• Characteristics of Updrafts in Thunderstorms

      Battan, Louis J.; Institute of Atmospheric Physics, The University of Arizona (Institute of Atmospheric Physics, University of Arizona (Tucson, AZ), 1978-08-31)
    • Doppler Radar Observations of a Mountain Hailstorm

      Battan, Louis J.; Institute of Atmospheric Physics, The University of Arizona (Institute of Atmospheric Physics, University of Arizona (Tucson, AZ), 1975-08-01)
      By means of an X-band, vertically pointing Doppler radar observations were made of a thunderstorm on 20 August 1973 producing hail about 6 mm in diameter. The observations confirm earlier ones showing a highly variable internal structure. Updrafts are composed of high velocity "eddies" having diameters of about a few 100 m to a kilometer. It is speculated that such hailstorm features as the size and layering of ice type and the sporadic nature of hail showers are explained by the highly variable character of each updraft region and the sequence, at periods of 3 to 4 minutes, of updraft formation.
    • Calculations of Doppler Radar Velocity Spectrum Parameters for a Mixture of Rain and Hail

      Martner, Brooks E.; Battan, Louis J.; Institute of Atmospheric Physics, The University of Arizona (Institute of Atmospheric Physics, University of Arizona (Tucson, AZ), 1975-02-15)
      The radar reflectivity factors, the reflectivity-weighted mean terminal velocities (VT) and the standard deviations (cr) of the resulting VT Doppler spectra were computed for specified size distributions of rain, dry and wet ice spheres (taken to be hailstones) and rain with hail. Unambiguous estimates of the mean velocity and standard deviation can be obtained from a radar measurement of reflectivity for rain alone and dry ice spheres as a function of maximum sphere size. The results for wet ice spheres are strongly dependent on the thickness of the liquid water coating on the ice core. When rain and hail coexist, large values of reflectivity are associated with large ranges of VT and crv. If the shape of the hail size distribution is known, an independent measurement of the maximwn hailstone diameter or a knowledge of the standard deviation of the observed Doppler velocity spectrum can reduce the uncertainty in estimates of VT.
    • Doppler Radar Observations of a Hailstorm

      Battan, Louis J.; Institute of Atmospheric Physics, The University of Arizona (Institute of Atmospheric Physics, University of Arizona (Tucson, AZ), 1974-02-01)
      A severe hailstorm, occurring on 10 August 1966, passed over a zenith pointing, X-band, pulsed-Doppler radar located on a mountain in southeastern Arizona. An analysis was made of measurements of radar reflectivity, mean Doppler velocity, variance of the Doppler spectrum and calculated updraft velocity. The vertical air motions and characteristics of the hydrometeors within the storm were highly variable over distances of a few hundred meters to a few kilometers. The storm consisted of a series of updraft cores containing a number of discrete volumes, 1 to 2 km in diameter, of rapidly rising air with smaller accompanying eddies. The updraft cores were separated by regions of weak updrafts or downdrafts. For the most part, the highest reflectivitives were outside the updraft cores. It is visualized that the hailstone growth was initiated within the updraft, not as a continuous process, but rather as pockets of hailstones within the fast rising distinct volumes. This process could account for the layers of clear and opaque ice within large stones by allowing them to pass through several rising volumes. It might also account for brief bursts of hail and short hailstreaks observed at the ground.
    • Survey of Weather Modification in the Soviet Union

      Battan, Louis J.; Institute of Atmospheric Physics, The University of Arizona (Institute of Atmospheric Physics, University of Arizona (Tucson, AZ), 1973-05-15)
      On the basis of a review of abstracts of articles published mostly since 1969, a summary has been prepared of Soviet research in weather modification. Hail suppression and precipitation stimulation still are major areas of activity in the USSR, but in recent years they have begun to do research on lightning suppression and the use of heat for the dissipation of warm fog in stratus. The articles surveyed show little evidence that Soviet scientists, unlike their American counterparts, are convinced of the value of randomized experiments in the evaluation of cloud seeding hypotheses and there is no evidence in this literature that Soviet scientists have been tackling the modification of large scale weather phenomena.
    • Wind Gradients and Variance of Doppler Spectra

      Battan, Louis J.; Theiss, John B.; Institute of Atmospheric Physics, The University of Arizona (Institute of Atmospheric Physics, University of Arizona (Tucson, AZ), 1971-12-15)
      An X-band pulsed-Doppler radar having its beam fixed at an elevation angle of 3 deg, was used to measure radial velocity spectra in a light shower. Observations were made at intervals of 152 m between radar ranges of 7 and 18 km. It was found that the mean Doppler velocity, variance of the Doppler spectrum and radar reflectivity varied markedly over distances of the order of 100 m. The observed variance was below about 1 m2 sec-2 in 80 percent of the observations, but in about 4 percent of the cases, it exceeded 3m2 sec-2. An analysis of ~V/~r, the radial gradient of the mean Doppler velocity yielded a nearly Gaussian curve having a mean of 0.2 x 10-3 sec-1 and a standard deviation of 5.9 x 10-3 sec-1. The largest value observed was 3 X 10- 2 sec-1. The effects of the radial gradient of the radial wind apparently can explain about 25 percent of the observed variance of the Doppler spectrum.
    • Observed Doppler Spectra of Hail

      Battan, Louis J.; Theiss, John B.; Institute of Atmospheric Physics, The University of Arizona (Institute of Atmospheric Physics, University of Arizona (Tucson, AZ), 1971-06-15)
      Observations of Doppler spectra from particles 610 m above the ground were obtained by means of a vertically pointing X-band radar during a period when large hail was falling at the ground. It was found that the variance of the Doppler spectrum was a fairly good indicator of maximum hailstone sizes. Calculations of ice-particle size spectra were made on the basis of assumptions of particle shape, composition and fall speed. The many assumptions needed to bring calculated ice-sphere spectra into approximate conformity with observations indicates the complexity of this procedure and the need for at least one more independent observation of the properties of the hailstones. Measurements of depolarization might yield an independent estimate of particle shape. It is concluded that the pronounced minima in the backscattering curves of large ice spheres should serve as an independent indicator of the speed of vertical air motions.
    • Detection of Hail By Means of Doppler Radar

      Battan, Louis J.; Theiss, John B.; Institute of Atmospheric Physics, The University of Arizona (Institute of Atmospheric Physics, University of Arizona (Tucson, AZ), 1968-05-01)
      The doppler spectrum obtained by means of a vertically-pointing Xband pulsed doppler radar may yield information on the size distribution of hail in the free atmosphere. It is concluded that the quantity A in the size distribution curve for hail, N = N0-AD e is sometimes more than twice the values 2.27 or 2.93 cm -1 proposed by earlier investigators. It is also shown that when both rain and hail are present the variance of the 2 doppler spectrum may exceed 20 m2 sec-2.
    • Silver Iodide Seeding and Radar Echoes from Convective Clouds

      Battan, Louis J.; Institute of Atmospheric Physics, The University of Arizona (Institute of Atmospheric Physics, University of Arizona (Tucson, AZ), 1967-10-15)
      Summer convective clouds over a fairly isolated mountain range over southeastern Arizona were seeded by means of airborne silver iodide generators. The selection of days to be seeded was made according to a randomization scheme involving pairs of days. A 3-cm vertically scanning radar set was used to observe the maximum echo height over the "target" area at 30 minute intervals. The data so obtained were used to examine the effects of the seeding on the vertical extent of the cloud echoes. Although there is a suggestion that the silver iodide nuclei may have initiated precipitation in some clouds and caused small vertical echo growths, the statistical analyses, for the most part, showed that the observed differences could easily have been caused by chance.
    • Measurement of Draft Speeds in Convective Clouds by Means of Pulsed-Doppler Radar

      Battan, Louis J.; Theiss, John B.; Institute of Atmospheric Physics, The University of Arizona (Institute of Atmospheric Physics, University of Arizona (Tucson, AZ), 1967-04-01)
    • Recent Studies on Hail and Hail Modification in the Soviet Union

      Battan, Louis J.; Institute of Atmospheric Physics, The University of Arizona (Institute of Atmospheric Physics, University of Arizona (Tucson, AZ), 1965-10-05)
    • Seasonal Precipitation and Temperature Data for Selected Arizona Stations

      Green, Christine R.; Institute of Atmospheric Physics, The University of Arizona (Institute of Atmospheric Physics, University of Arizona (Tucson, AZ), 1964-07-15)
      Annual tabulations of winter (November through April) and summer (May through October) precipitation and temperature for 23 Arizona weather stations have been analyzed in this report. Their relationships are shown and discussed briefly.
    • Observations of Convective Clouds by Means of Pulsed-Doppler Radar

      Battan, Louis J.; Kassander, A. Richard, Jr.; Theiss, John B.; Institute of Atmospheric Physics, The University of Arizona (Institute of Atmospheric Physics, University of Arizona (Tucson, AZ), 1963-01-15)
      A new pulsed-doppler radar set designed for measuring the vertical distribution of the particle size and vertical-velocity spectra is briefly described. The X-band radar set employs a vertically-pointing antenna producing a 1.3 degree beam. Measurements of the properties of the hydrometeors are made at 500-ft. intervals from 500 ft. to a maximum altitude of 63,000 ft. The intensities of the radar return from particles in each of ten velocity channels are recorded digitally. The analysis of echo returns from showers is discussed in some detail. The data allow inferences of the change of particle size as a function of altitude and time, as well as of the vertical air motions in the cloud. New observations of so-called "angel echoes" are presented. Most often the vertical velocities of the angel echoes were positive. These observations can be used to infer information about clear air convection.
    • Summer Rainy Days in Arizona

      Green, Christine R.; Institute of Atmospheric Physics, The University of Arizona (Institute of Atmospheric Physics, University of Arizona (Tucson, AZ), 1963-01-15)
      June through September rainy days for 22 Arizona weather stations with 50 or more years of record are tabulated, graphically presented, and discussed.
    • Separate Component Multiple-Effect Solar Distillation

      Hodges, Carl N.; Thompson, T. Lewis; Groh, John E.; Institute of Atmospheric Physics, The University of Arizona (Institute of Atmospheric Physics, University of Arizona (Tucson, AZ), 1962-11-01)
      Research concerning a desalting system which utilizes solar energy and separate components for evaporation and condensation has been conducted by The University of Arizona for the Office of Saline Water during the period from April 28 to October 28, 1962. While cost optimization has not been completed, equations have been developed for solar collector performance and specific productivity. Items of equipment, such as heat exchangers, packed towers, spray chambers, etc., have also received careful investigation. A model plant has been constructed and is presently being operated. I
    • Measurement of Atmospheric Water Vapor by a Spectrophotometric Technique

      McMurry, Earl W.; Institute of Atmospheric Physics, The University of Arizona (Institute of Atmospheric Physics, University of Arizona (Tucson, AZ), 1962-09-21)
      A spectroscopic technique was used to measure the total amount of water vapor between the point of observation and the sun. Measurements were taken continuously throughout the day, yielding a detailed picture of water vapor variations as a function of time. Results from 28 days of observation over a period of a year show a wide variety of situations ranging from days of relatively stable and constant precipitable water vapor W to days in which large changes occur, sometimes quite abruptly. The median value of the range of W within successive one-hour periods was found to be 0.05 in, with ten per cent of all ranges exceeding 0.12 in, the latter amounting to about fifteen per cent of the annual mean of W at the locality in question. It is concluded that significant W-fluctuations are commonly missed in routine radiosonde practice. Natural variations of Ware, on the average, somewhat greater than the instrumental errors of radiosondes. Crude estimates of moist 11 bubble11 diameters of 0.5 to 12 kilometers were obtained.
    • Distillation of Saline Water Utilizing Solar Energy in a Multiple-Effect System Consisting of Separate Collector, Evaporator, and Condensor

      Hodges, Carl N.; Kassander, A. Richard, Jr.; Institute of Atmospheric Physics, The University of Arizona (Institute of Atmospheric Physics, University of Arizona (Tucson, AZ), 1962-04-01)
    • Evaluation of Effects of Airborne Silver-Iodide Seeding of Convective Clouds

      Battan, Louis J.; Kassander, A. Richard, Jr.; Institute of Atmospheric Physics, The University of Arizona (Institute of Atmospheric Physics, University of Arizona (Tucson, AZ), 1962-03-01)
      Observations of the convective clouds over the mountain ranges of southeastern Arizona show that a large fraction of them reach temperatures far below freezing but fail to produce precipitation. During the summer periods of the years 1957 through 1960, a randomized cloud seeding experiment was conducted to test if these clouds could be modified by airborne silveriodide seeding. The essential features of the experimental design were the following: 1) An objective technique was evolved for predicting days with suitable clouds; 2) one of a pair of two adjacent days was seeded on a random basis; 3) measurements on all days were made with rain gages, radar and a pair of ground-located aerial cameras mounted at the ends of a 3-mile base leg, and visual observations were made of cloud-to-ground lightning; 4) the signrank test was used to make statistical evaluation of the effects of seeding. The results after four years are the following: 1, The rainfall statistics do not allow a conclusion that seeding had any effect. Statistically, the rainfall on both seeded and not-seeded days was the same. However, the sensitivity of the tests to changes in the quantity of precipitation was quite low. 2. The frequency of occasions of large thunderstorm echoes was statistically the same on seeded and not-seeded days. 3. The cloud-census and radar studies suggest that in some cases, seeding may have led to the initiation of precipitation echoes. 4. Although there were more cloud-to-ground lightning strokes on seeded days, the differences between their occurrence on seeded and not-seeded days were not statistically significant. Evidence is presented indicating that precipitation in convective clouds is not initiated by the ice-crystal process. Samples of days with heavy rain and light rain were compared in order to study the factors governing the quantity of rain. It was not possible to show that there was any relation between the region of echo initiation and the quantity of precipitation. On the other hand, it is clear that on days with heavy rain there were many more large clouds. The observations are best explained if it is assumed that the quantity of rain is governed by those properties of the atmosphere which determine the number and size of the convective clouds. The microphysical processes which determine the region of precipitation initiation do not appear to be as important as was once suspected. A new program of seeding tests is described which should be more sensitive to changes in quantity of rainfall. It differs in several fundamental aspects from the program conducted during the period 1957 to 1960.
    • Heating and Cooling Degree-Day Characteristics in Arizona

      Green, Christine R.; Institute of Atmospheric Physics, The University of Arizona (Institute of Atmospheric Physics, University of Arizona (Tucson, AZ), 1962-02)
      A twofold study of degree-day data has been made for 49 Arizona weather stations. The first section of the report analyzes the possibility of temperature trends occurring in Arizona. The second section discusses heating and cooling degree-day practical application with emphasis on the Tucson area.
    • Tables of the Radar Cross Sections of Water Spheres

      Herman, Benjamin M.; Browning, Samuel R.; Battan, Louis J.; Institute of Atmospheric Physics, The University of Arizona (Institute of Atmospheric Physics, University of Arizona (Tucson, AZ), 1961-12-01)