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http://www.cartoonstock.com/directory/e/el_nino.asp. The El Niño and La Niña Effects on the Hydrology of Texas Andy Chan CE 394K.2 – Surface Water Hydrology. NORMAL CONDITION. http://www.cpc.noaa.gov/products/analysis_monitoring/ensocycle/meanrain.shtml. EL NI Ñ O CONDITION.
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http://www.cartoonstock.com/directory/e/el_nino.asp The El Niño and La Niña Effects on the Hydrology of Texas Andy Chan CE 394K.2 – Surface Water Hydrology
NORMAL CONDITION http://www.cpc.noaa.gov/products/analysis_monitoring/ensocycle/meanrain.shtml
EL NIÑO CONDITION http://www.cpc.noaa.gov/products/analysis_monitoring/ensocycle/enso_schem.shtml
LA NIÑA CONDITION http://www.cpc.noaa.gov/products/analysis_monitoring/ensocycle/lanina_schem.shtml
EL NIÑO AND LA NIÑA YEARS 24 El Niño years 16 La Niña years
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.
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
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
EXAMPLE: PDSI MAPS 1915 (La Niña -1) 1916 (La Niña) 1917 (La Niña +1/El Niño -1) 1918 (El Niño) 1919 (El Niño +1)
1915 (La Nina -1) SPRING
1915 (La Nina -1) SUMMER
1915 (La Nina -1) FALL
1915 (La Nina -1) WINTER
1916 (La Nina) SPRING
1916 (La Nina) SUMMER
1916 (La Nina) FALL
1916 (La Nina) WINTER
1917 (La Nina +1/El Nino -1) SPRING
1917 (La Nina +1/El Nino -1) SUMMER
1917 (La Nina +1/El Nino -1) WINTER
1918 (El Nino) SPRING
1918 (El Nino) SUMMER
1918 (El Nino) FALL
1918 (El Nino) WINTER
1919 (El Nino +1) SPRING
1919 (El Nino +1) SUMMER
1919 (El Nino +1) FALL
1919 (El Nino +1) WINTER
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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