• 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.
    • Calculations of Mie Back-Scattering from Melting Ice Spheres

      Herman, Benjamin M.; Battan, Louis J.; Institute of Atmospheric Physics, The University of Arizona (Institute of Atmospheric Physics, University of Arizona (Tucson, AZ), 1960-09-01)
    • Calculations of Mie Back-Scattering of Microwaves from Ice Spheres

      Herman, Benjamin M.; Battan, Louis J.; Institute of Atmospheric Physics, The University of Arizona (Institute of Atmospheric Physics, University of Arizona (Tucson, AZ), 1959-12-31)
    • Characteristics of Summer Radar Echoes in Arizona, 1956

      Ackerman, Bernice; Institute of Atmospheric Physics, The University of Arizona (Institute of Atmospheric Physics, University of Arizona (Tucson, AZ), 1959-07-08)
      This report describes an investigation of the radar data obtained during the summer of 1956. Descriptions of the evaluation and analysis techniques, of the basic data and of the findings of this study are given in considerable detail. For the convenience of the more casual reader, all discussion and a summary of the findings are contained in sections VI and VII.
    • 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)
    • Cloud Photogrammetry with Ground-Located K-17 Aerial Cameras

      Kassander, A. Richard, Jr.; Sims, Lee L.; Institute of Atmospheric Physics, The University of Arizona (Institute of Atmospheric Physics, University of Arizona (Tucson, AZ), 1956-06-01)
      A technique is presented in which a pair of ground-located K-17 aerial cameras are used on a 1.30 mile baseline to determine cloud ranges to one mile accuracy at 4o miles and cloud height measurements to within 500 feet at this range. Details of the power supply, vacuum supply, and camera synchronization requirements are discussed as well as methods used in analysis. In particular, a detailed discussion is given of the theoretical and practical errors encountered in such a photogrammetric technique.
    • Cloudiness Over the Southwestern United States and its Relation to Astronomical Observing

      McDonald, James E.; Institute of Atmospheric Physics, The University of Arizona (Institute of Atmospheric Physics, University of Arizona (Tucson, AZ), 1958-02-24)
      A number of types of cloudiness statistics for Weather Bureau stations in the southwestern United States are analyzed in terms of their implications for astronomical observatory site-selection. In all but one of the analyses, Yuma proves to be distinctly superior to other stations with respect to clearness of skies. Lack of nearby mountain peaks extending above haze and dust layers plus poor seeing due to inevitably high thermal instability throughout much of the year render the immediate vicinity of Yuma astronomically unattractive, however. Hence the difficult task of comparing the relative cloudiness of the region roughly concentric with Yuma is the practical problem confronting the astronomer seeking new observing sites. Inherent limitations in available types of meteorological observations are disctissed; but these limitations are not precisely defined, since they are not quantitatively known to the meteorologist at present. In view of these uncertain limitations in each individual type of data, the safest procedure becomes that of assembling all possible types of independently observed data and assessing the site problem in terms of the overall implications of all of these data. ~e present report consists chiefly in such an assembly and assessment of meteorological data. In addition, a review of past studies of the site-selection problem is given. It is concluded that during the winter half-year (more significant to astronomical observing than the sunnner half-year for night-duration reasons), the area extending out about 200 miles northeast and east of Yuma 1s the best portion of Arizona for observing sites. Sites in this area will have clearer winter skies than those over coastal southern California, and will: be somewhat superior to those north of the Mogollon Rim where more frequent migratory cyclonic storms increase the mean winter cloudiness to values higher than those found to the south. The southeastern corner of Arizona is unattractive in the summer rainy season (July-August) due to high-frequency of thunderstorms, and equally undesirable in summer is the whole Mogollon Rim whose thunderstorm frequencies are nearly as high, on the average, as those of extreme southeastern Arizona. A rapid westward diminution of summer thunderstorm activity across southern Arizona (due to upper-level flow conditions governing moisture distribution over the Southwest) makes summer conditions increasingly more favorable from Tucson westward to Yuma; and in the winter the entire border area west of Tucson to and beyond Yuma is quite favorable. Haze and dust tops average about 5000 to 6000 ft. msl. in winter and probably 8000 to 10,000 ft. msl. in summer in southern Arizona. Areas of agricultural cultivation, as the Salt River Valley area around Phoenix, have a locally severe transparency problem. The general altitude of the haze and dust layers plus other seeing difficulties leave only a few peaks in southwestern .Arizona as feasible sites. A peak at 5672 ft. in the Harquahalas and Kitt Peak (6875 ft.) in the Quinlans seems to offer the the meteorologically best possibilities in .Arizona. Several California peaks considered by Irwin may be almost as favorable as those in southwestern .Arizona, but no first-order Weather Bureau station data are available for those areas. However, the only peaks above 6000 ft. msl. in the area. west of Yuma are those just south of San Jacinto Peak and these ranges undoubtedly have about as high a winter cloudiness as San Diego, which proves to be distinctly higher than either Tucson or Yuma.
    • Cooperative Punchcard Climatological Program, First Annual Progress Report

      McDonald, James E.; Institute of Atmospheric Physics, The University of Arizona (Institute of Atmospheric Physics, University of Arizona (Tucson, AZ), 1955-11-15)
    • Cooperative Punchcard Climatological Program, Fourth Annual Progress Report

      Green, Christine R.; Institute of Atmospheric Physics, The University of Arizona (Institute of Atmospheric Physics, University of Arizona (Tucson, AZ), 1958-11-15)
    • Cooperative Punchcard Climatological Program, Second Annual Progress Report

      DesJardins, Robert B.; Institute of Atmospheric Physics, The University of Arizona (Institute of Atmospheric Physics, University of Arizona (Tucson, AZ), 1956-11-15)
    • Cooperative Punchcard Climatological Program, Third Annual Progress Report

      DesJardins, Robert B.; Institute of Atmospheric Physics, The University of Arizona (Institute of Atmospheric Physics, University of Arizona (Tucson, AZ), 1957-11-15)
    • 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.
    • 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)
    • Distribution of Relative Humidity and Dew Point in the Southwestern United States

      Sellers, William D.; Institute of Atmospheric Physics, The University of Arizona (Institute of Atmospheric Physics, University of Arizona (Tucson, AZ), 1960-02-01)
      This report consists of three basic parts. In the first, average monthly values of relative humidity are presented for between one and four hours of the day at 126 weather observing stations in the southwestern United States, including all of Arizona, New Mexico, Colorado, Utah, and Nevada, and parts of California, Texas, Idaho, and Wyoming. The nature, accuracy, and import of these data are discussed briefly. It is shown that the month with lowest average humidities varies systematically from March in central Texas to August in northern Nevada, antedating the westward movement of the Atlantic high pressure system, with its moist unstable air. In the second section, the distribution of dew point over the Southwest is discussed. High values are found on the windward sides of most of the larger mountain ranges, near bodies of water, and in heavily irrigated farmland; low values are concentrated at higher elevations and in the dry desert regions bounded by the Sierra Nevada Mountains to the west and the Rocky Mountains to the east. Hourly data for Arizona indicate that the diurnal variation of dew point is small, with a tendency for the lowest values to occur in the midafternoon in dry regions and in the early morning in moist regions, i.e., those with a surface snow cover or with considerable crop irrigation. The final section outlines a method of estimating the mean relative humidity from the mean temperature. Ordinary linear regression techniques are used, with a correction added to account for the systematic geographical distribution of regression errors.
    • 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.
    • 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.
    • 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.
    • Evaluation of Potential Vorticity Changes Near the Tropopause, and the Related Vertical Motions, Vertical Advection of Vorticity and Flow of Radioactive Debris from Stratosphere to Troposphere

      Staley, D. O.; Institute of Atmospheric Physics, The University of Arizona (Institute of Atmospheric Physics, University of Arizona (Tucson, AZ), 1960-03-26)
      Individual potential vorticity change, vertical motion, vertical advection of vorticity and flow from stratosphere to troposphere are evaluated at different levels and for different times in an extratropical disturbancec Vertical motions are obtained from trajectories on three isentropic surfaces for two different times. The isentropes pass through or near a front in the upper troposphere, the lower stratosphere, and the high troposphere on the cold side of the front. Vertical motion is also evaluated at 500 mb from an adiabatic method designed to give instantaneous values to the extent that the system moves without change of shapeo Negative extremes of 8 to 10 cm sec-1 occur in the upper air front, with positive extremes of the same magnitude a short distance to the northeast, coinciding with the eastern exit of the frontal zone. From theory it is shown that potential vorticity is not conserved if there is either a gradient of diabatic heating or a component of curl, normal to the isentropic surface, of frictional force. The sum of these two effects is evaluated over the United States for two 12-hr periods on two isentropic surfaces which were common to parts of the lower stratosphere, upper troposphere and a front in middle and upper troposphere. Generally large, positive potential vorticity changes occur in the lower stratosphere and in the upper troposphere on the cold side of the front. Large negative values occur in the frontal zone and around the entire periphery of the positive area, or around the periphery of the trough in the upper air. The potential vorticity changes are related to simultaneous stability and vorticity changes of like sign. The potential vorticity changes are positive in the region of the so-called 1 tropopause funnel 1 ; changes everywhere appear attributable to vertical gradient of diabatic heating rather than curl of frictional force. ' ( I The terms in the vorticity equation which contain vertical velocity (vertical advection of vorticity and tilting terms) are shown by means of the thermal wind equation to depend only on the vertical motion and temperature fields in an isobaric surface. For the frequent case where negative motion is centered in the baroclinic or frontal zone and rising motion centered at the exit of the zone, each of the vertical motion terms has the same characteristic distribution. Positive values occur on the cold side of the zone and to the right of the downwind exit of the zone, and negative values occur on the warm side of the zone and to the left of the downwind exit of the zone. The vertical advection and the sum of vertical advection and tilting terms are evaluated at 500 mb. Magnitudes obtained compare with those of the divergence term, although magnitude depends considerably on the distances over which finite differences are evaluated. Isentropic trajectories trace air initially in the lower stratosphere downward to within 5000 ft of the surface within 24 hr. Diabatic incorporation into the troposphere is also noted. The total adiabatic mass flow into the troposphere associated with the number of typical upper air disturbances in existence at any time is estimated and found to be sufficient to give the observed short residence times of a few months for radioactive debris injected into the stratosphere by nuclear detonations.
    • 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.
    • 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.