Sea Breeze Events Research Articles

High-frequency observations of wind-forced onshore transport at a coastal site in Baja California

We investigated the effect of the daily sea breeze on the surface flow at Bahia Salsipuedes, Baja California, Mexico. Drifter-tracking experiments were conducted over a 2-week period in July, 1999. Surface drifters were deployed daily and their trajectories tracked from a small boat for 3–7h. Wind speed and direction, as well as the vertical distribution of temperature and current velocities were measured throughout the observation period. Our results indicate that strong winds associated with the daily sea breeze at the study area can produce onshore surface currents with velocities of up to 10cms−1 (net transport of up to 2km in a diurnal cycle). There was a hyperbolic relationship between onshore wind stress and net onshore transport of the drifters. A decrease in stratification and more consistent pattern of onshore transport were associated with sustained winds >6ms−1 towards the end of the study. Progressive vector diagrams computed from near-surface currents failed to predict the trajectory of drifters, especially on days where wind forcing was more consistent in terms of direction and magnitude. We discuss the implications of these results regarding the collection of settlement data and their interpretation in terms of larval supply to coastal populations.

都市の熱収支モデルを用いた夏季の東京首都圏における大気熱収支構造の地域性の比較

Heat island phenomena in Tokyo metropolitan area has spread more and more widely. The characteristics of this heat island phenomena are different for each regional area. Therefore, it is necessary to examine the atmospheric heat balance in more detail for each regional area. In this paper, the authors have simulated urban scale climate for Tokyo metropolitan area in summer, and compared the regional characteristic of atmospheric heat balance at the center of Tokyo, the southern part of Saitama, and Ichihara city, based on an "Urban Heat Balance Model". From the results of simulation and observation data, the sea breeze has great impacts on the climate at the center of Tokyo. The effect of sea breeze on the southern part of Saittama is not strong. At Ichihara city, the wind from windward side has some affect on the climate of this area. Additionally, the authors tried to classify the regional characteristic of air temperature by average temperature and diurnal range.

Cloud‐to‐ground lightning enhancement over Southern Louisiana

Fourteen years (1989–2002) of cloud‐to‐ground (CG) lightning data show a significant enhancement of lightning associated with Lake Charles and Baton Rouge, Louisiana. A peak density value of 7 flashes km−2 yr−1 exists on the western side of the Lake Charles urban area. A comparison of the Louisiana CG flash density distribution with the locations of PM10 (particulate matter less than 10 μm in diameter) sources strongly suggests that pollution plays a key role in lightning enhancement. Urban and sea breeze effects can be neglected. The values of median peak negative current show a sharp difference between land and the Gulf of Mexico; inland values are near 24 kA, while over the Gulf waters immediately offshore are over 30 kA. This observation, along with a relative minimum of negative peak current from the mouth of the Mississippi River southeastward seems to support the hypothesis that the underlying surface characteristics influence the calculated negative current distribution.

Identification and characterization of sea breeze days in northern France using singular value decomposition

AbstractDays subject to the development of sea breeze circulations are shown for the months of June and July 2000 in the north of France using an algebraic analysis, the singular value decomposition (SVD). The analysis is performed upon the NOAA‐AVHRR radiometric data (with the surface temperature data from the 22 available stations located in the study area). The geostatistical results show the characteristics of a sea breeze blowing from the English Channel and the North Sea. Meteorological situations with a sea breeze are not the prevailing mode in summer over the northern coast of France, but the sea breeze effect can be shown more than 40 km inland. In addition, the results of the SVD allow one to discriminate different weather systems associated with the thermo‐topographic winds. Copyright © 2003 Royal Meteorological Society

Synoptic-Scale Controls on the Sea Breeze of the Central New England Coast

Abstract Using routinely available hourly surface observations and United States surface analyses for 2001, a method was developed for predicting sea-breeze events. The method is adaptable to any coastal region in the world where surface data are available. Specific prediction guidelines have been developed using Portsmouth, New Hampshire, as the forecast site. Using Portsmouth METARs (translated roughly from the French as aviation routine weather report), 167 days were determined to have conditions favorable for the occurrence of a sea breeze. Each of these 167 days are classified as either sea-breeze, marginal, or non-sea-breeze events. Sea breezes were defined as insolation-driven local onshore winds. Marginal events were weak sea breezes. Non-sea-breeze events were those days on which sufficient insolation was present but failed to produce a sea breeze at Portsmouth. The surface analyses for these 167 days were used to define a set of synoptic classes based on the arrangement of large-scale pressure s...

Conditional Wavelet Technique Applied to Aircraft Data Measured in the Thermal Internal Boundary Layer During Sea-Breeze Events

We describe a wavelet-based technique to determine the spectral turbulentcontribution to the vertical flux of sensible heat in a position-wavelength representation. This technique combines awavelet transform (Morlet wavelet) with conditional sampling. We apply this methodto aircraft datacollected during a sea-breeze circulation (BEMA97 experiment) with heterogeneousturbulence conditions horizontally and vertically as well. The turbulent fluxes are analysed with the conditional wavelet techniqueas a function of the wavelength and the horizontal distance.The turbulent processes within the thermal internal boundary layer associatedwith the sea breeze are clearly identified. The results exhibit the wavelength bands through which the upward flux (originating fromthe surface) and the downward flux (originating from the top of theboundary layer) are important.

Jacobs receives AstraZeneca contract

During July 2008, we used an elastic backscattering LIDAR to monitor the aerosol vertical distribution at the coastal area of Dunkerque, France. Here we report the sea breeze event which was observed with more highlighted effect of aerosol on 25 July. By combining LIDAR measurements with Sun photometer-retrieved aerosol optical thickness, we estimated an average LIDAR ratio of 33 sr (± 14 sr) for the estimation of aerosol extinction profiles during the sea breeze. The LIDAR derived aerosol extinction in the first 200 m is clearly affected by the sea breeze and increases by more than 100% at the time of sea breeze arrival. A sharp convective boundary layer height decrease is observed in the LIDAR data due to the formation of the thermal internal boundary layer in the lowest part of the sea-to-land flow. PM2.5 concentration increases due to the thermal internal boundary layer formation and reaches its maximum between 1 and 2h after the front overpass. Except during the front overpass, the PM2.5 is well correlated to the inverse of the mixing height detected by the LIDAR.

名古屋市中川運河における海上遡上が体感気候に及ぼす影響

Water surfaces so as canals and rivers are expected to cool urban hot climate in summer. The objective of this paper is to clarify the effect of sea breeze along Nakagawa Canal in Nagoya on the urban sensational climate. Air temperature, humidity, wind speed, wind direction and solar radiation were observed along the canal and in the neighborhood of Nagoya station. The standard new effective temperatures SET* modified with the effect of solar radiation were calculated by the observation data. The results demonstrated that the sea breeze reached up to Nagoya station, and air temperature began to increase when wind speed slowed down. SET* under the sea breeze blowing kept to be lower and cooling effect of sea breeze on sensational climate was found.

Wind-driven circulation in coastal and marginal seas

This paper considers the spatial and temporal detail in knowledge of the wind that is required to estimate various consequences of wind forcing: coastal trapped waves, sea-surface fluxes related to the frequency spectrum, storm surges, coastal downwelling and upwelling, wind-stress curl and downwelling or upwelling, wakes and stratification, diurnal and seasonal stratification, coastal currents and plumes, sea breeze effects, and surface waves. For many of these phenomena, winds need to be resolved on scales of the order 10 km (related to topographically induced structure) and 1‐3 h (owing to rapid and non-linear responses). Relative errors in wind speed are typically multiplied by 2 or 3 for momentum inputs and mixing effects, respectively, which are particularly dependent on peak wind speeds (requiring correspondingly fine temporal resolution).

Observations and modeling of coastal internal waves driven by a diurnal sea breeze

During the Internal Waves on the Continental Margin (IWAVES) field experiments of 1996 and 1997 off of Mission Beach, California (32.75°N), we observed energetic, diurnal‐band motions across the entire study site in water depths ranging from 15 to 500 m and spanning a cross‐shore distance of 15 km. The spectral peak of the currents was at the diurnal frequency (σDi = 1 cpd) and was sufficiently well resolved to be clearly separated from the slightly higher local inertial frequency (ƒ = 1.08 cpd). These motions were surface enhanced and clockwise circularly polarized and had an upward phase propagation speed of ∼68 m d−1, suggesting that the motions were driven predominantly by the diurnal sea breeze. However, the downward energy (upward phase) propagation seems irreconcilable with the subinertial diurnal period, and moreover, the intermittent diurnal current events were not obviously associated with diurnal sea breeze events. We rationalize these features using a flat‐bottomed linear modal sum internal wave model that includes advection and refraction due to subtidal alongshore flow, V(x, t). Fluctuations in V at the observing site can change the “effective” local Coriolis parameter ƒ + Vx by as much as 50%, thus making the diurnal motions at different times effectively either subinertial or superinertial. The model is integrated numerically for 200 days at a latitude of 32.75°N under different wind and subtidal flow conditions: purely diurnal winds and no V, purely diurnal winds and a time‐independent V, narrow‐band diurnal winds and no V, and narrow‐band diurnal winds and subtidal, time‐dependent V. Model diurnal currents forced by narrow‐band diurnal winds and subtidal V show complex offshore structure with realistic intermittency and spectral broadening. This study suggests that continental margins in the vicinity of the 30° latitude (where σDi = ƒ) are regions that could potentially produce energetic, sea breeze‐driven baroclinic motions and that these motions could be regulated by the vorticity of the local subtidal currents.

Effect of Sea Breeze on Air Pollution in the Greater Athens Area. Part II: Analysis of Different Emission Scenarios

The Mediterranean Campaign of Photochemical Tracers–Transport and Chemical Evolution that took place in the greater Athens area from 20 August to 20 September 1994 has confirmed the role of sea-breeze circulation in photochemical smog episodes that had been suggested already by a number of experiments and numerical studies. The meteorological and photochemical modeling of this campaign were discussed in Part I. Part II focuses on the study of the 14 September photochemical smog event associated with a sea-breeze circulation. The objective of the study is to identify and to understand better the nonlinear processes that produce high ozone concentrations. In particular, the effect of land and sea breezes is investigated by isolating the effect of nighttime and daytime emissions on ozone concentrations. The same principle then is used to isolate the effect on ozone concentrations of the two main sources of emissions in the greater Athens area: the industrial area around Elefsis and the Athens urban area. Last, the buildup of ozone from one day to another is investigated. From this study, it comes out that ozone production in the Athens area is mainly a 1-day phenomenon. The increased values of photochemical pollutant (up to 130 ppb at ground level) reached during summertime late afternoons on mountain slopes to the north and northeast of the city are related mainly to the current-day emissions. Nevertheless, the recirculation of old pollutants can have an important effect on ozone concentrations in downtown Athens, the southern part of the peninsula, and over the sea, especially near Aigina Island.

Effect of Sea Breeze on Air Pollution in the Greater Athens Area. Part I: Numerical Simulations and Field Observations

Numerical simulations compared with field measurements are used to explain the effect of sea breezes on photochemical smog episodes in Athens during the Mediterranean Campaign of Photochemical Tracers on 12–14 September 1994. The numerical simulations, performed using a nonhydrostatic vorticity mesoscale model coupled to the Lurmann–Carter–Coyner photochemical module, are compared with ground-based lidar and aircraft measurements. The current analysis shows that the three selected days include the two main summertime flow patterns characteristic of the Athens peninsula, each of which lead to significantly different pollution amounts. On 12 and 13 September, a strong, northerly synoptic wind reduces the inland penetration of the sea breeze so that ozone concentrations within the greater Athens area remained low. In contrast, the weaker synoptic forcing on 14 September allowed the development of sea breezes over the whole peninsula and high ozone concentrations were found north and east of the city. An analysis based on pollution amounts and wind patterns is carried out to divide the peninsula into regions, each of which corresponds to a specific pollutant behavior.

Numerical simulation of wind-driven circulation in Lake Tanganyika

Abstract A three-dimensional numerical circulation model of Lake Tanganyika, developed within the Lake Tanganyika Research Project (LTR-FAO/FINNIDA) is described. The model is based on full non-linear hydrodynamics equations, modified according to hydrostatic and Boussinesq approximations. A space-splitting scheme is used for numerical approximation of governing equations. Numerical experiments with different wind loading revealed the rather complicated flow structure in Lake Tanganyika. Data for model validation have been collected since May 1993. Main hydrological and meteorological parameters such as water level, wind speed and direction, air temperature, humidity and water temperature are recorded with automatic devices. A simple Lagrangian approach with floating buoys and GPS system is used for current measurements. The obtained surface velocities in different locations lake-wide were compared with the calculated surface currents. Agreement between measured and simulated velocities was satisfactory. Accuracy of the simulations depends on the accuracy of the wind forcing reconstruction. Regular strong winds are observed over Lake Tanganyika during the dry season, a period of trade winds that starts at the end of May and lasts until late August or early September. Numerical experiments with a mesoscale meteorological model (Savijärvi, H., 1995. Sea breeze effects on large–scale atmospheric flow. Contr. Atmos. Phys. 68 335–344) showed that the lake-land breeze system is intensified during this period. The collected data and the numerical experiments with the circulation model provide a solid base for understanding the main hydrophysical processes on a lake-wide scale. Important knowledge has also been obtained on the spatial and temporal dynamics of currents.

Numerical simulation of wind-driven circulation in Lake Tanganyika

A three-dimensional numerical circulation model of Lake Tanganyika, developed within the Lake Tanganyika Research Project (LTR-FAO/FINNIDA) is described. The model is based on full non-linear hydrodynamics equations, modified according to hydrostatic and Boussinesq approximations. A space-splitting scheme is used for numerical approximation of governing equations. Numerical experiments with different wind loading revealed the rather complicated flow structure in Lake Tanganyika.Data for model validation have been collected since May 1993. Main hydrological and meteorological parameters such as water level, wind speed and direction, air temperature, humidity and water temperature are recorded with automatic devices. A simple Lagrangian approach with floating buoys and GPS system is used for current measurements.The obtained surface velocities in different locations lake-wide were compared with the calculated surface currents. Agreement between measured and simulated velocities was satisfactory. Accuracy of the simulations depends on the accuracy of the wind forcing reconstruction. Regular strong winds are observed over Lake Tanganyika during the dry season, a period of trade winds that starts at the end of May and lasts until late August or early September. Numerical experiments with a mesoscale meteorological model (Savijärvi, H., 1995. Sea breeze effects on large-scale atmospheric flow. Contr. Atmos. Phys. 68 335–344) showed that the lake–land breeze system is intensified during this period.The collected data and the numerical experiments with the circulation model provide a solid base for understanding the main hydrophysical processes on a lake-wide scale. Important knowledge has also been obtained on the spatial and temporal dynamics of currents.

The effect of sea breeze on beach morphology, surf zone hydrodynamics and sediment resuspension

Beach morphodynamic processes were investigated over part of a sea breeze cycle on a microtidal, low wave energy sandy beach in southwestern Australia. Prior to the onset of the sea breeze, offshore winds with speeds less than 5 m/s prevailed. During the sea breeze, alongshore winds with speeds higher than 10 m/s were experienced. The sea breeze induced pronounced changes to the nearshore morphodynamics which were similar to that of a storm event: (1) root mean square wave height increased from 0.3 to 0.5 m; (2) zero-upcrossing wave period decreased from 8 to 4 s; (3) mean cross-shore flows reached velocities of 0.2 m/s directed offshore; and (4) the longshore current increased in strength from 0.05 to 1.0 m/s. Before the sea breeze, sediment resuspension typically occurred during isolated high-wave events associated with the passage of wave groups. Flux coupling between the wave-oscillatory currents and the suspended sediment (Jaffe, B.E., Sternberg, R.W., Sallenger, A.H., 1984. The role of suspended sediment in shore-normal beach profile changes. Proc. 19th Int. Conf. Coastal Engineering, ASCE, pp. 1983–1996) induced net onshore suspended sediment transport, resulting in beachface accretion and a steepening of the foreshore profile. In contrast, during the sea breeze, sediment resuspension was almost continuous. The suspended sediment load increased six-fold and, as a consequence, the longshore suspended sediment transport rate increased by a factor of 100. During the sea breeze, cross-shore transport was directed offshore and primarily associated with mean offshore flows. This resulted in erosion of the beachface and deposition in the surf zone and, consequently, a flattening of the beach profile. The suspended sediment load was strongly related to the Shields parameter defined for the combined action of waves and currents. Investigation of the suspended sediment profiles indicated that the degree of vertical mixing, parameterised by the sediment diffusion coefficient, increased with distance from the bed. In addition, the sediment diffusion coefficient exhibited a large temporal variation, ranging between 0.005 and 0.018 m 2/s. The variability in the sediment diffusion coefficient is possibly due to changes in the sea bed morphology.

Easterly Wind Storms over Israel

Continental wind storms are common along the Mediterranean coast. Along the northern coast they are mostly cold, similar to the Bora or the Mistral, and along the southern coast they are mostly warm, e.g., the Ghibli or the Shirocco. At the eastern Mediterranean basin and the Levant region, these storms are intermittently warm and cold during the same season and often even during the same event. Quasi-stationary systems, as well as moving disturbances, are the cause of such wind storms. Accordingly, the resulting weather conditions may be extremely converse due to the characteristics of the advected airmass. Specific regions in Israel, sensitive to easterly storms, are influenced by these wind storms for about 10% of the year (e.g., the westerly slopes of the mountains and valleys with west-east orientation). The frequency, however, of widespread storms covering the entire region is only approximately 1.4% of the entire year. These wind storms are therefore classified in the present study according to their climatological and synoptic characteristics; indicating that the dominant synoptic situation is the Red-Sea trough and the warm advections. These storms appear only from October-May and are most frequent during the cold season. The diurnal course is characterized by a strengthening in the morning hours and a weakening at noon and in the afternoon hours, due to the opposing effect of the westerly sea breeze, suppressing the easterly winds and the effect of katabatic winds. Nevertheless, synoptic conditions may contribute to this tendency as well. Accordingly, a significant increase in the frequencies of easterly storms, in relation to distance from the seashore has been identified. Although most of the stormy days are with westerly winds, the easterly wind storms has vast environmental implications, creating damage especially to agriculture and occasionally also to property and life; coastal flooding, potential air pollution, intensifying of forest fires and occasionally dust and sand storms.

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

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-breeze circulation for offshore and onshore flow regimes is presented. In particular, detailed measurements of the sea-breeze return flow at upper levels are presented for both offshore and onshore flow events for the first time. The observed inland propagation speed for offshore and parallel flow events is consistent with calculated values for density currents. Onshore flow events, however, are observed to move inland at a rate that is slower than what is expected for a density current.

Thermal mesoscale circulations on the Baltic coast: 1. Numerical case study

A three‐dimensional mesoscale numerical model is utilized to investigate a well‐documented seabreeze event taken from experimental data. The simulations are not set up as a model validation. Instead, the model is driven by generalized and simplified initial and boundary conditions extracted from the field experiment data. The aim is to simulate the main characteristics, if not all the details, of the observed case. This generates a comprehensive set of fully three‐dimensional and time dependent data that can be used to obtain a more complete description of the case characteristics. Analyzing these data facilitates understanding of the flow mechanisms in more detail. Once such a control simulation is done, the case can be resimulated for slightly different forcing and the cause of observed features can be illuminated. Significant features in the simulation are the significant temperature difference between land and sea, moderate coastal terrain, and an almost 90° change in coastline orientation. Among the conclusions from the control simulation presented here is that the seabreeze stage is preceded by a coastal wind jet stage with a significant influence on the flow by the quite moderate topography. This is due to the ratio of the depth of the marine boundary layer to the terrain height; the terrain is acting on the flow in three ways. First, the stability impedes vertical motions and the terrain thus acts as a barrier inhibiting geostrophic balance. The flow is blocked and deflected down the synoptic‐scale pressure gradient. Second, it generates a perturbation in the temperature field causing local baroclinicity and a thermal wind. Finally, a slope flow is also generated that acts to enhance the temperature perturbation by advection of cold air to the coastal zone. A seabreeze evolves on both coastlines. The first forms on the offshore flow coast but remains stationary at the shoreline until the second, later, seabreeze on the almost perpendicular coastline, where the coastal jet dominates the flow well into the morning, moves inland and removes the offshore flow balancing the first seabreeze at the shoreline. After this obstruction is removed, the initial seabreeze rapidly propagates inland.

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

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.

Characteristics of temperature fields and its diurnal variations in the the Kanto district in summer

In general, the sea and land breezes are said to have a much effect on the heat island convection. The characteristics of sea and land breeze, however, depend much on daily larger scale conditions, such as the mesoscale pressure distribution. Thus it is needed to tolerate the local heat island phenomena. This study is, therfore, aimed firstly at investigating the existing sea and land breeze effect on the heat island phenomena in this area, and then at evaluating the effect of geostrophic wind on the convection.