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growth, and for more accurate classification of ice crystals than is possible with the 2D-C imaging probe. Snow will be collected at the ground for later silver analysis. Finding silver levels above the natural background does not prove that seeding enhanced the snowfall, because scavenging by natural snowflakes can also bring AgI to the surface. However, failure to detect increased silver indicates unsuccessful targeting. Thus, silver-in-snow measurements will sharpen delineation of seeded and nonseeded periods, Surface temperatures are often near freezing during snowfall on the experimental area. The resulting snowmelt makes identification of ice crystal types difficult, and can interfere with silver content sampling as the snow samples should be kept frozen until analysis, It is planned to construct a small refrigerated shelter near Allen Lake to be kept below freezing. Snow samples will be collected below openings in the roof. 1.5.7 Precipitation Observations. - A total of about 12 high-resolution precipitation gauges located located approximately 3 km apart along Lake Mary and Stoneman Lake Roads (see fig. 1.2), and near a trail which extends eastward from the southeast corner of Mormon Lake. The purpose of the gauge network will be to monitor precipitation rates and accumulations to be used in analysis of seeding effects. Enhanced precipitation at the surface is the desired final link in the chain of physical events following seeding. Consequently, the importance of adequate precipitation measurements cannot be overemphasized and substantial effort must be made to insure that such observations are reliably and accurately made, The Allen Lake target is particularly important, but observations from surrounding sites will greatly enhance demonstration of the area affected by seeding and the precipitation magnitudes involved. Radar may assist in delineation of the area of snowfall enhancement under some conditions, generally when natural snowfall in very light or nil. The precipitation gauge network will provide the only surface evidence of seeding effectiveness beyond the Allen Lake target, and a secondary target site used during some airborne seeding experiments (see sees. 1.5.7 and 1.7.5). High-resolution precipitation observations are needed for physical seeding experiments as shown by Super and Boe (1988) and the review by Reynolds (1988), The gauges must be able to resolve 0.1 mm or less water equivalent, and have a time resolution of 15 minutes of less. Conventional Belfort weighing gauge mechanisms may be used, with 45.4-cm-diameter orifices that provide five times the catch area of the standard 20.3-cm-diameter gauge. Manufacturer's specifications claim a resolution of 0.25 mm with standard orifices so the modified gauges should provide O,05-mm resolution. These large orifices gauges, successfully used on the Grand Mesa of Colorado (Super and Boe, 1988), also eliminate catch errors due to snowfall "capping" over the gauge openings. However, increasing the catch area reduces the gauge capacity (to about a 45-mm accumulation with a 45.4-cm orifice) so that frequent servicing is necessary. Recent developments in load cell gauges should be reviewed shortly before gauge procurement, as they could offer advantages in servicing frequency and data handling if temperature effects can be dealt with. For the purpose of minimizing wind-induced catch errors, each gauge will be located in a well-protected clearing in the forest, and will be equipped with an Alter-type windshield. It is well documented that even light winds can substantially reduce gauge catch as compared to actual snowfall on the surface. All gauges will be located near roads to make frequent servicing practical, as is necessary with gauges of high-resolution but limited capacity. Off-road travel is sometimes very difficult in the experimental area due to frequent mid-winter snowmelt periods, 16