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The El Niño and La Niña Effects on the Hydrology
of Texas Andy Chan CE 394K.2 Surface Water
Hydrology
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NORMAL CONDITION
http//www.cpc.noaa.gov/products/analysis_monitori
ng/ensocycle/meanrain.shtml
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EL NIÑO CONDITION
http//www.cpc.noaa.gov/products/analysis_monitori
ng/ensocycle/enso_schem.shtml
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LA NIÑA CONDITION
http//www.cpc.noaa.gov/products/analysis_monitori
ng/ensocycle/lanina_schem.shtml
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EL NIÑO AND LA NIÑA YEARS
24 El Niño years 16 La Niña years
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PALMER DROUGHT SEVERITY INDEX (PDSI)
The underlying concept of the PDSI The
difference between the actual precipitation and
the precipitation required for the near-normal
operation of the established economy of an area
represents a fairly direct measure of the
departure of the moisture aspect of the weather
from normal. When these departures are properly
weighted, the resulting index numbers appear to
be of reasonably comparable local significance
both in space and time. Palmer, W. C., 1965
Meteorological drought. Weather Bureau Res. Paper
45, U.S. Department of Commerce, Washington, DC,
P.58.
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PALMER DROUGHT SEVERITY INDEX (PDSI)
CAFEC Climatically Appropriate For Existing
Conditions
P ET R RO L P CAFEC Precipitation ET
CAFEC Evapotranspiration R CAFEC Soil
Moisture Recharge RO CAFEC Runoff L CAFEC
Soil Moisture Loss d P P d Moisture
departure for a particular month P Areal
average precipitation for a particular month
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TEXAS CLIMATE DIVISIONS
Low Rolling Plains
North Central Texas
High Plains
East Texas
Trans-Pecos
Upper Coast
Edwards Plateau
South Central Texas
South Texas
Lower Valley
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EXAMPLE PDSI MAPS
1915 (La Niña -1) 1916 (La Niña) 1917 (La Niña
1/El Niño -1) 1918 (El Niño) 1919 (El Niño 1)
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1915 (La Nina -1) SPRING
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1915 (La Nina -1) SUMMER
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1915 (La Nina -1) FALL
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1915 (La Nina -1) WINTER
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1916 (La Nina) SPRING
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1916 (La Nina) SUMMER
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1916 (La Nina) FALL
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1916 (La Nina) WINTER
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1917 (La Nina 1/El Nino -1) SPRING
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1917 (La Nina 1/El Nino -1) SUMMER
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1917 (La Nina 1/El Nino -1) FALL
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1917 (La Nina 1/El Nino -1) WINTER
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1918 (El Nino) SPRING
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1918 (El Nino) SUMMER
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1918 (El Nino) FALL
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1918 (El Nino) WINTER
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1919 (El Nino 1) SPRING
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1919 (El Nino 1) SUMMER
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1919 (El Nino 1) FALL
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1919 (El Nino 1) WINTER
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TAKE HOME MESSAGE

• El Niño
• Wetter than normal starting from late El Niño
  year to late
• El Nino 1 year
• Higher precipitation, temperature, and
  streamflow
• Lower evaporation
• La Niña
• Dryer than normal starting from late La Niña
  year to late
• La Niña 1 year
• Lower precipitation, temperature, and
  streamflow
• Higher evaporation
• These relationships are not strong enough for
  use in
• accurately predicting streamflow or droughts,
  they may be
• useful if they are expressed as probabilities
  of exceedance
• threshold levels (Piechota 1996)

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QUESTIONS?
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SEA SURFACE ANOMALIES (C) OF E. PACIFIC BASIN