Showing papers in "Journal of Applied Meteorology in 1979"
TL;DR: In this paper, Lanczos filtering is used to reduce the amplitude of the Gibbs oscillation, which is the principal feature of the Lanczos filter, and a pair of graphs is developed that can be used to determine filter response quality given the number of weights and the value of cutoff frequency.
Abstract: A Fourier method of filtering digital data called Lanczos filtering is described Its principal feature is the use of “sigma factors” which significantly reduce the amplitude of the Gibbs oscillation A pair of graphs is developed that can be used to determine filter response quality given the number of weights and the value of the cutoff frequency, the only two inputs required by the method Examples of response functions in one and two dimensions are given and comparisons are made with response functions from other filters The simplicity of calculating the weights and the adequate response make Lanczos filtering an attractive filtering method
2,142 citations
TL;DR: In this paper, the relative sultriness of warm-humid and hot-arid summer climates is assessed using the amount of clothing needed to achieve thermal comfort and the reduction in the skin's resistance needed to obtain thermal equilibrium.
Abstract: Using as bases the amount of clothing needed to achieve thermal comfort and the reduction in the skin's resistance needed to obtain thermal equilibrium, the relative sultriness of warm-humid and hot-arid summer climates is assessed. Conditions of equal sultriness are referred to a vapor pressure of 1.6 kPa in order to prepare a table of apparent temperature corresponding to summer temperatures and humidities.
810 citations
TL;DR: In this article, the authors used regression techniques to estimate hourly solar radiant energy incident at the earth's surface from geostationary meteorological satellite data, and the results showed that the standard error of the satellite-derived daily insolation when compared against pyranometers was 10% of the mean.
Abstract: Solar radiant energy incident at the earth's surface is a quantity of increasing importance in agricultural monitoring and solar power development. An experiment was undertaken in the summer of 1977 to determine if incoming visible radiation at the surface could be estimated from geostationary meteorological satellite data. The experiment entailed the collection of coincident satellite, conventional meteorological and pyranometer data over the Great Plains of the United States. Regression techniques were used to estimate hourly insolation from the satellite data. Hourly estimates were summed to give daily total insolation. The standard error of the satellite-derived daily insolation when compared against pyranometers was 10% of the mean, an accuracy more than sufficient for most agricultural uses. Problems of producing insolation operationally from both geostationary and polar-orbiting satellites are discussed.
343 citations
TL;DR: In this paper, a scale is derived in which any likely combination of summer temperature, humidity, wind and extra radiation can be expressed as apparent temperature, where the effect of extra radiation (direct and indirect insolation; terrestrial and sky radiation) is considerable.
Abstract: A scale is derived in which any likely combination of summer temperature, humidity, wind and extra radiation can be expressed as apparent temperature. The effect of extra radiation (direct and indirect insolation; terrestrial and sky radiation) is considerable. The effect of wind is relatively slight in summer. The total direct effect of altitude (barometric pressure) is negligible. These results are compared with the use of globe thermometers and linear formulas. Maps show wind and extra-radiation effects which combine with ambient temperature and humidity to give the distribution of summer-noon apparent temperature in Anglo-America.
236 citations
TL;DR: In this article, long-term evaporation measurements are expressed in the Priestley-Taylor (1972) framework for a spruce forest in Plynlimon, Wales, and a Scots Pine forest in Norfolk, England.
Abstract: Long-term evaporation measurements are expressed in the Priestley-Taylor (1972) “Potential evaporation” framework for a spruce forest in Plynlimon, Wales, and a Scots Pine forest in Norfolk, England. The results are used to illustrate the possibility of significant variability in evaporation from forest vegetation in response to precipitation input, and so provide a warning against the indiscriminate use of the Priestley-Taylor formula. A tentative suggestion is made regarding a possible role for potential evaporation in the forest environment.
224 citations
TL;DR: In this article, the authors reviewed the procedures currently employed to retrieve vector wind information from single-Doppler radar observations, and in particular those procedures implying a linearity hypothesis for the wind field are shown to be particular cases of a method termed VVP (Volume Velocity Processing).
Abstract: The procedures currently employed to retrieve vector wind information from single-Doppler radar observations are reviewed briefly. In particular, those procedures implying a linearity hypothesis for the wind field are shown to be particular cases of a method termed VVP (Volume Velocity Processing). This method, which makes full use of radar velocity data filling a volume, is first tested on simulated observations in order to assess its accuracy, then applied to actual data and shown to yield unbiased parameters of the horizontal vector wind field, as well as an estimate of the hydrometeor fall velocity and several control parameters.
209 citations
TL;DR: In this paper, the authors compared three data sets: an idealized concentration distribution to which the exact solution is known, a potential flow field, and surface ozone concentrations measured in the Los Angeles Basin on a particular day.
Abstract: In order to produce gridded fields of pollutant concentration data and surface wind data for use in an air quality model, a number of techniques for interpolating sparse data values are compared. The techniques are compared using three data sets. One is an idealized concentration distribution to which the exact solution is known, the second is a potential flow field, while the third consists of surface ozone concentrations measured in the Los Angeles Basin on a particular day. The results of the study indicate that fitting a second-degree polynomial to each subregion (triangle) in the plane with each data point weighted according to its distance from the subregion provides a good compromise between accuracy and computational cost.
204 citations
TL;DR: In this article, the radar history of 195 strong convective cells is studied and compared with information of a dense hail-pad network (323 pads per 1292 km2), and it is found that all hail-bearing cells are detected early in their development.
Abstract: One of the Soviet seeding criteria used to detect hail cells at an early stage of development is examined. The radar history of 195 strong convective cells is studied and compared with information of a dense hailpad network (323 pads per 1292 km2). It is found that all hail-bearing cells are detected early in their development. About 50% of the 71 cells which met the seeding criterion never produced hail on the ground. This corresponds to a 30% waste of seeding rockets. The criterion which uses six radar parameters can be replaced by a simpler and slightly more efficient criterion which necessitates only the determination of the height of the 45 dBZ contour H45 in relation to the melting level H0. The new criterion is compared with other criteria and its microphysical implications are discussed.
168 citations
TL;DR: In this paper, the applicability of the model of Priestley and Taylor (1972) for evaporation of saturated surfaces is examined for the former Lake Flevo (The Netherlands).
Abstract: The applicability of the model of Priestley and Taylor (1972) for evaporation of saturated surfaces is examined for the former Lake Flevo (The Netherlands). This lake had an area of about 460 km2 and an average depth of 3 m. Daily values of evaporation in the period July–September 1967, determined with the energy-budget method, are compared with the corresponding estimated values obtained by the Priestley-Taylor model. The agreement appears to be satisfactory. The diurnal variation of the parameter α of the Priestley-Taylor model is found to be pronounced. From standard meteorological observations at Oostvaardersdiep, a station at the perimeter of the lake, and an energy-budget model of Keijman (1974) an indirect extension of the available time series is obtained. In this way energy-budget data for the period April–October 1967 became available. Analysis of this data set leads to the preliminary conclusion that α has a seasonal variation. This is due to the fact that there is a linear relation be...
152 citations
TL;DR: In this article, the Fourier series is used to describe the seasonally fluctuating values of parameters in stochastic models of precipitation, and the maximum likelihood estimates of the coefficients are obtained to describe seasonal variability in the parameters.
Abstract: Fourier series are convenient expressions for the seasonally fluctuating values of parameters in stochastic models of precipitation. Least-squares methods are often used to estimate the Fourier series coefficients, but this method has two important disadvantages. First the “data” points are in fact estimates of parameters, and because of varying sample size, they may have unequal variances and should not be given equal weight. Second, there is no statistically sound procedure to test the significance of individual harmonics. In this paper we investigate methods to obtain maximum likelihood estimates of the Fourier coefficients to describe the seasonal variability in the parameters for a stochastic rainfall model. Parameters are obtained from a two-state Markov chain model for wet and dry day occurrence, and from a mixed exponential model for distribution of depth on wet days. The procedure is demonstrated on four sample stations scattered across the continental United States. A constrained multiv...
146 citations
TL;DR: In this paper, the authors developed a new global model of the surface albedo based on a detailed analysis of land use, which was used to determine the average surface albitude of the earth's surface in latitudinal bands for the four seasons of the year (January-March, April-June, July-September and October-December).
Abstract: We have shown in the past that the radiative-convective energy balance atmospheric model used at the General Motors Research Laboratories in our atmospheric physics research is extremely sensitive to the input value of surface albedo used. In response to this we developed a new global model of the surface albedo based on a detailed analysis of land use. The model has been used to determine the average surface albedo of the earth's surface in latitudinal bands for the four seasons of the year (January-March, April-June, July-September and October-December). In addition, global maps of surface albedo for elements 10° latitude by 10° longitude are provided. Our model involves: assigning one of 49 different types of surface to each of 77 040 areas for each of the four seasons. Each type of surface is assigned a different albedo for each season. The average surface albedo for a given latitudinal band is obtained by averaging the albedos for the areas in the desired latitudinal band. The average surfac...
TL;DR: In this paper, a method of determining the visible and infrared properties of high ice clouds using a ground-based lidar and infrared (IR) radiometer is described, followed by a method for the correction of the cloud backscatter coefficients for pulse attenuation in the clouds, using an experimentally determined back scatter to extinction ratio k.
Abstract: This article describes a method of determining the visible and infrared properties of high ice clouds using a ground-based lidar and infrared (IR) radiometer. A method of calibrating the lidar is described. This is followed by a method for the correction of the cloud backscatter coefficients for pulse attenuation in the clouds, using an experimentally determined backscatter to extinction ratio k. The IR emissivity is then calculated by assuming a value for the ratio between the visible extinction coefficient and the IR absorption coefficient which is invariant with altitude. This ratio is altered until the computed radiance is equal to the measured cloud radiance. Errors in the calculation of the backscatter coefficient, the visible and the IR optical depths and the IR emissivity are assessed for various errors in the backscatter to extinction ratio. It is found that errors in the cloud optical depth become extremely sensitive to errors in k when the cloud visible optical depth becomes large. How...
TL;DR: In this paper, a fast and efficient procedure was developed which allows the systematic interpolation of digital reflectivity data from radar space into Cartesian space, so that only one ordered pass through the original PPI scan data is necessary to complete the interpolation process.
Abstract: A fast and efficient procedure has been developed which allows the systematic interpolation of digital reflectivity data from radar space into Cartesian space. The algorithm is designed so that only one ordered pass through the original PPI scan data is necessary to complete the interpolation process. As a result, 100 cross sections may be interpolated and displayed for approximately five times the cost of producing PPI plots for the same volume. Computer-generated displays produced by the system include contoured and gray-scale plots of orthogonal sections and perspective images of two- and three-dimensional reflectivity surfaces.
TL;DR: In this paper, the results of seven field expeditions aboard the Naval Postgraduate School's R/V Acania, designed specifically to study the formation of marine fog along the California coast, are summarized.
Abstract: This paper summarizes the results of seven field expeditions aboard the Naval Postgraduate School's R/V Acania, designed specifically to study the formation of marine fog along the California coast. On the basis of observations and analyses, physical models have been formulated for the formation and persistence of at least four different types of marine fog which occur off the West Coast: 1) fog triggered by instability and mixing over warm water patches; 2) fog developed as a result of lowering (thickening) stratus clouds; 3) fog associated with low-level mesoscale convergence; and 4) coastal radiation fog advected to sea via nocturnal land breezes. In addition, it has been found that the triggering of embryonic fogs and further downwind development produces a synoptic-scale fog-stratus system and is responsible for redevelopment of the unstable marine boundary layer after Santa Ana events.
TL;DR: In this paper, a perturbation analysis of the equations of motion is used to predict the velocity deficit and turbulent energy fluctuations on a difference net in the x-z plane across the roadway for the case of the wind speed being much less than the vehicle speed.
Abstract: A theory for the velocity deficit in the wake of a moving vehicle in still air is derived from a perturbation analysis of the equations of motion. By suitable assumptions, expressions are found for the turbulent energy fluctuations in the wake. This theory is then applied to predict the velocity deficit and turbulent energy fluctuations on a difference net in the x-z plane across the roadway for the case of the wind speed being much less than the vehicle speed (i.e., the GM experiment). The predictions are then compared to data from the General Motors Sulfate Dispersion Experiment. Comparison of observations to predictions show that the theory predicts the velocity deficit and turbulent fluctuations accurately.
TL;DR: The parameterization of evaporation proposed by Priestley and Taylor (1972) is modified to take account of nonsaturated surfaces in this article, where it is suggested that evapore can be expressed as a function of net radiation, air temperature, a constant related to the nature of the surface, and a variable that is dependent on moisture availability.
Abstract: The parameterization of evaporation proposed by Priestley and Taylor (1972) is modified to take account of nonsaturated surfaces. It is suggested that evaporation can be expressed as a function of net radiation, air temperature, a constant related to the nature of the surface, and a variable that is dependent on moisture availability. The constant is equal to 1.26 for water and open grassland surfaces (as in Priestley and Taylor) but is nearer unity for some other surfaces. The variable is found to be directly related to near-surface soil moisture content for both bare and grassland surfaces.
TL;DR: In this paper, the authors compared the results of lidar and sodar for determination of mixing-layer heights during the month of October 1977, and found that the sodar results were consistently higher than the lidar values.
Abstract: Temperature profile, lidar and sodar results for determination of mixing-layer heights during October 1977 are compared. While the overall agreement was good, systematic differences do appear, particularly in early morning and late afternoon between lidar and sodar results, when the lidar values are consistently higher than the sodar. Temperature profile values are consistently lower than the other two methods. These differences are due to the slightly different behavior of the sensed variables near the capping inversion. Aerosols and particulates mix to larger heights than the top of the adiabatic temperature profile, while temperature fluctuations exhibit an increase at a height above the top of the adiabatic temperature profile but below the maximum height of particulate mixing.
TL;DR: In this article, it was shown that the much larger changes predicted by other models arise from additional water vapor evaporated into the atmosphere and not from the CO2 itself, and therefore, it appears that the larger changes in atmospheric temperature due to a doubling of CO2 concentrations arise from water vapor evaporation.
Abstract: Estimates of the atmospheric temperature changes due to a doubling of CO2 concentrations have been with a static radiative flux model. They yield temperature changes >0.25 K. It appears that the much larger changes predicted by other models arise from additional water vapor evaporated into the atmosphere and not from the CO2 itself.
TL;DR: The deuterium/hydrogen ratios (δD, in per mil, VSMOW) of the samples varied according to the elevation of the sample site and its position relative to the Sierra Nevada.
Abstract: Rain and snow were collected during major storms at 26 stations in California and Nevada during the exceptionally wet 1968–69 season. The deuterium/hydrogen ratios (δD, in per mil, VSMOW) of the samples varied according to the elevation of the sample site and its position relative to the Sierra Nevada. Eighteen storms were sampled at one or more stations. Eleven of them were sampled at almost all of 13 stations that lie east and southeast of the Sierra Nevada which allowed a storm-by-storm comparison of the influence of the topographic setting of the station and the synoptic meteorology of the storm on the δD characteristics of the precipitation. A model is presented that illustrates possible changes in δD values as a storm moves inland. It is calculated using probable starting values for moist air masses arriving from the Pacific and follows the meteorological and isotopic changes that should occur during adiabatic uplift, cooling and condensation. The model agrees satisfactorily with data from ...
TL;DR: In this article, a simple one-dimensional operational model is proposed to estimate reliable and realistic hourly mixing depths from routinely available upper air and surface data, where the model inputs are 0000 and 1200 GMT temperature soundings from the nearest radiosonde station and the hourly surface wind speeds and temperatures from a nearest representative surface station.
Abstract: The planetary boundary layer is defined as the layer of the lower atmosphere whose characteristics are directly influenced by the ground surface. In the atmosphere, turbulent mixing forms and maintains this layer; hence, the planetary boundary layer is also a mixing layer. Turbulent mixing can be either convectively or mechanically produced. A simple one-dimensional operational model is proposed to estimate reliable and realistic hourly mixing depths from routinely available upper air and surface data. The model inputs are 0000 and 1200 GMT temperature soundings from the nearest radiosonde station and the hourly surface wind speeds and temperatures from the nearest representative surface station. The model distinguishes between primarily convective and primarily mechanical mixing regimes. In a primarily mechanical regime, such as during nighttime hours or on cloudy or windy days, the mixing depth can be estimated from the surface wind speed and roughness length. During convective regimes, such as...
TL;DR: In this paper, a numerical model for the prediction of mulched soil temperature has been developed, which takes into account environmental condition as well as physical characteristics of both the mulch material and the soil.
Abstract: A numerical model for the prediction of mulched soil temperature has been developed. The model takes into consideration environmental condition as well as physical characteristics of both the mulch material and the soil. The ability of the model to predict the temperature of the mulched and unmulched soil is tested. It is shown that soil temperatures of a wet mulched soil are significantly increased, primarily due to the elimination of evaporation and partly due to the greenhouse effect of the polyethylene film. In the case of a dry mulched soil the greenhouse effect is dominant. Thus a smaller temperature increase is obtained.
TL;DR: In this article, the linear relationship u′(t + τ) = u′ (t)R(τ) + u″(t) is shown to be approximately valid for Lagrangian and Eulerian wind speed observations in the planetary boundary layer, where t represents any time and t + τ is some later time, u′ is the turbulent wind speed fluctuation, R(τ), the autocorrelation coefficient, and u″ a random wind speed component assumed to be independent of u′.
Abstract: The linear relationship u′(t + τ) = u′(t)R(τ) + u″(t) is shown to be approximately valid for Lagrangian and Eulerian wind speed observations in the planetary boundary layer, where t represents any time and t + τ is some later time, u′ is the turbulent wind speed fluctuation, R(τ) the autocorrelation coefficient, and u″ a random wind speed component assumed to be independent of u′. Eulerian wind data from the Minnesota boundary layer experiment and Lagrangian wind data from tetroon trajectories near Las Vegas and Idaho Falls are analyzed. At extreme values of u′(t) for the Eulerian data, u′(t + τ) tends to be slightly less than that predicted by the above relationship. An application of this formula to the calculation of diffusion yields results in agreement with Taylor's theory.
TL;DR: In this article, the area effectively covered by dual-Doppler radars is presented as a function of spatioal resolution and accuracy of horizontal velocity measurement, and the implications of this relationship for the spacing of a dual Doppler network tornadic storm research are discussed.
Abstract: The area effectively covered by dual-Doppler radars is presented as a function of spatioal resolution and accuracy of horizontal velocity measurement. Implications of this relationship for the spacing of a dual-Doppler network tornadic storm research are discussed.
TL;DR: In this paper, spatial cross correlations and interannual and month-to-month variations of monthly mean wind speed were studied at 40 sites throughout the United States, based on availability of 10 or more years of data from a fixed anemometer location and height and a climatological mean speed of 5 m s−1 (11 mph).
Abstract: Spatial cross correlations and interannual and month-to-month variations of monthly mean wind speed were studied at 40 sites throughout the United States. Sites were selected on the basis of availability of 10 or more years of data from a fixed anemometer location and height and a climatological mean speed of 5 m s−1 (11 mph) or higher. Spatial cross correlations of monthly deviations from climatic means were found to be about 0.5 for sites separated less than 200 km, with annual mean wind deviations from the climatic mean correlated with coefficient value 0.32 for similarly separated sites. Applications for using nearby “climatological” site wind speed data to adjust short-term “candidate” site data are examined with several methods. The best results show only minimal improvement in estimating the long-term annual mean over that obtained from one year of on-site data. These results indicate that, for candidate wind energy site evaluation, on-site data must be relied on more than originally consi...
TL;DR: In this article, the authors used digital infrared data from SMS 2 obtained on May 6, 1975 to study the vertical growth rate and cloud top structure in relation to the occurrence of severe weather (tornadoes, hail, and high wind) on the ground.
Abstract: Digital infrared data from SMS 2 obtained on May 6, 1975 are used to study thunderstorm vertical growth rates and cloud top structure in relation to the occurrence of severe weather (tornadoes, hail, and high wind) on the ground. All thunderstorms from South Dakota to Texas along a N-S oriented cold front were monitored for a 4 h period with 5 min interval data. Thunderstorm growth rate, as determined by the rate of blackbody temperature isotherm expansion and minimum cloud top temperature, are shown to be correlated with reports of severe weather on the ground.
TL;DR: In this article, the crosswind-integrated concentrations of a diffusing tracer were calculated from Lagrangian similarity theory and compared to field data at distances from 50-3200 m downwind of the ground-level tracer sources.
Abstract: The crosswind-integrated concentrations of a diffusing tracer were calculated from Lagrangian similarity theory and compared to field data at distances from 50–3200 m downwind of the ground-level tracer sources. The agreement between theory and data is good, supporting the usefulness of Lagrangian similarity theory for the prediction of ground-level concentrations to a dimensionless downwind distance of at least x/Z0=2×105. The comparison also demonstrates that 1) the eddy diffusivity of passive contaminants corresponds more closely to that of heat than that of momentum and 2) the effect of atmospheric stability on the ground-level concentrations may be closely predicted by altering the vertical scale of the diffusion without changing the form of the vertical distribution.
TL;DR: In this article, a simple prognostic equation for predicting the development of the nocturnal surface inversion height is constructed from the thermal energy equation, which is a simple method to estimate the NOI heights to augment the prediction of the mixed-layer heights.
Abstract: A simple prognostic equation for predicting the development of the nocturnal surface inversion height is constructed from the thermal energy equation. The purpose of the paper is to provide a simple method to estimate the nocturnal surface inversion heights to augment the prediction of the mixed-layer heights (Yamada and Berman, 1979) for regional-scale pollutant dispersion models. A significant improvement of the present model over previous simple models is the inclusion of atmospheric cooling due to longwave radiation. Another important difference, which considerably simplifies the present model, is the adoption of an empirical expression for the potential temperature profile. Predictions agree quite well with the data of the Wangara experiment.
TL;DR: In this paper, two case studies were used to examine the relationship of the sulfate concentration in surface precipitation to the microphysical characteristics of the precipitating cloud systems, and the data from one case study support the contention that existing sulfate aerosol was incorporated into cloud water by the nucleation process and accounted for nearly all of the observed cloud and precipitation water sulfate concentrations.
Abstract: Two case studies are used to examine the relationship of the sulfate concentration in surface precipitation to the microphysical characteristics of the precipitating cloud systems. The data from one case study support the contention that existing sulfate aerosol was incorporated into cloud water by the nucleation process and accounted for nearly all of the observed cloud and precipitation water sulfate concentration. These activated sulfate particles comprised nearly 60% of the clear-air sulfate mass concentration. Once nucleated, the sulfate particles accumulated water through the condensation process and were subsequently deposited at the surface after accretion on large snowflakes. The presumption of aqueous phase sulfate oxidation of SO2 was not necessary to account for the observed sulfate concentrations. The data from the second case study are more limited and difficult to interpret. Nucleation and below cloud washout appeared to be the main contributors to the surface sulfate concentration...
TL;DR: The drifts technique derives wind vectors from correlation analysis of spatial and temporal sequences of radiowave field strength at ground level as mentioned in this paper, and presents a new method (simplified Gaussian correlation analysis) suitable for large-scale processing.
Abstract: The drifts technique derives wind vectors from correlation analysis of spatial and temporal sequences of radiowave field strength at ground level. The paper examines the bases of the analysis, and presents a new method (simplified Gaussian correlation analysis) suitable for large-scale processing. Evaluation of the quality of derived winds vectors by means of internal consistency measurements is described. Methods of editing are surveyed, and a new method, based on the normalized time discrepancy, is demonstrated. Methods for securing maximum yield of winds vectors from raw data are described. The use of microprocessors for immediate data processing is outlined. Comparisons of winds obtained by the partial reflection technique with other experimental techniques are examined.
TL;DR: In this paper, the vertical structure of the troposphere was measured using a VHF radar during the passage of a warm front and the radar records indicated a descent of layers of enhanced humidity and temperature variations at the frontal surface.
Abstract: Measurements of the vertical structure of the troposphere were carried out using a VHF radar during the passage of a warm front. The radar records indicated a descent of layers of enhanced humidity and temperature variations at the frontal surface. It is shown that the radar measurements are in fair agreement with local and synoptic weather observations.