Sea Breeze Days Research Articles

Dynamical analysis of sea-breeze hodograph rotation in Sardinia

Abstract. This study investigates the diurnal evolution of sea-breeze (SB) rotation over an island at the middle latitudes. Earlier research on sea breezes in Sardinia shows that the onshore winds around various coasts of the island exhibit both the theoretically predicted clockwise rotation as well as seemingly anomalous anticlockwise rotation. A non-hydrostatic fully compressible numerical model (WRF) is used to simulate wind fields on and around the island on previously studied sea-breeze days, and is shown to capture the circulation on all coasts accurately. Diurnal rotation of wind is examined, and patterns of clockwise and anticlockwise rotation are identified. A dynamical analysis is performed by extracting individual forcing terms from the horizontal momentum equations. Analysis of several regions around the island shows that the direction of rotation is a result of a complex interaction between near-surface and synoptic pressure gradient, Coriolis and advection forcings. An idealized simulation is performed over an artificial island with dramatically simplified topography yet similar dimensions and latitude to Sardinia. Dynamical analysis of the idealized case reveals a rather different pattern of hodograph rotation to the real Sardinia, yet similar underlying dynamics. The research provides new insights into the dynamics underlying sea-breeze hodograph rotation, especially in coastal zones with a complex topography and/or coastline.

Temporal variations of air pollutant concentrations of during consecutive sea breeze days

Temporal variations of air pollutant concentrations of during consecutive sea breeze days

Sea breezes at Cotonou and their interaction with the West African monsoon

5-year 3-hourly wind speed and direction, air temperature over land and sea surface temperature data are analysed in order to characterize sea breezes at Cotonou (Republic of Benin, West Africa). A set of criteria based on the diurnal reversal of wind direction, the thermal gradient and the number of sunshine hours is used to identify sea breeze days. Statistics are presented that describe the occurrence, duration and strength of the sea breezes. It is found that the sea breeze occurs during all seasons in this region. Sea breeze occurrence is found to be strongly influenced by the West African monsoon. The frequency of occurrence shows clearly two regimes characterized by two maxima (December and May). Sea breezes occur about half of the days during non-monsoon season (winter). Land/sea breezes onset and cessation times show a pronounced seasonal variation. Sea breeze strength is greater during the West African monsoon season. A hodograph analysis reveals the existence of both clockwise and anticlockwise rotation. Average hodographs show clearly the onshore–offshore nature of the sea breeze circulation, but have indeterminate rotation. There is a significant seasonal effect of large-scale flows on sea breeze hodograph patterns.

The impact of sea breeze under different synoptic patterns on air pollution within Athens basin

Air quality in densely populated urban coastal areas is directly related to the coupling of the synoptic and the local scale flows. The dispersion conditions within Athens basin, under the influence of different meteorological forcings, lead to distinct spatio-temporal air pollution patterns. The aim of the current observational research is to identify and examine the effect of sea breeze under different atmospheric circulation patterns on air pollution levels for a one-year study period (2007). The study employs surface pressure maps, routine meteorological observations at two coastal sites and nitrogen monoxide (NO), nitrogen dioxide (NO2) and ozone (O3) concentrations from a network of four air quality stations within the Athens basin. A three-step methodology is applied that incorporates a set of criteria for classifying atmospheric circulation and identifying sea breeze events under each circulation pattern. Two types of sea breeze development are identified (pure sea breeze-PSB and modified sea breeze-MSB) with distinct characteristics. Sea breeze is found to develop more frequently under offshore compared to onshore and parallel to the shoreline background flows. Poor dispersion conditions (high nitrogen oxides-NOx and O3 concentrations) are connected to the pure sea breeze cases and to those cases where sea breeze interacts with a moderate northerly flow during the warm period. The levels of NOx and O3 for the northern Athens basin area are found to be significantly higher during the sea breeze days compared to the Etesian days. Regarding the diurnal variation of ozone for the sea breeze days, peak concentrations and higher intra-daily ranges are observed. Day-to-day pollution accumulation (build-up effect) is measured for O3 at the northern stations in the Athens basin.

Observed and simulated sea breeze characteristics over Rayong coastal area, Thailand

This work presents the detailed characterization of sea breeze (SB) over the Rayong coastal area, one of the most rapidly developed and highly industrialized areas during the last decade in Thailand, using observation data analysis and fine-resolution (2 km) mesoscale meteorological modeling with incorporation of new land cover and satellite-derived vegetation fraction data sets. The key characteristics considered include frequency of SB occurrence, sea-breeze day (SBD) identification, degree of inland penetration, and boundary layer development. It was found that SBs occur frequently in the winter due mainly to relatively large land–sea temperature contrasts and minimally in the wet season. Monthly mean SB onset and cessation times are at around 12–15 local time (LT) and 18–21 LT, respectively, and its strength peaks during the early- to mid-afternoon. Monthly SB hodographs generally exhibit clockwise rotations, and SB inland penetration (at PCD-T tower) ranges widely with the monthly means of 25–55 km from the coast. Mesoscale MM5 modeling was performed on two selected SBDs (13 January and 16 March 2006), on which the SBs are under weak and onshore strong influences from background winds, respectively. Simulated near-surface winds and temperature were found to be in fair-to-acceptable agreement with the observations. The SB circulation along the Rayong coast is clearly defined with a return flow aloft and a front on 13 January, while it is enhanced by the onshore background winds on 16 March. Another SB along the Chonburi coast also develops separately, but their fronts merge into one in the mid-afternoon, resulting in large area coverage by the SB. Simulated planetary boundary layer height over the land area is significantly affected by a thermal internal boundary layer (TIBL) induced by an SB, which is found to be low near the coast and increases toward the front (up to 800–1,000 m along the Rayong coast).

Integration of Lidar Data into a Coupled Mesoscale–Land Surface Model: A Theoretical Assessment of Sensitivity of Urban–Coastal Mesoscale Circulations to Urban Canopy Parameters

Abstract Urban–coastal circulations affect urban weather, dispersion and transport of pollutants and contaminants, and climate. Proper characterization and prediction of thermodynamic and dynamic processes in such environments are warranted. A new generation of observation and modeling systems is enabling unprecedented characterization of the three-dimensionality of the urban environment, including morphological parameters. Urban areas of Houston, Texas, are classified according to lidar-measured building heights and assigned typical urban land surface parameters appropriate to each classification. The lidar data were degraded from 1 m to the model resolution (1 km) with the goal of evaluating the impact of degraded resolution urban canopy parameters (UCPs) and three-dimensionality on the coastal–urban mesoscale circulations in comparison to typical two-dimensional urban slab approaches. The study revealed complex interactions between the sea breeze and urban heat island and offers a novel diagnostic tool, the bulk Richardson shear number, for identifying shallow mesoscale circulation. Using the Advanced Research Weather Research and Forecasting model (ARW-WRF) coupled to an atmosphere–land surface–urban canopy model, the authors simulated a theoretical sea-breeze day and confirmed that while coastal morphology can itself lead to complex sea-breeze front structures, including preferred areas of vertical motion, the urban environment can have an impact on the evolution of the sea-breeze mesoscale boundary. The inclusion of lidar-derived UCPs, even at degraded resolution, in the model’s land surface representation can lead to significant differences in patterns of skin surface temperature, convergence, and vertical motion, which have implications for many aspects of urban weather.

Study on deep inland penetration of sea breeze over complex terrain in the tropics

Characteristics of sea breeze circulations over a tropical Indian station have been studied, based on one year of observations, by Doppler Sound Detection and Ranging (SODAR) system at National Atmospheric Research Laboratory, Gadanki (13.5°N, 79.2°E), India. The effect of sea breeze circulations on the dynamics of low level flow patterns in atmospheric boundary layer over complex terrain in tropics is investigated. The study reveals that a sea-breeze front develops well along the eastern coastal plain of southern peninsular India and propagates over inland up to the distance about 80km. It is found that the sea-breeze signal is well recognized during the months of February, March and April due to the presence of tropical easterlies. In these three months, SODAR observations indicate a late afternoon intensification of sea-breeze flow in the height range 0.2–0.6km during 1400 and 2000 local time (LT). The decrease in temperature of 2°C and increase in relative humidity of 20% at surface level are observed on a sea breeze day as compared to a non-sea breeze day. Sea-breeze inland propagation is absent for the rest of the months due to the opposing meso-flow direction. ERA-Interim reanalysis U-velocity data over south-Asia grid also corroborates the deep-inland penetrations of sea breeze circulations over this site.

Meteorological observations of the coastal boundary layer structure at the Bulgarian Black Sea coast

Abstract. Continuous wind profile and turbulence measurements were initiated in July 2008 at the coastal meteorological observatory of Ahtopol on the Black Sea (south-east Bulgaria) under a Bulgarian-Russian collaborative program. These observations are the start of high resolution atmospheric boundary layer vertical structure climatology at the Bulgarian Black Sea coast using remote sensing technology and turbulence measurements. The potential of the measurement program with respect to this goal is illustrated with examples of sea breeze formation and characteristics during the summer of 2008. The analysis revealed three distinct types of weather conditions: no breeze, breeze with sharp frontal passage and gradually developing breeze. During the sea breeze days, the average wind speed near the ground (from sonic anemometer at 4.5 m and first layer of sodar at 30–40 m) did not exceed 3–4 m s−1. The onset of breeze circulation was detected based on surface layer measurements of air temperature (platinum sensor and acoustic), wind speed and direction, and turbulence parameters. The sodar measurements revealed the vertical structure of the wind field.

Development of selection algorithms and databases for sea breeze studies

We present an automated and manual algorithm for identifying past sea breeze episodes in the Bay of Alicante (southeastern coast of the Iberian Peninsula, IP, Spain) for a 6-year study period (2000–2005). The main goal was to provide databases for better understanding the functioning of sea breezes, which have a crucial influence on weather and climate in both coastal and inland areas and therefore affect human life in many ways. The algorithms apply a well-defined set of criteria based on meteorological and sea surface temperature measurements in order to detect past occurrences. The automated and manual identification techniques successfully identified a total of 475 and 1414 sea breeze events, respectively. A large database containing the significant characteristic parameters measured (onset time, cessation time, duration time, maximum wind speed, inland penetration, etc.) for these 475 sea breeze days is presented. We evaluated the accuracy of both selection techniques by means of comparison with independent objective and subjective techniques. Both databases are the major contribution of this paper and have been used in some climatological sea breeze studies and are also presented here for any coastal expert interested in numerical–theoretical, observational–experimental and climatological wind studies.

夏季日中における首都圏のヒートアイランド現象に海風が与える影響

We analyze the influence of sea breeze on temperature distribution in the Kanto Plain (central Japan) on a day that a sea breeze front was detected (known as sea-breeze front days) using high-resolution temperature data observed by our research team. The high-temperature area on sea breeze front days moves northwest from central Tokyo, and was located at Kawagoe city (middle Kanto Plain) at 14 JST, and the northern Kanto Plain at 16 to 18 JST, respectively. This high-temperature area appears at the head of the sea breeze front to the leeward of central Tokyo, where the daily maximum temperature is highest in Kawagoe city and the northern Kanto Plain. After the sea breeze front passes, the area where the temperature is higher than that at the circumference is distributed in the shape of a wedge. This wedge-shaped area is located to the leeward of central Tokyo where the wind from Tokyo Bay and Sagami Bay forms a convergence zone. The high-temperature area around Kawagoe city, which cannot be found on days with strong winds, is formed from the hindrance of cold air advection caused by sea breeze front penetration. On the other hand, high temperatures in the northern Kanto Plain may not be related to the penetration of sea breeze fronts, which do not reach the northern Kanto Plain on days when the daily maximum temperature is recorded. However, the temperature in the northern Kanto Plain is higher on sea breeze days than on strong southerly wind days, and this suggests that local circulation plays an important role in causing high temperatures in the northern Kanto.

Sea breeze forcing of estuary turbulence and air‐water CO2 exchange

The sea breeze is often a dominant meteorological feature at the coastline, but little is known about its estuarine impacts. Measurements at an anchored catamaran and meteorological stations along the Hudson River and New York Bay estuarine system are used to illustrate some basic characteristics and impacts of the feature. The sea breeze propagates inland, arriving in phase with peak solar forcing at seaward stations, but several hours later at up‐estuary stations. Passage of the sea breeze front raises the water‐to‐air CO2 flux by 1–2 orders of magnitude, and drives turbulence comparable to spring tide levels in the upper meter of the water column, where most primary productivity occurs in this highly turbid system. Modeling and observational studies often use remotely‐measured winds to compute air‐water fluxes (e.g., momentum, CO2), and this leads to a factor of two flux error on sea breeze days during the study.

PM 10 air quality variations in an urbanized and industrialized harbor

In this paper we investigate the PM 10 pollution episodes associated with meteorological situations in an urban and industrialized coastal site of the southern part of the North Sea, representative of a typical harbor for trade. In a first part, the spatio-temporal variability of PM 10, SO 2, NO x and O 3 concentrations at the urban scale suggests that both regional air masses and local emissions affect harbor's pollution. In a second part, hierarchical clustering analysis (HCA) performed on meteorological data and PM 10 concentrations reveals two main air quality (AQ) regimes. The first one is related to low PM 10 levels, which occur under low-pressure conditions due to meteorological conditions favoring a good dispersion of pollutants. The second one is characterized by higher PM 10 concentrations appearing under high-pressure conditions. The highest polluted days are characterized by the highest temperatures and hardly any rain. These pollution episodes predominantly occur during sea breeze days, but also as the result of occasional industrial releases. The HCA proved to be an appropriate method to define AQ regimes and to identify meteorological conditions favoring or not PM pollution episodes in Dunkerque conurbation.

Study of the development of the sea breeze and its micro-scale structure at a coastal site using a Multi-Tone Sodar system

The purpose of this paper is to study the development of the coastal flow i.e. its micro-scale characteristics within the surface layer at the sea-land transition and to investigate the development of inland formation of cloudiness during merging of sea/land and valley- mountain breeze regimes. The area is the mountainous southern tip of Italy, about 50 km wide and 300 km long, in the Central Mediterranean Basin. Here, thermal meso-scale circulations and cloud formations on the mountains are pronounced because of their peculiar elongated shape. Upslope flow is very strong, due to the steepness of Apennines, and sea-breeze circulation is supported by the thermally forced meso-scale flows. Here, we present preliminary results from a case study during six consecutive days where sea/land breeze circulation was well developed and discuss the effect on the formation of inland clouds. Sea breeze days are selected by a sodar and surface meteorological station measurements. Cloud development is analyzed by subjective inspection of METEOSAT MSG images in the visible channel. The WRF (Weather Research and Forecasting) model is used to analyze the meteorological situation. The Institute of Atmospheric Sciences and Climate CNR-ISAC in house modular Multi-Tone Sodar system (PC-MTSodar) and the surface meteorological station are installed and operated at a coastal site located at about 300 m from the coastline. Preliminary results show that the methodology is viable to study the development of thermally forced meso-scale circulations over Calabria at micro and large scale and that these circulations can be intense over the peninsula thanks to its peculiar shape. It is shown that the formation of afternoon cumulus clouds, which may result in rainfall, is modulated by synoptic scale conditions. Further development will be a climatic assessment of the role of breezes on local climate.

Study of the development of the sea breeze and its micro-scale structure at a coastal site using a Multi-Tone Sodar system

The purpose of this paper is to study the development of the coastal flow i.e. its micro-scale characteristics within the surface layer at the sea-land transition and to investigate the development of inland formation of cloudiness during merging of sea/land and valley- mountain breeze regimes. The area is the mountainous southern tip of Italy, about 50 km wide and 300 km long, in the Central Mediterranean Basin. Here, thermal meso-scale circulations and cloud formations on the mountains are pronounced because of their peculiar elongated shape. Upslope flow is very strong, due to the steepness of Apennines, and sea-breeze circulation is supported by the thermally forced meso-scale flows. Here, we present preliminary results from a case study during six consecutive days where sea/land breeze circulation was well developed and discuss the effect on the formation of inland clouds. Sea breeze days are selected by a sodar and surface meteorological station measurements. Cloud development is analyzed by subjective inspection of METEOSAT MSG images in the visible channel. The WRF (Weather Research and Forecasting) model is used to analyze the meteorological situation. The Institute of Atmospheric Sciences and Climate CNR-ISAC in house modular Multi-Tone Sodar system (PC-MTSodar) and the surface meteorological station are installed and operated at a coastal site located at about 300 m from the coastline. Preliminary results show that the methodology is viable to study the development of thermally forced meso-scale circulations over Calabria at micro and large scale and that these circulations can be intense over the peninsula thanks to its peculiar shape. It is shown that the formation of afternoon cumulus clouds, which may result in rainfall, is modulated by synoptic scale conditions. Further development will be a climatic assessment of the role of breezes on local climate.

Climatology and impact on air quality of sea breeze in an urban coastal environment

AbstractThe aims of this paper are to investigate the characteristics of the sea breeze that is developing in Volos area, a medium sized coastal city in central Greece, and to study the influence of sea breeze on concentration levels of ozone and PM10, during the period 2001–2005. The identification of sea breeze days is based on a set of strict, objective criteria, which include the wind direction and its diurnal reversal, the wind direction difference between the surface winds and the winds in the free atmosphere and the thermal contrast between the sea and the land surface. The statistical analysis reveals that sea breeze is developing in 85.6% of days from May until July, with maximum frequency of occurrence 89% in June. Its most frequent onset and cessation time periods are 09:00–11:00 and 20:00–22:00 LST respectively and its usual duration is approximately 10 h. The average maximum strength is 2.6 m/s, usually between 14:00 and 17:00 LST, while the maximum observed value equals 5.9 m/s. Studying the variation of ozone and PM10 levels during the cold and the warm period of the year (October–April and May–September respectively), it is concluded that sea breeze development is associated with an increase of the concentration of both pollutants. This increase is more pronounced during the cold period and is attributed to unfavourable meteorological conditions. Copyright © 2008 Royal Meteorological Society

An automated sea breeze selection technique based on regional sea‐level pressure difference: WeMOi

AbstractA recently defined regional teleconnection pattern for the western Mediterranean basin (western Mediterranean Oscillation, WeMO) has allowed an objective quantification of the synoptic circulation factor on the occurrence of sea breezes. The associated WeMO index (WeMOi) can be used as an initial objective filter for selecting ideal surface pressure conditions for sea breeze development. Applying this filter to the sea breeze database created for Alicante (reference synoptic station) and performing a manual selection method for the 2‐year period (1999–2000), we confirmed the potential use of this objective primary criterion. We used wind speed (WS) and direction (WD) data from 9 coastline meteorological stations to assess the WeMOi applicability to the Iberian Mediterranean coast and the Balearic Isles. The [−1, 1] threshold interval of the daily WeMOi was seen to be a good proxy for detecting weak pressure gradients at surface level. Observational and numerical sea breeze studies require quality databases in order to analyse in depth the main characteristics and physical processes controlling sea breezes. This automated selection technique enabled us to improve the accuracy and processing time of the filter methods for finding sea breeze days by adding a new objective criterion. This new threshold technique [−1, 1], based on regional sea‐level pressure (SLP) difference, is adaptable to any coastal region at mid‐latitudes where a regional barometric dipole can be defined. A regional teleconnection pattern, such as the WeMOi, could be used as a suitable tool for forecasting sea breeze occurrence. Copyright © 2008 Royal Meteorological Society

Impact of a sea breeze event on air pollution at the Eastern Tunisian Coast

In this paper, air pollutants concentrations are analyzed during two sea breeze days (18 July 2004 and 17 September 2005) at the Mediterranean sea, just in front of Sousse (35° 48′ N, 10° 38′ E), Tunisia. During these two cases, we found that Sousse and its suburbs have been contaminated by a nearby coastal power plant emissions of pollutants. On 18 July 2004, onshore synoptic wind was uniform (up to 4 m/s) and roughly perpendicular to the coast and made breeze occurrence easier. The observed wind breeze is about 2 m/s. No return flow was recorded, due to the onshore synoptic wind. During this breeze event, wind direction changed by about 30° to be aligned with power plant and Sousse sites. In these conditions O 3 and SO 2 concentrations were multiplied by a factors 1.5 and 3 respectively. On 17 September 2005, a similar sea breeze wind (2–3 m/s) took place at the region but without significant synoptic wind. Pollutant concentrations are also comparable to those of 18 July 2004. A calm synoptic conditions case (13 July 2004) is also studied and compared with the previous cases.

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

The climatology of sea breezes on Sardinia

AbstractHourly wind speed and direction data from 12 coastline stations on Sardinia, Italy, are analysed in order to characterize sea breezes in the region. A set of criteria based on the diurnal reversal of wind direction, and the thermal gradient necessary to drive the circulation, is used to identify sea breeze days. Statistics are presented that describe the occurrence, duration, and strength of the sea breezes. On a stationwide basis, sea breezes are most frequent in the summer months (May–August), when they appear on more than one‐third of the days. Sea breeze occurrence and duration are the greatest for the stations on the east coast of the island. The all‐station average sea breeze duration reaches a maximum of about 9 h in June. The strength of the sea breezes is roughly 3 m s−1 during summer months on average over all stations in the sample.An analysis of mean daily hodographs for the stations in the sample shows clearly the onshore–offshore nature of the sea breeze circulation, and the response of the sea breezes to the local coastline. Sea breezes are shown to develop simultaneously on all coasts of the island under appropriate synoptic conditions. Copyright © 2002 Royal Meteorological Society.

FORMATION AND TRANSPORT OF ATMOSPHERIC AEROSOL OVER ATHENS, GREECE

The effects of meteorology on ambient aerosol concentrations and aerosol transport, within the Greater Athens Area during the summer period, was investigated. Measurements of size fractionated anions and cations were made at two sites (inland at Ag. Stefanos and on the coast at Pireas) within the Greater Athens Area. The wind regime exhibited a distinctinfluence such that the sea-breeze circulation strongly enhanced the formation of secondary aerosols. For sulphate the difference in concentration between the two sites was,on average, 8 times greater on sea-breeze days compared with Etesian days (warm days with NE winds). During `normal' days,any differences in concentrations were possibly due to localemissions. Elevated concentrations in the fine mode were detectedat both sites during the sea-breeze days. The sea-breezecirculation enhances the development of secondary aerosolswhich was clearly shown at the inland site. Nitrous acid,hydrochloric acid and particulate nitrate, sulphate andammonium increase during sea-breeze days. Elevated levelsof nitrate, 4 μm diameter, were particularly observedon the days with a strong sea-breeze circulation. Sulphatewas well correlated with both sulphur dioxide and ammoniumsuggesting the production of NH4HSO4/(NH4)2SO4 aerosols, formedthrough the neutralisation of NH3 with sulphuric acids.Ammonium sulphate was found to be the major ammoniumcomponent in Athens.