The Clearing Index is a numerical estimate of the contamination dispersal capability of the atmosphere. Between July, 1969, and June, 1970, 192 rawinsonde flights were made in the Cache Valley at approximately the same time as officially scheduled flights at the Salt Lake City Weather Bureau Airport Station. Clearing Indexes were computed from various combinations of Salt Lake Valley and Cache Valley rawinsonde and maximum surface temperature data. These were examined from the viewpoint of recommending a standard procedure for providing Clearing Indexes on a daily basis for Intermountain valleys. The primary conclusions were that: 1. Actual Salt Lake Valley and Cache Valley Clearing Indexes were in the same operation classes 71% of the time 2. As presently computed, the Clearing Index is significantly less than a perfect indicator of the air pollution potential of the Cache Valley. 3. The improvement (if any) in the air pollution potential prediction for the Cache Valley, which should result from having an additional rawinsonde station in the Cache Valley, would be too little to justify the effort and expenses. The same is probably true for other Intermountain valleys. This conclusion could change if the procedures for estimating this potential were sufficiently improved.
Reynolds, George W.; McNeill, William; Johnson, Floyd; and Cleary, Janet, "An Examination of Approximately Simultaneous Salt Lake Valley and Cache Valley Clearing (Ventilation) Indexes" (1970). Reports. Paper 139.