|
|
|
A sophisticated system for measuring drought was developed by
National Weather Service meteorologist Wayne Palmer in 1965. Called the
Palmer Drought Severity Index, it uses temperature and rainfall
information in a formula to determine dryness. This index is now the
semi-official indicator of drought. The Palmer Index is most effective
in determining long-term drought (a matter of several months) and is not
as effective with short-term forecasts (a matter of weeks). The index
uses a 0 as normal, and drought is shown in terms of negative numbers;
for example, -2 is moderate drought, -3 is severe drought, and -4 is
extreme drought. In mid-August 2000, sections of many western states
were in the -4 range. [Images courtesy National Oceanographic and
Atmospheric Administration (NOAA)] |