Showing papers on "Sea breeze published in 1987"

The Influence of Soil and Vegetation on the Development of Mesoscale Circulations

Abstract: A two-dimensional mesoscale model including a detailed representation of the planetary boundary layer, the soil and the vegetation is developed. A sea breeze over flat terrain is simulated, thereby confirming the ability of the model to reproduce the known properties of this mesoscale phenomenon. The atmospheric response to soil and vegetation inhomogeneities is then examined with no synoptic flow over flat terrain. The results reveal the large influence of soil texture on surface moisture availability. The transition zone between bare soil and vegetation appears to be a preferred location for the initiation of moist convection. A vegetation canopy over very dry or very wet surfaces reduces the spread between sensible and latent heat fluxes.

The effect of latitude on the sea breeze

Abstract: Long-term (five-day) integrations of a nonlinear numerical model of the sea breeze at the equator, 20°N, 30°N and 45°N indicate the importance of latitude on the sea breeze circulation. During the hours of strong heating when friction is largest and the static stability is smallest, a local sea-breeze frontal circulation develops in a similar way at all four latitudes. Evaluation of the terms in the circulation theorem indicates the dominance of the solenoid term (horizontal pressure gradient force) associated with the strong temperature contrast during this period. During the rest of the period, however, the pressure gradient and frictional forces weaken, the static stability increases, and the Coriolis force is dominant (except at the equator). Therefore, quite different circulations evolve at the different latitudes. At the equator, the absence of the Coriolis force results in a sea breeze at all times. At the other latitudes, the Coriolis force is responsible for producing the large-scale lan...

Observations of sea-breeze fronts near the shoreline

Abstract: Results from an observational study of sea-breeze fronts as they cross a shoreline are presented. Two kinds of fronts are analyzed, one with an offshore regional wind and one without. Their structure is found to be substantially different, the former being steeper and having stronger gradients. Measurements of the profiles of the vertical component of the wind speed, its standard deviation and the structure parameter for temperature are presented along with time series of the structure parameters for water vapor pressure and wind speed. The vertical wind component, w, is found to be of the order of 1.0–1.5 ms−1 in the front zone of the sharp front but only 5 as large in the weaker front. The usual height variation laws under convective conditions are found to apply for both the vertical velocity variance and the temperature structure parameter, which in conjunction with the appropriate spectra indicate that local equilibrium is re-established fairly quickly after the passage of the front. Substantial differences have also been noted in the values of the structure parameters before and after the front, especially in the water vapor pressure and wind speed, differences which are of dissimilar magnitude and sign for the two kinds of fronts.

Energetics of Daytime Sea Breeze Circulation as Determined from a Two-Dimensional, Third-Order Turbulence Closure Model

Abstract: A two-dimensional, third-order turbulence closure model is developed to study the atmospheric boundary layer with one horizontal direction of inhomogeneity. Use of the Flux Corrected Transport scheme leads to numerical stability with low nonphysical diffusion. The case of a sea breeze circulation is simulated. The turbulence structure of the flow is described. The turbulent kinetic energy is included in the energetics of the circulation. The relations between convection and the dynamics of the sea breeze, including the velocity of the inland penetration of the front, are studied.

Mesoscale variations in surface stress, heat fluxes, and drag coefficient in the marginal ice zone during the 1983 Marginal Ice Zone Experiment

Abstract: A series of turbulence and mean meteorological measurements were made from an instrumented aircraft during the 1983 Marginal Ice Zone Experiment in the Greenland Sea in July 1983. Using the inertial-dissipation method, estimates of the surface fluxes of momentum, sensible heat, and latent heat have been obtained for five transects across the marginal ice zone (MIZ). The total heat flux was found to be about 30 W m−2 over the ocean and near zero over the ice. The 10-m neutral drag coefficient went from an average of 1.3 × 10−3 over the ocean to 3.3 × 10−3 over the pack ice (a total distance of about 160 km). Most of the change occurred in a region about 60 km wide. In “sea breeze” conditions the surface stress was reduced about a factor of 2 in the MIZ center by stability effects.

Turbulence Structure of Sea Breeze Front and Its Implication in Air Pollution Transport — Application of K-ε Turbulence Model —

Abstract: A k-e turbulence model was applied to a numerical simulation of sea breeze. The dynamical behaviors of eddy diffusivity, turbulent kinetic energy and its dissipation rate, associated with moving sea breeze front, were predicted and analyzed. Results demonstrated, for example, difference of the turbulence structure between thermal internal boundary layer and inland mixed layer, and the double maxima structures of turbulence-related quantities in their vertical profiles just behind sea breeze front. The properties of the computed sea breeze front agreed qualitatively with those of a gravity current in unstable environment, observed by Simpson et al. (1977). Furthermore, the possibility that air pollutants released in the sea breeze layer might be trapped within small circulating flow at the sea breeze front, and move with it was shown in an advection simulation of hypothetical fluid particles using flows obtained.

A Comparative Study of Various Parameterizations of the Planetary Boundary Layer in a Numerical Mesoscale Model

Abstract: Various parameterizations of the planetary boundary layer (PBL) currently used in three-dimensional (3D) mesoscale models are compared with a more complex scheme including a turbulent kinetic energy (TKE) equation. In the first set of simulations made with a ID model against the classical Wangara data, the mean wind, temperature and moisture calculated in the PBL are nearly insensitive to the choice of the parameterization. In the second set of simulations, the TKE parameterization is used in a 3D mesoscale model to simulate sea breeze flows over south Florida. A comparison is presented with previous simulations of Pielke, and Pielke and Mahrer, for the mean flow, and with the third-order turbulence closure model of Briere for the turbulent variables, including a discussion of the turbulent energy budget, The analysis of the results obtained with the TKE scheme shows that the predicted turbulent fields are qualitatively realistic and interact significantly with the sea breeze circulation. Finally...

Computational aspects of a fine-mesh sea breeze model

Abstract: Pielke's mesoscale numerical model was set up on minicomputers using a memory optimisation strategy and modification of the model constraints. Model performance was compared with that achieved using a CRAY and demonstrates that the minicomputers can reproduce similar results with a high degree of precision although at the expense of running time. The model was applied and validated for the 2-D and 3-D cases for the Perth region of Western Australia using a 2 km fine mesh grid stretching to 10 km. The 2-D validation illustrates that the predicted profiles display patterns and trends in close agreement with observations. However, the model is unable to simulate the sharp jump in mixing ratio accompanying the arrival of the sea breeze. The 3-D validation demonstrates the influence of lateral geographic variation and the predicted fields are comparable to observations. The 3-D model was extended to investigate and predict the temperature variations across the Perth metropolitan area. It illustrates the propagation of a sea breeze front across the region, the role of local river systems, and the creation of intensive temperature gradients along the coast.

Numerical study of lake-land breeze over lake vättern Sweden

Abstract: This paper describes a two-dimensional lake breeze model with turbulent energy closure. The simulated results show that (1) the front of the lake breeze progresses inland faster in the late afternoon than at the fully developed stage; and (2) the lake breeze and land breeze have larger, extension offshore than inland. The acceleration of the front in the declining phase of the lake breeze is explained in terms of the decreased turbulent friction acting on the head of the lake breeze. The larger, extension offshore, probably, is attributed to the smaller roughness of water surface and to the offshore synoptic wind.

Short range forecasting of sea breeze generated thunderstorms at the Kennedy Space Center: A real-time experiment using a primitive equation mesoscale numerical model

Abstract: The operational efficiency of using guidance from a mesoscale numerical model to improve sea breeze thunderstorm forecasts at and around the Shuttle landing strip was assessed. The Prognostic Three-Dimensional Mesoscale (P3DM) model, developed as a sea breeze model, reveals a strong correlation between regions of mesoscale convergence and the triggering of sea breeze convection thunderstorms. The P3DM was modified to generate stability parameters familiar to the operational forecaster. In addition to the mesoscale fields of wind, vertical motion, moisture, temperature, a stability indicator, a combination of model-predicted K and Lifted Indices and the maximum grid cell vertical motion, were proposed and tested. Results of blind tests indicate that a forecaster, provided with guidance derived from model output, could improve local thunderstorm forecasts.

A bulk model of the well-mixed boundary layer

Abstract: A bulk boundary-layer model is developed to predict surface fluxes and conditions in the well-mixed layer between the surface and the lower troposphere. The model includes the effects of all the dominant processes, including advection, in a dry boundary layer. The numerical model is compared with theoretical predictions for the growth of an internal boundary layer, and it is used to simulate the generation of a sea breeze by the diurnal cycle of radiative heating.

Modeling the polluted coastal urban environment: Volume 2, The dispersion model: Final report

Abstract: A three-dimensional Eulerian grid air pollution dispersion model was developed using meteorological parameters from a three-dimsnsional finite-difference planetary boundary layer (PBL) model. The PBL and dispersion models were used to simulate sulfur dioxide concentrations resulting from multiple area and point source emissions in New York City for a three-day period, during which a sea breeze front passed through the area. Predicted meteorological and concentration fields were compared with data collected during the period. Results from the initial simulations demonstrate that the dispersion model can correctly simulate most of the qualitative features of the observed time-varying three-dimensional surface and PBL sulfur dioxide concentration fields during periods with complex meteorological conditions associated with thermally generated mesoscale circulations. The model was somewhat less successful in accurately reproducing the values of the observed concentrations; however, most predicted concentration values were within a factor of two of corresponding observed values.

Modeling the polluted coastal urban environment: Volume 1, The PBL (planetary boundary level) model: Final report

Abstract: The two-dimensional vorticity-mode URBMET planetary boundary-layer model has been extended to three dimensions by use of a second vorticity component and a second stream function. The model is capable of simulating the time-varying distributions of velocity, temperature, and (sub-saturation) moisture in a Boussinesq, hydrostatic, and incompressible flow field. The model consists of a numerical soil layer, and in the atmosphere, both an analytical constant-flux layer and numerical transition layer. Sea breeze flow conditions in the New York City (NYC) area have been simulated utilizing first-order turbulence closure, with surface temperature and moisture predicted from energy and moisture balances. Results reproduced many of the observed features of sea breeze fronts in the NYC area. Predicted meteorological variables were used as input to a three-dimensional Eulerian-grid sulfur-dioxide dispersion model of point and area sources within the NYC area, as described in Volume II of this report. The model was also used to simulate sea breeze flow at an idealized coastline using the Level 2.5 turbulence parameterization of Mellor and Yamada. This formulation involves solution of an additional prognostic differential equations for turbulent kinetic energy. Results indicate that turbulence from the mid-morning unstable land area was advected offshore into the stable marine regionmore » for significant distances.« less

Numerical Simulation of a Satellite-Observed Calm Zone in Montetey Bay, California

Abstract: Satellite imagery from 18 April 1978 suggests the presence of a semicircular zone of calm or new-calm seas in Monterey Bay, California. It is hypothesized that sea breeze circulations account for the calm zone in the bay, although a lack of in situ surface and upper air observations prevents direct verification of this theory. A three-dimensional numerical model of the marine atmospheric boundary layer is used to simulate the development of the low-level wind field on the day in question, under sea breeze conditions. The model produces a zone of winds speeds under 1.0 m s−1 over the center of the bay, near the time of the satellite image. These model results suggest that a sea breeze circulation may have accounted for the zone of very light winds and calm sea.

Characteristics of air flow over Andaman islands including precipitation

Abstract: The characteristics of simulated air flow over Andaman Islands are studied with a two-dimensional version of the University of Virginia meso scale model (UVMM) Using the observed synoptic data as initial conditions, 24 hr simulations are obtained for a day each in April and November These days are chosen to study the variations in the simulated flow pattern under different synoptic conditions including precipitation effects A large scale condensation scheme is employed to consider the effect of latent heat release on the perturbations The results show that the latent heat released by condensation strengthens the intensity of perturbations and the topography accelerates the arrival of sea breeze by about an hour The model-simulated results, given in graphical form, are discussed and compared with available observations