Showing papers on "Sea breeze published in 1997"

Photooxidant dynamics in the Mediterranean basin in summer: Results from European research projects

Abstract: Most of the Mediterranean Sea is surrounded by mountains 1500 m or higher. Their east and south facing slopes favor the early formation of upslope winds, reinforcing the sea breezes. These slopes also act as orographic chimneys which link the surface winds directly with their return flows aloft, creating recirculations. To characterize the dynamics of pollutants in the Mediterranean basin and to compose a mosaic of the atmospheric circulations involved, the European Commission (EC) supported the following projects: (1) meso-meteorological cycles of air pollution in the Iberian Peninsula (MECAPIP), 1988–1991, intended to document the atmospheric circulations over the Iberian Peninsula; (2) regional cycles of air pollution in the west central Mediterranean area (RECAPMA), 1990–1991, which extended the characterization from the Atlantic coast of Portugal to Italy; and (3) south European cycles of air pollution (SECAP), 1992–1995, for the whole of the basin. The level of interpretation of the data and the elaboration and validation of working hypotheses across the basin have followed, in turn, with the corresponding lags in space and time. The purpose of this paper is to present a summary (to 1995) of the documented, as well as the postulated, processes involved. The MECAPIP and RECAPMA projects have shown that stacked layer systems form along the Spanish Mediterranean coasts, 2–3 km deep and more than 300 km wide, with the most recent layers at the top and the older ones near the sea. These act as a reservoir for aged pollutants to reenter land the next day, and tracer experiments have shown that turnover times are from 2 to 3 days. During the night, part of this system drifts along the coast. Under strong insolation these circulations become “large natural photochemical reactors,” where most of the NOx emissions and other precursors are transformed into oxidants, acidic compounds, aerosols, and O3 (exceeding some EC directives for several months). Finally, the preliminary analysis of the data obtained in the SECAP project supports the hypothesis that pollutants emitted in the Mediterranean basin could be transported toward the Intertropical Convergence Zone, located along northern Africa in summer, and pumped directly into the upper troposphere. If this is verified, the Mediterranean basin could be one place where all the links from the local to the global scales could be identified and documented.

Impact of sea-breeze activity on nearshore and foreshore processes in southwestern Australia

Abstract: In coastal regions sheltered from the direct impact of swell- and storm-wave activity, locally generated wind waves, particularly those associated with strong sea-breeze activity, play a dominant role in controlling nearshore and foreshore processes. Field data collected from the Perth Metropolitan Coast (western Australia) during a typical summer sea-breeze cycle, are presented. It is demonstrated that the nearshore environment responds rapidly to an increase in wind speed (up to 12 m s −1 ) during the sea breeze, resulting in considerable changes to the nearshore hydrodynamics and morphology. Incident wave energy increased during the sea breeze and was associated with development of a wind-wave field with significant wave heights up to 0.9 m. Nearshore currents responded to this change in wave climate with the development of net offshore near-bed currents and a rapid increase in the mean longshore current from −1 to 1.0 m s −1 A 10-fold increase in suspended sediment concentration and a 100-fold increase in the longshore sand transport resulted from the effects of the sea-breeze system. Erosion of the beachface was coincident with the development of the wind-wave field. Sea breeze wave-driven water circulation also completely eroded beach cusps (wavelength 20–30 m), overwhelmed the rip current system associated with the beach cusps and suppressed the infra-gravity wave frequencies in the incident wave and swash record. The beach cusps reformed after the cessation of the sea breeze. It is demonstrated that the beachface is in a constant stage of adjustment to the incident wave energy through the diurnal sea-breeze cycle alternating between dissipative and reflective morphodynamic regimes. The results may be used to determine the impact of a medium-sized storm on the beachface. It is clear that the sea-breeze system plays a major role in controlling the nearshore and foreshore processes not only in this region, but also on other geographic locations where strong sea breezes are present.

Influence of the Synoptic-Scale Flow on Sea Breezes Observed during CaPE

Abstract: Mean sea-breeze characteristics were determined by analyzing a number of sea-breeze events during offshore, parallel, and onshore flow regimes during the Convection and Precipitation/Electrification Experiment (CaPE). It was observed that offshore flow cases exhibited the widest, and relatively strongest, radar-detected thin lines. The thin-line reflectivity values steadily increased during the day. In contrast, a thin line was detected only during late afternoon on parallel flow days while no easily identifiable thin line was observed during onshore flow days. The gradients of temperature and moisture, as measured by a surface meteorological station during sea-breeze passage, were strongest and weakest during offshore and onshore flow days, respectively. In addition, the moisture and temperature gradients across the leading edge of the sea breeze steadily increased during the day and were strongest during late afternoon. Using dual-Doppler techniques, the detailed kinematic structure of the sea-...

An integrated air pollution modeling system for urban and regional scales: 2. Simulations for SCAQS 1987

Abstract: A new air quality modeling system, the surface meteorology and ozone generation (SMOG) model, is used to investigate the evolution and properties of air pollution in the Los Angeles basin during the southern California air quality study (SCAQS) intensive field program. The SMOG model includes four major components: a meteorological model, a tracer transport code, a chemistry and aerosol microphysics model, and a radiative transfer code. The fidelity of the coupled modeling system is evaluated by comparing model predictions against SCAQS data. Predictions of surface winds and temperatures are found to be in excellent agreement with measurements during daylight hours, when a strong sea breeze and mountain-upslope flows are predominant but are less reliable at night when winds are typically lighter and more variable. Winds aloft, including shear and temporal variations, are also simulated quite well, although the forecasts (which are not constrained through continuous data assimilation) tend to drift from actual conditions as time progresses. Accordingly, the large-scale flow is reinitialized each morning in the simulations. The dispersion patterns of two inert tracers released during the SCAQS period are accurately reproduced by the model. The two releases, one in the early morning hours and one around noon, led to quite different transport rates and distributions owing to the evolution of the sea breeze over die course of the day. Overall, the three-dimensional development of thermally induced winds and their influences on tracer transport in the Los Angeles basin are accurately captured by the model. The predicted surface concentrations of ozone and other key pollutants have been spatially and temporally correlated with measured abundance, and the values agree to within 25–30% for ozone, with somewhat larger mean differences for several other species. In the case of the vertical distribution of ozone, the SMOG simulations generate dense oxidant (ozone) layers embedded in the temperature inversion, explaining for the first time similar features seen during SCAQS. Sources of error and uncertainty in the simulations are identified and discussed. The broad agreement between SMOG model predictions and SCAQS observations suggests that an integrated modeling approach is well suited for representing the coupled effects of mesoscale meteorology, tracer dispersion, and chemical transformations on urban and regional air quality.

Lake‐induced atmospheric circulations during BOREAS

Abstract: Lake-induced atmospheric circulations over three lakes ranging from 3 to 10 km width are analyzed using data from three aircraft during the 1994 Boreal Ecosystem-Atmosphere Study (BOREAS). A well-defined divergent lake breeze circulation is observed over all three lakes during the day. Under light wind conditions, the lake breeze is not very sensitive to the water temperature, and the strength of the divergence over the lake decreases with increasing lake size. The boundary-layer development over the surrounding land can be very important for generating a horizontal pressure difference which drives the lake breeze. Diurnal and seasonal variations of lake breezes are investigated on the basis of repeated passes from the different aircraft at different altitudes from late spring to early fall of 1994. The lake breeze divergence increases with time during the day and reaches a maximum around 1300 LST. The latent heat flux over 10-km-wide Candle Lake increases steadily from spring to fall as the lake temperature increases. The latent heat flux over the land reaches a maximum during the summer due to evapotranspiration. The lake effect on area-averaged fluxes sometimes leads to a negative heat transfer coefficient for an averaging scale of several times the lake width.

Mesoanalysis of summertime convergence zones in central and eastern North Carolina

Abstract: It is demonstrated that it is possible to perform informative mesoanalysis of summertime convergence boundaries in the southeastern United States by combining capabilities of the new WSR-88D Doppler radar with Geostationary Operational Environmental Satellite imagery and conventional surface data. Observed phenomena are identified as thunderstorm outflow boundaries, sea-breeze fronts, horizontal convective rolls, deep synoptic-scale fronts, prefrontal troughs, shallow fronts (airmass boundaries lacking upper-level support), stationary and propagating boundaries of unknown origin, and the “Piedmont trough,” which is apparently a new feature discovered in the course of this research. The transition zone between the Piedmont and the Coastal Plain was found to be a preferred location for convergence boundaries. An unexpectedly far inland advance of the sea breeze to central North Carolina occurred in some instances. The very sensitive “clear air mode” of the WSR-88D radar, when used in combination wi...

An Observational and Numerical Study of the Nocturnal Sea Breeze. Part I: Structure and Circulation

Abstract: Characteristics of inland-penetrating nocturnal sea breezes at the Savannah River Site (SRS) in South Carolina are discussed. Detailed observations from an area tower network during the Stable Boundary Layer Experiment (STABLE) indicate passage of marine air through SRS on three different nights. Large-scale winds are directed onshore for the first two nights, resulting in similar boundary layer structure and stability on these nights, while synoptic winds on the third night are offshore, leading to stronger convergence and wedging of the marine air under the inland air mass. The Regional Atmospheric Modeling System (RAMS) is used to simulate conditions for the final two nights. General features of the sea breeze are captured by the model, including wind shifts, moisture increases, turbulence structure differences between the two nights, and the formation of Kelvin–Helmholtz billows along the interface of marine and return airflow.

Diurnal winds around lake Tanganyika

Abstract: Regular diurnal variations of coastal winds are observed around Lake Tanganyika during the dry season, when insolation is intense and the prevailing trade winds are weak. the long deep lake is at the bottom of the East African rift valley. A two-dimensional mesoscale model across the schematic rift-valley topography is used to study these local tropical winds. the full model gives a good simulation when compared with the observed winds on the east coast. It turns out that about half of the strong diurnal wind variation there, in the form of slope winds, is due to the sloping mountains. Roughly one quarter is due to the thermal lake effect (sea breeze), and one quarter is due to the existence of the south-easterly trade wind, which enhances the sea-breeze circulation component considerably during daytime, and adds on to the downslope winds during night-time. the wind field across the lake is quite variable from hour to hour and from place to place, yet predictable to a good extent during the dry season, when the external conditions are rather similar from day to day.

Recent changes in the climate at the dead sea - a preliminary study

Abstract: In the last decade pan evaporation measured at the Southern Dead Sea has significantly increased. Wind, temperature and humidity measurements at the Dead Sea starting in the 1930s as well as 3-D model simulations all seem to indicate a statistically significant change in the local climate of the Dead Sea region. The potential contribution to this climatic change through the weakening of the local land-sea breeze circulation caused by the reduction in the Dead Sea surface area in 1979–1981, is examined. It is suggested that since the breeze tempers the Dead Sea climate, its weakening has caused the air temperature to increase, the relative humidity to decrease and thus increased the pan evaporation. The climatic changes as implied by the MM4 Mesoscale PSU/NCAR model simulations, seem to fit the observed changes and to suggest a local tendency to the more arid climate that now prevails to the south of the study region.

The role of local circulations in summertime convective development and nocturnal fog in são paulo, brazil

Abstract: A non-hydrostatic, fully compressible, regional-scale numerical model of the atmosphere that includes parameterization of cloud microphysics is run in a two-dimensional mode. It uses two different observed vertical profiles of temperature, relative humidity and wind to simulate the local circulation evolution and impact on convection and nocturnal fog occurrence in Sao Paulo, Brazil. Theatmospheric behaviour generated by the model is similar to the observations of the two summer days with and without sea breeze progression over the plateau. The convective development occurs in the afternoon of the two experiments but with different features and intensities. In the experiment with sea-breeze progression, there is fog formation over the plateau during the following night, in accordance with the observations. A strong northwesterly flow acting in the lower troposphere, with intensity varying between 7 and 10 m s-1,appears as an inhibiting agent of the sea-breeze progression over the plateau and of convective development in the afternoon and of the nocturnal fog occurrence. In this case, observed gusts during the night are well simulated and appear to be related to the topography.

Influence of topography and urban heat island effects on the outbreak of convective storms under unstable meteorological conditions: a numerical study

Abstract: Analysis of observational data of convective storms in Northern England suggests that the particular combination of effects such as sea breezes, elevated terrain and the presence of large cities has an influence on the initiation and development of convective storms. To study the importance of these effects for the development of convection, a cloud physics model has been initialised with the topography and surface characteristics of Northern England. The model enabled inclusion of three principal influences: sea breezes, topography and urban heat islands. The results suggested that the presence of the Pennines, a north–south orientated ridge, could influence the initiation of convection due to its long sun-facing slopes, and to a lesser degree forced lifting along the slopes. Inclusion of urban heat island effects focused convection downwind of the principal urban areas. Copyright © 1997 Royal Meteorological Society

Sea Breeze Effects on Nearshore Coastal Processes

Abstract: The sea breeze, created by the diurnal solar heating and cooling cycle, is a well known meteorological phenomenon and occurs globally on a regular basis with varying intensity. The impact of the sea breeze system on nearshore coastal processes and sediment budget has received very little attention. In this paper, field data collected from two micro-tidal coastal regions: south-western Australia and Sri Lanka, are presented to illustrate the importance of the sea breeze system in these regions. It is shown that the rapidly changing wave climate, generated by the sea breeze, increases the cross-shore and longshore currents and sediment suspension on the beach. This results in an increase of the longshore sediment flux by up to a factor of 100. The effects of the sea breeze may be present up to 10 hours after the cessation of the sea breeze. The sea breeze system plays a major role in the coastal sediment budget in these regions.

Rainfall and Sea‐Breeze Circulation over South‐Western France

Abstract: South-western France (Aquitaine region) has an oceanic temperate climate but some climatic peculiarities (irregular patterns in isohyets) are observed along a narrow coastal belt. The spatial distribution of winter and summer precipitation shows a ‘rainy strip’ located around 20 to 40 km inland. Three features allow an explanation of this distribution: synoptic flow, sea-breeze and heterogeneous land roughness (presence of the Foret des Landes). To take into account the impact of these features, numerical simulations are examined using a three-dimensional mesoscale model. The occurrence of the forest increases the possibility of precipitation during irregular patterns in isohyets. © 1997 by the Royal Meteorological Society. Int. J. Climatol. 17: 535–549, 1997.

An Observational and Numerical Study of the Nocturnal Sea Breeze. Part II: Chemical Transport

Abstract: Chemical transport at the Savannah River Site (SRS) in South Carolina during nocturnal sea-breeze passage is examined using simulations from a three-dimensional mesoscale dynamic model [(RAMS) Regional Atmospheric Modeling System] and a Lagrangian particle dispersion model (LPDM) and supplemental surface measurements of sulfur hexafluoride (SF6) obtained during a 1988 field campaign. Plume dispersion and regional transport were characterized by nights with onshore and offshore synoptic winds. For onshore winds, the sea breeze lifts, redirects, and broadens an initially narrow plume but maintains its general structure. Regional calculations reveal particle translations exceeding 100 km under these conditions. On the other hand, with offshore synoptic winds, frontal passage leads to stronger lifting, turbulence, and vertical shearing that fragments the plume. In addition, complicated recirculation of pollutants is possible and may increase chemical concentrations in areas near the source. Observed ...

Breeze analysis by mast and sodar measurements

Abstract: During the year 1993, field measurements were carried out in a meteorological station located in the neighbourhood of Rome, 10 km from the coast (Tyrrhenian Sea). The monitoring station is composed of a 30 m mast and a three-axial Doppler sodar. A statistical analysis of data has been made in order to obtain the main parameters utilised by the dispersion model. Hourly, seasonal and conditional averages showed the strong influence of sea and land breeze circulation on the local characteristics of the atmospheric boundary layer. Such an aspect has to be considered in the numerical predictions of pollutant dispersion.

Relationships and Function of Coastal and Marine Environments

Abstract: The coastal dunes of southern Brazil are remarkably similar because Holocene sea-level changes have influenced their genesis (Pfadenhauer 1980; Schwarzbold and Schafer 1984), resulting in the sequential formation of depressions and dune ridges parallel to the shore. The most recent transgression-regression events moulded the 300–1000 m wide foredunes, with seasonally flooded freshwater marshes immediately interior of them. The flat marine terrace supplies a considerable amount of fine quartz sand to the beach (Pfadenhauer 1980), and the sandy substrate of windblown foredunes contains a high proportion of shell fragments but little organic matter (Cordazzo and Seeliger 1987). Since the tidal ranges are low (<50 cm), the dominant southeasterly and northeasterly onshore winds in the winter and summer, respectively, control seawater flooding of the beaches and shore profiles (Pfadenhauer 1980; Costa et al. 1984, 1991; Bernardi et al. 1987). Different orientations of the coast north and south of 33° S imply variations in onshore wind approach angles and impact. On the northern coast, NE onshore winds induce considerable beach-dune sand transport. In contrast, along the southern coast beach-dune sandflow is reduced because NE winds blow parallel to the shore, whilst SE winds blow directly onshore and cause inundation of beaches and landward erosion of backshore and foredune sands. Additionally, winter cold front passages lead to severe beach overwash and differentially affect sand dynamics along the northern and southern coasts.

Climatic controls of the cool human thermal sensation in a summertime onshore wind.

Abstract: Afternoon observations in summer comparing shoreline with inland atmospheric conditions were made during onshore winds at Victoria, British Columbia, Canada. The onshore wind came from a cool water surface. Mean monthly water temperatures near to shore were between 11 and 11.5° C. The onshore wind brought lower air, ground surface radiant and sky radiant temperatures; lower humidity and greater wind speed. All of these combine to produce a cooler human environment at the shoreline than inland. The relative importance of climatic elements in producing the cooler environment was assessed using sensitivity analyses with eight different human thermal exchange models/indices. Air temperature and wind speed had the greatest effect, followed by ground surface radiant temperature, sky radiant temperature and humidity. Wind speed is the most practical element to consider when trying to maximize human comfort along the shoreline.

Variability of the sea-breeze front from sodar measurements}

Abstract: Using sodar measurements of the wind in the vicinity of sea-breeze fronts, we have investigated the lateral movement of the incoming front. A characteristic of the sea-breeze front is related to periodic oscillations in wind direction, which are likely to be caused by the sea breeze and accompanying updrafts and downdrafts in the ambient flow.

A Climatology of the Sea Breeze at Cape Canaveral, Florida

Abstract: : A climatology of the Cape Canaveral, Florida sea breeze has been established using data from the warm seasons of 1995 and 1996. Data from the Cape Canaveral mesoscale tower network were used to locate the sea breeze, determine its inland penetration, and assess its time of passage. Visible satellite imagery centered over Melbourne, Florida also were used for this purpose. Radiosonde data were used to determine the large-scale flow over the region. A total of 357 days was analyzed. These days were classified as sea-breeze days, non-sea-breeze days, or undetermined. Undetermined days (40) were removed from the final sample, leaving a total of 317 days. River breezes and other local circulations were analyzed and related to the sea breeze, and the presence of convection was related to sea-breeze occurrence and large-scale flow.

Modeling of Pollutant Dispersion in Sea Breeze Conditions using a Lagrangian Model

Abstract: This work presents a numerical study of non-reactive pollutant dispersion in sea breeze conditions. Sea breeze circulation is investigated using a 3-D mesoscale meteorological model. Simulation was conducted for the area of Tarragona (Spain) which has an important petrochemical industry in the coastal region and complex terrain. Results from the meteorological model were used as input to a Lagrangian particle model in order to analyze the pollutant dispersion of an elevated plume emitting near the shoreline. The simulation was performed for 24 h and an analysis of the meteorological and concentration fields was untertaken for this time period. The results are compared with measured surface data. Good correlation exists between observed and simulated conditions indicating that the coupling of the meteorological and particle models provides a good tool for analyzing air pollution in complex situations.

The influence of topography on wind over the Sea of Japan

Abstract: Wind is the critical factor in determining regional weather patterns and climate. Also, winds over the ocean directly effect the exchange of heat, moisture and gases between the atmosphere and the ocean surface. In this paper, the wind distribution over the Sea of Japan is analyzed by using wind data observed by the NASA Scatterometer (NSCAT). A synoptic view of the wind fields over the Sea of Japan is provided in January 1997. Remarkable evidence of a land topography effect is shown as a convergence of the surface wind field during cold-air outbreaks. The Changbai mountains are located in North Korea upstream of the outbreak winds, and the wind field was deformed by them over the western part of the Sea of Japan. Strong northwesterly winds (westerly winds) of about 16 to 20 m/s were observed off Vladivostok (the Korea Peninsula). They converge while blowing over the sea. A wind shadow, in which the wind speed is less than 8 m/s, is seen downwind of the mountains and extends more than 200 km. Numerical experiments using a three-dimensional local circulation model were performed to investigate the formation mechanisms of the outbreak-wind deformation. The results shows that the land topography is essential to form the convergence of the surface winds observed by NSCAT.

Meteorological pre-processing over highly complex terrains

Abstract: A reliable method for meteorological pre-processing over complex topographies has been developed and implemented into the DETRACT code system, which is integrated into the RODOS decision support system. Shortcomings with respect to topography aspects, limited number of available stations and existing methods which depend on pure mathematics, have been tackled. The method relies on the efficient coupling of meteorology and topography. The main characteristic is the ground-attached cell classification according to land type, topography slopes and station range of influence. The interpolation scheme, for the wind field construction, is affected by the cell classification. The present method has been applied with reasonable success to two characteristic cases. First is the simulation of the MEDCAPHOT experiment in Attiki, Greece, where the regional meteorological conditions are determined by sea breeze development. Second is the simulation of the TRANSALP experiment over the Alps, where local valley winds play a key role in the meteorological situation. The simulated wind fields show that the main features are well reproduced.

Surface current response to land-sea breeze circulation in Monterey Bay, California as observed by a new multifrequency HF radar

Abstract: A new multifrequency (4-25 MHz) HF radar was installed at the Long Marine Laboratory (University of California at Santa Cruz) on the north coast of Monterey Bay CA in July, 1996. This radar is capable of observing near-surface currents at varying depths in the top two meters of the ocean. Observations were made over a three week period in March, 1997 during which there was a strong land-sea breeze circulation over Monterey Bay. Radial current measurements corresponding to depths of about 0.3, 0.5, 1.0 and 1.4 m were made during this period using HF radar data from four operating frequencies, 21.8, 13.4, 6.8 and 4.8 MHz. Fourier analysis of these data shows that very near the surface the strongest periodic component is a diurnal one corresponding to the diurnally varying surface stress from the land-sea breeze. At deeper depths the diurnal component decreases in strength, but remains dominant. A semi-diurnal component, corresponding to tidally driven current, grows in strength with increasing depth of the current measurement. Thus, multifrequency HF radar combined with deeper current measurements from buoys and moorings are able to investigate the upper layer of the coastal ocean where wind and tidally driven currents struggle for dominance. Installation and calibration of a second radar at the Moss Landing Marine Laboratory, south of Santa Cruz along the Monterey Bay coast, is in progress to allow measurement of vector currents from radial observations at the two radar sites.

Horizontal and Vertical Distributions of Atmospheric Nitrogen Dioxide on a Mountainside in the Seto Inland Sea Coast

Abstract: In the Seto Inland Sea District, most population and factories are concentrated in the narrow coastal plains. In this study, the distribution of atmospheric nitrogen dioxide (NO2) concentration was investigated on the seaside slope of Mt. Gokurakuji, Hiroshima Prefecture. The vertical concentration at an interval of every 50m from 100m altitude to the summit was measured by short- and long-term exposure methods from autumn, 1992 to spring, 1994. As a result, high NO2 concentrations were detected at altitudes of 100m and 150m, where the forest decline was outstanding, and the values decreased with elevation. With regard to seasonal fluctuations, it is relatively higher in spring and in summer. The most frequent wind direction at the southern foot of Mt. Gokurakuji was SSE In the summer, 1993 and in the spring, 1994, while in the autumn, 1993, and in the winter, 1994, it was in the NW direction. It is thought that the NO2 concentration was closely related to the horizontal wind, that is, land and sea breezes. Next, temperature profiles at night were observed on the seaside slope in June and in November, 1995, and was correlated to the NO2 concentration by the short-term exposure method. The result showed that the night-time concentration difference between the upper and lower sites was fairly large. From this, it was estimated that air pollutants are difficult to diffuse through the formation of an inversion layer, and they are not transported within the boundary layer during the night.