Measuring Precipitation. Assignment 4. Due February 9

Discussion: Review the information from the Snow Booklet on measuring snow and precipitation. You will compare the operating characteristics of the Campbell Scientific tipping bucket rain gauge to the converted Belfort Universal rain gauge.

Tipping bucket rain gauge. The rainfall increment is .01 in/tip. The accuracy reported by the manufacturer is +-1% for rainfall rates below 1in/hr and -3% for rainfall rates 1-2 in/hr.

Belfort weight rain gauge. As water collects in the bucket, a linear travel potentiometer outputs 230 millivolts/inch of water.

Calibration of tipping bucket. Fill the flask with valve with 40 ml of water. Open the stopcock so that water flows slowly (less than 1in/hr) . Be sure to record the rate at which the water enters the gauge (40 ml/total elapsed time). For a standard 8 inch diameter rain gauge, 8 ml should be equivalent to .01 inch.

Repeat a couple of times. How many tips did you record? How well calibrated is the tipping bucket? How much water may have collected on the sides of the flask and tubing? What other factors may contribute to differences in the number of tips?

Calibration of Belfort gauge. Repeat the previous calibration dumping 40 ml of water into the gauge. Do you need to add the water slowly or can you just dump it in? How well calibrated is the Belfort gauge? What other potential errors are there involved in calibrating this gauge?

Sources of errors:

Repeat a couple of times the experiment with the tipping bucket but dump the water from the graduated cylinder. How well did the tipping bucket do?

What are some of the other possible sources of errors for precipitation measurements?

Summarize the experiments conducted in class regarding the water equivalent of snow measured by the tipping rain gauge adapters. How sensitive were the measurements to the design of the inflow tube? What sources of error exist with this set up?