A meteorological transport and deposition interpolation model has been employed to estimate radioiodine deposition remote from the Nevada Test Site between points of observed deposition. The movement of the radioactive cloud across the United States is obtained from wind trajectories at various quasi-constant levels up to the top of the initial radioactive cloud. This model deals primarily with depositions beneath the passing cloud that are associated with precipitation. The fraction of radioiodine scavenged was inferred from a relationship derived statistically from fallout at locations having wet deposition. Therefore, estimation of deposition at locations between fallout observations is possible wherever precipitation occurred under the cloud. These estimates use very detailed historical records of precipitation available for virtually every county in the United States. Because significant dry and wet depositions also occur in areas that are not beneath the cloud, interpolation methods, such as kriging, are used to estimate fallout between the radioactivity observation locations. Ground-level radioactivity measurements are required for these alternative methods. Such observations are validated before being used, often by the use of supplementary low-level trajectories.
A composite distribution of tangential and upward components of air flow is determined by tracing particles of debris and cloud tag movements in scaled movies of a tornado. The greatest tangential speed measured is 170 m.p.h. and the greatest upward speed derived is 150 m.p.h. A distribution of the convergent radial component of motion in the lower 600 ft. of the vortex is synthesized and used t o generate a vertical speed distribution which nearly duplicates the observed vertical speed distribution. The observed radial distribution of the vertical component of relative vorticity at three levels is shown and convergence at the 500-ft. radius is computed using the synthesized radial speed distribution. Three-dimensional trajectories of air parcels in the lower portion of the vortex are also shown.
Drag coefficients were determined for a 152-cm (60-inch) tetrahedral Mylar plastic balloon in free flight as functions of Reynolds numbers ranging from 104 to 3.3 × 105. Vertical relative air speeds ranged from 9 to 270 cm sec−1. Most drag coefficients derived from the 186 tests lay between 0.7 and 0.8. The average drag coefficient was 0.73 for point-first motion and 0.72 for broadside-first motion. For relative speeds ≤100 cm sec−1, the range of interest of the Air Resources Laboratories, the average drag coefficient was 0.74 for both point- and broadside-first motions. Five force (free lift) category observations were duplicated on different days giving generally good repeatability of drag coefficients.
Abstract Constant volume balloon (tetroon) flights made over New York City at heights of about 300 metres during June of 1965 are analysed. The transponder‐equipped tetroons were tracked to distances exceeding 100 km by means of the wsr‐57 weather radar located in Central Manhattan. On non‐sea breeze days the tetroons tend to move towards low pressure with an angle of 35 degrees, and to move with about two‐thirds of the geostrophic wind speed. There is a correlation of 0.73 between lapse rate and tetroon‐derived r.m.s. vertical velocity, and of 0.43 between lapse rate and Lagrangian period of vertical oscillation. Tetroon‐derived vertical velocities are also used to obtain estimates of the mean Reynolds stress (1.3 dynes cm −2 at flight level) and the downwind variation of vertical diffusion over an urban area.
Tetroon flights across the northern California coast indicate the influence of a laterally extensive and fairly abrupt 100-m change in terrain height near the shoreline on the three-dimensional low-level air flow. Beneath the wind speed maximum at a height of 300 m, the wind speed is stronger over the land than over the sea, resulting in nearly equal horizontal mass transport between this height and the earth's surface. Across the 4-km interval bracketing the shoreline, the wind backs by 11° and 4° at heights of 200 and 400 m, respectively. The maximum upward velocity, of magnitude 6 cm sec−l, occurs 250 m above the sudden change in terrain height near the shoreline, with the compensating downward motion commencing 3 km inland. Over the hills inland from the coast, the magnitude of the tetroon height variation is closely related to the magnitude of the height variations of the underlying terrain, with tetroon oscillations in the vertical generally preceding the variations in terrain height by a distance exceeding the height of the tetroon above the ground.
Direct beam hourly solar radiation values, measured near solar noon under clear skies, were used to show the decrease in radiation in the United States caused by the debris cloud from the El Chichon volcanic eruption of March/April 1982. Maximum decreases of mean monthly direct beam occurred in December 1982, at Phoenix, Ariz., Boulder, Colo., and Bismarck, N.D. They were 11%, 17%, and 25% below the average December 1978–81 levels, respectively, at those locations. Data were taken from the National Oceanic and Atmospheric Administration solar radiation network. The El Chichon cloud “arrived” at Boulder and Bismarck in August and October 1982, Respectively, as determined by the first 1982 mean monthly radiation that was significantly below (5% level) the background data regression line. The arrival time at Phoenix was most likely in August. Cloud residence time was at least 11 months at Boulder. At Bismarck and Phoenix, cloud density had not yet begun to decrease in December 1982 after three and four months residence time, respectively. An anomalous, strong, and sudden short-period (7-day) drop in radiation was recorded in mid-May 1982 at Phoenix but not at Boulder or Bismarck. Similar mid-May drops were found, however, at Albuquerque, N.M., Las Vegas, Nev. and El Paso, Texas. Volcanic clouds causing large percentage decreases in direct beam radiation below expected climatological levels, such as observed in 1982 with the El Chichon cloud, when combined with the long cloud residence time, would be of considerable economic concern to solar energy systems, especially those depending primarily on direct beam radiation for energy input.
Wind data from the central five stations of the 1961 Weather Bureau boundary-layer-jet research pibal line are space-averaged as point data. In this form the information is compatible with other boundary-layer wind analyses made from composites of several points. Particular attention is paid to diurnal changes of jet speed, to Richardson numbers, and to inertial oscillations. Comparisons relative to the above items are made with two serial-data jet systems, as well as with theoretical models, and some similarities are found. Relationships among the jet, the geostrophic wind, and thermal wind are shown. The hodograph patterns for a jet with a surface inversion differ markedly from a jet imbedded in a temperature lapse. A certain combination of currently forecastable meteorological variables seems to be optimal for the development of the jet after sunset.
Pairs of constant volume balloons (tetroons) released ∼1 min apart from the same site at Haswell, Colo., and continuously tracked by two M-33 radars, are used to estimate the mutual consistency of tetroon vertical motions. In the strong well-organized vertical motion systems of midday and afternoon, it is possible unambiguously to relate the vertical oscillations of the two tetroons so long as the tetroon separation distance is less than about 3 km, implying that under these conditions the tetroons are indeed passing through the same systems (convection cells or thermals). At other times of day such a comparison becomes difficult, partly because of the smaller amplitude and period of oscillation. Where identification of the same vertical motion system is possible, the phase lag between vertical oscillations of adjacent tetroons is related in a meaningful way to the tetroon spacing and the relative position of the tetroon pair with respect to wind direction, and accordingly there is good evidence that tetroon vertical motions are basically consistent.
The Los Angeles Reactive Pollutant Project (LARPP) in the autumn of 1973 involved helicopter sampling of a volume of air “tagged” by means of three constant volume balloons (tetroons) released simultaneously from a point on the ground. Based on radar tracking of 35 tetroon triads at a mean height of 350 m above sea level, this paper considers the estimates of relative diffusion obtained from the rate of separation of the tetroons making up the triad. In the average, the median lateral standard deviation of tetroon position varies from 90 m after a travel time of 15 min to 800 m after 2 h, and from 140 m at a travel distance of 2 km to 1000 m at 20 km. The relative diffusion is indicated to be nearly twice as large in “neutral” as in “stable” conditions. Comparison with the results obtained by other investigators in other locations shows that the relative diffusion within the Los Angeles Basin is frequently unusually small, particularly with respect to travel time.
