Rainfall
Rain has a "scavenging" effect when it washes particulate matter out of the atmosphere and dissolves gaseous pollutants. Reduced particle concentrations after rain improves visibility. Rain acts as a solvent for gaseous pollutants, such as sulfur dioxide, forming acid rain resulting in potential damage to materials or vegetation where it falls.
Certain geographic areas, or particular times of the year, with frequent high rainfall are likely to have improved air quality.
The graph below shows how the amount of rainfall and number of days on which it rains are higher in summer months compared to winter months in Brisbane.
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Source: Bureau of Meteorology data |
Measurement of rainfall
Rainfall can be measured using a tipping bucket rain gauge, shown in the photograph above right, and illustrated below.
The gauge registers precipitation (rainfall) by counting any small increments of rain collected. When rain falls into the funnel it runs into a container divided into two equal compartments by a partition
The empty container has been designed to balance in stable equilibrium when resting against a stop. In its normal position it is tilted as shown with one side or the other resting against a stop.
When a specified amount of rain has drained from the funnel into the upper compartment the bucket tilts the opposite way so that the compartment containing the rain comes to rest against the stop on the opposite side. The collected water then empties out and the other compartment starts to fill.
The number and rate of bucket movements are counted and logged electronically. The calculated area of the funnel, and number and rate of bucket movements are converted into an amount and intensity of
Last updated: 28 November 2003