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Showing papers on "Sea breeze published in 2000"


Journal ArticleDOI
TL;DR: The response of the water column to varying conditions of stratification and wind forcing was investigated in Lake Kinneret (Israel) using data collected from thermistor chains and acoustic Doppler current profilers during 1997 and 1998 as discussed by the authors.
Abstract: The response of the water column to varying conditions of stratification and wind forcing was investigated in Lake Kinneret (Israel) using data collected from thermistor chains and acoustic Doppler current profilers during 1997 and 1998. The strong daily sea breeze was found to generate a vertical mode 1 internal Kelvin wave and basin-scale internal Poincarewaves of vertical modes 1, 2, and 3. The Kelvin wave, the dominant component of the internal wave field, was responsible for alongshore velocities in the nearshore regions. In the upwind nearshore regions, velocities were dominated by the forced response to the wind and were cross-shore in nature. In the lake interior, the Kelvin wave effect on the horizontal velocity field was minor compared to the higher vertical mode Poincarewaves. The Kelvin wave is shown to exist in resonant and nonforced states with the wind, whereas the vertical mode 1 Poincarewave energy remained relatively constant, despite large variability in the forcing condi- tions. The energy in the higher mode Poincarewaves varied greatly, both on daily and seasonal timescales. The results demonstrate that the wind energy forces multiple basin-scale internal wave modes and that prior motion in the water column must be considered when determining the subsequent internal wave response in periodically forced systems. Lake Kinneret (Israel) has long been an important regional resource, providing a substantial supply of drinking water as well as supporting a commercial fishery. The monomictic lake is forced daily during the summer by a powerful sea breeze, with stratification and wind patterns showing little variation from year to year. These factors, along with a fa- vorable bathymetric pattern, combine to make Lake Kinneret an ideal place for the field investigation of large-scale inter- nal waves and related phenomena such as the benthic bound- ary layer, horizontal transport, and vertical mixing processes. In addition to providing substantial insight into the local pro- cesses—and hence, influencing local management—study of the lake also provides fundamental knowledge of the dynam- ics of enclosed basins on a geophysical scale. During summer, the internal Rossby radius in Lake Kin- neret is typically one-half the basin width; hence, large-scale motion in the lake will be affected by the earth's rotation, and basin-scale internal waves may be of topographic Ross- by, Kelvin, or Poincareform. Topographic Rossby waves are sub-inertial frequency oscillations that exist only in rotating fluids with variable bathymetry (Mysak et al. 1985; Stocker and Hutter 1987), and these waves result from changes in depth affecting the relative vorticity of fluid elements. In the absence of vertical boundaries, wavelike solutions to the lin- ear inviscid equations of motion for a flat-bottomed region of homogeneous fluid with a constant rate of rotation are 1

166 citations


Journal ArticleDOI
TL;DR: In this article, the changes of a sea breeze and a daytime heat island due to land-use alteration during an 85-year period (1900-1985) have been numerically simulated.
Abstract: The changes of a sea breeze and a daytime heat island due to land-use alteration during an 85 year period (1900-1985) have been numerically simulated. The domain of interest is the Kanto Plain (15000 km 2 ), including the Tokyo metropolitan area. This urban area is located in the southern part of the plain and consists of many cities in Tokyo and its suburbs. The horizontal scale of the area is about 40 km and has increased by a factor of four during the 85 year period. The simulations were conducted under a summer synoptic condition with weak gradient wind and almost clear sky. The model is based on the three-dimensional anelastic equations, taking into account the hydrostatic assumption. First, it was confirmed that the simulated wind field and temperature distribution with using the land-use data for 1985, agreed with observed data. The simulations were then conducted using the land-use data for 1950 and 1900. From comparison among the three simulations, the following two major conclusions were obtained: (1) Land-use alteration modified the wind system over the Kanto Plain. In particular, the simulated sea breeze front in 1985 was more clearly defined around the northern end of the Tokyo metropolitan area. The time required for the sea breezes to reach inland areas increased by two hours. (2) The warming due to land-use alteration is found over the Tokyo metropolitan area and the northwestern part of the Kanto Plain. In particular, the area of the most prominent warming is found in the northern end of the Tokyo metropolitan area. Intensity of daytime heat island in the area were estimated as 3-4°C and 2-3°C during the 85 year period, and latest 35 years respectively. The above warming is confirmed to result from the enhanced sensible heat flux and the change of interaction between the boundary layer heating and sea breeze front.

143 citations


Journal ArticleDOI
TL;DR: In this article, a diurnally forced convection was observed over the Tiwi Islands, north of the Australian continent, as part of the Maritime Continent Thunderstorm Experiment.
Abstract: Diurnally forced convection was observed over the Tiwi Islands, north of the Australian continent, as part of the Maritime Continent Thunderstorm Experiment. Immature peninsula-scale (5–15 km) sea breezes were observed to initiate moist convection early each day, principally through convergence that results from the confluence or collision of peninsula breeze fronts. Convection initiated by peninsula-scale breezes usually fails to organize beyond a small cluster of cells and dissipates as a local event. Mature island-scale (∼100 km) breezes develop by late morning and subsequently play a pivotal role in the forcing and evolution of organized convection. The initiation of mesoscale convective systems (MCSs) is observed to be a direct consequence of breeze front collisions for only ∼20% of the days on which organized convection develops. This is referred to as “type A” forcing and it occurs when normal convective development is delayed or otherwise suppressed. Type A forcing is nature’s backup mech...

132 citations


Journal ArticleDOI
TL;DR: In this paper, 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 and 14 September 1994.
Abstract: 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...

85 citations


Journal ArticleDOI
TL;DR: The formation, dynamics and spatial distribution of heavy precipita- tion during the 1991/92 El Nino in Ecuador and northern Peru were examined by means of Meteosat-3 imagery, NOAA-AVHRR-based multichannel sea surface temperatures (MCSST) and additional meteorological observations as discussed by the authors.
Abstract: The formation, dynamics and spatial distribution of heavy precipita- tion during the 1991/92 El Nino in Ecuador and northern Peru were examined by means of Meteosat-3 imagery, NOAA-AVHRR-based multichannel sea surface temperatures (MCSST) and additional meteorological observations. The Convective and Stratiform Technique (CST) was used for rain retrieval by means of Meteosat IR data and a cross-correlation approach was applied to Meteosat image sequences to derive cloud motion winds (CMW) which are essential for the analysis of circulation patterns leading to severe precipitation. From an analysis of 45 days with severe precipitation it is proven that three mechanisms were responsible for the formation of heavy rains. Each mechanism reveals a specie c localized impact. (1) The most frequent mechanism (frequency of ~61%) represents an extended land-sea breeze system. During such weather conditions, predominantly locally conened precipitation patterns occured. Areas aA ected by the sea wind front during the day were the coastal plains up to the 1000m contour line on the western Andean slope. Local maxima in the frequency of cloudiness leading to precipitation could be found at isolated peaks of a lower coastal cordillera. At night the highest frequency of precipitation was found over the warm water surface of the Gulf of Guayaquil, mainly due to its coastal shape which signie cantly favours convergence of the nocturnal land breeze. (2) Convection, initiated in the coastal plain and on the western Andean slopes during the afternoon,was signie cantly intensieed by an entrainment ofremainders of cirrus shields from the Amazon basin. These cloud fragments spilled over the Andes with well-developed trades in the mid/upper troposphere which blew in the opposite direction to the daily sea/up-slope breeze. The spill over points were characterized by areas of deep convection on the western Andean slopes and were frequently valley axes perpendicular to the mountain chain as well as the Andean depression in southern Ecuador. (3) During the main El Nino phase (March- April), heavy and persistent precipitation was extended over wide areas of the coastal plain showing neither a distinct diurnal cycle nor preferential areas. Deep convection was frequently organized in mesoscale convective complexes (MCC) and was spatially correlated with MCSST > 27s . The extensive instability of the troposphere during these weather conditions was marked by convective cloud streets and an intensiecation of the meridional Hadley circulation oA the coast of southern Ecuador and Peru.

67 citations


Journal ArticleDOI
TL;DR: 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 seabreeze circulation in photochemical smog episodes that had been suggested already by a number of experiments and numerical studies.
Abstract: 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 ...

59 citations


Journal ArticleDOI
TL;DR: In this article, a mesoscale modelling of sea breezes blowing from a narrow strait into the lower Fraser valley (LFV), British Columbia, Canada, during the period of 17-20 July, 1985 was investigated.

42 citations


Journal ArticleDOI
TL;DR: In this paper, a numerical mesoscale model is used to study the wind field and the boundary layer structure of the island of Sardinia during typical summer conditions using a higher-order turbulence closure scheme.
Abstract: A numerical mesoscale model is used to study the wind field and the boundary layer structure of the island of Sardinia during typical summer conditions The numerical model is three-dimensional and employs a higherorder turbulence closure scheme The model simulations were performed for summer conditions characterized by weak synoptic forcing from the northwest and clear skies These conditions favor the development of thermal circulations, the most significant of which are the sea-breeze systems The nighttime wind patterns generally are dominated by topography, which leads to the development of strong drainage flow On the other hand, as revealed in the simulated wind field, at midday the wind has an onshore component at virtually every coastline The well-organized sea-breeze systems interact to produce convergence zones Another interesting feature is the development of a cyclonic eddy pattern during late-afternoon hours The model results are compared with observations taken at a network of near-surface wind stations and rawinsonde profiles from the Cagliari airport Available observations agreed relatively well with model predictions

39 citations


Journal ArticleDOI
TL;DR: In this article, the authors present average and extreme propagation conditions in the coastal area of Barcelona (NE Spain) calculated using three years of radiosonde data, related to local prevailing circulations such as the sea breeze with particular interest in the nearby Vallirana weather radar.
Abstract: Many weather radars are affected by some type of anomalous propagation (AP) with a wide variety of frequency and intensity. Some geographical areas have been described to be particularly prone to AP. Even in some sites, AP is not statistically abnormal at all but dominant. Severe AP cases have been reported in coastal areas affected by strong temperature inversions and humidity contrasts such as the Baltic Sea, the Indic Ocean or the Mediterranean. In this paper we present average and extreme propagation conditions in the coastal area of Barcelona (NE Spain) calculated using three years of radiosonde data. Occurrence of different propagation conditions is discussed and related to local prevailing circulations such as the sea breeze with particular interest in the nearby Vallirana weather radar. The effect of some extreme ducting episodes seems to be remarkable in beam blocking correction procedures leading to wrong precipitation estimates when anaprop and rainfall occur at the same time. The use of radiosonde and mesoscale NWP data to derive operationally propagation conditions jointly with other existing techniques based in the analysis of radar data is overviewed.

37 citations


Journal ArticleDOI
TL;DR: In this article, the role of Kelvin-Helmholtz instability (KHI) in determining the time and location of convection behind the sea-breeze front is examined.
Abstract: A three-dimensional numerical simulation of land–water circulations near Cape Canaveral, Florida, is performed using the Advanced Regional Prediction System. The role of Kelvin–Helmholtz instability (KHI) in determining the time and location of convection behind the sea-breeze front is examined. The model configuration attempts to improve upon limitations of previous work (e.g., resolution, surface characteristics, initial state). It provides a detailed and realistic simulation of the desired features. The simulation exhibits a single precipitating storm that forms behind the sea-breeze front. This postfrontal storm develops when an outflow boundary intersects a deep layer of upward motion above the marine air. The region of ascent initially is the remnant of a cell that formed along the sea-breeze front, but before the cell decays, a portion of its upward motion is intensified and displaced. The modification of the ascent is a product of KHI that is occurring on top of the sea-breeze interface i...

35 citations


Journal ArticleDOI
TL;DR: In this paper, the authors studied the relationship between mesoscale changes in geostrophic winds and low-level jet (LLJ) streams in the region between the Eastern Castilla-La Mancha and the Mediterranean coast of southeastern Spain.
Abstract: Sea breezes and low-level jet (LLJ) streams are studied in the region between the Eastern Castilla-La Mancha and the Mediterranean coast of southeastern Spain. The simplified concept of two-dimensional terrain and meteorological conditions explains the spatially and diurnally varying wind system consistently. The changes, as a function of time, height and distance to the coast, of temperature, pressure and wind as well as of certain observed phenomena, such as LLJs and strongly baroclinic zones, result from the response of the mesoscale flow to differential heating. Wind changes are generally found to be consistent with mesoscale changes in geostrophic winds as estimated from station pressure measurements. The LLJs mark the penetration depth of the sea breeze during daytime, where a baroclinic zone develops at the transition between continental air masses and marine air masses, typically at a distance of 150 km from the coast. The analysis is based on aerological data and ground-based measurements from the European Field Experiment in a Desertification Threatened Area (EFEDA) experiments in 1991 and 1994 as well as on 3-hourly data from three synoptic stations of the Spanish meteorological network for April–October in 1991 and 1994. After corrections were made for instrument errors and atmospheric tides, diurnal pressure variations document vertically integrated mass fluxes perpendicular to the coast. Amplitudes of diurnal pressure and temperature changes scatter significantly and are largest in midsummer. They are weakly correlated and pressure amplitudes remain large in spring and autumn when diurnal temperature changes are reduced. With about 6 h delay to the regular development of onshore winds at the coast during daytime, pronounced wind peaks are observed over the eastern plateau at Albacete and Barrax in the late afternoon. Case studies show that they are accompanied by development of baroclinically driven LLJs, whereas winds at Tomelloso, 220-km inland, show less pronounced diurnal changes and are beyond the normal penetration distance of sea breezes. Copyright © 2000 Royal Meteorological Society

Journal ArticleDOI
TL;DR: In this paper, the mesoscale wind field over most of the Baltic Sea is quite heterogeneous; themodifications primarily being caused by the land-seacontrasts.
Abstract: For two consecutive days during spring 1997, the windfield over the Baltic Sea has been studied. Thestrength of the geostrophic wind speed is the majordifference in synoptic conditions between these twodays. During both days, the mesoscale wind field overmost of the Baltic Sea is quite heterogeneous; themodifications primarily being caused by the land-seacontrasts. On the day with the weaker wind speed,sea-breeze circulations develop. As a consequence, thewind direction at lower levels is more or lessopposite to the geostrophic over large areas of theBaltic Sea and the surface wind speed decreases withoffshore distance. Wind speed maxima caused by the seabreezes are found along the east coasts in the studiedarea. For the other day, the slow growth of a stableinternal boundary layer over the sea also gives asurface wind speed decrease with offshore distancefrom the coast.

Journal ArticleDOI
TL;DR: In this paper, an important air quality surveillance network is organized by region, where each region has a number of measurement sites available, and measurement sites show highly correlated variations of daily ozone maxima during the summer periods.

Journal ArticleDOI
TL;DR: In this article, the relative importance of sea-land and mountain-valley thermal contrasts in determining the development of thermally forced mesoscale circulations (TFMCs) over a mountainous peninsula was studied.
Abstract: We study the relative importance of sea-land and mountain-valley thermal contrasts in determining the development of thermally forced mesoscale circulations (TFMCs) over a mountainous peninsula. We first analyse the energetics of the problem, and using this theory, we interprete the numerical simulations over Calabria, a mountainous peninsula in southern Italy. The CSU 3-D nonlinear numerical model is utilised to simulate the dynamics and the thermodynamics of the atmospheric fields over Calabria. Results show the importance of orography in determining the pattern of the flow and the local climate in a region as complex as Calabria. Analysis of the results shows that the energetics due to the sea-land interactions are more efficient when the peninsula is flat. The importance of the energy due to the sea-land decreases as the mountain height of the peninsula increases. The energy stored over the mountain gains in importance, untill it is released by the readjustment of the warm mountain air as it prevails over the energy released by the inland penetration of the sea breeze front. For instance, our results show that over a peninsula 100 km wide the energy over the mountain and the energy in the sea-land contrast are of the same order when the height of the mountain is about 700 m, for a 1500 m convective boundary layer (CBL) depth. Over the Calabrian peninsula, the energy released by the hot air in the CBL of the mountain prevails over the energy released by the inland penetration of the sea air. Calabria is about 1500 m high and about 50 km wide, and the CBL is of the order of 1500 m. The energy over the mountain is about four time larger than the energy contained in the sea-land contrast. Furthermore, the energetics increase with the patch width of the peninsula, and when its half width is much less than the Rossby radius, the MAPE of the sea breeze is negligible. When its half width is much larger than the Rossby radius, the breezes from the two opposing coastlines do not interact. Over Calabria peninsula, numerical simulations show that the flow is highly ageostrophic, and that the flow intensity increases from sunrise to reach its maximum in the afternoon but before sunset, which suggests that, in the late part of the day, the conversion of potential energy into kinetic energy is balanced by the dissipation.


Journal ArticleDOI
TL;DR: In this article, 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).
Abstract: 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.

Book ChapterDOI
01 Jan 2000
TL;DR: In this article, the authors studied the production and transport patterns of photochemical pollutants with a typical time-scale larger than 24 hours in the coastal zone of Portugal and found that the resulting pollutant emissions place a high pressure on the environment and natural resources of the Portuguese urban coastal areas.
Abstract: Portugal has a quite extensive coastline associated with significant terrain features and sea/land breeze circulation, which results in a complex wind field with strong implications for the production and transport patterns of photochemical pollutants with a typical time-scale larger than 24 hours. Since the coastal zone is a major component in global budgets and global resources availability and utilisation, effective sustainable management strategies in such areas require a special ability to think beyond divisions between different types of resources and human activities. Portuguese littoral is the region with the highest population density and economic development. The resulting pollutant emissions place a high pressure on the environment and natural resources of the Portuguese urban coastal areas.

Journal ArticleDOI
Ma Yimin1, T.J. Lyons1
TL;DR: In this paper, the development and movement of sea breezes under the influence of a thermally induced synoptic coastal trough and coastal terrain are simulated in the context of an extensive observational data set.
Abstract: The development and movement of sea breezes under the influence of a thermally induced synoptic coastal trough and coastal terrain are simulated. These simulations are analyzed in the context of an extensive observational data set. The synoptic trough acts to determine the presence and intensity of the sea breeze through the advection of warm air in the surface layer whereas local topography acts to enhance the breeze and turn the low-level flow. Interaction between the sea breeze circulation and the trough assists trough movement across the coastline.

Book ChapterDOI
01 Jan 2000
TL;DR: In this article, a meso-scale meteorological model was used to verify that the presence of the high mountains in the central Japan, which are taller than 2000 m, is a key for the formation of the flow resulting in medium range transport of pollutants.
Abstract: The Central Japan has notable topographical features such that high mountains of the Japanese Alps exist at its center, large plains extend in its coastal area, and it is bounded with complex coast lines at the south and north sides facing to the Pacific Ocean and the Sea of Japan, respectively. Thus various types of local flows develop in summer season. In this situation, medium range transport of air pollutants from highly developed urban area to mountainous rural area has attracted concern of many people in applied meteorology and atmospheric environment in Japan, since it occurs in an interesting combination of several types of local winds such as land and sea breezes, mountain and valley winds, and plain-plateau winds, and the transport repeated in summer season probably causes severe damage to eco-systems in the mountainous area. Kurita et al. (1985) pointed out that the pollutants discharged in Tokyo Bay area migrate to the mountains in central Japan, i.e. the travel distance of about 150 km within one day. The distance far exceeded what was expected in simple sea breeze situation in mid-latitudes, and thus the phenomena suggested importance of combined effects of sea breeze, valley wind, and plain to plateau wind for the transport. Later Kondo (1990) numerically verified using meso-scale meteorological model that the presence of the high mountains in the central Japan, which are taller than 2000 m, is a key for the formation of the flow resulting in the medium range transport of pollutants. Kitada et al. (1998) also discussed dominant role of the high mountains of the central Japan in temporal variation of sea breezes over coastal plain area in the Pacific Ocean side, i.e., the Nohbi Plain. It was made clear more than 10 years ago, as noted above, that the pollutants released from huge urban areas in the coastal Japan such as Tokyo can be transported more than 150 km within 12 hours mostly during the daytime and reach to the mountains.

Journal ArticleDOI
TL;DR: The coastal climates of France have been studied using temperature and precipitation data from 1961 to 1990 as mentioned in this paper, and it is found that the coastlines of the French Atlantic (and adjacent seas) and Mediterranean show many similar climatic features, but the coastal orientation and nearby topography cause some local climatic peculiarities.
Abstract: The coastal climates of France have been studied using temperature and precipitation data from 1961 to 1990. It is found that the coastlines of the French Atlantic (and adjacent seas) and Mediterranean show many similar climatic features, but the coastal orientation and nearby topography cause some local climatic peculiarities. The relatively flat topography near the coasts of the North Sea, English Channel and the Atlantic result in a fairly homogeneous coastal climate. In these coastal regions there are days of frost each year, but the precipitation amount is usually not high, especially in summer on the Atlantic coast. On the other hand, the mountainous areas of Provence and the Riviera, which are adjacent to the Mediterranean, cause a juxtaposition of varied coastal climates. Large temperature and rainfall differences are observed, especially between the capes and the heads of gulfs, but also between the narrow and wide gulfs. During the warm months, some sea breezes cause coastal thermal peculiarities, which depend on the orientation of the prevailing flow. Copyright © 2000 Royal Meteorological Society

Journal ArticleDOI
TL;DR: In this article, a statistical study of the spatial distribution of rainfall at annual and seasonal time-scales is performed for the Dobruja, a low plateau region of southeastern Romania.
Abstract: An original dataset for the Dobruja, a low plateau region of southeastern Romania, is used to perform a statistical study of the spatial distribution of rainfall at annual and seasonal time-scales. A principal component analysis (PCA) is carried out to identify the precipitation regimes. The high eigenvalue of PC1 attests of the prevailing temperate-continental regime, with a relatively dry winter opposed to a late spring and early summer rainfall maximum. PC2 shows the specific pattern of the coast, with a small secondary maximum in November. In spite of the relatively flat topography, annual rainfall is characterized by a strong gradient between the coast and the interior. Particularly low amounts are observed along the Black Sea coast. This spatial distribution arises from a combination of specific seasonal patterns among which the warm season presents the most acute spatial differentiation. Altitude and distance from the Black Sea are analysed as potential factors of this spatial distribution, reinforced during the warm season. Correlation and stepwise regression indicate that the altitude effect is moderate compared with the distance from the sea. During autumn and winter the sea-surface temperature (SST) is 2 or 3°C higher than that of the land surface: air instability is increased along the coast. During spring and summer, an opposite pattern is observed, with differences exceeding 6°C. A strong sea–land thermal gradient generates frequent sea-breeze circulations. Convective storms developing along the landward moving sea-breeze front, approximately 30–35 km inland, explain the high rainfall amount recorded over the plateau. In contrast, the Black Sea coast experiences dry and sunny summers. Copyright © 2000 Royal Meteorological Society

Journal ArticleDOI
TL;DR: In this article, the influence on the propagation of coastally trapped disturbances (CTD) of large gaps in the bounding coastal mountains is studied via application of the Colorado State University Regional Atmospheric Modeling System (RAMS).
Abstract: The influence on the propagation of coastally trapped disturbances (CTD) of large gaps in the bounding coastal mountains is studied via application of the Colorado State University Regional Atmospheric Modeling System (RAMS). By large gap it is meant that the width is of order 25–50% of the Rossby radius. In order to isolate the effects of the gaps, idealised simulations are used. Thus, RAMS is configured with a straight north-south coastline with a ramp-shaped coastal mountain range in which a gap is inserted and a gravity current-like CTD generated through cooling the low level atmosphere at the southern end of the domain. Radiative, land surface and cloud parameterisations are turned off to avoid sea breeze generation and other thermal effects and to focus on the dynamical effect of the gaps. Four simulations are conducted: no gap in the coastal mountain barrier, an insertion of a narrow (80 km) gap, a wide (160 km) gap, and an idealised island in the barrier. It is found that the gaps influence CTD propagation by effectively stalling the propagation at their mouth for a period and subsequently weakening the gravity current-like features (vertical extent, strength and abruptness of the wind and stratification changes at the leading edge). The idealised island has a less obvious impact since it is bounded by relatively narrow straits and does not allow communication with the model interior like the gaps do. Although lack of data and the nature of the idealised simulation prevents a detailed assessment of the simulations against real cases, qualitative comparisons with observed events in western North America and south-eastern Australia are made. Application of these results to air quality and forecasting issues is discussed. Copyright © 2000 Royal Meteorological Society

Journal ArticleDOI
TL;DR: 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 and important knowledge has also been obtained on the spatial and temporal dynamics of currents.
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 (Savijarvi, 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.

Journal ArticleDOI
TL;DR: In this paper, a response to the prevailing summer sea breeze was found in the currents of the coastal ocean at Sydney, south-eastern Australia, by analysing short periods (3-5 days) of sea breeze activity.
Abstract: Current meter data from the coastal ocean at Sydney, south‐eastern Australia, were analysed to seek evidence of a response to the prevailing summer sea breeze. A response to the sea breeze was found in the currents. This is significant since the magnitude of the sea breeze was small by comparison with winds associated with large‐scale pressure systems and the East Australian Current. Responses were determined by analysing short periods (3–5 days) of sea breeze activity as opposed to the whole 2‐month data set. The correlations between the alongshore nearshore diurnal‐period currents and the local wind stress during the sea breeze periods were significantly higher than the correlations during non‐sea‐breeze periods. Despite the stronger correlations the sea breeze could only account for around one‐quarter of the variance in the diurnal‐period currents. However, the detection of the response to the sea breeze is significant since the sea breeze has never previously been identified as a process for ...

Journal ArticleDOI
TL;DR: In this paper, meteorological features of Yamase (cold northeasterly wind) and sea breezes are investigated for the summer of 1997, and their invasion to the hilly mountain area on the Pacific side are discussed.
Abstract: The meteorological features of Yamase (cold northeasterly wind) and sea breezes are investigated for the summer of 1997, and their invasion to the hilly mountain area on the Pacific side are discussed.When sea breezes are present, solar radiation is generally large, but the temperature decreases on the coastal region of the Pacific due to the cold air masses brought by the wind from the ocean. During the Yamase period, both solar radiation and temperature decrease, and the lowest solar radiation areas are found on the eastern side of the mountains.The Yamase process has three stages: early, peak, and late. In the peak stage, there was a mixed layer from the surface to about 900hPa (1, 000m) and easterly winds reached above 800hPa (2, 000m). In the early and late stages there were stable layers at lower height with easterly winds. In spite of the different vertical profiles of stratification and easterly wind, clouds were formed at the same height (below 1, 500-2, 000m) through the three stages.Northeastern Japan was covered by a large and homogeneous air mass during the Yamase period, however, below 800hPa relative humidity and potential temperatures differed between the Pacific and Japan Sea sides. These differences were due to modifications of the low level air mass, by processes such as damming up of air masses by mountains and heating from the surface.In the study area (hilly mountain area), during the sea breeze period, the low temperatures were confined to the coastal area and the meteorological conditions differed from inland area. On the other hand, the potential temperatures were almost the same from the coastal to inland areas during the Yamase period. In this case, the air mass with mixed layers invaded from the coast to the inland with very small and/or no air mass modification.



Journal ArticleDOI
TL;DR: In this article, the authors investigated the behavior of sea breeze above Fukuoka City using AMeDAS data and field observations and concluded that the coherent structure may be due to the internal wave motion induced by the shear instability.
Abstract: Behaviors of sea breeze above Fukuoka City have been investigated on the basis of AMeDAS data and field observations. The land and sea breeze is influenced strongly by the topography near Fukuoka City and blows steady along the northwest-southeast line. Sea breeze observations performed by using a doppler sodar have revealed the existence of a coherent structure consisted of a pair of ascending and descending currents. The cross-correlation coefficients between horizontal andvertical velocities vary with 30 min period and take a value nearly equal to zero when the time lag is 0. Therefore, it is concluded that the coherent structuremay be due to the internal wave motion induced by the shear instability.

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TL;DR: In this paper, the results of the air quality assessment of a power plant in the Hongkong-Shenzhen area using regulatory models and an atmospheric dispersion modeling system, respectively.

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TL;DR: In this article, a mesoscale model has been applied over the Greater Sydney region to an air pollution episode resulting from fire hazard reduction burns from 12 to 14 April 1997, which concentrated smoke in the eastern part of the Sydney metropolitan area.
Abstract: A mesoscale model has been applied over the Greater Sydney region to an air pollution episode resulting from fire hazard reduction burns from 12 to 14 April 1997. The episode was characterised by two distinct events in a period of sustained light winds, which included humid sea breezes and land breezes. The first event occurred early in the period when the atmospheric circulation involved either weak sea breezes or no sea breeze at the coast. Described here are the meteorological conditions associated with the inter-regional transport of smoke from a prescribed, or hazard reduction, burn just north of Sydney, which concentrated smoke in the eastern part of the Sydney metropolitan area. The second event, which occurred late in the episode, was local in nature but was induced synoptically by the large-scale airflow by a change in wind direction that transported smoke and fog over a major highway. Also described are the meteorological conditions that contributed to the disruption of a major highway caused by a multiple vehicle pile-up just to the south-west of Sydney later in the period. Numerical model simulations using the University of New South Wales (UNSW) NWP model, which used archived real-time data, accurately predicted both the concentration of pollution in the eastern part of the Sydney metropolitan area in the first event and the hazardous smog formation and timing of the clearing south-west wind change in the second event. Copyright © 2000 Royal Meteorological Society