1. Precipitation Measuring Instruments
Length (depth) is the standard unit for measuring precipitation
Millimeters is WMO standard
U.S. uses the inch

2. Non-Recording Gauges U.S. Standard Rain Gauge
8 inch diameter at collector
Inner collection tube cross-section = 1/ collection area
Rim of collector is inches above ground
Funnel starts 2 inches below rim
Uses measuring stick to determine water amount.

3. British Standard Rain Gauge
5 inch diameter collector
Inner collection tube cross-section area = 1/10 collector area
Rim of collector 12 inches above ground
Funnel starts 4 inches below rim
Uses measuring glass to determine water amount.

4. Canadian Standard Rain Gauge
3.57 inch diameter collector
Collection area 10 square inches
Inner collection tube cross-section area = 1/10 collector area
Rim of collector 12 inches above ground

5. Recording Instruments
Fergusson Type Weighing Gauge
Bucket rests on platform supported by spring
Pen adjusted to record zero with bucket on platform
Weight of water moves platform down which moves pen arm down causing recording on moving chart

6. Advantages: Disadvantages
Removing funnel collector allows collection of solid precipitation
Good in cold climates
Disadvantages
Winds over 25 knots cause oscillations of the balance producing errors in the recording
Does not measure or record intensity.
Can make rough estimations.

7. Tipping Bucket Gauge
Water from collector is funneled into one side of the bucket mechanism
Each bucket can usually hold 0.01 inch of water
When full, the bucket tips and the second bucket moves under the funnell
Tipping causes momentary closure of a switch, usually mercury or reed.

8. Momentary current drives pen arm to record 0
Momentary current drives pen arm to record 0.01 inch of precipitation each time bucket flips.
Advantages:
Continuous remote recording
Disadvantages:
No record for less than 0.01 inch of precipitation
Not good for light rain, drizzle
Errors result if rainfall greater than 2 inches per hour - splashing from small bucket. Buckets cannot tip fast enough.
Cannot record rainfall intensity. Can make rough estimations.

9. Rate-of-Rainfall Recorders
Jardi Recorder
Rate of flow through opening is determined by height of float in a chamber which lifts a tapered spindle which allows more water to flow out of the bottom of the chamber.
Float rises until rate of flow into the chamber equals the rate of flow out. Position of pen on a graph is determined by height of the float in the chamber.

10. Optical Rain Gauge
Infrared beam transmitted across 0.5 m space through which precipitation falls
Sensors are 24 to 64 photodiodes mounted in an array approximately 200 mm apart.
Falling precipitation blocks IR beam from reaching sensor array, creating a shadow on some of the sensors.

12. Rain Gauge with Alter Shield

13. Another type Alter Shield

14. Turf Wall Rain Gauge

15. Measurement of Snow Snowfall - The depth (in. or cm) of new snow (Sf)
Snowfall Water Equivalent - Depth (in or cm) of water when snowfall is melted. (Sw)
Conversion:
Weighing a core sample
Melting a core sample and measuring
Melting a core sample and weighing
Use of a conversion factor

16. Snowcover: Areal extent of snow covered ground expressed as a percent of the total area of a given region.
Snow Density:
The ratio of the water equivalent to the depth of snow.