Breeze Flow Research Articles

Some Observational and Modeling Studies of the Atmospheric Boundary Layer at Mississippi Gulf Coast for Air Pollution Dispersion Assessment

Coastal atmospheric conditions widely vary from those over inland due to the land-sea interface, temperature contrast and the consequent development of local circulations. In this study a field meteorological experiment was conducted to measure vertical structure of boundary layer during the period 25-29 June, 2007 at three locations Seabee base, Harrison and Wiggins sites in the Mississippi coast. A GPS Sonde along with slow ascent helium balloon and automated weather stations equipped with slow and fast response sensors were used in the experiment. GPS sonde were launched at three specific times (0700 LT, 1300 LT and 1800 LT) during the experiment days. The observations indicate shallow boundary layer near the coast which gradually develops inland. The weather research and forecasting (WRF) meso-scale atmospheric model and a Lagrangian particle dispersion model (HYSPLIT) are used to simulate the lower atmospheric flow and dispersion in a range of 100 km from the coast for 28-30 June, 2007. The simulated meteorological parameters were compared with the experimental observations. The meso-scale model results show significant temporal and spatial variations in the meteorological fields as a result of development of sea breeze flow, its coupling with the large scale flow field and the ensuing alteration in the mixing depth across the coast. Simulated ground-level concentrations of SO2 from four elevated point sources located along the coast indicate diurnal variation and impact of the local sea-land breeze on the direction of the plume. Model concentration levels were highest during the stable morning condition and during the sea-breeze time in the afternoon. The highest concentrations were found up to 40 km inland during sea breeze time. The study illustrates the application of field meteorological observations for the validation of WRF which is coupled to HYSPLIT for dispersion assessment in the coastal region.

Application of high resolution land use and land cover data for atmospheric modeling in the Houston–Galveston metropolitan area, Part I: Meteorological simulation results

To predict atmospheric conditions in an urban environment, the land surface processes must be accurately described through the use of detailed land use (LU) and land cover (LC) data. Use of the U.S. Geological Survey (USGS) 25-category data, currently in the Fifth-generation Mesoscale Model (MM5), with the Noah land surface model (LSM) and MRF (medium-range forecast) planetary boundary layer (PBL) schemes resulted in the over-prediction of daytime temperatures in the Houston downtown area due to the inaccurate representation as a completely impervious surface. This bias could be corrected with the addition of canopy water in the urban areas from the evapotranspiration effects of urban vegetation. A more fundamental approach would be to utilize an LULC dataset that represents land surface features accurately. The Texas Forest Service (TFS) LULC dataset established with the LANDSAT satellite imagery correctly represents the Houston–Galveston–Brazoria (HGB) area as mixtures of urban, residential, grass, and forest LULC types. This paper describes how the Noah LSM and PBL schemes in the MM5 were modified to accommodate the TFS-LULC data. Comparisons with various meteorological measurements show that the MM5 simulation made with the high resolution LULC data improves the boundary layer mixing conditions and local wind patterns in the Houston Ship Channel, which is a critically important anthropogenic emission area affecting the HGB air pollution problems. In particular, when the synoptic flows are weak, the improved LULC data simulates the asymmetrically elongated Houston heat island convergence zone influencing the location of the afternoon Gulf of Mexico sea-breeze front and the Galveston Bay breeze flows. This paper is part I of a two-part study and focuses on the meteorological simulation. In part II, effects of using the different meteorological inputs on air quality simulations are discussed.

Remote sensing of PBL meteorology and air quality: the outcome of the ESCOMPTE experiment

In the French Mediterranean basin, the large city of Marseille and its industrialized suburbs (oil plants in the Fos-Berre area) are major pollutant sources which cause frequent and hazardous pollution episodes especially in summer when intense solar heating enhances the photochemical activity and when sea-breeze circulation redistributes pollutants further north in the countryside. This paper summarizes the findings of five years of research on the sea-breeze in southeastern France and related mesoscale transport and dilution of pollutants within the ESCOMPTE program held in June and July 2001 (field experiment to constraint models of atmospheric pollution and emissions transport), obtained thanks to a composite observing system and a combination of remote sensing and in situ systems which produced a wealth of data. Indeed, the combination of established and novel and highly sophisticated remote sensing instruments with conventional in situ measurements (dense surface network and radiosondes) allowed to capture previously unseen details of the fine structure of the sea breeze, allowed unprecedented insight into the structure of the sea breeze flow and its contribution to ozone redistribution and allowed the validation of ultrahigh-resolution numerical research and weather prediction models as well as chemistry transport models.

Variability of three-dimensional sea breeze structure in southern France: observations and evaluation of empirical scaling laws

Abstract. Sea-breeze dynamics in southern France is investigated using an airborne Doppler lidar, a meteorological surface station network and radiosoundings, in the framework of the ESCOMPTE experiment conducted during summer 2001 in order to evaluate the role of thermal circulations on pollutant transport and ventilation. The airborne Doppler lidar WIND contributed to three-dimensional (3-D) mapping of the sea breeze circulation in an unprecedented way. The data allow access to the onshore and offshore sea breeze extents (xsb), and to the sea breeze depth (zsb) and intensity (usb). They also show that the return flow of the sea breeze circulation is very seldom seen in this area due to (i) the presence of a systematic non zero background wind, and (ii) the 3-D structure of the sea breeze caused by the complex coastline shape and topography. A thorough analysis is conducted on the impact of the two main valleys (Rhône and Durance valleys) affecting the sea breeze circulation in the area. Finally, this dataset also allows an evaluation of the existing scaling laws used to derive the sea breeze intensity, depth and horizontal extent. The main results of this study are that (i) latitude, cumulative heating and surface friction are key parameters of the sea breeze dynamics; (ii) in presence of strong synoptic flow, all scaling laws fail in predicting the sea breeze characteristics (the sea breeze depth, however being the most accurately predicted); and (iii) the ratio zsb/usb is approximately constant in the sea breeze flow.

Wind flow and photochemical air pollution in Thessaloniki, Greece. Part I: Simulations with the European Zooming Model

The European Zooming Model (EZM) is applied to simulate the wind flow and the pollutant transport and transformation in the Greater Thessaloniki area (GTA) during a day characterised by weak synoptic forcing and a pronounced sea breeze circulation. Two chemical reaction mechanisms of different complexities, KOREM and EMEP, are used for these simulations. The evolution of the wind field and particularly the development of the sea/land breeze flow are investigated in relation to ozone concentration patterns. Comparison of model results to observations at a large number of locations showed the considerable skill of the model in predicting the major mesoscale features affecting the GTA: the sea breeze onset time and development, its inland penetration as well as its intensity. According to both observations and model results, ozone levels are kept at moderate levels. They are decisively affected by the break-up of the night-time inversion and the onset of the sea breeze. The compact mechanism KOREM is very sensitive to the VOC/NO x emission ratio. When this ratio is close to unity, i.e. inside urban areas, KOREM performs very well proving its appropriateness for regulatory use in such environments. The more sophisticated EMEP mechanism underestimates urban ozone levels but performs very well in rural areas remaining the most reliable choice for regional scale applications.

Regional accuracy of QuikSCAT gridded winds

The quality of gridded 00 UTC and 12 UTC QuikSCAT wind speed fields provided by the Florida State University (FSU) and NASA Jet Propulsion Laboratory (JPL) are analysed over the Bay of Bengal during May–August 2001. Additionally, an examination of these fields is performed over the Gulf of Mexico for the May–August period from 2001 to 2003. Both 00 UTC and 12 UTC time almost coincide with QuikSCAT sampling times (twice a day) and correspond to either early morning or late evening local time over these regions. The primary restriction for generating accurate maps with a temporal resolution of 12 hours and less is a lack of adequate sampling. Due to non‐uniform spatial‐temporal sampling of the scatterometer, interpolation procedures cannot provide proper estimates in data gaps over the regions not covered by a swath. Wind speed autocorrelation coefficients for gridded datasets have been compared with that of original QuikSCAT data and buoy winds. It is shown that the spatial and temporal interpolation used to obtain these datasets results in smoothing of the QuikSCAT wind speeds, reducing their original variance. This smoothing is amplified where substantial diurnal wind variability occurs. A comparison with buoy data shows that FSU and JPL gridded fields are unable to reproduce correctly observed low correlations in wind speed between morning and evening breeze flows and diurnal variability of winds, leading to a reduced difference between 00 UTC and 12 UTC values in comparison with buoys and swath QuikSCAT data. Rather, the FSU and JPL maps describe daily mean fields. Another consequence of the spatial‐temporal interpolation is that the winds are distorted at a frequency matching the dominant sampling interval (3–4 days) of QuikSCAT measurements over the Bay of Bengal.

Investigation on the fine structure of sea-breeze during ESCOMPTE experiment

Surface and remote-sensing instruments deployed during ESCOMPTE experiment over the Marseille area, along the Mediterranean coast, were used to investigate the fine structure of the atmospheric boundary layer (ABL) during sea-breeze circulation in relation to pollutant transport and diffusion. Six sea-breeze events are analyzed with a particular focus on 25 June 2001. Advection of cool and humid marine air over land has a profound influence on the daytime ABL characteristics. This impact decreases rapidly with the inland distance from the sea. Nearby the coast (3 km inland), the mixing height Zi rises up to 750 m and falls down after 15:00 (UT) when the breeze flow reaches its maximum intensity. A more classical evolution of the ABL is observed at only 11-km inland where Zi culminates in the morning and stabilizes in the afternoon at about 1000 m height. Fine inspection of the data revealed an oscillation of the sea-breeze with a period about 2 h 47 min. This feature, clearly discernable for 3 days at least, is present in several atmospheric variables such as wind, temperature, not only at the ground but also aloft in the ABL as observed by sodar/RASS and UHF wind profilers. In particular, the mixing height Zi deduced from UHF profilers observations is affected also by the same periodicity. This pulsated sea-breeze is observed principally above Marseille and, at the northern and eastern shores of the Berre pond. In summary, the periodic intrusion over land of cool marine air modifies the structure of the ABL in the vicinity of the coast from the point of view of stability, turbulent motions and pollutants concentration. An explanation of the source of this pulsated sea-breeze is suggested.

A model‐aided investigation of winter thermally driven circulation on the Italian Tyrrhenian coast: A case study

Data collected during a campaign carried out in and around Rome in February 1996 using sodars, tethered balloon, and surface data suggest the development of a winter sea breeze that could not be detected by conventional data and analyses. A model‐aided study is performed to verify the development of thermally driven local circulation and to prove the onset of a winter sea breeze regime, propagating inland and interacting with the urban heat island (UHI). The area of interest for the study is the central part of Italy (latitude 41°–43°N, longitude 10°–16°E). The MM5 mesoscale model was used at high resolution: three nested domains with up to 3 km of grid resolution were used in the area where the sea breeze was observed. To highlight the effect of the sea breeze, a simulation with a thick cloud layer in the innermost domain was performed. By removing the cloud layer the diurnal evolution of the horizontal temperature gradient led to the development of the sea breeze and the UHI circulation, in agreement with the data. Sensitivity tests were carried out to evaluate the effect of land use resolution and of satellite‐retrieved/climatological sea surface temperature on the simulation results. Doppler‐sodar data recorded at three sites, tethersonde profiles, and surface data were used to verify the results. As expected, using high‐resolution land use and the daily sea surface temperature retrieved by satellite observations led to improvements in the local circulation produced by the model. However, the model falls short in reproducing some of the sea breeze characteristics. It finds that the sea breeze starts too early and lasts for a shorter time than the observed one does, and the wind direction shows a too strong northerly component. Also, it slightly underestimates the daily temperature pattern. The interaction of the urban heat islands of Rome and Ostia with the sea breeze flow is analyzed to explain the causes of these discrepancies.

Recirculation of coastal urban air pollution under a synoptic scale thermal trough in Perth, Western Australia

Air pollutant recirculation is a common feature of coastal cities as a result of the diurnal variation of the land/sea breeze circulation. On the western coast of Australia, a thermally induced synoptic scale trough interacts with this local circulation to enhance the sea breeze flow, allowing pollutant to penetrate further inland. As well a low wind speed zone formed offshore near the trough axis leads to increased ozone concentrations and the rotation of the trough axis during its onshore movement spreads these higher concentrations of air pollutant over a larger area.

A laboratory investigation of land and sea breeze regimes

A laboratory experiment has been performed to simulate land and sea breeze (LSB) flows occurring in the atmosphere in the absence of a mean geostrophic wind (pure breeze). The experiment has been carried out in a temperature-controlled water tank. Three CCD video cameras have been utilised to acquire the images of the flow field produced by temperature gradients. Particle tracking velocimetry (PTV) is applied to evaluate the velocity field in a vertical section of the tank illuminated by a laser light sheet. Furthermore, temperature–time histories have been carried out by means of a thermocouple array positioned along a vertical profile. The system has been employed to generate and analyse the global circulation and the dynamics of the sea breeze front.

Inland Propagation of Sea Breeze under Opposing Offshore Wind

According to past experience, the nearly stagnant conditions caused by the presumed equilibrium between the Saronikos Gulf sea breeze and an opposing synoptic flow is identified as the principal mechanism leading to high pollution episodes in Athens during the summer. However, previous experimental work has not examined in detail the interaction of the sea breeze flow with the opposing background flow. In this context, recent experimental work covering the basic key-locations of the Athens Basin focused on the inland propagation of the southerly sea breeze from the coast to the northern part of the basin mainly under moderate northerly background wind. During this campaign, a network of four meteorological stations established along the Athens Basin and a high range acoustic sounder at the centre of Athens operated over a two months time period in the summer of 1993. In addition, tethered balloon flights in the centre of Athens and on a sea vessel about 15 km offshore were employed during an experimental day with moderate opposing background wind. The results from this experimental campaign include the documentation of the sea breeze delay and its intensity as a function of a sea breeze index and features of the vertical structure of the sea breeze over land as well as over sea.

Finite analytic method and its applications: a review

Abstract This paper describes the development of the finite analytic (FA) method and several engineering applications. In the finite analytic method, the governing differential equations are discretized into algebraic equations based on an analytic solution on the small computational element. Nine-point and five-point FA discretization schemes for two-dimensional Navier-Stokes equations are described for simple and complex boundaries. A 19-point FA discretization scheme for three-dimensional Navier-Stokes equations is also presented. The finite analytic method exhibits the properties of stability, convergence and grid independence. It is also shown that the FA method can be successfully used in problems with irregular domains. Evidence of the versatility of the FA method is demonstrated in successful modeling of two-dimensional turbulent sea breeze and three-dimensional channel flow with conjugate heat transfer.

Influence of sea breeze flows on air pollution over the attica peninsula

In the frame of the APSIS project (Athenian Photochemical Smog Intercomparison of Simulations) simulations of the flow and the air pollution over the Attica Peninsula have been carried out. The simulations are performed with the model system KAMM/DRAIS for 25 May 1990, using the RADM gas-phase chemical mechanism. They show the influence of the sea breeze on the diurnal cycle of the NO, NO 2 and O 3 concentrations in the Greater Athens Area. The formation of ozone due to industrial emissions at the coast of the Thriassion plain and from the traffic emissions in the city of Athens leads to peak ozone concentrations of nearly 400 μg m −3 northeast of the centre of the city. Measurements of wind speed, wind direction and temperature support that the development of the sea breeze in the basin of Athens is well described by the model. The comparison between the measured and calculated concentrations shows at most of the stations a satisfying agreement.

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.

Mixed-layer heat advection and entrainment during the sea breeze

A model is developed to simulate the potential temperature and the height of the mixed layer under advection conditions. It includes analytic expressions for the effects of mixed-layer conditions upwind of the interface between two different surfaces on the development of the mixed layer downwind from the interface. Model performance is evaluated against tethersonde data obtained on two summer days during sea breeze flow in Vancouver, Canada. It is found that the mixed-layer height and temperature over the ocean has a small but noticeable effect on the development of the mixed layer observed 10 km inland from the coast. For these two clear days, the subsidence velocity at the inversion base capping the mixed layer is estimated to be about 30 mm s−1 from late morning to late afternoon. When the effects of subsidence are included in the model, the mixed-layer height is considerably underpredicted, while the prediction for the mean potential temperature in the mixed layer is considerably improved. Good predictions for both height and temperature can be obtained when values for the heat entrainment ratio,c, 0.44 and 0.68 for these two days respectively for the period from 1000 to 1300 LAT, were used. These values are estimated using an equation including the additional effects on heat entrainment due to the mechanical mixing caused by wind shear at the top of the mixed layer and surface friction. The contribution of wind shear to entrainment was equal to, or greater than, that from buoyant convection resulting from the surface heat flux. Strong wind shear occurred near the top of the mixed layer between the lower level inland flow and the return flow aloft in the sea breeze circulation.

A Comparative Study of Various Parameterizations of the Planetary Boundary Layer in a Numerical Mesoscale Model

Abstract Various parameterizations of the planetary boundary layer (PBL) currently used in three-dimensional (3D) mesoscale models are compared with a more complex scheme including a turbulent kinetic energy (TKE) equation. In the first set of simulations made with a ID model against the classical Wangara data, the mean wind, temperature and moisture calculated in the PBL are nearly insensitive to the choice of the parameterization. In the second set of simulations, the TKE parameterization is used in a 3D mesoscale model to simulate sea breeze flows over south Florida. A comparison is presented with previous simulations of Pielke, and Pielke and Mahrer, for the mean flow, and with the third-order turbulence closure model of Briere for the turbulent variables, including a discussion of the turbulent energy budget, The analysis of the results obtained with the TKE scheme shows that the predicted turbulent fields are qualitatively realistic and interact significantly with the sea breeze circulation. Finally...

Inland convection and energy transfers in a sea breeze model

AbstractAvailability of potential energy in inland convection and in a sea breeze circulation are compared using a formulation of P. C. Manins and J. S. Turner for the convectively mixed atmospheric boundary layer, and a numerical model of a sea breeze. Entrainment processes during the mixed layer growth appear to affect both the convective scale and the mesoscale, decreasing the amount of potential energy available to the convective scale yet increasing the potential energy available at the mesoscale. The kinetic energy content of the sea breeze cell is explained in terms of a constant efficiency for the conversion of available potential energy inside a cell whose horizontal dimension increases in time. Results of numerical experiments indicate that the current value of the temporally integrated buoyancy flux at the ground is the most important parameter for the sea breeze flow. This parameter determines the strength of the flow as well as the inland movement of the sea breeze front.

Vertical structure and turbulent properties of wind field observed at a coastal complex site

Six experimental campaigns have been performed at the site of La Spezia Gulf (Northern Italy) from 1974 to 1977 jointly by three Italian research groups. Previous papers analysed various aspects of the collected data. The present paper deals with three topics not covered by preceding analyses. In studying the pibal data set, the statistics of wind field from ground level to free atmosphere has been studied; then an empirical expression, relating sea breeze flow to geostrophic circulation, is proposed; finally, examining no-lift balloon trajectories, turbulent properties, such as diffusion coefficients, turbulence intensities and so on, have been evaluated. The effects of the different surfaces, sea and land, on the turbulent parameters have been evidentiated.

Tetroon Trajectories in the Los Angeles Basin Defining the Source of Air Reaching the San Bernardino-Riverside Area in Late Afternoon

Abstract Tetroon trajectories within the Los Angeles Basin in the autumn of 1973 show that, on non-stagnation days, air located in the Los Angeles area in the morning can pass over the Puente Hills and reach the San Bernardino-Riverside area by mid-afternoon of the same day. However, the enhanced vertical mixing associated with these Hills would be expected to dilute any pollution present. Of perhaps more importance is the evidence that, on stagnation days when the atmosphere is stable, air from the Los Angeles area may drift southward in the early morning katabatic flow, stagnate for 2–3 h in the industrialized and high vehicle-density region north of Long Beach, and then move rapidly eastward with the sea breeze flow through Santa Ana Canyon, reaching the Riverside-San Bernardino area in late afternoon. In this case there would seem to be more potential for severe pollution in the latter area. However, the frequency of occurrence of this particular trajectory pattern is uncertain.

Mesoscale Transport and Dispersion of Airborne Pollens

Pollen transport and dispersion from generalized area sources was studied by 29 flights to distances of 100 km and heights of 3 km using an aircraft-mounted isokinetic sampler. Tree pollens and ragweed pollen served as tracers. Four types of flights were made to study various aspects of pollen transport: 1) ascents over a fixed location to investigate vertical distribution; 2) flights over a source-free area to document change of concentration with distance, 3) east-west flights along Long Island to study the influx of pollen from the mainland with westerly winds; and 4) vertical ascents and horizontal flights during sea breeze flows to determine their effect on pollen concentrations. It was found that large quantities of pollen are transported in orderly fashion from their source regions but pollen often travels in large, discrete clouds. Pollen is transported to Long Island from the mainland in some quantity. Sea breeze flows greatly decrease low-level concentrations but pollen is carried aloft at the sea breeze front and recirculated in the return flow aloft. Vertical distribution is reasonably well related to lapse rate although secondary concentration peaks which often occur below elevated inversions cannot be explained by the data obtained.