OCR Text |
Show Snow Collector for Recording Rain Gauge The measurement of snowfall or precipitation with an exposed precipitation gauge is difficult under the most favorable circumstances, and especially so in mountainous terrain where wind action is strong, for the amount of snow which actually falls into the orifice of the gauge seldom bears much relation to the average amount deposited on the ground. It is under just these most difficult conditions of windy storms in the mountains that the precipitation record is of most interest to avalanche forecasting. Several methods have been tested of controlling snowfall into a recording precipitation gauge in order to obtain a chart record of precipitation intensity during snowstorms. These include such standard methods as the use of wind shields around the gauge orifice. By and large these have been found unsatisfactory. The snow collector described here, while rather unorthodox in design, has stood well the test of use over a number of years. The mountain observer reaily notes that with any appreciable wind, the snow during a storm " falls" more horizontally than vertically. With winds above the critical level for avalanche formation ( around 15 mph), the horizontal motion of a snow particle in the air greatly exceeds the vertical motion. Since these circumstances are the ones of interest to avalanche formation, a useful snow gauge may be adapted to collect the horizontal rather than the vertical component of snowfall. The snow collector described here thus bears some family resemblance to the vectopluviometer which has been tested for measurement of mountain precipa-tation in California. It has, however, two, peculiarities of its own. Only a single inlet orifice is used, and this is kept directed into the wind by a wind vane which swings the pivoted collector. Though a simple elbow might at first glance seem to serve better to direct snow into the gauge, this leads to some difficulties in also directing the force of the wind against the collection bucket - 5 - |