An Observational Study of Sea- and Land-Breeze Circulation in an Area of Complex Coastal Heating
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The diurnal evolution of the three-dimensional structure of a mesoscale circulation system frequently occurring in the area of Kennedy Span Center-Cape Canaveral has been studied using the data from the Kennedy Space Center Atmospheric Boundary Layer Experiment (KABLE). The case was chosen from the spring intensive data-collection period when the greatest daytime temperature difference between land and water (sea and inland rivers) occurs and the local circulations are most intense. The daytime flow structure was determined primarily by the mesoscale pressure-gradient form created by the temperature contrast between land and water. A strong sea-breeze circulation, the dominant feature of the daytime flow field, was modified by a local inland river breeze known as the Indian River breeze, in that divergent flow over the river enhanced the sea-breeze convergence on the seaward side and generated additional convergence on the landward side of the river. The rivers near the coastline also modified the initial flow field by enhancing convergence in the surrounding areas and speeding up the movement of the sea-breeze front. The nighttime flow structure was dominated by a large-scale land breeze that was relatively uniform over the area and became quasi-stationary after midnight. The nonuniformity of the wind-vector rotation rate suggests that mesoscale forcing significantly modifies the Coriolis-induced oscillation. No clear convergence patterns associated with the rivers were observed at night. Detailed characteristics over a diurnal cycle of the sea-land breeze and of the river breeze onset time, strength, depth, propagation speed and both landward and seaward extension, are documented in this study. Some boundary-layer characteristics needed for predicting diffusion of pollutants released from coastal launch pads, including atmospheric stability, depth of the thermal internal boundary layer, and turbulent mixing are also discussed.Keywords:
Sea breeze
Convergence zone
Potential temperature
Forcing (mathematics)
The diurnal evolution of the three-dimensional structure of a mesoscale circulation system frequently occurring in the area of Kennedy Span Center-Cape Canaveral has been studied using the data from the Kennedy Space Center Atmospheric Boundary Layer Experiment (KABLE). The case was chosen from the spring intensive data-collection period when the greatest daytime temperature difference between land and water (sea and inland rivers) occurs and the local circulations are most intense. The daytime flow structure was determined primarily by the mesoscale pressure-gradient form created by the temperature contrast between land and water. A strong sea-breeze circulation, the dominant feature of the daytime flow field, was modified by a local inland river breeze known as the Indian River breeze, in that divergent flow over the river enhanced the sea-breeze convergence on the seaward side and generated additional convergence on the landward side of the river. The rivers near the coastline also modified the initial flow field by enhancing convergence in the surrounding areas and speeding up the movement of the sea-breeze front. The nighttime flow structure was dominated by a large-scale land breeze that was relatively uniform over the area and became quasi-stationary after midnight. The nonuniformity of the wind-vector rotation rate suggests that mesoscale forcing significantly modifies the Coriolis-induced oscillation. No clear convergence patterns associated with the rivers were observed at night. Detailed characteristics over a diurnal cycle of the sea-land breeze and of the river breeze onset time, strength, depth, propagation speed and both landward and seaward extension, are documented in this study. Some boundary-layer characteristics needed for predicting diffusion of pollutants released from coastal launch pads, including atmospheric stability, depth of the thermal internal boundary layer, and turbulent mixing are also discussed.
Sea breeze
Convergence zone
Potential temperature
Forcing (mathematics)
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Computations of peninsula-scale convergence in southern Florida reveal that daily-averaged surface convergence on sea-breeze days with relatively little rainfall is larger than on days with widespread rain. This negative correlation between surface convergence and area-averaged rainfall occurs as a result of significantly less surface convergence in the late afternoon and early evening on those days with considerable rainfall. The decrease in sea-breeze convergence during the late afternoon of the days with extensive rainfall is apparently a consequence of the downdrafts and thunderstorm-generated circus cloud cover produced by the deep convection that forms in the sea-breeze convergence zones. Before the typical midafternoon maximum of deep convection on sea-breeze days, there is no significant difference between the surface convergence averaged for days with widespread rain and for days with little rain. Important differences are observed, however, in the middle troposphere, where the sea-breeze days with widespread rain are more moist and have cooler temperatures than the days with little or no rain. The observations suggest that both the magnitude and timing of the convective response to the sea-breeze forcing during the afternoon are very sensitive to the moisture amount and some-what less sensitive to the thermal stability in the midtroposphere.
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Convergence zone
Synoptic scale meteorology
Peninsula
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The automatic weather station data were used to research the evolution and impact factors of tropical island sea breeze convergence in September 2, 2010. Temporal and spatial variation of sea breeze convergence zone, atmospheric background field, physical field and other relevant factors about a typical sea-land breeze process in Hainan Island were diagnostic analyzed. Mesoscale meteorological model WRF was created to simulate the sea-land breeze. The results showed that the subtropical and tropical cyclone were the main synoptic situation which affected the temporal and spatial variation of the sea breeze convergence zone, so there was a significant difference of sea breeze process between both sides of the island. Mesoscale meteorological model WRF simulated the vertical structural features of sea-land breeze circulation and the evolution low of sea breeze convergence zone successfully, resolution of 45 × 15km having a better simulation effect.
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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 × 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 and 6 March. On March 6, 2001, at 1300 LST, the sea breeze penetrated to around 20 km from the coast of Jakarta. In this season, over Java area a synoptic scale convergence line is formed by WSW and NW winds. This synoptic WSW wind blowing over Java tends to prohibit inlandward advancement of the sea breeze. Depth of the sea breeze, on 6 Mar 2001 at 1200, 1300, 1400, and 1500 LST was 0.5, 0.8, 0.4, and 0.2 km, respectively; because of subsidence behind the convergence line by the synoptic WSW wind and the sea breeze from Java sea, upper part of the sea breeze layer was warmed after 1500 LST and thus the depth of the sea breeze was suppressed. Predicted near-surface wind at 4-9 March 2001 appears dominantly with westerly wind. In mountain area, wind direction was affected by a mountain wave. Highpressure system tends to be formed to the northeast of the Sunda street because of the topography. Then this highpressure system in turn generates dry stable layer over Jakarta at 2, 000-4, 000 m height and may suppress vertical diffusion of pollutants over Jakarta.
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Abstract The interaction of a summer frontal bora and the sea‐land breeze along the north‐eastern Adriatic coast was investigated by means of numerical simulations and available observations. Available measurements ( in situ , radiosonde, satellite images) provided model validation. The modelled wind field revealed several regions where the summer bora (weaker than 6 m s −1 ) allowed sea‐breeze development: in the western parts of the Istrian peninsula and Rijeka Bay and along the north‐western coast of the island of Rab. Along the western Istrian coast, the position of the narrow convergence zone that formed depended greatly on the balance between the bora jets northward and southward of Istria. In the case of a strong northern (Trieste) bora jet, the westerly Istrian onshore flow presented the superposition of the dominant swirled bora flow and local weak thermal flow. It collided then with the easterly bora flow within the zone. With weakening of the Trieste bora jet, the convergence zone was a result of the pure westerly sea breeze and the easterly bora wind. In general, during a bora event, sea breezes were somewhat later and shorter, with limited horizontal extent. The spatial position of the convergence zone caused by the bora and sea‐breeze collision was strongly curved. The orientation of the head (of the thermally‐induced flow) was more in the vertical causing larger horizontal pressure gradients and stronger daytime maximum wind speed than in undisturbed conditions. Except for the island of Rab, other lee‐side islands in the area investigated did not provide favourable conditions for the sea‐breeze formation. Within a bora wake near the island of Krk, onshore flow occurred as well, although not as a sea‐breeze flow, but as the bottom branch of the lee rotor that was associated with the hydraulic jump‐like feature in the lee of the Velika Kapela Mountain. Copyright © 2010 Royal Meteorological Society
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Convergence zone
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Abstract The role of the sea/bay breeze in the planetary boundary layer evolution and air quality during a high ozone event day in the Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relevant to Air Quality (DISCOVER‐AQ) Texas 2013 campaign was examined. Data from surface air quality monitoring network stations, airborne lidar data, and additional ground‐based lidar instrumentation deployed during the campaign allowed for a unique three‐dimensional spatial and temporal study of the progression of both meteorological and air quality conditions in the Houston‐Galveston regions on 25 September 2013. The Weather Research and Forecasting model coupled with Chemistry model was used to examine the relationship of the land and bay/sea breeze circulations and its influence on air quality during the case study. Comparisons between observations and simulations revealed the largest discrepancies near the Galveston Bay shore areas where the highly localized ozone concentrations were observed and were linked to the strength and timing of the bay/sea breeze progression. Additionally, results indicate vertical downmixing from the remnants of the nighttime residual layer during morning hours into the convective boundary layer and from the lofted offshore return flow into the subjacent bay breeze flow.
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This study examines complex flow patterns associated with the Cape Canaveral sea breeze and sea-breeze front using dual-Doppler radar, sounding, and surface data collected on 26 July 1991 during the Convection and Precipitation/Electrification Experiment. This case focuses on (a) the structure of the sea breeze, an associated trailing convergence line, river-induced convergence zones, and thunderstorm outflow boundaries, and (b) the development of convection where these features interacted. Variations in the direction of the sea breeze in the vicinity of irregular coastlines, such as Cape Canaveral, can lead to persistent zones of convergence within the sea-breeze air. The findings show that these zones of convergence, in turn, can locally increase the depth of the sea-breeze air and create circulations at the top of the sea breeze, which can support the development of convection. The observational study is the first to document the development and evolution of the trailing convergence line over Cape Canaveral and show that its presence can be instrumental in thunderstorm initiation. Small inland water bodies, such as the Indian River, can have a strong influence on the location where thunderstorms first develop as the sea breeze propagates inland. Divergence over the small, relatively cooler Indian River during daytime was sufficient to maintain a quasi-stationary convergence zone that, when approached and disrupted by the sea-breeze front, triggered thunderstorms. The intersection point between the sea-breeze front and the river-induced convergence zone identified the location where successive thunderstorms developed during the day.
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Cape
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A remarkable decrease in water vapor was observed during daytime on calm days over coastal Thailand. Precipitable water vapor (PWV) and surface specific humidity (SSH) decreased by about 5 mm and 3 g kg -1, respectively, in Bangkok from the late morning to the late afternoon on sunny days with weak low-level winds between March 1998 and December 1999. A daytime moisture decrease occurs in the lower atmosphere over coastal areas near the Gulf of Thailand, where the sea breeze often prevails. The sea breeze is relatively strong near the northern gulf. Wind profile observed over Bangkok revealed strong descending flow in the lower atmosphere during daytime, suggesting divergence of the sea-breeze circulation. This descending flow explains the decrease in daytime moisture over coastal areas.A numerical experiment assuming calm conditions successfully simulated the daytime decrease in water vapor around Bangkok. The most remarkable drying associated with descending flow was simulated around the northern edge of the Bight of Bangkok, where the coastline is sheltered by inland areas. The shape of the coastline and the topography enhanced the sea-breeze circulation around Bangkok. In another model run assuming wet soil conditions, the diurnal range of water vapor was smaller than that simulated by the control run. Clear diurnal variation was observed on calm days, especially under dry soil moisture conditions. A large diurnal range in PWV tended to appear before the monsoon onset when the low-level wind was weak and the soil moisture was dry.
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Diurnal temperature variation
Precipitable water
Prevailing winds
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A local torrential rain process occurred on the 14th August,2008 and its dynamic mechanism were analyzed synthetically by using Doppler radar data,automatic station data,wind profile data and GPS vapor distribution.The modeling of WRF with a horizontal resolution of 0.5 km simulated the sea breeze circulation under the influence of topography.The results indicated that the torrential rainfall process was affected mainly by the subtropical high retreating easterly and closed low vortex at low and medium level,which was formed due to weak cold air moving to the south.There were wind shear convergence along the sea breeze frontal zone and thunderstorm high pressure around the center of torrential rainfall.The boundary layer perturbation produced by the sea breeze frontal convergence was main uplift element and warm and wet advection from southeast sea supplied ample water vapor and energy to the rainstorm.The severe convection triggered by the sea breeze frontal convergence was the direct cause of the torrential rainfall and the low level jet from the sea with abundant vapor played an important role on the torrential rain.The sea breeze extending to the inland resulted in convergence and ascending motion and then played an important role on the torrential rain which was induced by see breeze.
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Convergence zone
Mesoscale convective system
Intertropical Convergence Zone
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