Precipitation Measurement - Standard Gauge The Good: - Simple - Inexpensive The Bad: - Maintenance - Evaporation - No digital output - Spatial extent

Precipitation Measurement - Weighing Gauge The Good: - Time series - Simple (mostly) The Bad: - Messy maintenance - Moving parts - No digital output - Spatial extent - Pretty expensive

Data Logger Precipitation Measurement - Tipping Bucket The Good: - Digital time series - Accurate The Bad: - Snow? - Loss during tips

Precipitation Measurement - Piezoelectric The Good: - Very accurate - Digital data logger The Bad: - Expensive - Spatial extent

Acoustic Rain Gage The Good: - Very accurate - Spatially explicit - Digital data logger The Bad: - Expensive

Doppler Radar A standard rain gage will have a sample area of ~ ft 2, but radar will sample ~ hundreds mi 2

Stick gage - $400 Tipping bucket - $1,000 Weighing - $5,000+ Doppler - $5,000,000

Measurement Errors Placement (near structures) Wind Unequal distribution (rain is a spatial process) Placement:

Wind

1. Reduced effective catch area. 2. Rain gage will cause wind to lift and accelerate. Wind Error

Double Alter Wind Shield

Arithmetic Mean Thiessen Polygon Interpolation Dealing with Spatial Variability

Icacos, Puerto Rico 423 mm/yr Pico del Este, Puerto Rico 340 mm/yr Monteverde, Costa Rica 350 mm/yr Cloud Drip Some tropical watershed research shows that cutting cloud forests actually reduces stream flow.

Hail and sleet are frozen rain, where as snow crystals form when water vapor condenses directly into ice. As much as 75 percent of water supplies in the western United States are derived from snowmelt. 300 inches of snow that the Lake Tahoe area receives is equivalent to about 30 inches of rain.

Snow Measurement Snow pack Core sampling Snow “Pillow”

Getting Rain Data SJRWMD National Climate Data Center National Weather Service (NOAA)