WMOD00453 - Laserfiche WebLink

Home Browse Search

I ~I III. FACILITIES AND EQUIPMENT Figure 25.-Heated Tipping-bucket Snow-rate Sensor. detector, electronic amplifier and strip chart read- out. The entire circuit is powered by a 6-volt wet cell that operates for 10 days without significant discharging. Snowflakes falling through the light beam produce an a.c. signal output from the CdS cell which is amplified and smoothed before re- cording. The threshold is 0.01 inch H20 jhr. in- stantan~ous rate and full scale for our operations is set at 0.3 inch H20 jhr. Dual units mounted orthogonally were calibrated in the test area against 19 the shielded snow-board and short period snow samples collected with 10 ft.2 polyethylene sheets. The resulting calibration chart, figure 29, includes runs under calm conditions and with winds to about 20 mph, and for snowcrystal types ranging from needles to spatial dendrites to stellar plates. For field checks, a reticle-type calibrator, powered by a 6-volt battery is employed, figure 29a. The time con- stant of the optical sensor is easily changed; we use 20 seconds because it gives adequate record smoothing without affecting any of the frequency components of interest in the rate history. Figure 30 shows a data sample. An optical snow-rate sensor was used at each measurement station in Phase 1 to gather data for the power spectrum analysis. The recorder that we use produces a 2y:?-inch record width and is powered by a 60 c.p.s. a.c. motor or a 6 volt d.c. motor, depending on availability of commercial power. At one station we used a chrono- metricaUy-governed 6 volt d.c. motor, but the gov- erning mechanism generated an unacceptably large noise field that was picked up by the sensor elec- tronics. As a result, we are planning to record chronometer-generated timing pips at all four d.c. locations in Phase II, and continue with the un- governed motors. The a.c.-powered units at the 11 other sensor stations have synchronous motors. Meteorological Measurement Equipment Aerovane wind speed-direction sensors are in- stalled at Buffalo Pass, Rabbit Ears Pass, figure 31, Steamboat Springs, Mt. Harris, and Emerald Moun- tain. On Emerald Mountain, there are two sensors installed at 50 foot and 12 foot heights to gather r O.5In. HaO/llr. l I RUS~R~ -"~~ - - +-= :=t=;:~:1.~.. on - -- = - --~.-. ~._..- ~T _: -~ .:e- -- i:::=' c=:~g=::-t~~t--::c __::...L__ - -...- ,- -- ----. = -, - === ,-:c_ --: .... ,- ,- === =- -- -1= ~t==3~-- - on - -- __:c- -- -- - --- - u_ - -- :':: -- - .... :: -..--- c - - -- -, - - '- ~ ..- - c: -- --- \: _._.~ ---- ='- = - - - N '" . - on ::.1=--' - U) .... lD . . . . . . . . . . . . . . . . . . . . fa .. .. .. >> . . . .I~..t~L -- -- ~ 10 mln.-=r Figure 26.-Sample of Snow fRain-rate Sensor Data.