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Jason K. S. Ching

Abstract

Data from Period III (19 June–2 July, 1969) of the Barbados Oceanographic and Meteorological Experiment (BOMEX) are used to compute the vorticity budget in the planetary boundary layer. The computed residual, assumed to be the curl of the stress, is then used to obtain an estimate of the drag coefficient. This estimate compares well with results obtained by other BOMEX investigators and in other independent experiments. The top of the planetary boundary layer is assumed to be located at the level where both the stress and stress gradient, computed from the momentum conservation equations, vanish. This is at approximately 1300 m, but tests indicate that the results are rather insensitive to assumed values in the range of 1300 to approximately 1600 m, the base of the trade-wind inversion. Computations for a relatively undisturbed period show a near-balance between anticyclonic vorticity generation by boundary layer divergence and vorticity destruction by friction. However, during a mildly disturbed period the advection and local change terms no longer appear to be negligible.

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Jason K. S. Ching

Abstract

Comparison of wind speeds measured by ship mast and boom instrumentation during the Barbados Oceanographic and Meteorological Experiment (BOMEX) are presented. It was found that the mast wind measurements are strongly affected by the ship's superstructure when the ship is lying broadside to the wind.

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Jason K. S. Ching and J. A. Businger

Abstract

The equations for horizontally homogeneous planetary boundary layer flow with constant eddy viscosity are integrated in time and height. The special case for which the direction of the pressure gradient force is a periodic function of time is studied in detail. The nondimensional number F=z(4Kt)−½ is seen to be the proper scale which describes the flow response to the boundary layer.

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Vlad Isakov, John S. Irwin, and Jason Ching

Abstract

Atmospheric processes and the associated transport and dispersion of atmospheric pollutants are known to be highly variable in time and space. Current air-quality models that characterize atmospheric chemistry effects, for example, the Community Multiscale Air Quality model (CMAQ), provide volume-averaged concentration values for each grid cell in the modeling domain given the stated conditions. Given the assumptions made and the limited set of processes included in any model’s implementation, there are many sources of “unresolved” subgrid variability. This raises the question of the importance of the unresolved subgrid variations on exposure assessment results if such models were to be used to assess air toxics exposure. In this study, the Hazardous Air Pollutant Exposure Model (HAPEM) is applied to estimate benzene and formaldehyde inhalation exposure using ambient annually averaged concentrations predicted by CMAQ to investigate how within-grid variability can affect exposure estimates. An urban plume dispersion model was used to estimate the subgrid variability of annually averaged benzene concentration values within CMAQ grid cells for a modeling domain centered on Philadelphia, Pennsylvania. Significant (greater than a factor of 2) increases in maximum exposure impacts were seen in the exposure estimates in comparison with exposure estimates generated using CMAQ grid-averaged concentration values. These results consider only one source of subgrid variability, namely, the discrete location and distribution of emissions, but they do suggest the importance and value of developing improved characterizations of subgrid concentration variability for use in air toxics exposure assessments.

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Edward E. Uthe, William Viezee, Bruce M. Morley, and Jason K. S. Ching

Development and validation of transport models for the study of regional acid deposition require improved observations of pollutant transport and dispersion processes. No suitable method for air-parcel tracking along nonconstant density surfaces is available. The feasibility of using an airborne lidar system to observe atmospheric transport and dispersion of fluorescent-dye-particle (FDP) tracers was demonstrated for various meteorological conditions and FDP-release scenarios in the general area of the Cross-Appalachian Tracer Experiment (CAPTEX) during October 1983. This paper presents some of the results obtained on six case studies, each of which illustrates a unique application of the technique.

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Tanya L. Otte, Avraham Lacser, Sylvain Dupont, and Jason K. S. Ching

Abstract

An urban canopy parameterization (UCP) is implemented into the fifth-generation Pennsylvania State University–National Center for Atmospheric Research Mesoscale Model (MM5) to improve meteorological fields in the urban boundary layer for finescale (∼1-km horizontal grid spacing) simulations. The UCP uses the drag-force approach for dynamics and a simple treatment of the urban thermodynamics to account for the effects of the urban environment. The UCP is evaluated using a real-data application for Philadelphia, Pennsylvania. The simulations show that the UCP produces profiles of wind speed, friction velocity, turbulent kinetic energy, and potential temperature that are more consistent with the observations taken in urban areas and data from idealized wind tunnel studies of urban areas than do simulations that use the roughness approach. In addition, comparisons with meteorological measurements show that the UCP simulations are superior to those that use the roughness approach. This improvement of the treatment of the urban areas in the meteorological model could have implications for simulating air chemistry processes at this scale.

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Francis A. Schiermeier, William E. Wilson, Francis Pooler, Jason K. S. Ching, and John F. Clarke

Spurred by the rising sulfate concentrations in the northeastern United States, the Environmental Protection Agency (EPA) has established the Sulfur Transport and Transformation in the Environment (STATE) program to quantitatively determine the impact on local air quality of distant source pollutants and their transformation products. The first major STATE field study was the August 1978 Tennessee Plume Study conducted near the Cumberland Steam Plant in northwestern Tennessee. Representatives from 25 governmental agencies, universities, research institutes, and private contractors participated in this joint meteorological/chemical study in an attempt to define plume transport, dispersion, transformation, and removal rates under various meteorological conditions. A description of the field activities reveals the preplanned experimental guidelines and the flexibility with which the sampling activities were performed. The analytical priorities have since been established and various investigators are performing analyses of the collected data with results to be forthcoming.

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Jason Ching, Michael Brown, Steven Burian, Fei Chen, Ron Cionco, Adel Hanna, Torrin Hultgren, Timothy McPherson, David Sailor, Haider Taha, and David Williams

Based on the need for advanced treatments of high-resolution urban morphological features (e.g., buildings and trees) in meteorological, dispersion, air quality, and human-exposure modeling systems for future urban applications, a new project was launched called the National Urban Database and Access Portal Tool (NUDAPT). NUDAPT is sponsored by the U.S. Environmental Protection Agency (U.S. EPA) and involves collaborations and contributions from many groups, including federal and state agencies, and from private and academic institutions here and in other countries. It is designed to produce and provide gridded fields of urban canopy parameters for various new and advanced descriptions of model physics to improve urban simulations, given the availability of new high-resolution data of buildings, vegetation, and land use. Additional information, including gridded anthropogenic heating (AH) and population data, is incorporated to further improve urban simulations and to encourage and facilitate decision support and application linkages to human exposure models. An important core-design feature is the utilization of Web portal technology to enable NUDAPT to be a “community” based system. This Web-based portal technology will facilitate the customizing of data handling and retrievals (www.nudapt.org). This article provides an overview of NUDAPT and several example applications.

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