OCR Text |
Show tolerance, and should be used for selecting airborne treatment patterns. 3. 3 Climatological Data This section summarizes significant findings of relationships involving area precipitation, upper wind patterns, and local and mesoscale patterns of orography in the Park Range. Measurements from the dense data network including optical snow rate sensors, modified weighing bucket snow gauges, snow boards, plastic sheet snow samplers, the special SCS (Soil Convervation Service) snow courses, and the Mt. Harris rawinsonde and PPI radar facility were used extensively to derive the mesoclimatology herein. The data sample used is one of the largest of its kind ever compiled for such high altitude mountainous topography. Several well-organized repetitive patterns in snowfall distribution are revealed, which can be related to upper wind direction and attendant dynamical effects from local barrier orientation, The danger of selecting control sites in mountainous terrain without sufficien! know ledge of the degree of similarity of local orographic effects between target and control areas is revealed. 3. 3. 1 Mesoclimatology of Seasonal Precipitation F~om five seasons of special SCS snowcourse readings, a surprisingly stable pattern of seasonal snowpack was noted when the readings were normalized to the Buffalo Pass Tower Station. Three seasons of normalized snow coursi readings are shown in Figure 66. A study of these readings indicates season· values of ridge-to-valley precipitation ratios ranging from near 3. 5 for the south end of the target area (Rabbit Ears) to 4. 5 on the north end (Buffalo Pai northward). While these ratios are repetitive within + 12% from one season to another, they vary widely from one precipitation e;ent to another (and evei within the same event). This short period variance is a complicated function of air mass stability, moisture content and total lifting mechanism (orographl + large scale converge nce). Steamboat Springs average monthly precipitation (November-April) is shown in Table 9. It can be seen that approximately 55 inches of water should be stored at Buffalo Pass on 1 May of a normal year (based on a ridge - to-valleJ ratio of 4). 3. 3. 2 Precipitation Rates, Duration, and Attendant Synoptic Features The climatological frequency of winter (November-April) precipitation over the Park Range by 24 hour period is about 45%. Precipitation events are frequently n e ar 12 hours in length but may range from 1 or 2 hours to as much as 48 hours; the result is approximately 1000 hours of measurable precipitation p e r winter season. 106 |