|
<br />,~;!';'_. t-\.:$,' fJ:~ ~.:~,~.:':~;( -'~:;;;-~:~'i
<br />",*~~~..,,,,,,,.:~.
<br />i: --,.. . . ..... .' - ~~ .-- ~ ~,~~ .
<br />
<br />
<br />
<br />Ano. 1978
<br />
<br />MELVIN ]. SCHROEDER AND GERARD E. KLAZURA
<br />
<br />507
<br />
<br />~
<br />
<br />sweep. The analyst must be aware of the output of the
<br />edit and/or area repOrts before evaluating the volume
<br />information. Calculations assume a constant elevation
<br />step throughout a wlume scan.
<br />Volume scans up to at least 120 in elevation are taken
<br />every 5 min. HopeIully, a complete set of cloud top
<br />and areal data is obtained simultaneously. This mode
<br />of data gathering allows cloud-top measurements at
<br />25 km of -6.1 km, which is less than expected cloud
<br />tops, but it is a reasonable compromise for the data
<br />desired.
<br />The rain report normally provides radar estimated
<br />rainfall information computed using the Marshall-
<br />Palmer (M-P) , Z= 200R1.6 (Marshall and Palmer,
<br />1948), and the North Dakota Pilot Project (NDPP),
<br />Z= 155R1.88 (Smith et al., 1975), relationships. Other
<br />Z-R relationships can easily replace these if desired.
<br />Total rain volume, average cloud base area and cloud
<br />lifetime are tabulated for each case.
<br />Along with date and time, the cloud-base area (km2)
<br />is displayed, followed by the values computed for
<br />average and maximum rainfall rate (mm h-l) and rain
<br />volume (ha-cm and acre-ft per 5 min) for the M-P and
<br />NDPP relationships.
<br />Cloud-base area is computed by accumulating all the
<br />bin areas containing rainfall which extend from approxi-
<br />mately 30-150 km at 10 elevation and from approxi-
<br />mately 25-29.9 km at 20 elevation. Cloud-base height
<br />(km) is input by the analyst and the program calculates
<br />the appropriate elevation-range pairs. Total rain
<br />volume, average cloud-base area and cloud lifetime are
<br />tabulated for each case.
<br />The characteristics report is generated by a program
<br />which decodes the 10 characters of each cell and lists
<br />the number of reflectivity peaks, cell origin, seeding
<br />status, echo data quality and mergers with other cells.
<br />The latitude and longitude location is also printed, as
<br />is the cloud base area (km2) and equivalent circle area
<br />radius (km).
<br />
<br />6. Concluding remarks
<br />
<br />HIPLEX radar systems are capable of generating
<br />one 2400 ft, 800 cpi magnetic tape every hour. With
<br />this large amount of data, a concerted effort has been
<br />made to eliminate unreliable and insignificant echo data
<br />so as to decrease the size of the data set and make only
<br />useful radar data available to the HIPLEX scientists
<br />and the scientific community. Very real considerations
<br />were the type of computer and the amount of computer
<br />time available to the HIPLEX program. With these in
<br />mind, a processing system was designed to integrate
<br />manual and computer. techniques where they were
<br />most efficient and effective. Manual intervention re-
<br />mains a very integral part of the computerized system
<br />to maintain quality. The system is automated to the
<br />extent where digital radar tapes from the two C band
<br />radar systems can be analyzed within several months
<br />of the end of the operational season.
<br />
<br />Two magnetic tape files of great interest to the re-
<br />search scientist are the Z. and Case Study Summary
<br />File for detailed precipitation and climatological
<br />analyses, respectively. With a fairly straightforward
<br />technique, the Z. file may be used to generate "foot-
<br />prints" for hourly, daily, monthly and seasonal pre-
<br />cipitation. Reflectivity gradients, raingage comparison,
<br />attenuation, Z-R, areal and hourly rainfall studies are
<br />only a matter of accessing the appropriate Z. files.
<br />For a climatology of convective clouds, the Case
<br />Study Summary File contains sufficient information to
<br />describe sizes and their frequency, regions and times of
<br />occurrence, life cycles, rainfall and reflectivity fre-
<br />quency distributions for each definable cloud complex
<br />of the HIP LEX program.
<br />Although no significant changes are expected to be
<br />made tD algorithms, methods to decrease processing
<br />time (manual and machine) are being investigated. An
<br />automated cell identification and tracking scheme are
<br />currently being implemented.
<br />
<br />Acknowledgments. The work was supported by Bureau
<br />of Reclamation Contract No. 14-06-D-7581, Division
<br />of Atmospheric Water Resources Management, Denver,
<br />Colo. Appreciation is also extended to Dr. Patrick J.
<br />Brady and Ms. Mary Stoudt for assistance with the
<br />preparation of this paper, Mr. Lee Brueni for writing
<br />the programs, and Ms. Lorraine Fortin for typing the
<br />paper. We acknowledge Mr. David Dahl for his in-
<br />genuity in designing the HIPLEX radars and thank
<br />Mr. William Harrison for clarifying radar hardware
<br />details and providing information on calibration
<br />procedures.
<br />
<br />REFERENCES
<br />
<br />Greene, D. R., 1971: Numerical techniques for the analysis of
<br />digital radar data with applications to meteorology and
<br />hydrology. Ph.D. dissertation, Texas A&M Unive'l'Sity,
<br />125 pp.
<br />Hildebrand, P., 1978: Iterative correction for attentuation of 5 cm
<br />radar in rain. J. Appl. Meteor., 17, 508-514.
<br />Lhermitte, R. M., and E. Kessler, 1965: A weather radar signal
<br />integrator. Proc. Int. Conf. Cloud Physics, Tokyo and
<br />Sapporo, 301-308.
<br />Marshall, J. S., and Wm. 'K. Palmer, 1948: The distribution of
<br />raindrops with size. J. Meteor., 5, 165-166.
<br />Probert-Jones, J. R., 1962: The radar equation in meteorology.
<br />Quart. J. Roy. Meteor. Soc., 88, 485-495.
<br />Sirmans, D., 1972: Digital processing of meteorological radar
<br />signals. Bureau of Meteorology, Dept. of Science, Australian
<br />Govt. Pub!. Serv., Canberra.
<br />-, and R. J. Doviak, 1973: Meteorological radar signal in-
<br />tensity estimation. NOAA Tech. Memo., ERL NSSL-64,
<br />National Severe Storms Laboratory, Norman, Okla.
<br />Smith, P. L., Jr., 1977: Evaluation of Miles City SWR-75 weather
<br />radar. Rep. 77-1, Inst. Atmos. Sci., South Sakota School of
<br />Mines and Technology, 55 pp.
<br />-, D. E. Cain, A. S. Dennis and J. R. Miller, Jr., 1975: De-
<br />termination of R-Z relationships for weather radar using
<br />computer optimization techniques. Rep. 75-3, Inst. Atmos.
<br />Sci., South Dakota School of Mines and Technology, 89 pp.
<br />
|