Drought characteristics, Causes and Prediction

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Drought characteristics, Causes and Prediction
Drought Characteristics, Causes and Prediction
Randall M. Dole NOAA Climate Diagnostics Center
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Drought scene
North Platte river, May 22, 2002 Mean flow 1310
cu. ft/sec Observed flow 0 cu. ft/sec.

• the last rains came gently, and they did not
  cut the scarred earth .the sky grew pale and the
  clouds that had hung in high puffs for so long in
  the spring were dissipated. John Steinbeck,
  Grapes of Wrath.

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Drought characteristic 1 - Severe
Characteristics of the current drought
1. The drought is severe. Precipitation Perce
ntiles - Past 12 months Pinks - 1-2 Reds
- 2-5 Orange - 5-10 In parts of the
country, this is a 50 to 100 year event.
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Drought characteristic 2 - sustained
2. This is a long-term, sustained drought.
Standardized Precipitation Index Northern New
Mexico
Normal
Drought
Severe
Years
0
1
2
3
4
6
5
In most locations, this is a multi-year drought.
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Drought characteristic 3 - large scale
3. This drought is large-scale.
Over the U.S.
Part of a larger global pattern
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Drought characteristic 4 - impacts are regional.
4. Intensity and impacts are regionally-dependen
t.
Most direct impacts on water supply
(and demand), agriculture, fire risk. But
manifold indirect impacts as well, e.g., on
recreation, energy production, water quality, air
quality, species preservation.
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Drought causes -
Drought Causes

• Are the tropical oceans playing an important
  role?
• Evolution of tropical Pacific Sea Surface
  Temperatures
• 
  
  

1998
El Niño
La Niña onset
1999
2000
2001
2002
La Niña ends
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La Nina impacts
La Niña Effects on U. S. Precipitation
Observed Departures (Oct. 2001-present)
La Niña Composite (Oct.-May)
La Niñas effects on precipitation are most
robust in SW and SE.
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Indian Ocean warming
Effects of warm Indian Ocean
Wintertime Response of NCAR Climate Model to warm
Indian Ocean
Temperature
Precipitation
Models responses to warm Indian Ocean reinforces
La Niña tendency for dry, warm conditions in SE
and along east coast, as well as part of the
northern plains. The Perfect Drought?
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Other factors
Other factors

• Other potential factors in the current drought
• Random component
• Land surface/veg. feedbacks, esp. for drought
  - heat waves
• Other oceans
• Large scale modes of variability
• Solar variations
• Determining the links between climate and
  weather (precipitation) variability is vital to
  understanding the causes of droughts.

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Drought predictions - short-term outlook
Drought Predictions

• The outlook over the next few months (Climate
  Prediction Center)
• Also increased risk of
• Heat waves where soil moisture is depleted
• Major wildfires, western U.S.
• Western hydrological drought will continue
  through at least summer.

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Longer-term

Longer-term Will depend significantly on
the evolution of tropical sea surface
temperatures (SSTs). Present indications are
that an El Niño event will continue to
develop, and that La Niña conditions are
most unlikely. NOAA NCEP Model Forecast SSTs
Oct-Dec.2002
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El Nino effects

Effects of El Niño Observed
precipitation, previous El Niños
(Oct-May) El Niños are associated
with above normal precipitation in most, but not
all, of the regions currently experiencing
drought.
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El Nino vs. La Nina

• Key point Climate forecasts are always
  probabilistic.
• Model-derived Seasonal Precipitation
  probabilities
• for New Mexico

La Niña
El Niño

• The model results illustrate how wet La Niña
  conditions or dry
• El Niño conditions in New Mexico are both
  possible, but unlikely.

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Take home points
Take home points

• The current drought is severe, sustained, and
  large scale. Specific impacts vary across
  regions, depending on climate, environmental, and
  human factors.
• Drought conditions were forced in part by a
  persistent La Niña and a warming Indian Ocean.
• Climate forecasts are intrinsically probability
  forecasts. Current forecasts indicate that El
  Niño development is likely. The effects on
  drought regions will depend on the magnitude of
  the El Niño, which is uncertain at this time.
• Drought impacts are often experienced
• regionally and locally. Regional partnerships
• can be very helpful in identifying climate
• information that would best serve the needs
• of the public and decision makers in
• managing and mitigating the effects of this
• and future droughts.

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Animation
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The End
The End