The El Niño and La Niña Effects on the Hydrology of Texas 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 1901 1911 1921 1931 1941 1951 1961 1971 1981 1991 2001 1902 1912 1922 1932 1942 1952 1962 1972 1982 1992 2002 1903 1913 1923 1933 1943 1953 1963 1973 1983 1993 2003 1904 1914 1924 1934 1944 1954 1964 1974 1984 1994 1905 1915 1925 1935 1945 1955 1965 1975 1985 1995 1906 1916 1926 1936 1946 1956 1966 1976 1986 1996 1907 1917 1927 1937 1947 1957 1967 1977 1987 1997 1908 1918 1928 1938 1948 1958 1968 1978 1988 1998 1909 1919 1929 1939 1949 1959 1969 1979 1989 1999 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 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) FALL

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 La Niña 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)

http://www.cartoonstock.com/directory/f/forces_of_nature.asp QUESTIONS?

SEA SURFACE ANOMALIES (°C) OF E. PACIFIC BASIN Year DJF JFM FMA MAM AMJ MJJ JJA JAS ASO SON OND NDJ 1950 -1.8 -1.5 -1.4 -1.2 -0.9 -0.8 -1 1951 -0.6 -0.4 -0.2 0.1 0.4 0.5 0.6 0.7 1952 0.3 -0.3 -0.1 1953 1954 0.2 -0.5 -0.7 -1.1 1955 -2.1 -1.7 1956 1957 0.8 0.9 1.2 1.5 1958 1.6 1.1 1959 1960 1961 1962 1963 1 1964 1965 1.4 1966