1. The El Niño and La Niña Effects on the Hydrology of Texas
The El Niño and La Niña Effects on the Hydrology of Texas
Andy Chan
CE 394K.2 – Surface Water Hydrology

2. NORMAL CONDITION

3. EL NIÑO CONDITION

4. LA NIÑA CONDITION

5. 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

6. 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.

7. 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

8. 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

9. EXAMPLE: PDSI MAPS 1915 (La Niña -1) 1916 (La Niña)
1917 (La Niña +1/El Niño -1)
1918 (El Niño)
1919 (El Niño +1)

10. 1915 (La Nina -1)
SPRING

11. 1915 (La Nina -1)
SUMMER

12. 1915 (La Nina -1)
FALL

13. 1915 (La Nina -1)
WINTER

14. 1916 (La Nina)
SPRING

15. 1916 (La Nina)
SUMMER

16. 1916 (La Nina)
FALL

17. 1916 (La Nina)
WINTER

18. 1917 (La Nina +1/El Nino -1)
SPRING

19. 1917 (La Nina +1/El Nino -1)
SUMMER

20. 1917 (La Nina +1/El Nino -1)
FALL

21. 1917 (La Nina +1/El Nino -1)
WINTER

22. 1918 (El Nino)
SPRING

23. 1918 (El Nino)
SUMMER

24. 1918 (El Nino)
FALL

25. 1918 (El Nino)
WINTER

26. 1919 (El Nino +1)
SPRING

27. 1919 (El Nino +1)
SUMMER

28. 1919 (El Nino +1)
FALL

29. 1919 (El Nino +1)
WINTER

43. 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)

44.
QUESTIONS?

45. 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