Showing papers on "Sea breeze published in 1983"

On the Linear Theory of the Land and Sea Breeze

Abstract: Given that the earth's atmosphere may be idealized as a rotating, stratified fluid characterized by the Coriolis parameter f and the Brunt–V¨is¨l¨ frequency N, and that the diurnal cycle of heating and cooling of the land relative to the sea acts as a stationary, oscillatory source of energy of frequency ω (=2π day−1), it follows from the linear theory of motion that where f > ω the atmospheric response is confined to within a distance Nh(f−2 – ω −2)−1/2 of the coastline, where h is the vertical scale of the heating. When f < ω, the atmospheric response is in the form of internal-inertial waves which extend to “Infinity” along ray paths extending upward and outward from the coast. Near the ground, the horizontal extent of the sea breeze is given by the horizontal wale of the dominant wave mode, Nh(ω2 – f−2)−1/2. Although these concepts are familiar from the linear theory of motion in a rotating, stratified fluid, their relevance with respect to the interpretation of linear models of the land and ...

Numerical Simulation of the Airflow over Lake Michigan for a Major Lake-Effect Snow Event

Abstract: A mesoscale model is used to simulate the airflow over Lake Michigan for the major lake-effect snowstorm of 10 December 1977. This storm was characterized by a land breeze circulation and a narrow shore-parallel radar reflectivity band. The model successfully simulated the major atmospheric circulation features including a mesoscale low pressure center and a land breeze front. The model also captured the general character of the observed precipitation pattern which was typified by a narrow band of heavy precipitation along the eastern shore of Lake Michigan. Further simulations were made to examine the effects of latent heat release, lake surface temperature distribution and model grid resolution upon the simulation. Latent heat release was found to have an important effect in strengthening convection. However, the basic land-breeze circulation was found to develop for the simulated conditions even without latent beating. For a given mean lake-land temperature difference, details of the lake surf...

Wind-driven circulation of Cockburn Sound

Abstract: The water circulation within the Cockburn Sound embayment in Western Australia is predominantly wind-driven. Observations by moored current meters showed the mean velocities to be less than 0.05 m s-1 within Cockburn Sound and 0.07 m s-1 in the adjacent open coastal waters. Maximum tidal currents were very low, with an amplitude of the order of 0.01 m s-1. The importance of the wind-forcing was evident in the time-history data collected by the wind and current meters, particularly under storm conditions when winds greater than 15 m s-1 produce currents, within the Sound, between 0.10 and 0.25 m s-1. The wind records from Fremantle were examined and recurring patterns, such as sea breeze on and winter storms, were identified and their annual frequency of occurrence was estimated. A time- dependent, vertically integrated wind-driven numerical model was used to simulate the various water circulation patterns of each wind category. The circulation Froude number was shown to be of the order of thus allowing a description in terms of the stream function. Correlation between the data collected by the moored current meters and predicted by the model ranged between 0.05 and 0.76. Profiling data showed that under near calm wind conditions (<2 m s-1), local horizontal density gradients, caused by evaporation and heating, produced currents of up to 0.1 m s-1. This inverse estuary nature of the flow appears to play a significant role in the dynamics at low wind speeds. Under these conditions there was little or no volume exchange with the open sea. By contrast, the wind-driven circulation model showed that under a sea-breeze pattern 1.4 × 107 m3 was typically exchanged diurnally, and a 2-day winter storm may exchange about 1.1 × 108 m3, which is small compared with the volume of the Soand (1.2 × 109 m3). The bathymetry is such that the Sound acts mainly as a closed system.

A Laboratory Experiment on the Dynamics of the Land and Sea Breeze

Abstract: The land and sea breeze (LSB) circulation was simulated in a laboratory using a temperature controlled water tank. Flow visualization by tellurium and phenolphthalein and velocity measurement by laser-Doppler velocimeter were carried out in addition to temperature measurements. from similarity considerations, the simulated flow pattern was shown to have good correspondence with that in the atmosphere. It was shown that the overall features of the LSB flow pattern consist of a closed circulating motion caused by the periodically changing horizontal temperature difference between the land and the sea, and several kinds of small-scale motions induced by the periodic variation of the land surface temperature itself. The most important small-scale motion is the cellular convection which occurs all over the land surface due to unsteady heating from below in the morning calm. Other small-scale motions such as longitudinal vortex rows which are formed inland throughout the sea breeze layer, and gravity c...

A comparison between computed and measured oceanic winds near the British Columbia coast

Abstract: Winds measured over the continental shelf off Vancouver Island during the summers of 1979 and 1980 are compared with winds computed by the National Marine Fisheries Service (Monterey, California), using synoptic surface atmospheric pressures. Although there is considerable qualitative similarity between the two sets of data, the computed 6-hourly winds fail accurately to resolve short-period fluctuations associated with transient wind systems and tend to underestimate the percentages of time of low and high wind speeds. In the frequency domain, the computed winds are representative of the oceanic winds for periods exceeding roughly 2 days but only marginally representative for periods of 1½–2 days. At periods less than about 1½ days, computed winds are not reliable indicators of oceanic wind variability. Moreover, the computed winds possess a large-amplitude sea breeze (diurnal) component that is present in the inner shelf wind data but not in the outer shelf wind data. This sea breeze component in the computed winds originates through use of land-based atmospheric pressure values and is not indicative of the offshore wind field. Spectra of the observed winds suggest a k−5/3law behavior (k is the horizontal wave number) consistent with the existence of a mesoscale, two-dimensional, reverse cascading energy inertial range. Spectra for computed winds, on the other hand, are more consistent with a k−3 law appropriate to geostrophic turbulence and the existence of a macroscale, two-dimensional, cascading enstrophy inertial range.

Effects of External Parameters on the Flow Field in the Coastal Region—A Linear Model

Abstract: The land and sea breeze (LSB) and steady conviction (SC), superimposed on the geostrophic wind U, were analyzed by a linear model, the SC being driven by the diurnal-mean land-sea temperature difference and causing seasonal changes in the climate in the coastal region. An extension of Walsh's model (1974) was made to include SC and the effect of the Prandtl number (Pr). The influences of U, as well as the Coriolis force f/w, mean atmospheric stratification Grr (a form of Grashof number) and Pr on the LSB and SC were investigated. The LSB and SC are similar in their effects on the flow pattern, the wind speed and spatial dimensions being almost the same as at middle and higher latitudes when U = 0. The vertical dimension, the horizontal dimension and the wind speed are proportional to Gr0rPr¼, Gr0.387rPr0. and Gr−½rPr−⅔, respectively. The f/w effect is very small except for the dimensions of SC. The wind speeds of the LSB and SC created by a unit temperature difference between land and sea, as wel...

Spatial and temporal aspects of the surface wind regime on the canterbury plains, New Zealand

Abstract: Seasonal and diurnal patterns produced by the interaction of synoptic scale winds and two thermo-topographic systems, the land/sea breeze and mountain/plain winds, are investigated in a spatial context. Together with gradient winds and the shallow ‘lee trough’ north-easterlies these local winds create a wind regime composed of several distinctive regional element, the boundaries of which are transitional in nature and dependent on time day and year and the strength of synoptic influences. The sea breeze maximum frequency by day in summer in coastal areas whereas katabatic flows are most frequent by night, in winter adjacent to the Alps. Banks Peninsula strongly influences the wind regime by funnelling north-easterly airflow onto the plains and possibly creating a zone of sea breeze convergence extending inland. South of Banks Peninsula the interaction of onshore wind components with north-easterly synoptic winds appears responsible for the diurnal rhythm in the synoptic wind, a phenomenon already observed north of Banks Peninsula in relation to south-westerly gradient winds. Practical and theoretical implications of the regional study are discussed.

A Numerical Simulation of Local Winds and Photochemical Air Pollution (I): Two-Dimensional Land and Sea Breeze

Abstract: Caracteristiques fondamentales de l'influence des vents locaux sur la pollution photochimique de l'air

The sea breeze with mean flow

Abstract: A quasi-geostrophic mean flow can form the basic state upon which a sea breeze is superimposed; a model is described. With a mean flow perpendicular to the coast the speed of the sea breeze front is shown to be a linear function of the onshore component of the mean flow. When a constant mean flow is introduced the general structure of the sea breeze is unchanged. In particular, for a constant energy input the intensity is also unaltered. In contrast, a shear changes the general qualitative structure but leaves the speed of the front and the intensity of the sea breeze unchanged. These features are consistent with the available potential energy of the system and a constant transfer, per unit area, of this into kinetic energy. Model results and other studies are discussed.

A Simulation of Lake Michigan's Winter Land Breeze on 7 November 1978

Abstract: A two-dimensional mesometerological model was originally constructed by Alpert et a.. to simulate the summer air circulation in the area between the eastern Mediterranean waters and the Golan Heights involving en route Lake Kinneret (the Sea of Galilee). In this study the same model is applied to the case of the nocturnal circulation across southern Lake Michigan. The case simulated is for a wintry day in November 1978, the data for which were documented in a recent article by Passarelli and Braham. The results of the simulation are very encouraging. Particular mention should be made of the fact that the predicted location of the maximum upward velocities close to the Wisconsin shore of Lake Michigan and the associated lake-breeze front at the convergence zone of the lake breezes of the opposite shores are well predicted by the model. The observed land-breeze front was accompanied by the development of snow bands. The main purpose of this study is to demonstrate that a computationally inexpensive...

Inland convection and energy transfers in a sea breeze model

Abstract: Availability of potential energy in inland convection and in a sea breeze circulation are compared using a formulation of P. C. Manins and J. S. Turner for the convectively mixed atmospheric boundary layer, and a numerical model of a sea breeze. Entrainment processes during the mixed layer growth appear to affect both the convective scale and the mesoscale, decreasing the amount of potential energy available to the convective scale yet increasing the potential energy available at the mesoscale. The kinetic energy content of the sea breeze cell is explained in terms of a constant efficiency for the conversion of available potential energy inside a cell whose horizontal dimension increases in time. Results of numerical experiments indicate that the current value of the temporally integrated buoyancy flux at the ground is the most important parameter for the sea breeze flow. This parameter determines the strength of the flow as well as the inland movement of the sea breeze front.

Modeling mesoscale diffusion and transport processes for releases within coastal zones during land/sea breezes

Abstract: This document discusses the impacts of coastal mesoscale regimes (CMRs) upon the transport and diffusion of potential accidental radionuclide releases from a shoreline nuclear power plant. CMRs exhibit significant spatial (horizontal and vertical) and temporal variability. Case studies illustrate land breezes, sea/lake breeze inflows and return flows, thermal internal boundary layers, fumigation, plume trapping, coastal convergence zones, thunderstorms and snow squalls. The direct application of a conventional Gaussian straight-line dose assessment model, initialized only by on-site tower data, can potentially produce highly misleading guidance as to plume impact locations. Since much is known concerning CMRs, there are many potential improvements to modularized dose assessment codes, such as by proper parameterization of TIBLs, forecasting the inland penetration of convergence zones, etc. A three-dimensional primitive equation prognostic model showed excellent agreement with detailed lake breeze field measurements, giving indications that such codes can be used in both diagnostic and prognostic studies. The use of relatively inexpensive supplemental meteorological data especially from remote sensing systems (Doppler sodar, radar, lightning strike tracking) and computerized data bases should save significantly on software development costs. Better quality assurance of emergency response codes could include systems of flags providing personnel with confidence levels as to the applicabilitymore » of a code being used during any given CMR.« less

The Formation of the Morning Glory

Abstract: The hypothesis that the Morning Glory is formed when a sea breeze interacts with an inversion is examined by developing an analytical model which describes the main features of the flow. The predictions of the model are then tested against observations of the Morning Glory and encouraging agreement is found.

Three-dimensional airflow over Sardinia

Abstract: By using Pielke and Mahrer 3D mesoscale model, the air-flow over Sardinia has been studied for three typical meteorological situations. North-westerly flow (Maestrale), characterized by dry cold wind, shows strong downdrought over the desertic part of the island. Southeasterly flow (Scirocco), in summer, shows little interaction between the large-scale flow and the lower atmospheric layer over land. Sea breezes are usually advected easterly by the prevailing winds. Comments on practical applications and on limitations in local weather forecasting follow.

Terrain roughness and atmospheric stability at a typical coastal site

Abstract: Directional dependence of horizontal wind direction fluctuations (Σθ) is studied at the coastal site of Madras Atomic Power Project, Kalpakkam with significant inhomogeneity in roughness element distribution around the location of measurement. Σθ is measured by a potentiometric wind vane mounted on a 30 m meteorological tower. Values of Σθ showed as high as threefold variation for the same atmospheric stability depending on the effective roughness length of the upwind sector. Average Σθ values separated for sea- and land-breeze conditions, when correlated with Pasquill stability categories showed a monotonic decrease with increasing stability for land breeze but was found to increase for change from D to F category during sea breezes presumably due to the influence of an internal boundary-layer development.

On the Effect of the Planetary Boundary Layer Parameterizations in Mesoscale Numerical Weather Prediction

Abstract: A mesoscale 14 layer sigma-coordinate primitive equation model with 157 × 117 grid points at each layer has been developed for NASA. The horizontal grid length is 48 km and the upper boundary is chosen at 100 mb. This model includes a planetary boundary layer (PBL) parameterization scheme based on generalized similarity theory, concept of free convection, turbulent kinetic energy equation, surface energy budget and soil-surface moisture budget. Realistic features such as short and long wave radiation, cloudiness, static stability of the atmosphere, time varying PBL depth, entrainment at the top of the PBL, as well as heat conduction and moisture supply from the soil below the surface are included. Two case studies are shown to illustrate the effect of the PBL physics in severe storm development. In the 4 June 1980 case, model simulation shows that differential surface temperature and differential development of the mixed layer triggered the inland sea breeze effect which led to strong convection and tornado outbreak in the vicinity of Grand Island of Nebraska. The differential surface temperature was caused by downslope adiabatic warming, warm advection, spatial variation in initial surface temperature and soil moisture content. In the 2 April 1982 case, the model simulation shows a sharp horizontal gradient of the PBL depth in the proximity of Paris, Texas where severe thunderstorms and tornadoes occurred. It is displayed that one of the factors that triggered the blitz was the underrunning of the moist air out from beneath the lid of the PBL along its lateral boundary. Results of 40 additional case studies support the conclusion that the inclusion of full physics of the PBL plays an important role in the prediction of the severe storm development. On the contrary, runs with constant surface temperature, constant PBL depth and constant drag coefficient parameterization produce markedly different and less realistic mesoscale circulation systems.

Numerical stimulation of photochemical air pollution over the Ise Bay District.

Abstract: Using meteorological data and emission data gotten in the Ise Bay District on 4-5, Aug., 1977, a numerical simulation of photochemical air pollution was conducted. The wind field was represented through an interpolation of observed data. Diffusion and photochemical reaction were computed respectively with the diffusion equation and simplified chemical equations. The simulation could represent for these days that developing high O3 masses drifted northeasterly by the sea breeze which arose in the eastern or southern part of Nagoya around Atsumi bay. Computational error remained below the tolerable level in most of the object area. However, the simulation overestimated distinctly at the limited part of the Chita peninsula late on the morning of 5 th. As a cause of the deviation, it is supposed that local western sea breeze continued in this period and pollutants were tossed into higher layers over the region, because topographic and thermal convection affected the wind greatly across the peninsula. These thermal plumes could not be represented in the interpolated wind field. The probability of the above-mentioned cause was supported by two-dimensional test computation of the western sea breeze, including thermal and topographic effect.

Analysis of particles trajectories during a land-sea breeze cycle using two-dimensional numerical meso-scale models

Abstract: It is now a current trend for scientists engaged in studies connected with atmospheric pollution to try to link closer and closer the respective knowledges in the conventional pollution and in the meteorology research domains. For a great number of problems, this is widely due to the very strong relationship between thermodynamic properties of the atmosphere and the physicochemical behaviour of atmospheric pollutants.

Surface Currents During The ARSLOE Storm Measured By The CODAR Crossed-Loop System

Abstract: Data from a single-site CODAR system were used to study near-shore surface currents during a storm at ARSLOE. The dominant surface currents resulted from the storm winds and waves; tidal currents observed were nearly an order of magnitude weaker. The onshore and alongshore current components changed direction when these components of the wind reversed. Average current speed was 2.13% of the wind. Overall surface current direction was more nearly parallel to the coast than the wind. One notable exception occurred then the onshore wind component that had been blowing several days ceased; surface flow was nearly all offshore as the storm-surge sea level dropped back to normal.