Coastal Meteorology

This study aimed to establish numerical models to replicate wind conditions for nearshore waters, sensitive to onshore topography, and to compare the characteristics of computational fluid dynamic (CFD) and mesoscale models. Vertical Doppler light detection and ranging (LiDAR) observation data were measured at an onshore site, which showed that wind conditions were affected by thermodynamic phenomena, such as land and sea breeze, and dynamical effects from neighboring onshore topography. The estimation accuracy of the CFD model depended on the height of the LiDAR data input. A height close to the target, such as the hub height of wind turbines, seemed appropriate as input data, considering that the accuracy of the wind speed shear replicated in a CFD numerical model may be uncertain. The mesoscale model replicated the wind through the thermodynamic effect and reliably estimated wind speed over nearshore waters without observation correction. Larger estimation errors were detected in...

Results are given of a delailed study to detennine the spatial and temporal (seasonal) distributions of the plane1ary boundary layer depths (PBLD) over the Mediterranean Basin. More then 65,000 upper-air measurements from 45 rawinsonde s1ations in the Basin were compiled and analysed for two consecutive years from spring 1986 through winter 1988. A methodology using both tested and newly developed criteria was applied to determine PBLD values. As expected, the values prove to be generally higher over land and are probably minimum over the eastern and western ends of the Mediterranean Sea. Factors influencing this spatial distribution are mainly topography, the distance from the shoreline, and to a lesser extent, synoptic weather systems. The most striking temporal effect on PBLD distribution over the Mediterranean Basin is caused by larger scale synoptic weather systems. The second effect is the diurnal cycle, which has its largest impact mainly during the summer months. The PBLD values are displayed as analysed seasonal maps, from which typical values are extracted and presented in a Iabular form. The results can be used as input values for dynamic meteorological models in order to better assess the transport and dispersion over the Mediterranean Basin.

h summer, the coastal city of Perth, Western Australia is influenced mainly by easterly synoptic winds, with strong southwesterly sea breezes dominating during the afternoon period. In this paper we use both data analysis and mesoscale meteorological modelling to reveal the major meteorological mechanisms conducive to high ozone levels in the region. Analysis of the data revealed that practically all high-ozone days appear to be associated with recirculation of ozone or its precursors over the Perth area. Numerical modelling points to both same-day and next-day recirculation of surface air over the Perth region in easterly synoptic flow as being conducive to high ozone levels. An hydraulic jump effect over the nearby escarpment is both observed and predicted under moderate easterly synoptic flow. The locally well known West Coast Trough produces southeasterly surface flow off the coast of Perth, and the modelling in this study has confirmed that the trough is caused mainly by differential heating between the land and sea.

The purpose of this paper is to analyse the effect of the sea-breeze on photochemical pollution in Athens, Greece. To this end, the SOs, NO, NO,, 0s and CO concentrations, the vertical structure of the atmospheric boundary layer, the pollution emission rates and wind data are examined simultaneously for two typical days in August 1981 with well-defined sea-breeze circulation. The tendency of the complicated seabreeze flow field to stratify the atmosphere and thus generate layers with different constituents affects the con~ntrations measured near the ground and causes relatively high oxidant levels at night. As inversion layers descend or disappear, abrupt changes and short-period oscillations in concentrations are found, and can be explained by a simple multilayer box model. The diurnal variation and considerations based on simple ground-level wind trajectories indicate that recirculation of pollutants by the sea-breeze cell takes place, possibly aided by the small size of the basin and the closed topography. The passage of the sea-breeze front seems to have no direct effect. No day-today pollution accumulation is noticed. Thus, it becomes clear that if modeling of photochemical pollution in such coastal regions with pronounced relief is to be successful, it needs to pay close attention to both the flow field details and the verticai structure of the atmosphere, especially the ground-based inversion break-up and boundary layer collapse.

The aim of this paper is to analyze current and expected air quality in Israel and to identify the main responsible sources. To this end, the current (2010) air quality regarding five main air pollutants, PM 10 , PM 2.5 , NO 2 , SO 2 , and O 3 , was analyzed and the pollutant emission inventories were determined. Next, the expected emission inventories for the target years (2015 and 2020) were estimated. Based on these results, dispersion models (AERMOD, CHIMERE, FARM, and TREFIC) were used to forecast the expected air quality for the target years. The findings indicate that current policy measures are not sufficient and additional policy measures are required, particularly in the transport, industry, energy, and households sectors.

In most countries, national meteorological services either generate or have access to seasonal climate forecasts. However, in a number of regions, the uptake of these forecasts by local communities can be limited, with the locals instead relying on traditional knowledge to make their climate forecasts. Both approaches to seasonal climate forecasting have benefits, and the incorporation of traditional forecast methods into contemporary forecast systems can lead to forecasts that are locally relevant and better trusted by the users. This in turn could significantly improve the communication and application of climate information, especially to remote communities. A number of different methodologies have been proposed for combining these forecasts. Through considering the benefits and limitations of each approach, practical recommendations are provided on selecting a method, in the form of a decision framework, that takes into consideration both user and provider needs. The framework c...

Thermally driven circulations over urban areas, such as sea, lake, and land breezes and mountainvalley and urban heat island (UHI) circulations, strongly determine local weather and air quality conditions over highly populated areas. This study investigates the influence of sea breeze (SB) propagation on the development of the urban boundary layer (UBL) in the Metropolitan Region of Sao Paulo (MRSP), Brazil, an urban area with complex topography. This investigation is undertaken observationally by analyzing surface and upper air observations conducted in 2013 during the MCITY BRAZIL Project field campaigns and is conducted numerically by performing a set of Weather Research and Forecasting (WRF) simulations. The observational analysis highlights two SB events in the MRSP, one in February (austral summer) and the other in August (winter). In both seasons, the passage of the SB front disrupts the convective growth of the UBL and establishes a thermal internal boundary layer, thereby reducing the UBL height. The cooling also momentarily disrupts the UHI circulation. The results indicate that topography enhances SB propagation because it helps the marine air to go up the MRSP coastal escarpment and to reach the plateau while forcing adiabatic cooling of this air, intensifying the thermal gradient between the southern part of the plateau and the urban area. The UHI further increases the thermal gradient (from 0.5 K to 2 K in summer and 1 to 2.5 K in winter), accelerating the SB propagation. Synoptic conditions determine whether the SB front reaches the urban area and also may dislocate the convergence center of the UHI circulation.

Thermally driven circulations over urban areas, such as sea, lake, and land breezes and mountainvalley and urban heat island (UHI) circulations, strongly determine local weather and air quality conditions over highly populated areas. This study investigates the influence of sea breeze (SB) propagation on the development of the urban boundary layer (UBL) in the Metropolitan Region of Sao Paulo (MRSP), Brazil, an urban area with complex topography. This investigation is undertaken observationally by analyzing surface and upper air observations conducted in 2013 during the MCITY BRAZIL Project field campaigns and is conducted numerically by performing a set of Weather Research and Forecasting (WRF) simulations. The observational analysis highlights two SB events in the MRSP, one in February (austral summer) and the other in August (winter). In both seasons, the passage of the SB front disrupts the convective growth of the UBL and establishes a thermal internal boundary layer, thereby reducing the UBL height. The cooling also momentarily disrupts the UHI circulation. The results indicate that topography enhances SB propagation because it helps the marine air to go up the MRSP coastal escarpment and to reach the plateau while forcing adiabatic cooling of this air, intensifying the thermal gradient between the southern part of the plateau and the urban area. The UHI further increases the thermal gradient (from 0.5 K to 2 K in summer and 1 to 2.5 K in winter), accelerating the SB propagation. Synoptic conditions determine whether the SB front reaches the urban area and also may dislocate the convergence center of the UHI circulation.

A pollution episode occurred early in November 198 1, In the heavily industrialized area of Bilbao, a deep estuarine valley in northern Spain. Hourly average values from the automatic SO2 monitoring network indicate that 800 and 4OOpg (Nm3)-' were exceeded 2 and 55 times. respectiveI>. under stagnating anticyclonic conditions with weak gradient flow. In these conditions a meso-meteorological cycle developed whereby night drainage winds carried the pollutants to the sea, followed by their re-entry with the sea-breeze the next day. High emissions, or those which penetrated the ground based inversion. were initially dispersed out of the area. However, once the subsidence joined the anticyclonic and night-time inversions. all emissions were trapped within the reflux cycle resulting in the highest observed SOI ground levels. Unequal reaches within the cycle brought a net daily influx of clean ocean air which avolded a larger accumulation of pollutants in the area.

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This study evaluated 1950–2005 summer [June–August (JJA)] mean monthly air temperatures for two California air basins: the South Coast Air Basin (SoCAB) and the San Francisco Bay Area (SFBA). The study focuses on the more rapid post-1970 warming period, and its daily minima temperature Tmin and maxima temperature Tmax values were used to produce average monthly values and spatial distributions of trends for each air basin. Additional analyses included concurrent SSTs, 40-yr European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-40) sea level coastal pressure gradients, and GCM-downscaled average temperature Tave values.Results for all 253 California National Weather Service (NWS) Cooperative Observer Program (COOP) sites together showed increased Tave values (0.23°C decade−1); asymmetric warming, as Tmin values increase faster than Tmax values (0.27° versus 0.04°C decade−1) and thus decreased daily temperature range (DTR) values (0.15°C decade−1). The spatial di...

Strong southerly, terrain parallel winds often occur along the coast of north-central Chile (25°–35°S) embedded in the marine atmospheric boundary layer and the lower part of the capping temperature inversion. Their offshore structure and variability have received considerable attention because of the effect on open-ocean processes and connection with the southeast Pacific cloud layer. Mesoscale low-level circulations linked to the coastal topography (e.g., coastal jets and sea breeze) are less studied in Chile, but are particularly relevant as they alter the upper-ocean circulation and the cloud pattern in the nearshore strip. Surface, radiosonde, and airborne meteorological observations near point Lengua de Vaca (LdV)–Tongoy Bay (TB) at 30°S are used alongside numerical modeling to understand the local circulation near a prominent upwelling center. Most observations were gathered during the Variability of the American Monsoon Systems (VAMOS) Ocean–Cloud–Atmosphere–Land Study Chile...

In most countries, national meteorological services either generate or have access to seasonal climate forecasts. However, in a number of regions, the uptake of these forecasts by local communities can be limited, with the locals instead relying on traditional knowledge to make their climate forecasts. Both approaches to seasonal climate forecasting have benefits, and the incorporation of traditional forecast methods into contemporary forecast systems can lead to forecasts that are locally relevant and better trusted by the users. This in turn could significantly improve the communication and application of climate information, especially to remote communities. A number of different methodologies have been proposed for combining these forecasts. Through considering the benefits and limitations of each approach, practical recommendations are provided on selecting a method, in the form of a decision framework, that takes into consideration both user and provider needs. The framework c...

Integral quantities, wind run, S, and recirculation factor, R, useful for describing air flow, are calculated and combined with CO 2 mixing ratios. Meteorological observations were obtained from a RASS sodar and CO 2 mixing ratios from a continuous analyzer installed at a rural site in the upper Spanish plateau. The measuring campaign spread over 3 years and two approaches were followed. The first approach considered integral quantities on a daily basis and two classifications of air flow, to date scarcely used. The first classification distinguished among stagnation, recirculation, and ventilation, the second considering synoptic, meso-, and local scales. Moreover, 52.94% of daily values handled in this paper corresponded to ventilation and 49.70% to synoptic scale. The main goal of this approach is the subsequent link between the two classifications: the synoptic scale was associated with ventilation, mesoscale with recirculation and local scale partially with recirculation. CO 2 observations were distributed in air flow groups following these classifications and mesoscale processes were satisfactorily described since noticeable evidence of transport from nearby cities was observed. In the second approach, S and R pairs were used and CO 2 mixing ratios were distributed following percent intervals of ventilation, calculated by binning these pairs. The main goal of the second approach is to consider only three groups of mixing ratios. In the first group, with high ventilation, mixing ratios were low. With intermediate ventilation, mixing ratios were medium, and with low ventilation mixing ratios were high. A contrast of 21 ppm between the third and first groups was obtained at the 95th percentile. Finally, the second group provided a contrast of 3 ppm between north and south directions and also between east and west attributed to transport from nearby cities.

h i g h l i g h t s Association between circulation weather patterns, air recirculation and pollution. K-means clustering associates the recirculation potential to circulation patterns. Ventilation events dominate but recirculation and stagnation occurs frequently. High NO2, SO2 and O3 levels events varies substantially among the airsheds. Methodology can be adapted to other geographical areas.

Air pollution is determined by the combination of different factors, namely, emissions, physical constrains, meteorology and chemical processes [1,2,3]. The relative importance of such factors is influenced by their interaction on diverse scales of atmospheric motion. Each scale depicts different meteorological conditions, which, when combined with the different air pollution sources and photochemistry, result in varying ambient concentrations [2]. Identifying the dominant scales of atmospheric motion over a given airshed can be of great importance for many applications such as air pollution and pollen dispersion or wind energy management [2]. Portugal has been affected by numerous air pollution episodes during the last decade. These episodes are often related to peak emissions from local industry or transport, but can also be associated to regional transport from other urban areas or to exceptional emission events, such as forest fires. This research aims to identify the scales of atmospheric motion which contribute to an increase of air pollution. A method is proposed for differentiating between the scales of atmospheric motion that can be applied on a daily basis from data collected at several wind-measuring sites in a given airshed and to reanalysis datasets. The method is based on the daily mean wind recirculation and the mean and standard deviation between sites. The determination of the thresholds between scales is performed empirically following the approach of Levy et al. [2] and also through a automatic statistical approach computed taking into account the tails of the distributions (e.g. 95% and 99% percentile) of the different wind samples. A comparison is made with two objective approaches: 1) daily synoptic classification for the same period over the region [4] and 2) a 3-D backward trajectory approach [5,6] for specific episodes. Furthermore, the outcomes are expected to support the Portuguese authorities on the implementation of strategies for a sustainable management of environmental risks.

We present a study on the characteristics of the sea breeze flow at a coastal site located in the centre of the Mediterranean basin at the southern tip of Italy. This study is finalized to add new data on breeze circulations over a narrow peninsula and present a unique experimental coastal site at about 600 m from the coastline in a flat open area at the foot of a mountain chain located in a region of complex orography. We study the seasonal behaviour of the sea-land breeze circulation by analysing two years of hourly data of wind speed and direction, temperature, radiation and relative humidity from a surface meteorological station, eighteen-months data from a wind profiler, and two-year data from the ECMWF analysis. Results show that breezes dominate the local circulation and play a major role for the local climate. They are modulated by the season, through the sea-land temperature difference and the large-scale flow. The large-scale forcing acts in phase with the diurnal breeze and opposes the nocturnal breeze. In summer, the daytime difference between the land surface temperature and the SST (Sea Surface Temperature) reaches its maximum, while the nigh-time difference has its minimum. This causes a strong, frequent and intense diurnal breeze and a weak nocturnal breeze. In winter and fall the nocturnal difference between the sea and land surface temperature reaches a maximum value, while the diurnal difference is at its minimum value. This causes a strong, frequent and intense nocturnal breeze despite of the large-scale forcing that is usually opposed to local-scale flow.

This study evaluated 1950–2005 summer [June–August (JJA)] mean monthly air temperatures for two California air basins: the South Coast Air Basin (SoCAB) and the San Francisco Bay Area (SFBA). The study focuses on the more rapid post-1970 warming period, and its daily minima temperature Tmin and maxima temperature Tmax values were used to produce average monthly values and spatial distributions of trends for each air basin. Additional analyses included concurrent SSTs, 40-yr European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-40) sea level coastal pressure gradients, and GCM-downscaled average temperature Tave values. Results for all 253 California National Weather Service (NWS) Cooperative Observer Program (COOP) sites together showed increased Tave values (0.23°C decade−1); asymmetric warming, as Tmin values increase faster than Tmax values (0.27° versus 0.04°C decade−1) and thus decreased daily temperature range (DTR) values (0.15°C decade−1). The spatial d...

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High ozone levels are regularly measured during summer months over the inland and mountainous regions of Israel. Studies analyzing the back trajectories of air masses responsible for the high ozone levels showed that the precursors originated from the densely populated Israeli coastline. In order to better understand the contribution of those emission sources to ozone production, it is essential to have an accurate emission inventory that can be inputted into a photochemical model. The present paper describes the methods used in preparing an emission inventory for Israel based on information available and published until 1998. The source and accuracy of the data available are described. The calculations performed and the assumptions taken in order to obtain data not directly available are clarified. The sources reported in the inventory were the major polluters (power plants, oil refineries, and cement industries); industry; transportation; and biogenic sources. The pollutants studied were SO 2 , NO x , CO, saturated and unsaturated hydrocarbons, ethylene, isoprene, toluene, xylene, formaldehyde, and aldehydes. The inventory showed that transportation is responsible for almost the entire CO and 30% of the volatile organic compounds emitted, although transportation itself accounts for only a fifth of total fuel consumption. About 75% of the NO x emitted can be attributed to industrial sources and the remaining 25% to transportation. Model simulations using the emission inventory were performed and compared to data available from a monitoring station situated 30 km east of Tel Aviv. The results showed good agreement, validating the accuracy of the emission inventory. The present emission inventory provides an important database as input to photochemical models used in forecasting ozone levels over Israel.

Integral quantities, wind run, S, and recirculation factor, R, useful for describing air flow, are calculated and combined with CO 2 mixing ratios. Meteorological observations were obtained from a RASS sodar and CO 2 mixing ratios from a continuous analyzer installed at a rural site in the upper Spanish plateau. The measuring campaign spread over 3 years and two approaches were followed. The first approach considered integral quantities on a daily basis and two classifications of air flow, to date scarcely used. The first classification distinguished among stagnation, recirculation, and ventilation, the second considering synoptic, meso-, and local scales. Moreover, 52.94% of daily values handled in this paper corresponded to ventilation and 49.70% to synoptic scale. The main goal of this approach is the subsequent link between the two classifications: the synoptic scale was associated with ventilation, mesoscale with recirculation and local scale partially with recirculation. CO 2 observations were distributed in air flow groups following these classifications and mesoscale processes were satisfactorily described since noticeable evidence of transport from nearby cities was observed. In the second approach, S and R pairs were used and CO 2 mixing ratios were distributed following percent intervals of ventilation, calculated by binning these pairs. The main goal of the second approach is to consider only three groups of mixing ratios. In the first group, with high ventilation, mixing ratios were low. With intermediate ventilation, mixing ratios were medium, and with low ventilation mixing ratios were high. A contrast of 21 ppm between the third and first groups was obtained at the 95th percentile. Finally, the second group provided a contrast of 3 ppm between north and south directions and also between east and west attributed to transport from nearby cities.

Wind flow conditions play an important role in the assimilative capacities of urban airsheds. It is desired that urban planners associate due importance to wind flow conditions while designing the cities considering its likely impact on ambient air quality. Further, considering the explosive growth of megacities across the world it is required to rank these cities as per their assimilative capacities where wind flow conditions can play an important role. This study scrutinizes wind flow conditions (stagnation, ventilation and recirculation), associated air quality and emissions for two megacities namely, Delhi and Mumbai to illustrate the pivotal role, the meteorology could play in location of urban airsheds. The study shows a dominance of stagnation conditions with few cases of recirculation events over Delhi. Ambient levels of pollutants were found to correlate positively with stagnation conditions in Delhi. Mumbai was found to have higher ventilation and recirculation events and lower ambient levels of the pollutants. Further, this study for two megacities demonstrated that persistently poor air flow conditions for an urban airshed could lead to poorer air quality even with lower emissions (Delhi) in comparison to a city with lower pollution potential and higher emissions (Mumbai). Simple methodologies as adopted here could be practiced to scrutinise carrying capacities of the cities and to rank these for their pollution potential that could be helpful to regulators for emission control strategies.

An initial investigation of recirculation is carried out for the coast of the Black Sea. The local mesoscale circulations (land-sea breezes, mountain and valley winds) in coastal areas are shown to be an additional risk factor in creating favorable conditions for air stagnation and accumulation of air pollutants in the surface atmosphere layer. Two types of annual recirculation patterns are revealed for northern and north-eastern coast of the Black Sea. Long-term changes in recirculation are investigated. It is shown that the recirculation parameter values remained quasistable until the mid-1970s. Since 1976–1977, steady intensification of recirculation in both winter and summer is identified.

We present a study on the characteristics of the sea breeze flow at a coastal site located in the centre of the Mediterranean basin at the southern tip of Italy. This study is finalized to add new data on breeze circulations over a narrow peninsula and present a unique experimental coastal site at about 600 m from the coastline in a flat open area at the foot of a mountain chain located in a region of complex orography. We study the seasonal behaviour of the sea-land breeze circulation by analysing two years of hourly data of wind speed and direction, temperature, radiation and relative humidity from a surface meteorological station, eighteen-months data from a wind profiler, and two-year data from the ECMWF analysis. Results show that breezes dominate the local circulation and play a major role for the local climate. They are modulated by the season, through the sea-land temperature difference and the large-scale flow. The large-scale forcing acts in phase with the diurnal breeze and opposes the nocturnal breeze. In summer, the daytime difference between the land surface temperature and the SST (Sea Surface Temperature) reaches its maximum, while the nigh-time difference has its minimum. This causes a strong, frequent and intense diurnal breeze and a weak nocturnal breeze. In winter and fall the nocturnal difference between the sea and land surface temperature reaches a maximum value, while the diurnal difference is at its minimum value. This causes a strong, frequent and intense nocturnal breeze despite of the large-scale forcing that is usually opposed to local-scale flow.

Near-surface temperature difference (i.e. the difference between land surface skin and 2-m air temperatures-∆T) drives numerous ecological and biophysical processes on Earth, constituting an essential parameter in process-based Earth System Modeling. ∆T is known to be governed by factors like incoming solar radiation and wind, which vary according to synoptic-scale circulation via horizontal pressure gradient and cloud cover. ∆T is also affected by land surface characteristics and vegetation dynamics. Here, we assess the role of seasonality, synoptic-scale circulation and vegetation dynamics, using satellite Normalized difference vegetation index (NDVI) and latent heat estimates (LE), on the ∆T in the Eastern Mediterranean (EM). ∆T was calculated using land surface temperatures derived from the Moderate resolution imaging spectroradiometer (MODIS) and air temperatures measured at 94 meteorological stations in the EM for 2006-2010. The effect of circulation on ∆T is demonstrated for four synoptic categories covering all seasons, showing that the influence of synoptic scale circulation may be sometimes stronger than that of the seasonal signal in this region. ∆T showed negative relationships with NDVI indicating that vegetation is attenuating the near ground temperature difference, with a gradual effect increasing from southern drylands to the more humid northern vegetated areas in the EM. The relationship between ∆T and NDVI was stronger for specific synoptic classes than for seasonal division, implying the combined role of vegetation cover dynamics and synoptic scale conditions on ∆T. Findings from this study show promise for continuous spatiotemporal estimations of ∆T from LST and NDVI satellite data.

We present a study on the characteristics of the sea breeze flow at a coastal site located in the centre of the Mediterranean basin at the southern tip of Italy. This study is finalized to add new data on breeze circulations over a narrow peninsula and present a unique experimental coastal site at about 600 m from the coastline in a flat open area at the foot of a mountain chain located in a region of complex orography. We study the seasonal behaviour of the sea-land breeze circulation by analysing two years of hourly data of wind speed and direction, temperature, radiation and relative humidity from a surface meteorological station, eighteen-months data from a wind profiler, and two-year data from the ECMWF analysis. Results show that breezes dominate the local circulation and play a major role for the local climate. They are modulated by the season, through the sea-land temperature difference and the large-scale flow. The large-scale forcing acts in phase with the diurnal breeze and opposes the nocturnal breeze. In summer, the daytime difference between the land surface temperature and the SST (Sea Surface Temperature) reaches its maximum, while the nigh-time difference has its minimum. This causes a strong, frequent and intense diurnal breeze and a weak nocturnal breeze. In winter and fall the nocturnal difference between the sea and land surface temperature reaches a maximum value, while the diurnal difference is at its minimum value. This causes a strong, frequent and intense nocturnal breeze despite of the large-scale forcing that is usually opposed to local-scale flow.

When the temperature difference between land and sea surface along coastline is large enough, thermally induced circulation is likely developed in the coastal region, called as Sea/Land (S/L) breeze. It has been an important issue in coastal region because of its significant role for the transport, dispersion of air pollutants generated in coastal regions. Meso-scale modeling was carried out using the commercial modeling tool ‘A2C flow / A2C t&d (A2C represents the Atmospheric to Computational fluid dynamics and t&d represents the transport and diffusion)’ to characterize the meso-scale circulation of pure breeze in the study region (125.22E, 36.32N to 127.95E, 38.39N) in late July for typical summer conditions of Korea. Maximum potential temperature differences were approximately 5K and 14K in early morning and mid day, respectively in the study domain. Strong land breeze was observed around 6AM and it was neutralized to transition stage between 9AM ~ 10AM then the sea breeze start...

Objectives for the current study included use of SCOS97-NARSTO data to understand transport factors in the occurrence of high ozone concentrations during 4-7 August 1997. Meteorological data for the case study included observations at 110 SCOS97-NARSTO surface sites, and upper-air measurements from 12 rawinsonde and 26 profiler sites. Analysis showed that the peak ozone resulted from an infrequent combination of large-scale upper-level synoptic forcing associated with a weak local coastal 700 mb ridge. Its movements over the California South Coast Air Basin lowered and strengthened the coastal subsidence inversion and also rotated the upper-level synoptic background flow from its normal westerly onshore direction to a less common offshore easterly flow during the nighttime period preceding the peak-ozone hours. Resulting easterly upper-level background winds produced easterly surface flow directions at inland sites, so that a surface frontal convergence zone formed where this flow met the westerly onshore combined sea breeze and upslope flows. The maximum inland penetration of the convergence zone on the peak-ozone day was to the western side of the San Gabriel Mountains, the location of maximum ozone concentrations.

h i g h l i g h t s Association between circulation weather patterns, air recirculation and pollution. K-means clustering associates the recirculation potential to circulation patterns. Ventilation events dominate but recirculation and stagnation occurs frequently. High NO2, SO2 and O3 levels events varies substantially among the airsheds. Methodology can be adapted to other geographical areas.

High ozone levels are regularly measured during summer months over the inland and mountainous regions of Israel. Studies analyzing the back trajectories of air masses responsible for the high ozone levels showed that the precursors originated from the densely populated Israeli coastline. In order to better understand the contribution of those emission sources to ozone production, it is essential to have an accurate emission inventory that can be inputted into a photochemical model. The present paper describes the methods used in preparing an emission inventory for Israel based on information available and published until 1998. The source and accuracy of the data available are described. The calculations performed and the assumptions taken in order to obtain data not directly available are clarified. The sources reported in the inventory were the major polluters (power plants, oil refineries, and cement industries); industry; transportation; and biogenic sources. The pollutants studied were SO 2 , NO x , CO, saturated and unsaturated hydrocarbons, ethylene, isoprene, toluene, xylene, formaldehyde, and aldehydes. The inventory showed that transportation is responsible for almost the entire CO and 30% of the volatile organic compounds emitted, although transportation itself accounts for only a fifth of total fuel consumption. About 75% of the NO x emitted can be attributed to industrial sources and the remaining 25% to transportation. Model simulations using the emission inventory were performed and compared to data available from a monitoring station situated 30 km east of Tel Aviv. The results showed good agreement, validating the accuracy of the emission inventory. The present emission inventory provides an important database as input to photochemical models used in forecasting ozone levels over Israel.

A conically scanning, continuous-wave LIDAR is placed on an island in the central Baltic Sea with large open-water fetch, providing wind and turbulence profiles up to 300 m height. LIDAR and Weather Research and Forecasting (WRF) profiles from one year are used to characterize the marine boundary layer, at the same time performing an evaluation of the WRF model against LIDAR measurements with a focus on low-level jet representation. A good agreement is found between the average wind speed profile in WRF and LIDAR, with the largest bias occurring during stable conditions. The LLJ frequency is highest in May with frequency of occurrence ranging between 18% and 27% depending on the method of detection. Most of the LLJs occur during nighttime, indicating that most of them do not have local origin. For cases with simultaneous LLJs in both data sets the WRF agrees well with the LIDAR. In many cases, however, the LLJ is misplaced in time or space in the WRF simulations compared to the LIDA...

The main objective of this research is to identify the possible pollutant transport trajectories from the source to the receptor and to identify the location of areas of high pollution potential for ozone. In order to identify the regions which would most probably be affected by ozone and its precursors, a mesoscale trajectory model is developed and forward air‐parcel trajectories

High air pollution levels are, under certain conditions, closely related to mesoscale atmospheric circulations. Observational studies reveal that particularly in the Athens area the sea-breeze system causes a recirculation of air pollutants. In this paper a mesoscale numerical model is presented for the simulation of the flow field in the Athens basin. This model allows the description of the planetary boundary layer over land and sea, and is based on the hydrostatic assumption. Prognostic conservation equations for momentum, heat, and water vapor are solved. A major feature of the model is the solution of a non-linear heat balance equation for the surface temperature. As a first approach, a two-dimensional simulation of the sea-breeze circulation in Athens has been performed. Simulation results are presented, discussed, and compared with observations. The predicteddiurnal variation of the ground level air temperature is in good agreement with measurements. The present model may be useful for obtaining results on the transport and dispersion of air pollutants.

Results are given of a delailed study to detennine the spatial and temporal (seasonal) distributions of the plane1ary boundary layer depths (PBLD) over the Mediterranean Basin. More then 65,000 upper-air measurements from 45 rawinsonde s1ations in the Basin were compiled and analysed for two consecutive years from spring 1986 through winter 1988. A methodology using both tested and newly developed criteria was applied to determine PBLD values. As expected, the values prove to be generally higher over land and are probably minimum over the eastern and western ends of the Mediterranean Sea. Factors influencing this spatial distribution are mainly topography, the distance from the shoreline, and to a lesser extent, synoptic weather systems. The most striking temporal effect on PBLD distribution over the Mediterranean Basin is caused by larger scale synoptic weather systems. The second effect is the diurnal cycle, which has its largest impact mainly during the summer months. The PBLD values are displayed as analysed seasonal maps, from which typical values are extracted and presented in a Iabular form. The results can be used as input values for dynamic meteorological models in order to better assess the transport and dispersion over the Mediterranean Basin.

h i g h l i g h t s Association between circulation weather patterns, air recirculation and pollution. K-means clustering associates the recirculation potential to circulation patterns. Ventilation events dominate but recirculation and stagnation occurs frequently. High NO2, SO2 and O3 levels events varies substantially among the airsheds. Methodology can be adapted to other geographical areas.

The main objective of this research is to identify the possible pollutant transport trajectories from the source to the receptor and to identify the location of areas of high pollution potential for ozone. In order to identify the regions which would most probably be affected by ozone and its precursors, a mesoscale trajectory model is developed and forward air-parcel trajectories originating from Brisbane city are estimated. Eight trajectories per day, starting at 00, 03, 06, 09, 12, 15, 18 and 21 hours, are calculated for one complete calendar year. The probability distribution of trajectories shows seasonal and diurnal characteristics and prevailing transport routes of air pollution. Computer-driven trajectories indicate that air parcels are concentrated in a region between mountainous ranges in the West and islands in the East. This study identifies potential pollutant transport paths and zones of high concentrations that would assist planners in selecting appropriate areas for future industrial and urban development.

A weak-wind region, whose horizontal scale is comparable to that of an urban area, is occasionally formed ahead of the sea-breeze front, over a large coastal urban area (Yoshikado and Kondo 1989; Yoshikado 1990; Ohashi and Kida 2001). In this study, the characteristics and the formation mechanism of the weak-wind region were investigated, using a 2D mesoscale atmospheric model. The following results were obtained: The weak-wind region is created by the development of the heat-island circulation over the urban area; the heat-island circulation (i.e., the urbanward pressure-gradient-force) weakens the inlandward ambient wind during the morning hours. At that time, the sea-breeze circulation is inessential in creating this weak-wind region. The weak-wind region cannot be created under the influence of the seaward ambient wind. Subsequently, the weak-wind region is persistently formed ahead of the sea-breeze front, and gradually moves inlandward. A long-term balance between the urbanward pressure-gradient-force, and the turbulent mixing, causes such a phenomenon. Thus, interactions among the sea-breeze circulation, heat-island circulation, and inlandward ambient wind play an important role in the above processes. The spatial scale of the weak-wind region strongly depends on the urban size (width), i.e., the spatial scale of the heat-island circulation developing over the urban area, during the daytime hours.

h i g h l i g h t s Association between circulation weather patterns, air recirculation and pollution. K-means clustering associates the recirculation potential to circulation patterns. Ventilation events dominate but recirculation and stagnation occurs frequently. High NO2, SO2 and O3 levels events varies substantially among the airsheds. Methodology can be adapted to other geographical areas.

Chapter 1. Introduction 1.1 Synoptic climatology and synoptic systems 1.2 Overview of the E. Mediterranean (EM) synoptic systems 1.3 Earlier synoptic classifications Chapter 2. Goals Chapter 3. Synoptic Classification Overview 3.1 Method of Discriminant Analysis 3.2 Subjective definition of the EM synoptic systems 3.3 Modification of DA 3.4 Results: the daily classified EM synoptic systems and their primary statistics 3.5 Refinement of a classification scheme: a second-order classification Chapter 4. Seasons Overview 4.1 Synoptic definition of the Eastern Mediterranean seasons 4.2 Calendaricities and multimodality in the EM climate Chapter 5. Long-term trends and teleconnections Overview 5.1 Long-term trends in the EM synoptic systems 5.2 The EM teleconnections Chapter 6. Analysis of the General Circulation Models (GCMs) runs through synoptic classification Overview 6.1 The ECHAM4/OPYC3 and HadCM3 GCMs 6.2 The GCM simulations of long-term trends in the EM synoptic systems 6.3 The GCM simulations of seasonality in the EM synoptic systems Chapter 7. Summary Appendices A Names for the EM synoptic systems B The EM daily synoptic classification for January and July C Joint first-order/second-order classified (FC/SC) groups D Supplemental figures E Stability of the classification results

We present a study on the characteristics of the sea breeze flow at a coastal site located in the centre of the Mediterranean basin at the southern tip of Italy. This study is finalized to add new data on breeze circulations over a narrow peninsula and present a unique experimental coastal site at about 600 m from the coastline in a flat open area at the foot of a mountain chain located in a region of complex orography. We study the seasonal behaviour of the sea-land breeze circulation by analysing two years of hourly data of wind speed and direction, temperature, radiation and relative humidity from a surface meteorological station, eighteen-months data from a wind profiler, and two-year data from the ECMWF analysis. Results show that breezes dominate the local circulation and play a major role for the local climate. They are modulated by the season, through the sea-land temperature difference and the large-scale flow. The large-scale forcing acts in phase with the diurnal breeze and opposes the nocturnal breeze. In summer, the daytime difference between the land surface temperature and the SST (Sea Surface Temperature) reaches its maximum, while the nigh-time difference has its minimum. This causes a strong, frequent and intense diurnal breeze and a weak nocturnal breeze. In winter and fall the nocturnal difference between the sea and land surface temperature reaches a maximum value, while the diurnal difference is at its minimum value. This causes a strong, frequent and intense nocturnal breeze despite of the large-scale forcing that is usually opposed to local-scale flow.

The impact of the air pollution generated by any industrial activities may be further aggravated if the location of the industrial area is exposed to certain atmospheric characteristics. Under such conditions, the likelihood of accumulation of local air pollution is high. This paper uses two approaches (statistical and numerical simulation) to investigate the contribution of atmospheric processes towards degradation of air quality. A case study of the two approaches was conducted over Sohar Industrial Area in the Sultanate of Oman. Measured wind data were used to account for specific atmospheric characteristics such as stagnation, ventilation, and recirculation using the statistical approach. In the second approach, numerical weather prediction model was used to simulate mesoscale circulation phenomena such as sea breeze and its contribution to the processes affecting the air quality. The study demonstrates that the atmospheric processes appear to contribute substantially to the degradation of air quality in the Sohar Industrial Area. The statistical analysis shows that the atmospheric dilution potential of Sohar Industrial Area is prone to stagnation and recirculation, rather than ventilation. Moreover, model simulation shows that there is a seasonal variation in the contribution of atmospheric processes to the degradation of the air quality at Sohar Industrial Area.

A pollution episode occurred early in November 198 1, In the heavily industrialized area of Bilbao, a deep estuarine valley in northern Spain. Hourly average values from the automatic SO2 monitoring network indicate that 800 and 4OOpg (Nm3)-' were exceeded 2 and 55 times. respectiveI>. under stagnating anticyclonic conditions with weak gradient flow. In these conditions a meso-meteorological cycle developed whereby night drainage winds carried the pollutants to the sea, followed by their re-entry with the sea-breeze the next day. High emissions, or those which penetrated the ground based inversion. were initially dispersed out of the area. However, once the subsidence joined the anticyclonic and night-time inversions. all emissions were trapped within the reflux cycle resulting in the highest observed SOI ground levels. Unequal reaches within the cycle brought a net daily influx of clean ocean air which avolded a larger accumulation of pollutants in the area.

An estimation of SO 2 dispersion over complex terrain is attempted, using the diagnostic wind ®eld generated from limited meteorological data. This eort aims to face the realistic requirement of emergency-response in case of industrial plants settled in poorly instrumented areas. The combination of three numerical procedures is utilized: (1) detailed topographical simulation; (2) meteorological diagnosis using experimental data and accounting for terrain in¯uences; and (3) dispersion calculations based on the diagnosed conditions. For the meteorological diagnosis a conditional exploitation of the measurements is made, allowing the inclusion of topographical eects. This is achieved by recognizing dierent terrain features, such as plains, valleys, slopes and coasts. This allows the division of the terrain into areas expected to follow the same withÐor dierent fromÐthe station,¯ow regime. Application is made for a power plant at Megalopolis valley, Greece. The hourly meteorological measurements from one surface station are used, with synoptic information from weather charts. The SO 2 dispersion from three buoyant sources is calculated for several days. The obtained daily average concentrations at nine locations are compared with observational values, using the bootstrap resampling evaluation method.

Western Java area has been numerically investigated using PSU-NCAR MM5. Mesoscale numerical simulation was performed under the synoptic scale meteorology by ECMWF data with a resolution of 0.50 X 0.50. Five days long simulation on 4-9 March 2001 was carried out. During this period, the quite strong sea breeze developed on 5

Integral quantities, wind run, S, and recirculation factor, R, useful for describing air flow, are calculated and combined with CO 2 mixing ratios. Meteorological observations were obtained from a RASS sodar and CO 2 mixing ratios from a continuous analyzer installed at a rural site in the upper Spanish plateau. The measuring campaign spread over 3 years and two approaches were followed. The first approach considered integral quantities on a daily basis and two classifications of air flow, to date scarcely used. The first classification distinguished among stagnation, recirculation, and ventilation, the second considering synoptic, meso-, and local scales. Moreover, 52.94% of daily values handled in this paper corresponded to ventilation and 49.70% to synoptic scale. The main goal of this approach is the subsequent link between the two classifications: the synoptic scale was associated with ventilation, mesoscale with recirculation and local scale partially with recirculation. CO 2 observations were distributed in air flow groups following these classifications and mesoscale processes were satisfactorily described since noticeable evidence of transport from nearby cities was observed. In the second approach, S and R pairs were used and CO 2 mixing ratios were distributed following percent intervals of ventilation, calculated by binning these pairs. The main goal of the second approach is to consider only three groups of mixing ratios. In the first group, with high ventilation, mixing ratios were low. With intermediate ventilation, mixing ratios were medium, and with low ventilation mixing ratios were high. A contrast of 21 ppm between the third and first groups was obtained at the 95th percentile. Finally, the second group provided a contrast of 3 ppm between north and south directions and also between east and west attributed to transport from nearby cities.

We present a study on the characteristics of the sea breeze flow at a coastal site located in the centre of the Mediterranean basin at the southern tip of Italy. This study is finalized to add new data on breeze circulations over a narrow peninsula and present a unique experimental coastal site at about 600 m from the coastline in a flat open area at the foot of a mountain chain located in a region of complex orography. We study the seasonal behaviour of the sea-land breeze circulation by analysing two years of hourly data of wind speed and direction, temperature, radiation and relative humidity from a surface meteorological station, eighteen-months data from a wind profiler, and two-year data from the ECMWF analysis. Results show that breezes dominate the local circulation and play a major role for the local climate. They are modulated by the season, through the sea-land temperature difference and the large-scale flow. The large-scale forcing acts in phase with the diurnal breeze and opposes the nocturnal breeze. In summer, the daytime difference between the land surface temperature and the SST (Sea Surface Temperature) reaches its maximum, while the nigh-time difference has its minimum. This causes a strong, frequent and intense diurnal breeze and a weak nocturnal breeze. In winter and fall the nocturnal difference between the sea and land surface temperature reaches a maximum value, while the diurnal difference is at its minimum value. This causes a strong, frequent and intense nocturnal breeze despite of the large-scale forcing that is usually opposed to local-scale flow.