Drought
What is Drought?
According to the National Drought Mitigation Center, a drought is a normal,
recurrent feature of climate. Drought is a temporary aberration; it differs from
aridity, which is restricted to low rainfall regions and is a permanent feature
of climate. Although considered a rare and random event, drought occurs in
virtually all-climatic zones.
As an
insidious hazard of nature, it originates from a deficiency of precipitation
over an extended period of time, usually a season or more.
However,
drought should not be viewed as merely a physical phenomenon or natural event.
Its impacts on society result from the interplay between a natural event (less
precipitation than expected resulting from natural climatic variability) and the
demand people place on the water supply.
Top
What are the impacts of a Drought?
There is a complex web of impacts that spans many sectors of the economy and
reaches well beyond the area experiencing physical drought. There are two types
of impacts: direct and indirect.
Some
examples of direct impacts are reduced crop, rangeland, and forest productivity;
increased fire hazard, reduced water levels, and damage to wildlife and fish
habitats. Indirect impacts are the consequences of the direct impacts. For
example: a reduction crop, rangeland, and forest productivity may result in
reduced income for farmers and agribusiness, increased prices for food and
timber, unemployment, reduced tax revenues because of reduced expenditures and
disaster relief programs.
The impacts
of drought can be categorized as economic, environmental, or social. Droughts
also bring increased problems with insects and diseases to forests and reduce
growth. The incidence of forest and range fires increases substantially during
extended droughts, which in turn places both human and wildlife populations at
higher levels of risk. Drought is also associated with increases in insect
infestations, plant disease, and wind erosion.
Although
environmental losses are difficult to quantify, growing public awareness and
concern for environmental quality has forced public officials to focus greater
attention and resources on these effects.
The social
impacts involve public safety, health, conflicts between water users, reduced
quality of life, and inequities in the distribution of impacts and disaster
relief.
Top
Mitigating Drought
Taking actions in advance of drought to reduce
its long-term risk can involve a wide range of tools. These tools include
policies, activities, plans, and programs. On March 20, 3002, Governor
Napolitano signed Executive Order 2003-12, establishing the Arizona Drought Task
Force. If you would like to participate in Drought Task Force activities, please
send and e-mail to dtf@adwr.state.az.us.
Top
According
to the National Drought Mitigation Center predicting drought a month or more in
advance is complex. Currently, scientists don’t know how to predict drought in
advance for most locations. Predicting drought depends on the ability to
forecast two fundamental meteorological surface parameters, precipitation and
temperature. From the historical record we know that climate in inherently
variable. Anomalies of precipitation and temperature may last from several
months to several decades.
Studies
conducted over the past century have shown that meteorological drought is never
the result of a single cause. Global weather patterns have been the topic of
research in recent years. These patterns tend to recur periodically with enough
frequency and with similar characteristics over a sufficient length of time to
offer opportunities to improve the ability for long-range climate prediction.
High pressure inhibits cloud formation and results in lower relative humidity
and less precipitation. The immediate cause of drought is the predominant
sinking motion of air (subsidence) that results in compressional warming or high
pressure.
Prolonged
droughts occur when large-scale anomalies in the atmospheric circulation patters
persist for months or season. It is now known that a major portion of the
atmospheric variability that occurs on time scales of months to several years is
associated with variations in tropical sea surface temperature.
The
potential for improved drought predictions in the near future differs by region,
season, and climatic regime. For more information on drought visit the links
below:
National
Drought Mitigation Center -
http://www.drought.unl.edu/index.htm
University
of Arizona Institute for the Study of Planet Earth Climate Assessment for the
Southwest –
www.ispearizona.edu/climas/forecasts/swoutlook.html
2003
Southwest Drought Summit Summary Report –
www.mpcer.nau.edu/megadrought/drought_summit_report/index.htm
Arizona Governors Drought
Task Force -
http://www.water.az.gov/gdtf/
Top
|
