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
Precipitation Measurement - Tipping Bucket
The Good:
- Digital time series
- Accurate
The Bad:
- Snow?
- Loss during tips
Data Logger
Precipitation Measurement - Piezoelectric
Sensor cover
Piezo detector
Sensor frame
Electronics + Software
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
~ ft2, but radar will sample ~ hundreds mi2
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
Wind Error
1. Reduced effective
catch area.
2. Rain gage will cause wind to
lift and accelerate.
Double Alter Wind Shield
Dealing with Spatial Variability
Arithmetic Mean
Thiessen Polygon
Interpolation
Cloud Drip
Icacos , Puerto Rico
423 mm/yr
Pico del Este, Puerto Rico
340 mm/yr
Monteverde, Costa Rica
350 mm/yr
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)