Precipitation Measurement - Standard GaugeThe Good:- Simple- InexpensiveThe Bad:- Maintenance- Evaporation- No digital output- Spatial extent

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

Data Logger

Precipitation Measurement - Tipping BucketThe Good:- Digital time series- AccurateThe Bad:- Snow?- Loss during tips

Sensor frame

Sensor cover

Piezo detector

Electronics + Software

Precipitation Measurement - Piezoelectric

The Good:- Very accurate- Digital data loggerThe Bad:- Expensive- Spatial extent

Acoustic Rain Gage

The Good:- Very accurate- Spatially explicit- Digital data loggerThe Bad:- Expensive

Doppler Radar

A standard rain gage will have a sample area of ~ ft2, but radar will sample ~ hundreds mi2

Stick gage - $400Tipping bucket - $1,000Weighing - $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• http://fawn.ifas.ufl.edu• SJRWMD• National Climate Data

Center• National Weather Service

(NOAA)