Showing papers on "Sea breeze published in 1982"

Thermodynamic and Circulation Characteristics, of Winter Monsoon Tropical Mesoscale Convection

Abstract: During the December 1978 field phase of the International Winter Monsoon Experiment (Winter MONEX), a regular diurnal cycle of deep convective activity occurred over the South China Sea immediately to the north of Borneo. The convection was initiated during the late night hours by convergence of the low-level northeast monsoon flow with the land breeze along Borneo's north coast. The precipitation feature that developed was characterized during its mature stage by a nearly continuous stratiform cloud, referred to here as a mesoscale anvil, of ∼ 100–500 km dimension extending from the mid-troposphere (∼5 km) to near the tropopause (∼ 17 km). Using rawinsonde data from the sounding network, thermodynamic and Circulation characteristics of the convection are documented. Mesoscale upward motion is found to within the anvils, with a MCSOMC downdraft below producing a warm, dry region over a lame area just above the boundary layer. Air flow relative to the anvil on both its leading and trailing edges i...

An Observational Study of Sea Breezes Along the Alaskan Beaufort Sea Coast: Part I

Abstract: Though sea breezes are not often associated with the arctic, atmospheric environmental data collected in August 1976, 1977 and 1979 along the Beaufort Sea Coast of Alaska offer both circumstantial and direct evidence of the existence of sea breezes at 70°N latitude. To estimate total atmospheric boundary layer turning, a two-dimensional least squares technique is used to calculate a three hourly geostrophic wind (above the atmospheric boundary layer) with data from irregularly distributed surface pressure stations for simultaneous comparison to surface wind data. Results indicated the average turning of the wind from above the boundary layer to the surface was 120° on sea breeze days. Rotary spectra from time series data of surface winds measured at offshore and inshore sites have shown the horizontal extent of sea breeze influence to include at least a 20 km zone centered on the coastline. The sea breeze is largely responsible for the increased persistence of surface onshore (northeasterly and e...

Numerical Simulation of Land-Breeze-Induced Snowbands Along the Western Shore of Lake Michigan

Abstract: Case studies are presented which describe a type of lake-effect snowband which forms along the western shore of Lake Michigan when a cold anticyclone to the north sets up an easterly gradient over the lake. Numerical simulations indicate that the snowband coincides with a narrow band of upward motion which results from the convergence of easterly winds over the lake and north to northwesterly winds over land. The northerly winds are part of a land breeze circulation which forms when cold air is heated by the relatively warm lake surface. Initial data for model simulations are obtained by objective analysis of upper-air data from the eight upper-air stations closest to Lake Michigan at six levels in the lower troposphere. Model results show that a pool of cold air over the lake up to about 850 mb favors rapid growth of the planetary boundary layer over the western half of the lake, and that latent heat release plays an important role in intensifying the land breeze circulation.

Characteristics of Summertime Circulations and Pollutant Ventilation in the Los Angeles Basin

Abstract: A cross-sectional numerical primitive-equation model is used to simulate the summertime airflow pattern in the Los Angeles basin for calm synoptic-scale wind conditions. The contributions of the sea breeze, the urban heat island effect and the mountain-valley wind are quantified. The mountain-valley and sea-breeze circulations are of the same sense (landward at the surface, toward water aloft) and strength (maximum of 5-10 m s−1 at surface), but the urban heat island effect is negligible. Correct specification of the land surface characteristics is found to be important to the quality of the simulation. Model output is then used to calculate estimates of the space and time variation of boundary-layer ventilation. Ventilation, defined as the product of the height of the planetary boundary layer and the mean wind speed therein, is found to be enhanced in the vicinity of the sea breeze front, and generally increases with distance from the ocean. In the stable marine air layer behind the front, the v...

Winds between San Diego and San Clemente Island

Abstract: Dense ship observations off San Diego were used to capture the diurnal and seasonal wind trends. The land breeze regime extends to 40 km off San Diego in the winter, but goes to less than 10 km when averaged for the winter. Significant diurnal variations in wind speed occur in all seasons from the coast to beyond 140 km. Ship observations were averaged over 0.2° of latitude and longitude. These have significant structure that is obscured in other studies based upon 1° averages. Wind speeds decrease by a factor of 2 or more from 140 km offshore to the coast in both the northerly and westerly component. The mean flow has a weak summer southerly component. This is in opposition to earlier studies which indicated northerly mean monthly flow all year. Ship observations were compared to San Diego Airport and San Clemente Island measurements in order to check the accuracy of allowing land measurements to substitute for over water measurements. San Diego winds were found to be very representative of the nearest 10 km of ocean in wind speed and direction on the diurnal and seasonal scales. San Diego would be a good proxy station from which to infer the long-term near shore meteorlogical conditions. San Clemente Island wind speeds are systematically less than the ship observed wind speeds in the easterly component. But the correspondence between the northerly component at San Clemente and ships is irregular in the diurnal and monthly means. This station could not be used to infer the northerly component without an uncertain and elaborate correction.

Possible Triggering Mechanisms for Severe Storms in SESAME-AVE IV (9–10 May 1979)

Abstract: The SESAME-AVE IV (9–10 May 1979) rawinsonde data were analyzed to uncover possible triggering mechanisms for severe storms that developed over western Oklahoma and Texas. The high frequency of observations (at 3 h intervals) and high vertical resolution of reported data (at 25 mb intervals) at all stations permitted investigation of the diurnal variation of the planetary boundary layer on the synoptic scale. Thunderstorms developed first just ahead of a stationary front over the Texas panhandle on the afternoon of 9 May. This area was characterized by the absence of a strong inversion (or “lid”) that represented an interface between very warm and dry air aloft, and warm moist tropical air below. Apparently, mesoscale low-level ascending motion associated with frontal lifting and/or the inland sea breeze effect led to the removal of the lid. Another noteworthy feature in this storm event was the strong vertical wind shear at low and middle levels over the storm area. When combined with the development of ...

A Mathematical Model of Sea Breezes Along the Alaskan Beaufort Sea Coast: Part II

Abstract: A nonlinear, time-dependent, two-dimensional sea breeze model allowing imposition of prevailing large-scale wind conditions has been developed. The model is an extension of Estoque's model with modifications in the treatment of the continuity equation, eddy diffusivity (unstable conditions), surface heating function and the numerical scheme. The model is applied to a cross section of the Beaufort Sea Coast using typically measured arctic conditions as input. These include u-w plane velocity vectors, isotachs of the u, v and w wind velocity components, temperature contours, surface wind vectors at varying distances from the coastline, and wind speed and direction profiles for various simulated synoptic wind directions. The mathematical results reproduced measurements of atmospheric boundary layer turning of the wind with height (pilot balloon data), temporal surface wind vector turning and inversion height variations, while also giving evidence that sea breeze circulation could be strengthened by ...

Rainfall and wind circulation in Coastal Tanzania

Abstract: The prevailing macro-scale and local components of circulation over East Africa are considered Using detailed data for the wind circulation at the surface and 850 mb for Dar es Salaam, Tanzania the importance of local diurnally-varying land- and sea-breezes is illustrated There is a marked change in wind direction at the surface in all seasons such that mean three-hourly data clearly depict a regular alternation between land- and sea-breezes These are superimposed on an interact with the prevailing trade wind circulation to produce different timings of rainfall through the day and night at the different seasons

Further considerations on modeling the sea breeze with a mixed-layer model

Abstract: Mixed-layer models have been used to simulate low-level flows under a variety of situations, including flow over complex terrain and in the vicinity of coastal zones. The advantage of mixed-layer models compared to multilevel models is their simplicity and minimal computational requirements. A disadvantage is that the atmosphere above the mixed layer is not modeled explicitly and approximations pertaining to this layer become necessary. This paper examines five approximations for treating this upper layer for a simple sea-breeze circulation. Approximating the flow immediately above the mixed-layer height h by the mixed-layer velocity and using this velocity to advect potential temperature above h gives a better simulation of the sea breeze than the approximation used by Anthes et al. (1980), which neglected horizontal advection at this level.

The sea breeze at Venice, as related to daily global solar radiation

Abstract: Although the sea breeze at Venice and on her hinterland is influenced by orography - mainly the Alps — to the north and the Po Valley to the west, the search for a correlation between the frequency of development of the sea breeze and the daily global solar radiation seems to be desirable, and may be useful for the management of emissions from the industrial area near Venice. Three different cases are examined: (i) the sea breeze occuring in the absence of any appreciable gradient wind; (ii) the sea breeze superimposed on a prevailing wind; (iii) the sea breeze not developing at all. The frequency distributions of these cases related to the global solar radiation at Venice are discussed.

Uncertainties Associated with the Estimation of Mass Balances and Gaussian Parameters from Atmospheric Tracer Studies

Abstract: Data resulting from two atmospheric tracer experiments in the land-sea breeze winds in Los Angeles, CA are used to compare the observed and released amounts of tracer (a mass balance). The mass balance calculation indicated that essentially all of the tracer transported to sea during the land breeze was transpoted back across the shore during the subsequent sea breeze. A methodology for calculating a mass balance and the associated uncertainties is presented. The experimental and calculation procedures presented allowed mass balance estimates with less uncertainty than is present in individual measurements of concentration or mixing height. Similarly, a methodology for calculating dispersion parameters for the gaussian plume model from tracer data is discussed and applied to the results of two atmospheric tracer studies conducted during the afternoon sea breeze in the Santa Barbara Channel of California. The method presented involves the integral definitions of the statistical quantities. By considering only tracer concentrations greater than 10% of the maximum concentration, and by considering sufficiently many data points, the uncertainty associated with the parameter estimation was again less than the relative uncertainties in any individual data point. These studies were primarily designed to relate the uncertainties in estimates of mass balances andmore » in estimations of gaussian parameters to the uncertainties inherent within field data.« less

Local climate processes in the Illawarra

Abstract: the climate of the Illawarra apart from that found in Sydney or on the far south coast Global air circulation Is generated by the necessity to balance the heat surplus at the equator with the deficit at the poles caused by the differential heating effect of the sun with latitude Superimposed on this general circulation are secondary circulation effects such as high and low pressure cells, cyclones, and fronts These effects are generated by regional heating or cooling effects over land and water and are controlled in position seasonally by the apparent migration of the sun On a local scale, air circulation patterns can be generated by differential heating and cooling caused by topographic effects such as mountains, valleys, landsea boundaries and the works of man Local climatic processes in the lIIawarra can be discussed under 5 headings as follows: 1 Sea breezes 2 Gravity or katabatic winds 3 Slope or anabatic winds 4 Foehn winds 5 Industrialization effects

Observations of a Sea Breeze Event in the Rome Area

Abstract: The low Tiber valley district can be considered representative of a complex terrain, being a large valley open towards the sea, surrounded by hills and mountains and within its centre the Rome city.

The diurnal trend in surface mixing ratio at Padova, Italy

Abstract: The diurnal cycle of the mixing ratio MR is discussed for Padova, sited about 30 km from the sea. In the morning a noticeable increase of the MR can be noted until the nocturnal inversion is completely eroded; afterwards convective activity mixes the humid sublayer with dry air aloft, so that an abrupt drop in MR follows the break-up of the inversion; the minimum is generally reached after noon. The minimum is primarily due to the enhanced activity of the thermals at mid day. During the day, increases in wind speed are generally accompanied by the arrival of new air masses, so that no general statements about the MR can be made without knowledge of the local dynamic climatology. Clouds cause an increase in MR, due to the out-of-phase relation between the dampings of the turbulent diffusion coefficient for water vapour and of the evaporation rate of the soil. In the afternoon the MR increases again until after sunset, when the sea breeze (final phase) transports humid marine air inland practically unaltered.

Kahuku kite wind study. II. Kahuku foothills

Abstract: In a test to compare the instruments, eight kites were flown in a close pattern. The test did not reveal calibration bias among the kite heads and the anemometers. Between 23 to 28 April 1981, a ridge was surveyed where a number of wind turbines are planned. The kites were flown continuously for 36 hours after which the trade winds disappeared. The kite winds were compared with those measured at two high meteorological towers on the ridge. Kites were flown at 120 ft and 240 ft for two periods during May to June 1981 close to the Kahuku Opana anemometer site where wind instruments have been maintained for over five years. Considerably lower winds during late night-early morning hours during the second period as compared with the first stemmed from a land breeze component opposing the prevailing trades. The relatively large 42 to 120 ft speed gradient at the site is partly attributable to trees upwind. Four methods to estimate long term wind speeds were tested. One is based on long term statistics and hourly vertical gradients of speed observed during the survey; the other three use simultaneously-collected hourly mean winds at the kite levels and at 42 ft. Ofmore » these estimates, those based on linear regression and on statistical parameters developed from the survey period are close to the gradient estimate. Kites were flown continuously for six days at 120 and 240 ft above a potential wind mill site. Field calibrations and subsequent software calibrations are improved. At the site, trade winds prevailed and showed some unexpected features. During an August and September 1981 survey of three potential wind turbine ridges, the kite heads worked reasonably well. However, substantial design changes are recommended. Evidence of a vortex created by morning solar heating was found along exposed ridge slopes upwind of some of the sites. Only marginally-useful winds were estimated for the eastern-most ridge during trades.« less

Kahuku kite wind study. I. Kahuka beach boundary layer

Abstract: In the coastal plain of Kahuku, Oahu, during August 1980 and February to April 1981, the boundary layer and the mechanism that creates it were investigated. Four sets of two automatically-recording tethered aerodynamically lifting anemometer (TALA) kites flying continuously at 100 and 300 ft, and conventional 30 ft instruments were used concurrently at four sites along a transect parallel to the prevailing trade winds. Hand-held short-term kite measurements were used to verify the data from the prototype automatic kites during the first survey. Because of surface heating and vertical mixing, a rapidly expanding boundary develops soon after sunrise. Other forces that modify the daytime air flow in the lower layers are: surface friction, local scale thermal wind, a sea breeze and mechanical forcing. The nighttime boundary is established through heat conduction from the surface air to the ground. This layer grows slowly and reaches only a few hundred feet in depth. Other mechanisms that modify the winds in and around the nighttime boundary layer include: confluence into the boundary layer, local scale thermal wind, land breeze-drainage winds, and friction. In the second survey, the boundary layer was neither as high nor as well-developed as in the first because the groundmore » was saturated after the winter rains. The consequent latent heat exchange prevented extreme surface temperature fluctuation. The commonly-used wind profile law exponent was found to depend on speed in the lower 100 ft of the atmosphere above which the exponent is constant. Estimates of long-term speeds at some sites differed by up to four mph between the two surveys. This underlines the importance of surveying not only all major wind regimes but also under different surface conditions. Long term speed estimates for the sties are high enough to make the area probably profitable for wind power development.« less

Mixing ratio at padova, italy

Abstract: The diurnal cycle of the mixing ratio MR is discussed for Padova, sited about 30 km from the sea. In the morning a noticeable increase of the MR can be noted until the nocturnal inversion is completely eroded; afterwards convective activity mixes the humid sublayer with dry air aloft, so that an abrupt drop in MR follows the break-up of the inversion; the minimum is generally reached after noon. The minimum is primarily due to the enhanced activity of the thermals at mid day. During the day, increases in wind speed are generally accompanied by the arrival of new air masses, so that no general statements about the MR can be made without knowledge of the local dynamic climatology. Clouds cause an increase in MR, due to the out-of-phase relation between the dampings ofthe turbulent diffusion coefficient for water vapour and of the evaporation rate of the soil. In the afternoon the MR increases again until after sunset, when the sea breeze (final phase) transports humid marine air inland practically unaltered.