Showing papers on "Sea breeze published in 1988"

Evaluation of vegetation effects on the generation and modification of mesoscale circulations

Abstract: The effects of the presence of vegetation cover on modifying sea breeze and thermally induced upslope flows during daytime were investigated, and the possibility of the generation of mesoscale circulations due to nonuniform vegetation cover was evaluated. Scale analysis and numerical model simulations were used to provide quantitative evaluations of the circulations involved in the two vagetation effects, using several illustrative cases. The cases considered demonstrate that the impact of vegetated surfaces is highly dependent on the environmental conditions as well as vegetation characteristics.

The Effect of Variations in Surface Moisture on Mesoscale Circulation

Abstract: A two-dimensional numerical Model with moist physics is used to simulate circulations induced by horizontal variations in surface-moisture availability. The model contains prognostic equations for water vapor, cloud water, and rain water, with a simple parameterization of cloud microphysical processes. Four geometric variations of surface-moisture availability are examined: 1) an edge geometry which includes a land-water contrast (classic sea breeze) and moist land adjacent to dry land (inland sea breeze), 2) a single strip of moist land surrounded by dry land 3) alternating bands of moist and dry land, and 4) a single strip of dry land surrounded by moist land. For convectively unstable initial conditions with a relative humidity of 50%, lifting associated with the sea-breeze front induces a precipitation system which propagates inland from the coast. The sea-breeze circulation associated with dry land is considerably stronger than that produced by moist land; however, the evaporation over land ...

Quantitative and Qualitative Evaluation of a Three-Dimensional Mesoscale Numerical Model Simulation of a Sea Breeze in Complex Terrain

Abstract: This study presents an evaluation of the performance of the Colorado State University (CSU) three-dimensional numerical mesoscale model. The evaluation consists of quantitative and qualitative comparisons of the model output with observed data. The observations were undertaken in the lower Fraser Valley of British Columbia, Canada on 23 August 1985 utilizing up to 23 fixed stations for anemometry, three acoustic sounders, one tethersonde and one set of instruments for determining the surface energy budget terms. The modeling covers a 24-hour period during which a wed-developed sea breeze was observed. While the results of the model evaluation apply to the single case presented, they have implications for a wide range of cases. The statistical methods of Willmott are applied to hourly averaged variables to assess the model's performance. The evaluation shows that the model is capable of providing very realistic wind and temperature fields within the broad coastal valley which makes up the bulk of ...

Flow Mechanism for the Long-Range Transport of Air Pollutants by the Sea Breeze Causing Inland Nighttime High Oxidants

Abstract: Flow mechanism causing nighttime smog was investigated by analyzing 1) continuous records of meteorological data and concentration of Oxidants (Ox) for 15 days and 2) aircraft data along the transportation route of a polluted air mass. It was found that an air mass which passed over the large emission sources along the coastline was transported inland as a sea breeze in the form of a gravity current. A high concentration layer was created in the upper part of the gravity current. It descended at the rear edge of a gravity-current head due to the internal circulation within the head, thus yielding the highest concentration of Ox near the ground there.

The Sea-Breeze Front Analytical Model

Abstract: Analytical solutions to the nonlinear equations of motion are used to describe the sea breeze front. It is found that the front can develop when the atmosphere stratification in the heated layer is neutral or unstable. The temperature drop due to front passage is proportional to the square of the difference between the front speed and the synoptic wind. This square of the difference, on the other hand, is proportional to [2θ(s)/θm]ga where θ(s) is the mean potential temperature drop across the front and a is the front radius. Fronts which have the same speed of propagation and size, have a larger temperature drop when the synoptic wind blows in the opposite direction to the direction of propagation. Onshore winds associated with strong convergence are obtained in the lower part of the front, while the return current associated with strong divergence is observed in the upper part. The vertical velocity reaches values of some meters per second in the front region. The front propagation is studied...

Doppler sounder observations of trade winds and sea breezes along the African west coast near 34°S, 19°E

Abstract: Summer weather conditions along the west coast of Africa near 34 ° S, 18 ° E are investigated using doppler acoustic sounder profiles Case studies were selected from a two-year record to form composite analyses over the diurnal cycle The SE trade wind exhibited a low level jet at the level of the temperature inversion due to a sharp reversal in the thermal wind vector aloft Mean wind speeds reached 14 m s−1 just before midnight as the surface and upper inversions strengthened Seabreezes were categorised by the supporting gradient wind and found to have mean depths of 400 m, speeds of over 6 m s−1 at the 200 m level, and advance/retreat times of 09 hr and 16–20 hr During seabreezes and weak on-shore gradient flow conditions, the thermal internal boundary layer (TIBL) was monitored with sounder transects in the first 12 km of the coastal zone The growth height was observed to be 1:20 in the first 5 km and 1:50 farther inland The sounder climatology, together with surface network and aerial survey results, illustrate the four-dimensional characteristics of trade winds and seabreezes near Cape Town

Numerical simulation of local thermal effects on the wind field of the Canterbury Plains, New Zealand

Abstract: The results of a mesoscale wind field modelling study are presented. A three dimensional model is used to simulate thermal effects on airflow over the Canterbury Plains. The main emphasis is on examining the sea breeze effect and its interaction with the broader scale gradient airflow and the topographic effect of Banks Peninsula. The model is used to investigate both diurnal and seasonal variations in the sea breeze effect Simulations suggest that localised sea breezes develop to the north and south of Banks Peninsula under weak gradient wind conditions. These results are supported by empirical evidence. However, under stronger prevailing winds, the sea breeze effect may be to merely enhance or modify that airflow. Results suggest that rapid changes in land-sea temperature difference are likely to influence the magnitude of any sea breeze effect in this region. It is concluded that the application of such models at the mesoscale is becoming important in extending our knowledge of local airflow s...

A 3-D sea breeze model of the PBL including pollutant dispersion

Abstract: A 3-D sea breeze model has been developed to study the sea breeze and the pollutant dispersion over a coastal area. Topography is also included. Similarity theory is adopted while a turbulent kinetic energy equation is used to study turbulence and to parameterize eddy diffusion. The integration is repeated in diurnal cycles and the results — meteorological and pollutant — are compared with data from the Athens area.

Interactions between local winds and coastal sea surface temperatures near the Canterbury coast

Abstract: A modelling and observational study was conducted in 1982–83 into the relationships between airflow and sea surface temperature along the Canterbury coast near Banks Peninsula. Near‐shore sea surface temperatures dropped by as much as 3–4 °C during periods of strong offshore airflow, particularly north‐westerlies. This may have been associated with coastal upwelling. A following southerly may also have contributed to this temperature drop by moving colder water from the south. The colder water appeared to produce enhanced sea breezes owing to the resulting increased temperature difference between land and sea. Both modelling and empirical evidence is given to support this. Coastal upwelling of cold water appeared to produce decreased air temperatures near the coast, although the onshore airflow wanned up as it moved inland over warmer surfaces.

Characteristics of Local Wind Arase Blowing in the Spinach Cultivation Area in Saijo City, Ehime Prefecture

Abstract: In order to make clear the meteorological characteristics of local wind “Arase” in Saijo City, Ehime Prefecture, the observations were carried out in the large spinach cultivation area of 2×4km2 during the winter from 1986 to 1987.(1) In the clear-fine night, the thermal belt and the cold air lake were observed on a slope at the middle zone of the mountain and the low flat ground, respectively. The wind with the direction of S to SW blowing down from the Ishizuchi mountain range to the foot of Takatoge mountain was recognized as the katabatic wind or cold air current, however, the wind blew little at the low flat ground. According to the observations, the local wind “Arase” was concluded as a katabatic wind.The relative humidity was low at the mountain foot and high at the low flat ground. Neither dew nor frost was not observed at the foot, but both were observed at the flat ground. The frost occurred at the northern range of the low flat ground and the dew between the foot and the northern range. On Jan. 29, 1987, 10-min-mean maximum wind speed was 4.8m/s (6.5m/s at 4m height), wind direction SSW, air temperature 5.7°C and relative humidity 41% at the height of 1m at the observation base, on the contrary at the east side point of mobile observation, 0.1m/s, calm, -1.2°C and 77%, respectively. Surface temperature at the 150m height slope and at the low flat ground was 5.8°C and -1.9°C, respectively. The typical katabatic wind seemed to be developed under the conditions of potential temperature difference 5K, elevation difference 1400m and slope length 12km.The katabatic wind at night on a fine day was a warm and dry wind for a spinach crop transferring the sensible heat from the wind, the condensations of dew and frost on a crop being small. Therefore, the mountain foot region of Takatoge was suitable for a spinach cultivation. On the other hand, the frequency of the warm wind blown decreased gradually from the mountain foot to the northern low flat ground, and the air temperature was low due to radiation cooling, particularly significant at the area surrounded with banks. The humidity was high at the area of high groundwater level causing the crop desease and pest. Consequently, this low flat region was not suitable for spinach cultivation resulting in the relatively worse quality and lower quantity.(2) During the clear-fine daytime, the air temperature was generally high at the mountain foot and low at the low flat ground and vice versa for the humidity. The wind was strong at the northern region by sea breeze and monsoon, and weak at the mountain foot, reversely at the nighttime. The northerly wind blew in the case of the circulation of land and sea breeze, but the westerly wind in the case effected by monsoon.(3) At the flat ground, the spatial differences of meteorological phenomena were not only small on a rainy day but also rather small at the daytime on cloudy and fine days. Therefore, the meteorological condition at the nighttime on a fine day had a most important effect on the spinach growth.

Providing operational guidance for the development of sea breeze thunderstorms at the Kennedy Space Center - An experiment using a mesoscale numerical model

Abstract: The effectiveness of a mesoscale numerical model to provide improved local forecast guidance is evaluated with respect to sea breeze convection storms at the Kennedy Space Center The model and operational forecast guidance production are described A case study is presented for sea breeze convection storms and lightning events on July 1, 1986 It is found that the mesoscale numerical model outperforms purely subjective predictions of sea breeze convection The range of applications for the model are considered

The sea breeze circulation during the Land Sea Breeze Experiment (LASBEX) in central California.

Abstract: : The sea breeze circulation was investigated using a combination of acoustic doppler sodar, doppler lidar and conventional observations in central California on the coast of Monterey Bay. The study was called LASBEX (Land Sea Breeze EXperiment). A monostatic three-axis phased-array doppler sodar was able to detect the various features of the sea breeze front, which has many of the characteristics of a gravity head current produced in laboratory experiments, such as the longitudinal vortex, lobe and cleft structure, and strong regions of turbulence and convergence. Profiles of the wind field and its component variances were generated every five minutes. Vertical velocities up to 1.0 m/s were detected in the updraft region at the front. Vertical velocity fields were used to derive the horizontal divergence associated with the sea breeze and values of convergence in the range of .004/s and greater were calculated. These are believed to be more accurate values than any found in previous sea breeze studies. Doppler lidar radial velocity information was useful in mapping the various layers and wind structure of the sea breeze. The wind field of the sea breeze by the lidar was compared with the sodar. The results of this comparison showed that the sodar was well suited to investigate features under 600 meters in height, such as the updraft region behind the front and the variance of the wind, whereas the lidar was better at describing the larger scale flow, such as the return flow of the sea breeze, the convergence zone along the sea breeze front and prevailing synoptic winds. Together, these instruments gave a comprehensive and complete description of the sea breeze frontal structure, evolution and movement. Theses.

Sea Breeze Wind Field Prediction in Atmospheric Dispersion Modelling

Abstract: The estimation of the dispersion of an airborne radioactive release presupposes the knowledge of the windfield and the level of diffusion in the region under consideration.

An Application of a Diagnostic Wind Model to Describe Atmospheric Transport

Abstract: In this paper a diagnostic model is used to reconstruct the wind field on the basis of measurements: An initial wind field generated from available sparse measured data is corrected to satisfy mass conservation by solving a three-dimensional elliptic differential equation. The actual orography is taken into account by transforming this equation to a terrain-following coordinate system. For the solution of the transformed equation a fully vectorized fast elliptic solver is applied. By the aid of the obtained wind fields air parcel trajectories may be calculated to elucidate the prevailing atmospheric transport mechanisms. As an example, wind fields and air parcel trajectories are presented for the Athens basin. The results confirm the features of the sea breeze circulation hinted at by observations and by previous calculations. The identified air movements are discussed in view of the elevated pollution levels in Athens.