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<br />over the Allen Lake region, as well as through adjoining natural cloud. Mormon Mountain will <br />block scanning north of a line running west-southwest from the radar, but airflow is rarely from the <br />west or northwest during storms (Super et aI., 1989). Sector scanning will be used through a range <br />of elevation angles over the region of interest to provide observations of cloud tops and structure. <br />An antenna beam width in the range of 1.00 to 1.60 will enable reasonable spatial resolution over <br />the target region. Periodic wind measurements will result from tracking aircraft-released radar <br />chaff. These wind observations will help evaluate targeting for the seeding experiments. The <br />Doppler capability will permit real-time display of the wind component toward and away from the <br />radar which should be representative of the wind over iillen Lake. The Doppler information will <br />be especially valuable in postseason analysis of the experiments. <br /> <br />At least some of the observations from each of the below noted Allen Lake systems, and some from <br />other project locations, will be routinely transmitted to the Mormon Lake radar site which will be <br />the project operations center. Satellite photos, weather maps and other forecast products also will <br />be received there by satellite downlink. The FC (field wordinator), with the project forecaster's <br />assistance, will use this information in deciding when and how to conduct experiments and what type <br />they should be. For example, SL W must be present for seeding to have any substantial effect. The <br />low-level winds must be from the general direction of the generators to affect the target area with <br />ground seeding. Wind observations and targeting model predictions will be used to direct the <br />seeding aircraft where to release AgI. Seeding would not be initiated if the radar revealed marked <br />changes in the approaching cloud structure which would mask seeding effects. <br /> <br />The primary reason for colocating the project operations center and the radar is that in order to <br />coordinate experiments the FC needs real-time visual access to the patterns of reflectivity factor and <br />Doppler winds. The needed information is portrayed on the radar "scopes" (cathode ray tubes), but <br />it would be quite difficult to transmit that much data e:lsewhere in real-time. In contrast, other <br />information needed by the FC readily can be transmitted to the radar. <br /> <br />1.5.6 Target Site. - The Allen Lake target site willi have several instruments. A microwave <br />radiometer will be operated there in the vertically pointed mode to monitor whether excess SL W <br />is passing overhead. Hogg et a1. (1983) discuss the theory and use of radiometers for monitoring <br />integrated water vapor and liquid water amounts along their field of view. A Doppler acoustic <br />sounder will monitor winds in the lowest kilometer above ground to aid in targeting assessment. <br />A tower will be erected near the radiometer and equipped with sensors for wind velocity, <br />temperature, humidity, and icing measurements well above treetop levels. The tower will also have <br />a nondirectional radio beacon to assist in aircraft navigation. An acoustical ice nucleus counter will <br />be operated to detect whether AgI is being transported to the site. This will have particular <br />importance with ground seeding when the AgI plume should impact the surface. Aircraft-released <br />AgI also may be detected if it is carried to the surface by precipitation and released, possibly by <br />sublimation of tiny crystals. A laser ceilometer will be operated to monitor the cloud base above <br />the rim. This measurement will likely coincide with the lower boundary of the SL W when it is <br />present. Ice particles can be expected to continue growing until they fall below the liquid cloud. <br /> <br />An aspirated ice particle imaging probe (PMS 2D-C) (Humphries, 1985) will be operated in a <br />sheltered location in the forest near Allen Lake to estimate IPC, crystal sizes, and types. It will <br />provide minute-by-minute observations. Very high-resolution precipitation rate observations will <br />be made nearby. An accurate balance or load cell will. be used to weigh precipitation amounts <br />falling on the surface. Microphotographs of ice particles will taken for documentation of accretional <br /> <br />15 <br />