Land-sea Breeze Circulation Research Articles

Transient land breeze: Eclipse induced wind flow modifications—Observations over plant canopy

An experiment is conducted over Cassava plant canopy at a coastal station at CTCRI, Thiruvananthapuram (8°29'N, 76°59E) to study the response of meteorological parameters and land–sea breeze circulations to the annular solar eclipse on January 15, 2010. Observations reveal decrease of solar radiation to a minimum of 96Wm−2 during the peak eclipse period. Air temperature drops by 4°C and relative humidity increases by 20%. Sensible heat flux reduces to zero. Transient land breeze occurs for a few minutes with a time lag of about 1h possibly due to outflow from the umbra region or temperature gradient over land with the eclipse progressing in the eastward direction. Sea breeze is delayed by about 3h on the next day of eclipse. Spectral energy density of wind (u, v, w) and temperature attains a minimum value during totality and increases later, attributable to reduction in turbulence due to eclipse-induced stability.

Fog Prediction for Road Traffic Safety in a Coastal Desert Region

Modern weather prediction models use relatively high grid resolutions as well as sophisticated parametrization schemes for microphysical and other subgrid-scale atmospheric processes. Nonetheless, with these models it remains a difficult task to perform successful numerical fog forecasts since many factors controlling a particular fog event are not yet sufficiently simulated. Here we describe our efforts to create a mechanism that produces successful predictions of fog in the territory located on the north coast of the Arabian Peninsula. Our approach consists in the coupling of the one-dimensional PAFOG fog model with the three-dimensional WRF 3.0 (Weather Research and Forecast) modelling system. The proposed method allows us to construct an efficient operative road traffic warning system for the occurrence of fog in the investigated region. In total 84 historical situations were studied during the period 2008–2009. Moreover, results of operative day-by-day fog forecasting during January and February 2010 are presented. For the investigated arid and hot climate region the land-sea breeze circulation seems to be the major factor affecting the diurnal variations of the meteorological conditions, frequently resulting in the formation of fog.

Assessment of the impact of the meteorological meso-scale circulation on air quality in arid subtropical region

In this paper, COSMO numerical weather prediction model is used to simulate land-sea breeze circulation in the north coast of Oman and to analyze the variability of the PBL depth. Typical summer day 1st August 2009 and winter day 1st January 2009 were simulated and verified by surface observations. The COSMO model was initialized using the German global model which runs as 40km resolution and 40 vertical layers. The simulations show differences in the onset, strength, and inland penetration of the sea breeze. The high sea-land thermal contrast in the summer season induces earlier onset and progression of the sea breeze with larger horizontal and vertical extents. The summer and winter inland penetration is simulated around 150 and 65km, respectively. The PBL depth was defined from the verticals profiles of the turbulence kinetic energy (TKE). The simulated PBL height varied at 1,600m in summer and 700m in the winter case. These results are in general in good agreement with the simulations of the National Centers for Environmental Prediction Global Data Assimilation System (NCEP-GDAS) model. The dispersive ability of the atmosphere was tested through the vertical mixing coefficient (VMC) generated by NCEP-GDAS simulations. The VMC during the summer simulated case is approximately four times larger than the respective one during the winter case. Consequently, during the advection of winter sea breeze, a shallow dome less than 100m is shaped and forms an obstacle to the air-pollutant dispersion.

Modeling Air–Land–Sea Interactions Using the Integrated Regional Model System in Monterey Bay, California

The air–land–sea interaction in the vicinity of Monterey Bay, California, is simulated and investigated using a new Integrated Regional Model System (I-RMS). This new model realistically resolves coastal processes and submesoscale features that are poorly represented in atmosphere–ocean general circulation models where systematic biases are seen in the long-term model integration. The current I-RMS integrates version 3.1 of the Weather Research and Forecasting Model and version 3.0 of the Community Land Model with an advanced coastal ocean model, based on the nonhydrostatic Monterey Bay Area Regional Ocean Model. The daily land–sea-breeze circulations and the Santa Cruz eddy are fully resolved using high-resolution grids in the coastal margin. In the ocean, coastal upwelling and submesoscale gyres are also well simulated with this version of the coupled I-RMS. Comparison with observations indicates that the high-resolution, improved representation of ocean dynamics in the I-RMS increases the surface moisture flux and the resulting lower-atmospheric water vapor, a primary controlling mechanism for the enhancement of regional coastal fog formation, particularly along the West Coast of the conterminous United States. The I-RMS results show the importance of detailed ocean feedbacks due to coastal upwelling in the marine atmospheric boundary layer.

Simulation of Wind Circulation and Pollutant Diffusion Over the Pearl River Delta Region

Changes in urban surface areas and population growth have significantly affected the weather and environment. Emissions of nitrogen oxides are increasing in the Pearl River Delta region. Nitrogen compounds emitted by factories and motor vehicles are the major sources of nitric pollution. To study the impacts of urbanization and the relationship between pollutant diffusion and the atmospheric environment, the nonhydrostatic mesoscale forecast model MM5 (v3.73), which was developed by Penn State University and the National Center of Atmospheric Research, and a mass continuity equation for air pollutants, were used in this study. Two experiments were designed. One experiment (BE) applied horizontal grid resolutions of 27, 9, 3, and 1 km in four nested domains. The other experiment adopted new land-use data (in domain 4) directly retrieved from Landsat Thematic Mapper imagery to replace the 1980s data of the United States Geological Survey in BE. A 48-h simulation (from 0000 UTC on 21 October to 0000 UTC on 23 October 2008) was conducted, with the first 12 h being the spin-up time and the remaining 36 h being the effective simulation, so as to capture the diurnal features of the thermally induced winds associated with the land–sea breeze and urban heat island circulations. The different results obtained from the two tests for wind circulation and air pollution dispersion and transportation in the Pearl River Delta region were analyzed. The simulated results show that the both experiments can well simulate land–sea breeze circulation and remarkable land–sea breeze evolution, comparing with observation data. The height of the PBL had a significant diurnal cycle. The structure of the wind field can obviously impact the dispersion of the NO x in three dimensions. Nitrogen oxides mainly diffused along the dominant wind direction (east or southeast wind), therefore the majority of the pollutants accumulated in the northwest region of the fine domain in both simulation experiments. However, it induced the pollutants concentration in an irregular pattern due to the fine-resolution grid spaces and complicated inland wind field in the northwest area of the inner domain. Moreover, increasing the proportion of urban surface caused sensible heat flux increase, latent heat flux decrease and humility reducing relatively in the region of urban surface characteristics apparently. Urbanization will cause pollution accumulated severely over the urban surface.

Wind Climate in Kongsfjorden, Svalbard, and Attribution of Leading Wind Driving Mechanisms through Turbulence-Resolving Simulations

This paper presents analysis of wind climate of the Kongsfjorden-Kongsvegen valley, Svalbard. The Kongsfjorden-Kongsvegen valley is relatively densely covered with meteorological observations, which facilitate joint statistical analysis of the turbulent surface layer structure and the structure of the higher atmospheric layers. Wind direction diagrams reveal strong wind channeled in the surface layer up to 300 m to 500 m. The probability analysis links strong wind channeling and cold temperature anomalies in the surface layer. To explain these links, previous studies suggested the katabatic wind flow mechanism as the leading driver responsible for the observed wind climatology. In this paper, idealized turbulence-resolving simulations are used to distinct between different wind driving mechanisms. The simulations were performed with the real surface topography at resolution of about 60 m. These simulations resolve the obstacle-induced turbulence and the turbulence in the non-stratified boundary layer core. The simulations suggest the leading roles of the thermal land-sea breeze circulation and the mechanical wind channeling in the modulation of the valley winds. The characteristic signatures of the developed down-slope gravity-accelerated flow, that is, the katabatic wind, were found to be of lesser significance under typical meteorological conditions in the valley.

군집분석과 상세기상모델을 통한 포항지역 계절별 바람장 특성

The typical characteristics of seasonal winds were studied around the Pohang using two-stage (average linkage then k-means) clustering technique based on u- and v-component wind at 850 hpa from 2004 to 2006 (obtained the Pohang station) and a high-resolution (0.5 km grid for the finest domain) WRF-UCM model along with an up-to-date detailed land use data during the most predominant pattern in each season. The clustering analysis identified statistically distinct wind patterns (7, 4, 5, and 3 clusters) representing each spring, summer, fall, and winter. During the spring, the prevailed pattern (80 days) showed weak upper northwesterly flow and late sea-breeze. Especially at night, land-breeze developed along the shoreline was converged around Yeongil Bay. The representative pattern (92 days) in summer was weak upper southerly flow and intensified sea-breeze combined with sea surface wind. In addition, convergence zone between the large scale background flow and well-developed land-breeze was transported around inland (industrial and residential areas). The predominant wind distribution (94 days) in fall was similar to that of spring showing weak upper-level flow and distinct sea-land breeze circulation. On the other hand, the wind pattern (117 days) of high frequency in winter showed upper northwesterly and surface westerly flows, which was no change in daily wind direction.

Variations of respirable suspended particulates in Hong Kong: cross-boundary and local effects

Analysis of the spatial and temporal variability of respirable suspended particulates (RSP) observed in 11 Hong Kong general stations over the period 2000–2008 shows a high concentration in the northwest and low concentration in the southeast and coastal areas, with the central area in between. Seasonally, RSP concentration is highest in winter, followed by autumn, and is lowest in summer. A bimodal peak in diurnal cycle with peaks in the morning (7–8 a.m.) and early evening (6–7 p.m.) can be attributed to rush-hour traffic flows as well as local land–sea breeze circulations. The effect of vehicular emission is also demonstrated in a distinct weekly cycle, with a Sunday minimum. Analysis of RSP concentration for different wind directions shows the importance of cross-boundary transport of pollutants from the Pearl River Delta area, with 43% of noncompliant cases associated with cross-boundary transport. An empirical orthogonal function (EOF) analysis shows that the first EOF pattern of RSP changes is characterized by changes of the same sign for all 11 general stations, with the second pattern dominated by changes in the Yuen Long station. Time series analysis shows that changes in the second EOF leads the first, indicating that changes in Yuen Long (northwest) precede changes elsewhere. Stations located in the coastal area change last. Tap Mun shows significant increasing trends in RSP concentration, particularly for incidences of high RSP occurrences, which may be attributed to increases in shipping in the Yan Tian International Container Terminal. Raymond Kwok-Cheung Lok is currently affiliated with the HK Transport Department.

Assessment of the canopy urban heat island of a coastal arid tropical city: The case of Muscat, Oman

The spatio-temporal variability of the canopy-level urban heat island (UHI) of Muscat is examined on the basis of meteorological observations and mobile measurements during a span of 1 year. The results indicate that the peak UHI magnitude occurs from 6 to 7 hours after sunset and it is well developed in the summer season. The warm core of the UHI is located in the Highland zone of Muscat, along a narrow valley characterized by low ventilation, high business activities, multi-storied buildings and heavy road traffic. Topographically, this valley is surrounded by mountains formed of dark-colored rocks such Ophiolites that can absorb short wave radiation and contribute, herewith, to the emergence of this warm urban core. In addition, this mountainous terrain tends to isolate this location from the cooling effect of the land–sea breeze circulation during the day time. In this warm valley the hottest temperature is encountered in the compact districts of old Muscat. In comparison, the urban thermal pattern in Lowland zone of Muscat is fragmented and the urban–rural thermal difference is reduced because of the lower urban density of the residential quarters. In addition, the flat alluvial terrain on which these residential quarters are located is consistently exposed to the land breeze circulation. Also, the study illuminates and emphasizes the importance giving due consideration to the nature of the rural baseline when assessing the urban effect on an area's climate. For Muscat City, irrespective of the rural baseline used, a significant difference in the value of the urban heat island is registered.

Integral assessment of air pollution dispersion regimes in the main industrialized and urban areas in Oman

This paper presents a rather complete picture of conditions of stagnation, recirculation and ventilation factors in the main industrialized and urban areas in Oman, developed along the coastal area. This study focuses on four sites; Sohar, Muscat, Sur, and Salalah. Each site has a local emission sources from transportation, industry and energy production activities. For the calculation of the integral quantities of the ability of the atmosphere dilution, hourly data of the wind velocity measured at a height of 10 m during 5 years (2000–2005) were used in the analysis. The results show that in the northern coast of Oman, along the bay of Sea of Oman, where 56% of the total population is concentrated and the main heavy industries of the country are amassed, the atmosphere is prone to stagnations in 74.4% of the time, while in the southern and east part of Oman, they occur only 23% and 51%, respectively. The bay of sea of Oman is high affected by land–sea breeze circulation that plays a substantial role in the simultaneous occurrence of recirculation equally to stagnation. This meso-scale effect is altered gradually during the passage of the synoptic-scale flow of the southeasterly summer monsoon that enhances the occurrence of the ventilation in Salalah (24.6% of time) and Sur (15.5%). In the northern coast of Oman, where the Hajir mountains suppressed the effect of the summer monsoon, a very weak tendency towards ventilation is observed (less than 6%). The southern summer monsoon over Oman is a source of life in this arid area and as well a source of clean air.

Simulation of coastal winds along the central west coast of India using the MM5 mesoscale model

A high-resolution mesoscale numerical model (MM5) has been used to study the coastal atmospheric circulation of the central west coast of India, and Goa in particular. The model is employed with three nested domains. The innermost domain of 3 km mesh covers Goa and the surrounding region. Simulations have been carried out for three different seasons—northeast (NE) monsoon, transition period and southwest (SW) monsoon with appropriate physics options to understand the coastal wind system. The simulated wind speed and direction match well with the observations. The model winds show the presence of a sea breeze during the NE monsoon season and transition period, and its absence during the SW monsoon season. In the winter period, the synoptic flow is northeasterly (offshore) and it weakens the sea breeze (onshore flow) resulting in less diurnal variation, while during the transition period, the synoptic flow is onshore and it intensifies the sea breeze. During the northeast monsoon at an altitude of above 750 m, the wind direction reverses, and this is the upper return current, indicating the vertical extent of the sea breeze. A well-developed land sea breeze circulation occurs during the transition period, with vertical extension of 300 and 1,100 m, respectively.

Analysis of Wind Roses Using Hierarchical Cluster and Multidimensional Scaling Analysis at La Plata, Argentina

Knowledge of frequency wind patterns is very important for air pollution modelling, especially in a city like La Plata (approximately 850,000 inhabitants) with high vehicular and industrial activities and no air monitoring network. An hourly wind analysis was carried out on data from two local weather stations (points A and J). An initial result was that, in spite of differences in data quality, the local weather stations observations were consistent with local and regional National Meteorological Service (NMS) monthly based observations. Two non conventional multivariate statistical methods were employed to further analyse hourly data at points A and J. Hierarchical cluster resulted in a good summarising tool to visualise prevailing hourly winds. Resultant vectors emerging from the clustering process showed good similarity between sites and seasons; this allowed a further visualization of the average diurnal wind development. Multidimensional scaling (MDS) permitted a pairwise comparison of a large number of hourly wind roses. These wind roses were more similar to each other in colder seasons and at site A (the one that is closer to the river) than in warmer seasons and at site J. Most of the observed variations regarding seasons and sites revealed by cluster and MDS analysis are explained in terms of the sea-land breeze circulations. The methodology applied proved to be of utility for simplifying the analysis of high dimensional data with numerous observations.

Urban heat island effects of the Pearl River Delta city clusters—their interactions and seasonal variation

Previous studies have shown that urbanization in the Pearl River Delta (PRD) region in southern China can have significant effect on the land-sea breeze circulation in the region. In this study, some characteristics of this urban heat island (UHI) effect are further investigated by some idealized numerical experiments. This study focuses on three aspects of the UHI effects. Firstly, the interaction of UHI effects associated with different city clusters in the PRD region. Secondly, the UHI effect and the strength of the background wind field. Thirdly, seasonal variation of the UHI effect. Experiment results suggest that the interaction of the UHI effects due to the closely distributed city clusters in the PRD region is not significant, while the UHI effect in the region may depend on the strength of the background wind. The seasonal-mean UHI effect in the region shows a significant variation associated with the change of seasons.

A planetary‐scale land–sea breeze circulation in East Asia and the western North Pacific

AbstractThe diurnal wind variation over the East Asian continent is commonly considered to be a combination of a land‐sea breeze near the coast and a mountain–valley breeze along the slopes of the Tibetan Plateau. The local land–sea breeze along the coastline typically spans < 100 km into the ocean. However, a detailed examination of the global reanalysis data suggests that this local land–sea breeze circulation apparently couples with the global‐scale diurnal atmospheric pressure tide to produce a planetary‐scale land–sea breeze with a spatial scale of ∼1000 km over the western North Pacific. Computations of the momentum budget and equivalent potential temperatures indicate that the atmospheric diurnal tidal wave contributes the most to this circulation feature. A diagnosis of the water vapour budget further suggests that the convergence of water vapour flux, which is related to the convergence of low‐level wind induced by the seasonal change of diurnal tidal wave, leads to different times of occurrence of maximum diurnal rainfall over East Asia between summer and winter. Copyright © 2010 Royal Meteorological Society

The seasonal characteristics of the breeze circulation at a coastal Mediterranean site in South Italy

Abstract. 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.

Analysis of the Surface Ozone During Summer and Autumn at a Coastal Site in East China

The levels and temporal variations of surface ozone at a coastal site in East China during summer and autumn were analyzed and the influences of meteorological parameters on ozone were investigated. An inland city was chosen as a comparison site. The main results and conclusions of this study are: (1) ozone pollution, with a maximum 1 h concentration of 150.98 ppbv, was severe during summer and autumn at the coastal site; (2) the ozone level was obviously higher at the coastal site than that at the inland site in September; (3) besides temperature and solar radiation, sea-land breeze circulation is an important factor influencing the ozone level at the coastal site, and sea breeze often induce high ozone levels (the average ozone concentration for sea breeze was about 13 ppbv higher than that for land breeze).

On the Tropospheric Ozone Variations in a Coastal Area of Southwestern Europe under a Mesoscale Circulation

Abstract It is well established that surface ozone levels are greatly affected by orography, solar radiation intensity, meteorological conditions, and the levels of their precursors. In this work, the authors study the sea–land breeze circulation in its relation with the behavior of ozone in a coastal area, located in southwestern Europe, with high levels of solar radiation and an important industrial complex emitting air pollutants. Hourly mean data over a 7-yr period (1999–2005) have been used in the study. Two patterns of sea–land breeze have been identified after analyzing 2298 days of measurements: a “pure” breeze (179 cases) and another one, called a “nonpure” breeze (284 cases), which is the resulting flow of the former and northwesterlies synoptic forcing. Among other results, the highest levels of surface ozone were observed under pure sea–land breeze, with hourly values up to 100 μg m−3 in the mean daily evolution. In contrast, for a nonpure breeze, the 24-h average daily value was lower than the corresponding one under a pure breeze by a factor of 1.16 and could reach 1.60 in representative real cases. These findings give evidence that the formation and accumulation of ozone are favored by the conditions under a pure sea–land breeze: that is, perpendicular wind directions toward the coastline, effective recirculation of air masses, and formation of ozone residual layers above the sea. Because these atmospheric conditions occur in other coastal regions in the world, the conclusions of this study could be extended to them.

라그랑지안 입자확산모델을 이용한 광양만 권역에서의 공기괴 재순환현상 수치모의

Air mass recirculation is a common characteristic in the coastal area as a result of the land-sea breeze circulation. This study simulates the recirculation of air mass over the Gwangyang Bay using WRF-FLEXPART and offers a basic information about the effective domain size that can reflect recirculation. For this purpose, WRF is set up four nested domains and three cases are selected. Subsequently FLEXPART is operated on the basis of WRF output. During the clear summer days with weak wind speed, particles that emitted from Yeosu national industrial complex and Gwangyang iron works flow into emission sources because of the land-sea breeze. When land-sea breeze is strengthen, the recirculation phenomena appears clearly. However particles aren't recirculated under weak synoptic condition. Also plume trajectory is analyzed and as a consequence, the smallest domain area have to be multiplied by 1.3 to understand recirculated dispersion pattern of particles.

Random-walk model simulation of air pollutant dispersion in atmospheric boundary layer in China

In this study, the land-sea breeze circulation model coupled with a random-walk model is developed by the analysis of the formation and the mechanism of the land-sea breeze. Based on the data of the land-sea circulation in Dalian, China, the model simulated the diurnal variation of pressure, flow, temperature, and turbulent kinetic energy field and also provides a basis for solving the air pollutant concentration in the land-sea breeze circulation so as to estimate the economic cost attributable to the atmospheric pollution. The air pollutant concentration in the background of land-sea circulation is also simulated by a Gaussian dispersion model, and the results revealed that the land-sea circulation model coupled with the random-walk model gives a reasonable description of air pollutant dispersion in coastal areas.

Lightning characteristics observed by a VLF/LF lightning detection network (LINET) in Brazil, Australia, Africa and Germany

Abstract. This paper describes lightning characteristics as obtained in four sets of lightning measurements during recent field campaigns in different parts of the world from mid-latitudes to the tropics by the novel VLF/LF (very low frequency/low frequency) lightning detection network (LINET). The paper gives a general overview on the approach, and a synopsis of the statistical results for the observation periods as a whole and for one special day in each region. The focus is on the characteristics of lightning which can specifically be observed by this system like intra-cloud and cloud-to-ground stroke statistics, vertical distributions of intra-cloud strokes or peak current distributions. Some conclusions regarding lightning produced NOx are also presented as this was one of the aims of the tropical field campaigns TROCCINOX (Tropical Convection, Cirrus and Nitrogen Oxides Experiment) and TroCCiBras (Tropical Convection and Cirrus Experiment Brazil) in Brazil during January/February 2005, SCOUT-O3 (Stratospheric-Climate Links with Emphasis on the Upper Troposphere and Lower Stratosphere) and TWP-ICE (Tropical Warm Pool-International Cloud Experiment) during November/December 2005 and January/February 2006, respectively, in the Darwin area in N-Australia, and of AMMA (African Monsoon Multidisciplinary Analyses) in W-Africa during June–November 2006. Regional and temporal characteristics of lightning are found to be dependent on orographic effects (e.g. S-Germany, Brazil, Benin), land-sea breeze circulations (N-Australia) and especially the evolution of the monsoons (Benin, N-Australia). Large intra-seasonal variability in lightning occurrence was found for the Australian monsoon between the strong convection during build-up and break phases and the weak active monsoon phase with only minor lightning activity. Total daily lightning stroke rates can be of comparable intensity in all regions with the heaviest events found in Germany and N-Australia. The frequency of occurrence of such days was by far the largest in N-Australia. In accordance with radar observed storm structures, the intra-cloud stroke mean emission heights were found distinctly different in Germany (8 km) as compared to the tropics (up to 12 km in N-Australia). The fraction of intra-cloud strokes (compared to all strokes) was found to be relatively high in Brazil and Australia (0.83 and 0.82, respectively) as compared to Benin and Germany (0.64 and 0.69, respectively). Using stroke peak currents and vertical location information, lightning NOx (LNOx) production under defined standard conditions can be compared for the different areas of observation. LNOx production per standard stroke was found to be most efficient for the N-Australian and S-German thunderstorms whereas the yield from Brazilian and W-African strokes was nearly 40% less. On the other hand, the main NO contribution in Brazil was from intra-cloud (IC) strokes whereas in Benin it was due to cloud-to-ground (CG) components. For the German and Australian strokes both stroke types contributed similar amounts to the total NO outcome.