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Volume 28 Number 1 April 1 996 Weathermodification Association - the JOURNAL of WEATHERMOD/FICATION Volume 28 Number 1 April 1 996 WeatherModification Association - THE JOURNAL OF WEATHERMOD/FICATION- CO VER: Hydrometeoridentification with polarization radar. NOAA/EnvironmentalTechnology Laboratory Ka-band (8. 66 ram) radar RHI images from a winter snowstorm observed during the Winter Icing and Storms Project (2 km range rings, 2039 UTC08 February 1994, Erie, Colorado). Reflectivity (top image) showsa vertical slice through a precipi- tating, -5 to + 11 dBZ convective cell, and an underlying -7 to -20 dBZ layer cloud. The correspondingelliptical depolarization ratio (EDR,bottom image) defines three distinct polarization regimes, one of the convective cloud, one for the layer cloud, and one where the hydrometeors from the two are mixing. In the layer cloud, EDRchanges sig- nificantly (by 10 dB) from low elevation angles to zenith; this pattern and the depolari- zation values matchtheory for ice crystals of the thick plate growth habit. In the con- vective cell, EDRis invariant with elevation angle but larger in magnitudethan a -14.8 dB value corresponding to spheres and drizzle; this signature corresponds to less-than- spherical graupel. These signatures were verified by samples of graupel that scavenged thick plates, taken at the ground in the zone of the mix (insert, sample from the NCAR microphysics van). See article by Reinking, Matrosov, and Bruintjes in this issue for applications to weather modification. (Cover photo courtesy Roger Reinking, National Oceanic and Atmospheric Administration) Inside back cover: Attendees of the 44th Annual Meeting held in Durango, Colorado, May 1995. (Photos by the Editor) EDITED BY~ PRINTEDBY: JamesR. Miller, Editor Fenske Printing Connie K. Crandall, Editorial Assistant Rapid City, South Dakota USA Institute of Atmospheric Sciences South Dakota School of Mines and Technology 501 E. St. Joseph Street Rapid City, South Dakota 57701-3995 U.S.A. Phone: (605) 394-2293 FAX: (605) 394-6061 PUBLISHED BY: The Weather Modification Association Additional copies of the Journal of P. O. Box 26926 WeatherModification are available for Fresno, California 93729-6926 U.S.A. U.S. $25.00 each (members) and Phone & FAX: (209) 434-3486 U.S. $50.00 each (non-members). U.S. $600.00 for complete set of all 28 volumes/30 issues (members and non-members). Appreciation to the South Dakota Community Membershipinformation is available by Foundationfor partial support for the contacting the WMAAssociation at the the production of Volume 28 is Fresno, California, address shownabove. greatly acknowledged. Current MembershipCosts per Year: Corporate Members $ 200. O0 Member $ 50. O0 Student Member $ 10. O0 Retired Member $ 25. O0 Honorary Member $ O. O0 ISBN: 0739-1781 - THE JOURNAL OF WEATHER MODIFICATION - WEATHER MODIFICATION ASSOCIATION VOLUME28 NUMBER1 APRIL 1996 TABLEOF CONTENTS: PAGE THEWEATHER MODIFICATION ASSOCIATION .................................................. iv PRESIDENT’SMESSAGE and EDITOR’SMESSAGE .............................................. v Robert Czys and JamesR. Miller - REVIEWEDSECTION - HYDROMETEORIDENTIFICATION WITH ELLIPTICAL POLARIZATION RADAR: APPLICATIONSFOR GLACIOGENIC CLOUD SEEDING ........................................... Roger F. Reinking, Sergey Y. Matrosov, and Roelof T. Bruintjes THE ASSESSMENTOF SNOWPACKENHANCEMENT BY SILVER IODIDE CLOUD-SEEDINGUSING THE PHYSICS AND CHEMISTRYOF THE SNOWFALL........ 19 Joseph A. Warburton, Steven K. Chai, Richard H. Stone and Lawrence G. Young EVIDENCEOF EFFECTIVENESSOF HYDROSCOPICCOLLECTOR EMBRYOS ............ 29 Albert H. Schnell and Wallace E. Howell DEVELOPMENTOF IMPROVEDCRITERIA FOR HAIL SUPPRESSION SEEDINGIN SERBIA ......................................................................................... 35 D. Radinovi~ and D. Banjevie CALIFORNIACLOUD SEEDING AND IDAHO PRECIPITATION ................................. 39 J. Go MacCrackenand J. O’Laughlin VARIATIONS IN CONTRAIL MORPHOLOGYAND RELATIONSHIPTOATMOSPHERIC CONDITIONS ................................................. 50 David J. Travis CLIMATOLOGICAL AND MICROPHYSICAL CLOUD FEATURES TOWARDSRAIN ENHANCEMENTFORAGRICULTURE IN GREECE .................................................. 59 N. R. Dalezios, S. I. Spanos, N. Papamanolis, and T. W. Krauss SOMEPOTENTIAl ERRORSIN THE IDENTIFICATION OF HAIL SWATHS ANDSEEDED STORMS ..................................................................................... 75 Jos~ L. Sanchez, Roberto Fraile, AmayaCastro, Maria T. de la Fuente and Jose L. Marcos - NON-REVIEWEDSECTION - CHANGINGPERCEPTIONS OF THE ISRAELI WEATHERMODIFICATION PROGRAM ................................................................ 83 Arnett S. Dennis IMPLICATIONS FROM THE NORTH DAKOTA TRACER EXPERIMENT OF 1993 FOR THE GLACIOGENIC SEEDING OF SUPERCOOLEDCONVECTIVE CLOUDS TO SUPPRESSHAIL.............................................................................................. 86 Mark Bloomer and Andrew G. Detwiler - WEATHERMODIFICATION ASSOCIATION - GENERALINFORMATION - ARTICLES OF INCORPORATIONOF THE WEATHER MODIFICATIONASSOCIATION.. ........................................................................ 92 STATEMENT ON STANDARDS AND ETHICS FORWEATHER MODIFICATION OPERATORS ..................................................... 95 QUALIFICATIONS AND PROCEDURES FORCERTIFICATION ....................................................................................... 97 WMA CERTIFIED WEATHERMODIFICATION OPERATORS/MANAGERS AND HONORARYMEMBERS .................................................................................... 99 WEATHER MODIFICATION ASSOCIATION OFFICERSAND COMMITTEES .......................................................................... 100 WMA AWARDS THUNDERBIRD AWARD, BLACK CROW AWARD, SCHAEFERAWARD, INTERNATIONAL AWARD .................................................. 101 WMAMEMBERSHIP DIRECTORY - INDIVIDUAL ANDCORPORATE MEMBERS ........................................................................... 103 JOURNAL OF WEATHERMODIFICATION - 30 AVAILABLEPUBLICATIONS ........................................................................ 110 HISTORIC INDEX OF PUBLISHEDPAPERS IN THE JOURNAL OF WEATHERMODIFICATION, VOL. 23, NO. 1 (Apr 1991) THROUGHVOL. 27, No. 1 (Apr 1995) ....................... 112 JOURNAL NOTES, ADVERTISEMENTINFORMATION, SCHEDULEDWMAMEETINGS - 1996/97 .......................................................... 118 AUTHOR’SGUIDE ........................................................................................... 119 ADVERTISEMENTS iii 6 JOURNAL OF WEATIIER MODIFICATION VOLUME 28 HYDROMETEOR IDENTIFICATION WITH ELLIFrlCAL POLARIZATION R.ADAR: APPLICATIONS FOR GLACIOGENIC CLOUD SEEDING Roger F. Reinkinga, Sergey Y. Matrosovb, and~ Roelof T. Bruintjes aEnvironmental Technology Laboratory, NOAA/ERL,Boulder, CO 80303 bCIRES, University of Colorado/NOAA,Boulder, CO 80309 CResearch Applications Program, NCAR,Boulder, CO 80301 Abstract. Polarization capabilities of 8.66-mm-wavelengthradar and corresponding hydrometeor depolarization calculations nowprovide the basis for identifying individual types of ice and liquid hydrometeors within clouds and precipitation. Model results and radar measurements with correlated snow crystal samples from winter stratiform and convective orographic clouds are examined. The results are interpreted to illustrate howthis methodfor estimating hydrometeor types can be applied to monitor cloud evolution and evaluate the potentials and effects of glaciogenic cloud seeding. This information is derived from hydrometeor depolarizations (and related cloud reflectivities) associated with cloud phase transition, snowcrystal growth habit, graupel development,snow crystal aggregation, the presence and nature of the melting level, and the distinction of rain from drizzle below the melting level. The radar’s polarization capability offers the opportunity to monitor the developmentof hydrometeorsin the volumeof cloud affected by seeding or by natural processes. Spatial gradients in hydrometeor types, rates at which a volumeis transformed, and the form of precipitation can also be estimated. These features are all important for verifying the changes in hydrometeors introduced by seeding and interpreting the rates and mechanismsby which the changes occur. 1. INTRODUCTION Research (NCAR)microphysics van and a Weather Modification, Inc., Cheyenne II aircraft. In this Measurementcapabilities and applied theory are paper, the previously reported measurementsand new nowallowing hydrometeortypes to be identified with depolarization data are interpreted in the context of 8.66-mm-wavelengthelliptical polarization radar cloud modification. The results illustrate howice and (Kropfli et al., 1995). Snowcrystals of the various liquid hydrometeor identification using elliptical growth habits depolarize backscattered millimeter- polarization radar can be applied in real-time wavelengthradiation according to their aspect ratio, monitoring or post facto analysis to evaluate the orientation, and bulk density, and ~he polarization potential for and effects of precipitation enhancement state of incident waves (Matrosov, 1991a,b). The by cloud seeding. effect of the hydrometeorson the incident radiation can be measuredas an elliptical depolarization ratio 2. CAPABILITIES IN MEASUREMENTAND (EDR). The variation of EDRwith radar elevation THEORY angle or specific polarization state translates to an estimate of the hydrometeortype. Polarization signa- The Ka-band radar will detect clouds with tures of drizzle, thick plates, dendrites, aggregates
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