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<br />3.4 Mobile Radiometer <br /> <br />The DRI mobile microwave radiometer, first used during the 1991 field season, will again be used to <br />investigate spatial SLW distributions over the Plateau. The system is mounted on a 1-ton truck platform. <br />The dual-channel radiometer is capable of monitoring vertically-integrated water vapor and liquid water as <br />the truck is driven along the Plateau's highways. <br /> <br />3.5 Radar and Radiometer Site <br /> <br />The RRS (radar/radiometer site) will be located at 2975 m near the southern end of the upwind highway. <br />This very exposed site, between the heads of the North and South Forks of Birch Creek Canyon, will be <br />equipped with a dual-channel microwave radiometer, a radar, surface weather sensors and other equipment. <br />A scientist with access to these measurements will coordinate experiments from this location via the Project <br />radio network. <br /> <br />A fixed radiometer belonging to Reclamation (Bureau of Reclamation's) will monitor vertically-integrated <br />SLW and water vapor above the RRS. This system is similar to the DRI mobile radiometer and 1991 <br />comparisons between the two systems provided excellent agreement. <br /> <br />During experiments a Ka-band radar at RRS will make volume scans of radar reflectivity factor. The radar <br />does not have Doppler capability. The radar may be able to occasionally detect seeding plumes when natural <br />precipitation returns are very limited. Its main use will be to monitor precipitation tops and general storm <br />structure (e.g. passage of bands) that may be related to natural precipitation variations. Such variations may <br />mask real seeding effects, or be mistaken for real seeding effects, if the related storm structure is not <br />monitored. <br /> <br />Aluminum chaff (1/2 wavelength) will sometimes be released from the radar to provide wind trajectories <br />near the Plateau top. Chaff measurements will be limited to periods with weak hydrometeor returns so that <br />chaff returns are not obscured. However, trajectories measured during non-storm periods will be related to <br />fixed wind measurements (e.g. Doppler acoustic sounder) which will provide data throughout storm periods. <br /> <br />The RRS NCAR IN counter will monitor AgI IN concentrations. A sequential sampler will take air samples <br />over 0.5 h intervals for later analysis of SF 6 gas. <br /> <br />The RRS Rosemount icing detector will monitor SLW at about 8 m AGL (above gro~d level) where wind <br />speed and direction will be measured by a heated anemometer and vane, respectively. <br /> <br />A crew trailer will provide minimal living facilities and storage space while two diesel generators will provide <br />electrical power to the RRS site. <br /> <br />3.6 Target Site <br /> <br />The TAR (Target Site) will be near the center of the area intended to be affected by seeding during direct <br />detection experiments. It will be on an exposed, windy, north-south oriented ridgeline 400 m south of the <br />intersection of the Emery/Carbon county border with Highway 264. The TAR elevation will be 2905 m. A <br />vane-mounted 2D-C probe, similar to that used on the van, will monitor ice particles at about 8 m AGL. <br />This approach should provide ice particle observations without the errors that can result from aspirated 2D- <br />C probes on the ground (e.g., crystal breakup due to impacting the sides of the aspirator). <br /> <br />An NCAR IN counter in the combination equipment/crew trailer will monitor AgI. A sequential sampler <br />will take 0.5 h air samples for later analysis of SF6 gas. <br /> <br />6 <br />