OCR Text |
Show Standard terminology and abbreviations are to be used. If an unfamiliar term is used, or a familiar one in an unusual sense, it will be explained. Use the 24- hour clock system. The observation day is from 1700 to 1700. Final readings are taken at the end of the observation day. The most important single record is the Standard Snow Studies Chart, a compilation of daily observation. ( Figure 49) Section 1, Temperature: From the maximum- minimum thermometers of the thermograph. The former is preferred. Section 2, Wind: Col. 1. Record average velocity for the calendar day. Col. 2. Record average velocity at 6- hour intervals. Hourly velocities, if of interest, would be recorded on a storm plot. Col. 3. If recording weather vane not available, observer must estimate. Col. 4 and 5 « Observer's estimate of wind transport of snow at valley and peak elevations. Record as 0, light, moderate or heavy. Section 3, Precipitation: Col. 1. Measure 24- hour snowfall by means of a snowstake on a movable platform which can be reset on the surface at the end of each observation day. Col. 2. Obtain this figure as follows: take a snow core from the platform of the 24- hour stake in the 8- inch snow can, reduce to water. Pour into measuring tube and use the standard rain gage scale. This record to be kept as a check even if automatic precipitation gages are in use. Average density of snowfall is computed by dividing snowfall into water content. Col. 3. Record marked changes in type of snowfall with inches of each type if possible. Col. 4. Read the total snow depth to the nearest inch. Record as total inches, not feet and inches. Col. 5. Compute settlement as follows. If there has been no new snowfall, subtract today's total snow depth from yesterday's. The difference is settlement. If there has been snowfall, add this to yesterday's depth. Subtract today's total depth. Examples: Yesterday's total snow depth 100" Today's snowfall 12" Total 112" Today's total snow depth 110" Settlement 2" The settlement ratio is obtained by dividing the settlement by the snowfall: Settlement 5" : Settlement ratio .5 or 50^ Snowfall 10" Section 4, State of Weather: Col. 1. It is desirable to record the daily official weather forecast, preferably a forecast for the elevation of your station, as a check on dependability. Col. 2. Describe sky condition as clear, partly cloudy or cloudy. Record time precipitation starts and stops, including any breaks that last over half an hour. These times are important as the basis for computing snowfall intensities and precipitation intensities. Describe precipitation as intermittent, light, moderate or heavy. Record phenomena such as thunder, lightening, freezing rain, etc. - 130 - |