• 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.
    • 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.
    • 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.
    • 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)
    • Arizona Statewide Rainfall

      Green, Christine R.; Institute of Atmospheric Physics, The University of Arizona (Institute of Atmospheric Physics, University of Arizona (Tucson, AZ), 1959-11-30)
      A statistical method of deriving a statewide average annual preciptation value for Arizona has been developed in this study. The techniques employed and several examples showing how these calculations may be used to determine any given year's average rainfall amount for the state or for any smaller state subdivision are presented.
    • Probabilities of Drought and Rainy Periods for Selected Points in the Southwestern United States

      Green, Christine R.; Institute of Atmospheric Physics, The University of Arizona (Institute of Atmospheric Physics, University of Arizona (Tucson, AZ), 1960-01-31)
      This report presents the results of an investigation of rainfall and drought probabilities in the southwestern United States. Daily weather records for ten weather stations were used to compute the empirical probabilities that droughts of 5, 10, 15, 20, or 25 days or rainy periods of 3, 5, 10, or 15 days will start on any day between April 15 and September 15. The results are presented graphically in smoothed form in 24 figures.
    • The Annual March of Precipitation in Arizona, New Mexico, and Northwestern Mexico

      Bryson, Reid A.; Institute of Atmospheric Physics, The University of Arizona (Institute of Atmospheric Physics, University of Arizona (Tucson, AZ), 1957-06-07)
      This report is concerned with the annual march of monthly precipitation amount in an area comprising the states of Arizona, New Mexico, Sonora, Sinaloa, Durango, and western Chihuahua. Fourier analysis was used to reduce the twentyyear mean monthly values to six harmonic terms, four of which were then plotted on charts and studied. The results of this study indicate that an area consisting largely of the Sierra Madre Occidental in northwestern Mexico, and the portion of Arizona southeast of Tucson constitute a single rainfall province with a strong summer maximum of rainfall. This province also has a winter maximum but only in Arizona does the semi-annual term exceed the annual in amplitude. Within the United States the Gila and Rio Grande valleys constitute rainfall provinces of internally similar annual march, while the upland areas tend to resemble the Pacific coastal pattern to the west.
    • Some Factors in Tucson Summer Rainfall

      Bryson, Reid A.; Institute of Atmospheric Physics, The University of Arizona (Institute of Atmospheric Physics, University of Arizona (Tucson, AZ), 1957-05-31)
      This report describes an investigation of several synoptic and airmass factors as they relate to the occurrence and amount of daily rainfall at Tucson, Arizona. Of the variables considered as predictors of rain later the same day, three stand out as useful: total precipitable water, Shownlter Stability Index, and distance south of the last closed contour of the circumpolar vortex at 500 mb. Better than 90 percent correct short-term forecasts appear attainable for occurrence of rain, while about twice as many correct forecasts as might be expected by chance were obtained in forecasting rain amount class.
    • Fourier Analysis of the Annual March of Precipitation in Australia

      Bryson, Reid A.; Institute of Atmospheric Physics, The University of Arizona (Institute of Atmospheric Physics, University of Arizona (Tucson, AZ), 1957-05-31)
      Monthly standard normal rainfall data for about 200 Australian stations was subjected to Fourier analysis. Charts were then plotted for phase angle and amplitude of each of the first four harmonics. These provide an objective description of the pattern of annual march of rainfall, and clearly delineate certain rainfall regions and climatic divides.
    • The Role of Precipitable Water Vapor in Arizona's Summer Rains

      Reitan, Clayton H.; Institute of Atmospheric Physics, The University of Arizona (Institute of Atmospheric Physics, University of Arizona (Tucson, AZ), 1957-01-31)
      The relation between Arizona's summer rains and the amount of water vapor in the air over Arizona was examined. It was found that the occurrence of rain was primarily determined by the moisture content of the air over the state, defined in this study by the amount of precipitable water at Phoenix. The effects of vertical wind shear and stability on the occurrence of rain were examined, but could not be precisely determined and are probably small as compared with the effects of precipitable water. Precipitation efficiency was found to vary directly with variations in the amount of precipitable water, but could be explained by changes in the evaporation of raindrops between cloud bases and ground in environments of differing precipitable water contents.
    • Significance of Different Vertical Distributions of Water Vapor In Arid and Humid Regions

      Byers, Horace R.; Institute of Atmospheric Physics, The University of Arizona (Institute of Atmospheric Physics, University of Arizona (Tucson, AZ), 1957-03-15)
      The vertical distribution of water vapor can be expressed by an index coefficient which provides information about eddy and advective transports in a region or in an air mass. The relationship between evapotranspiration and eddy diffusivity of water vapor can be studied in this way. Striking differences in conditions between the arid Southwest and the remainder of the country are shown.
    • Variability of Precipitation in an Arid Region: A Survey of Characteristics for Arizona

      McDonald, James E.; Institute of Atmospheric Physics, The University of Arizona (Institute of Atmospheric Physics, University of Arizona (Tucson, AZ), 1956-12-31)
      A number of statistical and meteorological aspects of the temporal and spatial variability of precipitation in Arizona have been examined in terms of their bearing on the water resources of the arid southwestern United States. Most of the work summerized has been of the nature of initial exploratory investigations made in order to lay the foundation for the much more extensive studies that will shortly be begun as part of the University of Arizona-U.S. Weather Bureau Cooperative Punchcard Climatological program. A selected sample of long-record Weather Bureau precipitation stations in Arizona were analyzed for their historic variability properties, a number of statistical and calculational techniques were tested, and a general plan has been developed for the next phases of the Institute's variability program. It is believed that these findings will be of interest not only to investigators in arid regions themselves but also to investigators chiefly concerned with more humid areas; for, in many respects, the statistical characteristics of arid-lands precipitation pose the most stringent of all requirements on statistical methodology. In that sense, the quantitative results of the present report may serve as useful indicators of upper bounds on the effects of non-normality, skewness, and heteroscedasticity of precipitation frequency distributions for North America in general.
    • 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.
    • 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.
    • 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.
    • 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.
    • 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.
    • 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)