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NASA NTRS1982

NASA participation in the 1980 PEPE/NEROS project: Data archive

Eight experimental air quality measurement systems were investigated during July and August 1980 as part of the EPA PEPE/NEROS fiel measurement program. Data from those efforts have been entered into an archive that may be accessed by other researchers. The data sets consists of airborne measurements of regional mixed layer heights and aerosol and ozone distributions as well as point measurements of meteorological parameters and ozone obtained during diurnal transitions in the planetary boundary layer. This report gives a discussion of each measurement system, a preliminary assessment of data quality, a description of the archive format for each data set, and a summary of several proposed scientific studies which will utilize these data.

Brewer, D. A.↗
NASA NTRS1981

Multiple-scale turbulence modeling of free turbulent flows

As part of an investigation into the application of turbulence models to the computation of flows in advanced scramjet combustors, the multiple-scale turbulence model has been applied to a variety of flowfield predictions. The model appears to have a potential for improved predictions in a variety of areas relevant to combustor problems. This potential exists because of the partition of the turbulence energy spectrum that is the major feature of the model and which allows the turbulence energy dissipation rate to be out of phase with turbulent energy production. To establish the general reliability of the approach, it has been tested through comparison of predictions with experimental data. An appreciable overall improvement in the generality of the predictions is observed, as compared to those of the basic two-equation turbulence model. A Mach number-related correction is found to be necessary to satisfactorily predict the spreading rate of the supersonic jet and mixing layer.

Fabris, G.↗
NASA NTRS1981

The 'preferred mode' of the axisymmetric jet

Detailed distributions of different time-average and phase-average flow properties for an axisymmetric free jet under controlled perturbation at the jet preferred mode are explored. The data are compared with the corresponding unexcited jet data. It is found that the effect of the perturbation is to increase jet spread and mean velocity decay, as well as to increase the peak values of the time-average fluctuation intensities and Reynolds stress in the axisymmetric mixing layer.

Hussain, A. K. M. F.↗
NASA NTRS1982

The NASA participation in the 1980 EPA PEPE/NEROS field measurements program

The Persistent Elevated Pollution Episode (PEPE)/Northeast Regional Oxidant Study (NEROS) Project consisted of a series of field measurements sponsored by the EPA during July and August, 1980. NASA participation in the Project had several purposes: (1) use remote sensing to help determine mixed layer height and ozone profiles regionally; and (2) provide opportunity for development, testing and evaluation of several NASA 'emerging' airborne remote sensing systems. NASA also provided information on the hazy pollution episodes throughout the summer of 1980 with satellite imagery. This paper describes findings on atmospheric aerosols, ozone profile and ozone column and discusses the instruments (airborne and ground-based sensors) and techniques used to obtain the relevant data. Associated archived data is also discussed.

Remsberg, E.↗
NASA NTRS1981

Higher level simulations of turbulent flows

The fundamentals of large eddy simulation are considered and various approaches to this simulation are compared. The subgrid model required by large eddy simulation is discussed as well as the use of this type of simulation in the development of models for the Reynolds-averaged equations and the application of direct simulation to the testing of both subgrid scale and Reynolds-averaged models. Numerical methods used in large eddy and direct simulation are described with emphasis on special purpose methods. Topics covered include the simulation of homogeneous flow, free shear flows, the mixing layer, wakes, and wall-bounded flows including channel flow and the boundary layer. Applications of large eddy simulation in the laboratory as in meteorological and other environmental flows are examined. Directions in which the work is proceeding and what can be expected from higher levels simulated on are examined.

Ferziger, J. H.↗
NASA NTRS1982

Warm water mass formation

Seasonal heat storage, massive upwelling, and cold water advection are shown by a thermodynamic model of the interacting atmospheric and oceanic mixed layers.

Csanady, G. T.↗
NASA NTRS1983

Experiments using atmospheric forcing from a FGGE analysis to drive an upper ocean model

Results are presented of a series of numerical experiments in which an upper ocean model is driven by surface heat fluxes and stress fields derived from the FGGE SOP-1 GLAS analysis/forecast system (Halem, et al., 1982). The model results show that most changes in the mixed layer height and horizontal velocity occurs in the first days. On the other hand, changes in the temperature field take a longer time to develop. In the most realistic case (real initial conditions, instantaneous forcing fields from the atmospheric analysis), the resulting changes in temperature were larger than observed and the correlation between observed and predicted changes was poor. The deficiency in the forecast of SST changes may be due to several factors: lack of sufficient ocean resolution, improper initialization, lack of feedback between the ocean and the atmosphere and the absence of transports by the strong boundary currents, and perhaps unrealistic surface fluxes of heat and momentum. Unless these problems are alleviated it is not reasonable to perform coupled atmospheric ocean forecasts.

Camerlengo, A.↗
NASA NTRS1981

Lidar meteorology

Current and future lidar applications to meteorological studies are presented. In water vapor, temperature, and pressure measurement applications, differential absorption lidar (DIAL) techniques are used, employing a minimum of two wavelengths. The DIAL technique has proven particularly accurate in pressure measurements. For wind measurements, lidar investigations generally use the Doppler shifting of laser light backscattered from aerosols, and a pulsed low-power CO2 Doppler lidar is being developed for airborne platform applications. At visible to near-infrared wavelengths, spatial distribution of aerosol and clouds can be obtained from lidar, and this information can help determine such atmospheric parameters as mixed layer height and cloud height distributions. A Shuttle lidar facility, being developed for the end of the 1980's, will enable laser remote sensing techniques to be applied to studies of the lower atmosphere.

Browell, E. V.↗
NASA NTRS1982

Satellite estimates of ocean-air heat fluxes during cold air outbreaks

A method for estimating the heat and moisture fluxes of coastal waters using the cloud free path, the sea surface temperature, and the saturation water vapor mixing ratio is presented. Generalized nomograms for the surface sensible and latent heat fluxes are developed using the Stage and Businger (1981) mixed-layer model. The fluxes are found to be slightly dependent on wind speed. The results are found to be applicable to any path within the cloud-free region, with heat fluxes obtainable by multiplication of the mean heating by the mean wind speed in the boundary layer. Higher stability causes lowered heating. It is shown that the latent heat flux is linear. Applications of the method to lake-effect snowstorms and for verification of boundary-layer models are indicated.

Chou, S.-H.↗
NASA NTRS1982

A one-dimensional model of the atmospheric electric field near the Venusian surface

A one-dimensional model is developed for the development of an electric field below the Venus cloud layer, assuming an absence of cloud-to-ground lightning. The ion-bearing medium is considered as a collision dominated, partially ionized gas. Ion production by cosmic rays is accompanied by a sink of recombining positive and negative ions. The net diffusion of ions to the surface was examined, and modeled as resulting from differences between the ion diffusivities and electrical activity within the clouds. Calculations were made of the conduction and diffusion currents profiles, positive and negative ion densities, and the net space charge. Higher positive ion diffusivity was found to enhance the surface positive charge, producing an electric field which depended on the boundary layer mixing. Charge separation in the clouds also produces an electric field. Assuming a fair weather conduction current similar to earth leads to an electric field of 5 kV/sq m at the surface, with continuity to a few kilometers altitude.

Tzur, I.↗
NASA NTRS1984

Crossed hot-wire data acquisition and reduction system

The report describes a system for rapid computerized calibration acquisition, and processing of data from a crossed hot-wire anemometer is described. Advantages of the system are its speed, minimal use of analog electronics, and improved accuracy of the resulting data. Two components of mean velocity and turbulence statistics up to third order are provided by the data reduction. Details of the hardware, calibration procedures, response equations, software, and sample results from measurements in a turbulent plane mixing layer are presented.

Westphal, R. V.↗
NASA NTRS1984

Problems with the process partitioning theory of stratocumulus entrainment

Three different approaches to partitioning were proposed. Ball (1960), Lilly (1968), and Deardorff et al. (1969, 1974) considered the sign of the net buoyancy flux at each level. If the net flux is positive, it is counted as TKE producing; otherwise, it is counted as TKE consuming. This approach can be called Eulerian partitioning. The second approach can be called process partitioning. It is assumed that the various processes acting in concert each produce and consume the same energy as if they acted independently (Manins and Turner, 1978). The total rates of TKE production and consumption are obtained by summing the effects of all the forcing processes. The third approach is Lagrangian partitioning. Each air parcel is considered as either producing or consuming TKE, according to the sign of the product of its density and vertical velocity anomalies. Stage and Businger (1981a,b) have applied process partitioning to the cloud topped mixed layer. One of the most important processes influencing entrainment into such a layer is cloud top radiative cooling. The production and consumption due to entrainment and radiative cooling are thus closely related. Model results are sensitive to the choice of formulation.

Randall, D. A.↗
NASA NTRS1984

Can cloud-top entrainment promote cloud growth?

The primary significance of Cloud Deepening through Entrainment (CDE) is that it can prevent the cloud top entrainment instability from destroying a cloud deck. Without suppressing the instability, CDE transforms it from a cloud destroyer to a cloud builder. The analysis does not depend on an entrainment hypothesis. Moreover, it is not restricted to PBL stratocumulus sheets. Stratiform clouds in the free atmosphere can be subject to CDE we need only reinterpret Ps as the pressure at the base of an elevated turbulent mixed layer. Modest departures from well mixedness will alter the results quantitatively but not qualitatively. Processes other than entrainment, such as surface evaporation, radiative cooling, and advection will often work with CDE to build a cloud layer; but of course they can also oppose CDE by reducing the relative humidity. If we make the weak assumption that the deepening of a cloud layer favors an increase in the cloud top entrainment rate (without specifying any particular functional relationship) we are led to speculate that CDE can cause runaway cloud growth, even in the absence of cloud top entrainment instability. through CDE entrainment leads to a deeper cloud, which leads to stronger entrainment.

Randall, D. A.↗
NASA NTRS1983

A modeling study of SO(x)-NO(x)-hydrocarbon plumes and their transport to the background troposphere

The behavior of a complex urban plume and its transport to the background troposphere are analyzed in terms of a model including sulfur oxide, nitrogen oxide and hydrocarbon (HC) photochemistry. A reaction mechanism consisting of 73 NO(x), SO(x) and HC reactions is employed in a model taking account of plume dilution, entrainment, deposition and the development of a diurnal mixing layer from a ground-based nocturnal inversion. When simulation results are compared with field measurements of the urban plumes leaving St. Louis and Milwaukee, and a power plant within the Milwaukee plume, the predicted concentration profiles of NO(x), SO2 and O3 are found to be in close agreement with the measurement, although agreement with the rate of transformation of SO2 to SO4(2-) is less good. Simulations made for a hypothetical urban location under a range of background concentrations and initial HC concentrations show particulate sulfate concentrations to depend strongly on the HC/NO(x) ratio, indicating that the homogeneous gas-phase transformation may occur at night.

Balko, J. A.↗
NASA NTRS1984

Numerical simulation of turbulent flows

Computational models of turbulence in incompressible Newtonian fluids governed by the Navier-Stokes equations are reviewed. The governing equations are presented, and both direct and large-eddy-simulations are examined. Resolution requirements and numerical techniques of spatial representation, definition of initial and boundary conditions, and time advancement are considered. Results of simulations of homogeneous turbulence in uniform shear, the evolution of a turbulent mixing layer, and turbulent channel flow are presented graphically and discussed.

Rogallo, R. S.↗
NASA NTRS1984

An Eulerian transport/transformation/removal model for SO2 and sulfate. I - Model development. II - Model calculation of SO(x) transport in the eastern United States

A three-dimensional, time dependent Eulerian atmospheric SO2 and sulfate transport/transformation/removal model is described and applied to the eastern U.S. The model was developed in anticipation of increased input to the atmospheric sulfur content by coal-burning power plants in the near future and is intended as an aid in identifying sources of SO2. The Eulerian transport model incorporates functions for chemical transformations, dry deposition, spatial topographical variations, spatial and temporal variations of mixing layer heights, the wind field, eddy diffusivities, deposition velocities, and temperature and water concentration profiles. Attention is also given to the SO2 photochemical oxidation mechanism and rates. Results from a 72-hr simulation of SO(x) transport over the eastern U.S., using actual 1974 meteorological data, illustrate the model's capability to depict interactions between emissions, transport, chemistry and removal. Concentration distributions are demonstrated to have significant spatial and temporal variations.

Carmichael, G. R.↗
NASA NTRS1984

Turbulence characteristics of the noise producing region of an excited round jet. II - Large scale structure characteristics

A conditional sampling of digital hot wire records obtained at several radial positions of an axisymmetric jet indicates the existence of regions within the mixing layer which are more orderly than a fully chaotic turbulent flow. A Fourier decomposition of the flow has shown that most of the turbulent energy is contained in the fundamental frequency of the excitation and the first harmonic.

Baltas, C.↗
NASA NTRS1984

Satellite color observations of the phytoplankton distribution in the eastern Equatorial Pacific during the 1982-1983 El Nino

Images provided by the Coastal Zone Color Scanner (CZCS) onboard Nimbus-7 show the effect of the 1982-1983 El Nino upon the phytoplankton distribution around the Galapagos Islands, located on the equator. The CZCS scenes document a major redistribution of phytoplankton around the Galapagos Island during a period when sea-surface temperatures (SST) were anomalously high (28 to 29 C). The mixed layer was unusually thick for this region, and the winds and both the surface and subsurface flows changed directions. It is pointed out that the El Nino is characterized as one of the most spectacular examples of a large-amplitude, interannual response of the ocean to atmospheric forcing. The 1982-1983 El Nino is the best documented event of its kind to date, and details of its effects are discussed.

Feldman, G.↗