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CHANDRAKANT M. BHUMRALKAR

Abstract

A two-dimensional theoretical model is developed to analyze the properties of perturbations induced when air flows over an isolated warm portion of the earth's surface. The model equations include continuity equations that predict water vapor, cloud water, and liquid water. The nonadiabatic effects of condensational heating and evaporational cooling are also incorporated.

The theoretical model is developed in conjunction with a specially designed observational field program for testing the model predictions. The field program and its results are described in Part I.

The model has been able to reproduce the observed conditions quite realistically; in particular, the observed and predicted patterns of cloud distributions and rainfall compare very well. The study has demonstrated the important influence of evaporational cooling of the environment on the behavior of perturbations induced by the heat source.

Numerical integrations of the model have also been performed to examine the dependence of the induced perturbations on the following factors: (1) temperature excess of the heat source, (2) speed of the normal component of the prevailing flow, (3) speed of the parallel component of the prevailing flow, and (4) width of the heat source. The results show that the larger the temperature excess of the heat source, the greater the intensity of the induced disturbance. The strength of the normal and the parallel components of the prevailing flow have opposite influences on the perturbations—a stronger normal component tends to weaken the disturbance whereas a stronger parallel component tends to intensify it.

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Chandrakant M. Bhumralkar

Abstract

This Note describes a method of deriving a modified form of the hydrostatic equation by making allowance for the presence of moisture in an atmospheric column.

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Chandrakant M. Bhumralkar

Abstract

The Rand two-level general circulation model has been integrated to compute ground surface (bare land) temperature by solving: 1) the interface heat balance equation without soil heat flux; 2) the interface heat balance equation by including parameterized soil heat flux; and 3) a prognostic equation which includes the heat capacity of the soil as well as an explicit formulation for soil heat flux.

The integrations were performed for 48 hours for the month of January. A comparison of results shows that the most realistic distribution of the ground surface temperature with respect to the amplitude, diurnal range, and the phase relationship between the ground temperature, solar radiation, and soil heat flux is given by the solution of the prognostic equation.

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CHANDRAKANT M. BHUMRALKAR

Abstract

In Part I of the two-part paper, we describe the results of a field program that was especially designed for testing the results of a theoretical model. The observations included measurements by an instrumented aircraft and a special surface network over an island with physical features that satisfy approximately the model assumptions. Panoramic cloud photographs and time-lapse movies of the clouds were also taken.

The observations show that evaporational cooling of the environment has an important, influence on the behavior of perturbations induced by the heated island.

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Chandrakant M. Bhumralkar, Arthur J. Slemmons, and Kenneth C. Nitz

Abstract

A two-dimensional, vertical cross section, numerical atmospheric mesoscale model has been applied to study the potential local/regional atmospheric effects of the installation of a 100 MWe solar thermal central receiver power plant at Barstow, California. Such a plant consists of heliostats (mirrors) which cover a portion of ground surface and reflect sunlight onto a central receiving tower. The model can simulate the changes in surface characteristics associated with the installation of heliostats and other power plant ancillaries, and can simulate the effects of waste heat from cooling towers. The model equations have been integrated to simulate typical summer, and atypical summer.

The results for typical summer conditions at Barstow and the surrounding region show that the power plant has the potential to increase local humidity and wind circulation but cannot induce the formation of clouds or rain. The results for atypical summer conditions show that the solar power plant has the potential to increase the wind circulation and to form clouds and rain. However, the life cycle of such formations is only 2–3 h.

Sensitivity to the type and location of cooling tower has been tested and described. The atmospheric effects of a dry cooling tower located upwind are not as significant and intense as those produced using a wet cooling tower. However, this result is not conclusive and should be researched further. The effect of a wet cooling tower located at the downwind edge of the power plant is not as intense as is the case when the tower is located at the upwind edge of the power plant.

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Nelson L. Seaman, Francis L. Ludwig, Evelyn G. Donall, Thomas T. Warner, and Chandrakant M. Bhumralkar

Abstract

The Pennsylvania State University (PSU)/National Center for Atmospheric Research (NCAR) mesoscale model was modified and used to simulate the evolution of meteorological conditions in the vicinity of St. Louis, Missouri, from near sunrise to noon on 25 July 1975. Observations obtained during the METROMEX (Metropolitan Meteorological Experiment) and RAPS (Regional Air Pollution Study) field programs were available for comparison with modeled conditions. The PSU/NCAR model used a nested grid with two-way interaction between the coarse mesh (7.5 km) and the fine mesh (2.5 km), where the fine domain covered the city and its immediate suburban and rural surroundings. Realistic three-dimensionally variable initial and lateral boundary conditions were obtained from the observations so that the numerical experiments could be used for quantitative evaluation of certain urban effects. After simulation of the actual conditions (control experiment), the importance of a number of processes on the urban planetary boundary layer (PBL) structure were investigated. The PBL effects were isolated by using realistic surface parameters as well as those based on the preurban conditions and an expanded urban environment. Sensitivities to surface evaporative fluxes, radiative processes, and different surface roughness associated with urbanization were examined. The control simulations of the temperature, boundary layer depth, specific humidity and wind fields exhibited essentially the same behavior as observed in the urban PBL throughout the morning forecast period. Unlike many other documented cases that displayed strong urban-induced low-level convergence, the confluence on this morning was relatively weak, with the center of the heat island displaced (in both the simulation and the observations) downwind (south) of the city. A relative minimum in windspeed was associated with the center of the displaced heat island. The sensitivity experiments clearly demonstrated and maintenance of the urban PBL perturbation.

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