dynamics of the sea and land breezes, was based on an overestimate of the speed and an excessive underestimate of the landward penetration of the sea breezes. In 1934 Brunt suggested that the Earth's rotation may be important. Neither Jeffreys nor Brunt seem to have been aware of yon Hann's statement and examples. Haurwitz (1947) was the first to show dynamically that the Coriolis force can explain the observed diurnal directional turning of the sea and lan...

Numerical Simulation for the Topographical Effect on the Sea-Land Breeze in the Kyushu Island

Abstract: Simulation d'un modele 3D. La topographie impliquee comprend la ligne irreguliere de cote et les montagnes, deux aspects dont on analyse les effets

Acoustic sounding of land and sea breezes

Abstract: Sodar measurements have been made at La Spezia, Italy during land- and sea-breeze conditions. The backscatter returns are discussed qualitatively, including their relation to the vertical structure of the boundary layer as revealed by vertical soundings of wind and temperature. During inversion conditions, the sodar signals may be difficult to interpret especially when there is a land breeze flowing over irregular terrain.

The Sea-Breeze-Induced Coastal Calm Zone as Revealed by Satellite Data and Simulated by a Numerical Model

Abstract: Meteorological satellite scanning radiometer data from a visual sensor during daylight hours are characteristically influenced by sunglint from the ocean surface as the sensor scans in the direction toward the sun (between the satellite subpoint and solar subpoint). When seas are calm in the region near the primary specular point (PSP), the sun's rays are either reflected directly into the spacecraft sensor yielding a high energy (bright) response, or away from the sensor yielding a low energy (dark) response. The particular effect depends on the proximity of the calm area to the PSP. This paper shows examples of bright and dark linear patterns adjacent to and tending to parallel coastlines. The patterns are interpreted to be sea-breeze-induced calm zones originating during periods of offshore flow when the pressure gradient causing the sea breeze is exactly counterbalanced by the larger-wale synoptic gradient. A two-dimensional planetary boundary layer (PBL) numerical model successfully simulate...

The impact of wind circulation on the incidence and nature of rainstorms over Dar es Salaam, Tanzania

Abstract: Using storm rainfall data from a dense network of autographic raingauges at Dar es Salaam, Tanzania, storm characteristics (morphology, alignment and time of occurrence) are related to prevailing gradient wind. There is a pronounced seasonal variation in the time of day at which storms generally occur, related to seasonal changes in the larger-scale wind regime between the north-easterly and south-easterly trade winds. Many storms occur at times when there is a convergence between locally-generated land- or sea-breezes and the gradient wind, and their origin along these lines of convergence is further demonstrated by occurrence of both elliptical and linear morphology storms aligned along the coast. The trend of the coast is shown to control the alignment of storms, particularly by day, whereas by night gradient wind is more important. At this time, storms tend to form along the direction of the gradient wind. The most active storms form in the middle of the day, are linear in nature, aligned parallel to the coast, and occur when the gradient wind is either offshore or blows along the coast from the south-south-east.

Nimbus 7 SMMR Derived Seasonal Variations in the Water Vapor, Liquid Water and Surface Winds over the Global Oceans

Abstract: Monthly mean distributions of water vapor and liquid water contained in a vertical column of the atmosphere and the surface wind speed were derived from Nimbus Scanning Multichannel Microwave Radiometer (SMMR) observations over the global oceans for the period November 1978 to November 1979. The remote sensing techniques used to estimate these parameters from SMMR are presented to reveal the limitations, accuracies, and applicability of the satellite-derived information for climate studies. On a time scale of the order of a month, the distribution of atmospheric water vapor over the oceans is controlled by the sea surface temperature and the large scale atmospheric circulation. The monthly mean distribution of liquid water content in the atmosphere over the oceans closely reflects the precipitation patterns associated with the convectively and baroclinically active regions. Together with the remotely sensed surface wind speed that is causing the sea surface stress, the data collected reveal the manner in which the ocean-atmosphere system is operating. Prominent differences in the water vapor patterns from one year to the next, or from month to month, are associated with anomalies in the wind and geopotential height fields. In association with such circulation anomalies the precipitation patterns deduced from the meteorological network over adjacent continents also reveal anomalous distributions.

Atmospheric electric modulation during a sea breeze

Abstract: An increase of more than 40% in both the mean and fluctuating parts of the electric field strength and air-earth current has been observed during the day-time development of the convective boundary layer under the influence of the sea breeze. This is attributed to the advection and turbulent organization of surf- and wave-generated space-charge. Fluctuations in the electric field strength have been subjected to variance spectral analysis in the range 0.001

Calibration with experimental data of a 2D sea breeze model by heating parametrization

Abstract: A new scheme of vertical distribution of sensible heat flux has been introduced in a bidimensional numerical sea breeze model which uses a prescribed flux at the ground. The scheme has been suggested by inspection of thermal and dynamical fields observed during a case study along the coast of northern Adriatic Sea. Agreement with data is shown to be considerably increased.