Lecture 9: Measuring Precipitation

What factors affect the accuracy of rain gauges?

Orifice size (must be above 30mm diameter)

Orifice orientation (Should be horizontal)

Orifice height and wind

Observation time

Gauge position

Site conditions

Where are most rain gauges located?

In wealthier countries such as America, Europe, etc

Less in South America, Africa, etc

Are the number of rain gauges increasing or decreasing?

Decreasing

How is Radar used to measure precipitation?

A radio wave is transmitted and the echoes are analyzed

The reflectivity is measured as the amount of transmitted power returned to receiver to estimate rainfall rate

What are some Pro’s and Con’s of measuring precipitation from weather stations?

Pros:

Direct measurement

Most accurate method

Cons:

Point measurement may not be representative of the entire region

Gauges may be too sparse to estimate regional precipitation

What are some Pro’s and Con’s of measuring precipitation using Remote Sensing?

Pros:

More spatial coverage

Cons:

Expensive

Greater uncertainty as the algorithms used to translate reflectivity are complicated