Critical Issues in Weather Modification Research (2003) / Chapter Skim
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4 Tools and Techniques for Advancing Our Understanding
4 Tools and Techniques for Advancing Our Understanding
Pages 45-66
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From page 45... ...
Allis chapter identifies important developments in observational technologies and modeling and data assimilation capabilities and discusses how these new tools and techniques can best be applied to studies of enhancing atmospheric water resources and mitigating hazardous weather. MEASUREMENT AND OBSERVING TECHNOLOGIES Several large weather modification research programs were carried out in the late 1960s and early 1970s, including the National Hail Research Experiment aimed at hail suppression, the Sierra Cooperative Pilot Project aimed at snowpack enhancement, and the High Plains Experiment aimed at warm-season rainfall enhancement (among others discussed in Chapter 2 and Appendix A)
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From page 46... ...
The following observational tools ar likely to provide contributions to future weather modification steadies. Doppler Radars At the time of the major weather modification field studies mentioned earlier ~ the use of Doppler radar was embryonic, the performance characteristics of Doppler radars were still topics of research' and multiple Doppler networks were just emerging In the subsequent decades attendant research led to operational deployment of Doppler radars for precipitation measurement, severe weather detection and warning (the Next Generation Radar, or NEXRAD, network)
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From page 47... ...
and Chandrasekar, 2001~. These capabilities are of great potential value in assessing cloudseeding experiments For individual cloud studies, polarimetric particle classifications have the potential to reveal the transformation of supercooled liquid water droplets to ice crystals in glaciogenic seeding arid the development of large drops in hydroscopic seeding They can also follow the movement and dispersion of seeding aerosols using microwave chaff tubers as tracers (as discussed later)
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From page 48... ...
Most dual-polarization research in the Ur~ited States has been conducted with the large S-band (3 GHz) weather surveillance radars, such as those at NCAR, NOAA's National Severe Storms Laboratory, and Colorado State University.
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These kinds of active/passive remote sensing combinations could benefit eloud-seedi~g research' particularly if the theory and technology can be extended to scanning applications. Perhaps the most impressive demonstration of the combined use of cloud radar arid microwave radiometers in a cloud-seeding experiment is the ease described by Reinking et al.
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for measurements of column-integrated water vapor, a necessary measurement in weather modification research. Dense networks of such measurements could be cost-effectively deployed in future experiments.
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~7\~DERSTANDI.INTG 5! of cloud optical properties cloud liquid water, and ice-water content.
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The principal improvements of the CIP are added stability against vibration' decreased response time, and decreased dead tickle that provides for better resolution, sizing, and more accurate particle concentrations. The liquid water content detector uses technique described by King ~ 19783.
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Limitations exist for all instruments measuring LWC, but for the King probes, errors occur when droplet diameters become greater than 50 Em as droplets break up on the sensing element and are removed by the airflow before they evaporate completely; this causes an underestimation of liquid water. Large quantities of ice particles also are a limiting factor (FIeishauer et al., 2002~.
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From page 54... ...
Nevertheless, tracers ale likely to be an important part of future seeding research because they offer vital observations of both the seeding material deliver>" arid else cloud r espouse. MODELING AND DATA ASSIMILATION Numerical modeling should be a lcey component of weather modification research.
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The top panels (a) illustrate the concept of releasing silver iodide seeding nuclei and chaff together- and tracking their movement with polarimetric radar.
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From page 56... ...
They may be used to recreate cloud-seeding experiments from the past to help in the evaluation of those cloud-seeding effects. alley can be used to simulate the dispersion trajectories of seeding material, provide r eal-time forecasting in support of field experiments and operations' examine flee potential effects of cloud seeding outside of the seeded area, and aid in the statistical analysis of weather modification experiments.
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From page 57... ...
or shallow cloud-topped mixed layers (Kogan et al., 1995) , for which the microphysics consists of purely liquid water processes.
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The formulation for the explicit spectral-bin microphysical processes is based on solving stochastic kinetic equations for the size distribution functions of water droplets and several types of ice particles. Due to extensive computation, this microphysical scheme can only be run on the two-dimensional version of the model SOURCE: Wei-Kuo Tao, NASA/Goddard Space Flight Center.
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From page 59... ...
For exampl e, the f ormati on of I ong-l i ved real dual ci rrus sheets i s cri ti cal to the radi ati on budget, which then feeds back into the cloud dynamics. Also precipitation efficiencya the fraction of cloud liquid water that reaches the ground as rains is important both for climatological and weather-forecasting purposes, and it apparently is strongly dependent on mi crophysi cal processes.
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~For example, in a model with many different bins of ice and water species, the rate at which ice particles (of size 1 mm to 2 mm) combine with water droplets (of 1/8 mm to 1/4 mm)
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provide an excellent overview of the state of cloud physics laboratory work as of 1990. The most significant development in cloud physics laboratory studies since the early 1990s is the successful use of electrody~amic levitation chambers, in which nucleation and vapor deposition properties of individual, freely suspended hydrometeors earl be studied in a fully controlled environment (Straw et al., 2000; Swanson et al., 19994.
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is embedded in a larger-scale surrounding flow. The lack of computer power and adequate observations, especially over the oceans' needed to properly represent initial conditions have been among the greatest difficulties in hurricane modeling More than 20 different types of hurricane models have been developed since 1959.
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There are, of courser constraints on the types of problems that can be addressed through laboratory steadies; thus flee greatest progress can be made when laboratory studies are linlced to theoretical and numerical modeling studies and observational world. D ~ — ~ ~ ~ _ ~ _ _ J , FIELD STUDIES Physical concepts, laboratory findings, and n~nerical models must ultimately be tested in the field.
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From page 64... ...
This array of observing systems with its attendant ir~frastructure presents an unprecedented opportunity to pursue fundamental questions facing the weather modification community. While the Oklahoma/Kansas location will not address all problems of weather modification research, fundamental questions involving flee formation of precipitation, the distribution and nature of cloud liquid water and ice in large convective storms, and a host of other more sophisticated experiments, which could involve actual treatment, are among important problems that can be tackled.
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From page 65... ...
Instrument Aerosols Aerosol observation n/a system Additional systems Cimel sunphoton~eter Multifilter rotating sl~adowband Radiometer Raman lidar Atmospheric profiling Balloon-borne sounding system Microwave radiometer Radars lidar 50 MHz r adar wind profiler and radio acoustic sounding system MASSE 915 MHz radar wind profiler and RASS Clouds Belfort laser ceilometer Micropulse lidar MilJimeter-wavelength cloud radar Microwave radiometer Video time-lapse camera Whole-sky invader Narrow field-of-view sensor Raman lidar Atmospheric emitted radiance interferometer Absolute solar transmittance interferometer Cimel sunphotometer Infrared thermometer Microwave radiometer Narrow field-of-view sensor Rotating shadowband spectrometer Shortwave spectrometer Solar radiance transmission interferometer Multifilter rotating shadowband radiometer MFR (upwelling) Pyranometers Radiometers MFRSR-related Broad-band instruments Radion~etric instrument systems Pyrgeometers Pyrhe]
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From page 66... ...
66 CRJ7~(-~,4 L ISSlJES IN IDEA TI-IER AlODIFR-A TIO.V RESEARCI-f Surface energy flux Eddy con elation system Energy balance Bowen ratio station Infrared thermometer Soil waters and temperature system Surface meteorology Chilled mirror Surface meteorological observation system instruments 60-m tower: temperature and humidity sensors Temperature, humidity, wind, and pressure sensors Instruments of Radiometers Solarinfrared radiation station extended facilities of Multifilter rotating shadowband the CART/ARM site radiometer Surface energy flux Eddy correlation systems Energy balance Bowen ratio stations Soil water and temperature system Surface n/a meteor ological observation system instruments Instruments at Balloon-borne sounding system boundary facilities of the CART/ARM site Microwave radiometer Vaisala ceilometer Atmospheric emitted radiance interferometer Temperature, humidity, wind, and pressure sensors Instep uments at 91 5-MHz radar wind pi ofiler intermediate facilities Radio acoustic sounding system of the CART/ARM site
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