Seasonal To Interannual Climate Fluctuations And
Related Events
The climate of the Earth continually experiences natural fluctuations on
seasonal to interannual time scales, as evidenced by the El Niño cycle
(see figure). These naturally occurring fluctuations
can lead to extreme climate events such as droughts, heat waves, and floods.
Extended periods of drought and heat can increase the susceptibility of urban
settlements and forest lands to fire, can disrupt food production and water
supplies, and in developing regions, can
occasionally lead to massive human migrations. Prolonged and excessive periods
of precipitation can cause flooding, delay planting, contaminate water
resources, and temporarily disrupt patterns of production and trade.
An improved ability to document and then forecast trends and patterns of
change in ocean temperature, snow cover, sea ice, and other factors that
contribute to changes in the global climate over seasonal to interannual
scales could lead to a reduction of adverse impacts from potentially
destructive climate events. Early warnings enable communities to develop
strategies to better prepare for
these events by, for example, implementing revised planting schedules,
switching crops, and modifying water management, all of which have been
demonstrated to lead to reduced costs and impacts.
Observations and analyses indicate that in some regions of the globe, seasonal
to interannual variations of atmospheric conditions can be predicted up to two
years in advance. These predictions are based on observed variations in
parameters such as sea surface temperature, soil moisture, and snow and sea-
ice cover. Significant changes in seasonal to interannual climate may be a key
to the detection of longer-term climate changes.
Proposed Future Research on Seasonal and Interannual Climate
Highlights of USGCRP research in FY 1996 include programs
to:
- Monitor the tropical Pacific to better determine its influence
on climate and
to improve predictions. Variations in the tropical Pacific Ocean,
particularly
variations of sea surface temperature, exert a tremendous influence on the
climate of many tropical and mid-latitude countries, including the United
States. The USGCRP, in collaboration with its international research partners,
has put in place a unique observation array of instruments to constantly
monitor the state of the tropical Pacific Ocean and transmit data to research
and operational centers in real time.
- Incorporate field data into models to improve forecasts of
climate variability. Air-sea interaction processes in the western
tropical Pacific Ocean are important to the evolution of the El Niño-Southern Oscillation (ENSO) phenomenon.
High quality data sets resulting from a recent international field campaign in
the western Pacific are being analyzed to improve understanding of the
coupling between the ocean and the atmosphere in this climatically important
region.
- Map global precipitation and its relationship to climate
change. Rainfall
distributions in the tropics and in several key locations outside the tropics
are closely tied to large-scale atmospheric circulation patterns that are
forced by the interactions between the atmosphere and the tropical oceans. By
merging estimates from a wide range of ground based and satellite measuring
systems, the USGCRP, in cooperation with many international partners, has
produced the first reliable maps of global precipitation. Continued
improvements in mapping global precipitation will benefit the global community
through improved management of water resources and through better
understanding
of and ability to predict the climate system.
- Conduct research to improve prediction skills, particularly over
the U.S.
While USGCRP research has made possible the ability to forecast El Niño
events up to a year in advance, the forecasts are limited in that they focus
on
the evolution of the tropical Pacific sea surface temperature and related
climate impacts. Forecast skill is highest in the tropics, near the source of
El Niño events and diminishes at higher latitudes (e.g., over North
America) where other processes may play a greater role. Further research is
planned to extend predictability of climate fluctuations beyond the tropical
Pacific to include the effects of the other tropical oceans, higher latitude
oceans, and land-surface processes that are believed to contribute
significantly to seasonal-to-interannual climate variability, particularly at
higher latitudes. The results of such research will improve modeling of
precipitation anomalies like those that occurred in the U.S. Midwest in 1993
and this past winter in California (see figure).
- Establish research centers to improve forecast model
development.USGCRP-supported modelers are making their experimental
forecast products available to a limited number of tropical countries (e.g.,
Brazil and Peru). These forecasts are rudimentary and are presently prepared
in a research mode,
without the routine system for production and distribution that is required
for worldwide use. A multi-national planning process is underway to establish
a network of research centers to enhance the development of regional climate
forecast models and methodologies and to sponsor training of scientists from
participating countries. One center, the International Research Institute for
the Seasonal-to-Interannual Climate Prediction Program, will have the
specialized responsibility of producing, assessing, and distributing forecast
guidance to interested nations on a regular basis.
- Assess human vulnerability to climate variations and identify
options for
adaptation based on improved prediction information. An understanding
of the
social and economic factors that render individuals, communities, and economic
sectors more or less vulnerable to seasonal or yearly climatic fluctuations is
critical for reducing that vulnerability and improving adjustment. To
capitalize on advances in climate analysis and predictive capability, climate
information needs to be incorporated into management decisions in climate-
sensitive sectors (e.g., hydropower, insurance, transportation, fisheries, and
agriculture). Moreover, lessons learned from adapting to natural variability
will help society be prepared for the possibility that longer term climate
change may manifest itself as changes in the frequency and magnitude of
extreme events.
For comments, please contact the GCRIO Web Team at: help@gcrio.org
Last updated 04/10/96
