Search Results

You are looking at 1 - 10 of 10 items for

  • Author or Editor: Darryl Randerson x
  • Refine by Access: All Content x
Clear All Modify Search
Darryl Randerson

Abstract

No abstract available.

Full access
Darryl Randerson

Abstract

A radar echo survey for two warm seasons is used to determine the spatial variability of the relative frequency of occurrence of an echo day in six selected areas. These areas include the Las Vegas Valley, Lake Mead and the Spring Mountains, all located in extreme southern Nevada. Also included are the Tonopah and Nevada Test Site areas as well as the Cedar City, Utah, area. The occurrence of an echo in these areas is related to both the K and Z indices, calculated from the Yucca Flat, Nev., 1200 GMT sounding. The relative frequency of occurrence of an echo was determined for various categories of K and Z. The resulting charts should have practical value for estimating the probability of the occurrence of moist convection over mountainous terrain.

Full access
Darryl Randerson

The general concept of a regional scale developed from the application of atmospheric pollution models to predict or diagnose air quality over air sheds. The regional scale is proposed to be the β- and α-mesoscale subrange, which includes atmospheric phenomena having horizontal wavelengths of 25–2500 km. To support this definition, examples are presented of unusual regional-scale flow regimes. Moreover, documentation is provided of the transport of suspended atmospheric pollutants over distances of 100–1000 km. Descriptions are provided of ongoing and future field programs for measuring regional-scale atmospheric phenomena. A review is made of many region-scale numerical models including both weather-prediction and air-quality models. Potential contributions of regional-scale meteorology to assessing the impact of new energy technologies are also described.

Full access
Darryl Randerson

Abstract

An evaluation is made of the variations of σy and K H over a 70-hr period as derived from analyses of radiological and meteorological data collected during extensive aerial sampling of a single nuclear debris cloud. These data reveal that for t<1 hr and t>10 hr, σyT 0.5 and K H≈constant; however, for 1<t<10 hr, the diffusive process is accelerated so that σyT 1.2 and K H≈σ1.17 y.A constant-diffusivity model for the Ekman layer, developed by Csanady, is assessed. The model yields close approximations to σy through the period of “shear-induced” diffusion between 1 and 10 hr after detonation. In both cases the constant-diffusivity model is highly dependent on U 2 g

Full access
Darryl Randerson

Abstract

Meteorological data are analysed to determine the location and intensity of the rainstorms that led to flash flooding in the Las Vegas Valley and resulted in approximately $4.5 million in damages on 3 July 1975. The effective precipitation contributing to the flood was found to cover an area of 550 km2. Within this area two centers of heavy rainfall were found, one situated approximately 14 km southwest of the central business district and the other about 13 km north-northwest. Maximum rainfall amounts are estimated to be of the order of 3.0 inch. A maximum rainfall rate of 1.0 inch per hour was detected in a weighing-bucket raingage. Hail and surface wind gusts of about 50 kt were observed in the northwestern portion of the city. Furthermore, the area of heavy rainfall is shown to have developed over the Las Vegas Valley and not over the surrounding mountains. Integration of an isohyetal analysis shows that, at least, 2.3×107 m3 (1.9×104 acre ft) of water was available before infiltration. This amount of detail in the documentation of southwestern desert rainstorms is rarely available.

Full access
Darryl Randerson

Abstract

Discriminant analysis is used to develop a cumulonimbus prediction equation (Z index) for a single station during the period June through September. Based on dependent data, the Z index explains 43% of the variance, while the more commonly used K index explains only 34% of the variance in the same data set. Verifications with 4 years of independent data demonstrate that the Z index yields a lower seasonal Brier Score than the K index, precipitable water content, persistence and the climatological average of cumulonimbus activity for June–September. It is concluded that the Z index provides a meaningful first approximation to the probable development of local cumulonimbus activity during the period June–September.

Full access
Darryl Randerson
Full access
Darryl Randerson
Full access
John S. Cornett and Darryl Randerson

Abstract

Four numerical models are described for predicting mesoscale winds aloft for a 6 h period. These models are all tested statistically against persistence as the control forecast and against predictions made by operational forecasters. Mesoscale winds aloft data were used to initialize the models and to verify the predictions on an hourly basis. The model yielding the smallest root-mean-square vector errors (RMSVE's) was the one based on the most physics which included advection, ageostrophic acceleration, vertical mixing and friction. Horizontal advection was found to be the most important term in reducing the RMSVE's followed by ageostrophic acceleration, vertical advection, surface friction and vertical mixing. From a comparison of the mean absolute errors based on up to 72 independent wind-profile predictions made by operational forecasters, by the most complete model, and by persistence, we conclude that the model is the best wind predictor in the free air. In the boundary layer, the results tend to favor the forecaster for direction predictions. The speed predictions showed no overall superiority in any of these three models.

Full access
Darryl Randerson, Joe G. Garcia, and Victor S. Whitehead

Abstract

Detailed analyses of an Apollo 6 stereographic photograph of a smoke plume which originated in southern Arizona and crossed over into Mexico are presented to illustrate how high-resolution photography can aid meteorologists in evaluating specific air pollution events. Photogrammetric analysis of the visible smoke plume revealed the plume was 8.06 mi long and attained a maximum width of 4000 ft, 3.0 mi from the 570-ft chimney emitting the effluent. Stereometric analysis showed that the visible top of the plume rose nearly 2400 ft above stack top, attaining 90% of this total rise 1.75 mi downwind from the source. Photometric analysis of the plume revealed a field of plume optical density that portrayed leptokurtic and bimodal distributions rather than a true Gaussian distribution.

A horizontal eddy diffusivity of about 6.5 × 105 cm2 sec−1 and a vertical eddy diffusivity of 2.3 × 105 cm2 sec−1 were determined from the plume dimensions. Neutron activation analysis of plume samples revealed the elemental composition of the smoke to be copper, arsenic, selenium, indium, antimony, with trace amounts of vanadium and scandium.

Full access