the effect of enso on precipitation in san diego, california andrew horan
TRANSCRIPT
The Effect of ENSO on Precipitation in San Diego, California
Andrew Horan
WHY?
Does El Nino directly correspond to increased rainfall in San Diego?
Increased rainfall tends to cause more landslides Desert by the sea Plan better for a “rainy” year
DATA
El Nino-Southern Oscillation Index (SOI) Negative numbers typically correspond
to El Nino year Data from 1866-2008, prior to 1935
used with caution Rain Data-monthly average (in.) from
San Diego-Lindbergh Field International Airport (SAN)
1880 1900 1920 1940 1960 1980 20000
5
10San Diego Rain Data (in.)
1880 1900 1920 1940 1960 1980 2000-10
-5
0
5
101866-2008 SOI Index
ATTEMPTING TO CORRELATE
-8 -6 -4 -2 0 2 4 60
1
2
3
4
5
6
7
8
9
10San Diego Precipitation vs. SOI signal
San
Die
go P
reci
p (in
.)
SOI signal
R=-0.1061Pvalue=0.0940
•Low correlation•Not significant•Too much data
4-MONTH RUNNING MEAN
-8 -6 -4 -2 0 2 4 60
1
2
3
4
5
64-Month Runnning Mean Precipitation vs. SOI
SOI data
Pre
cipi
tatio
n (in
.)
R=-0.1603Pvalue=0.1072
•Data still insignificant•Too much noise•12-month mean then cross spectral analysis
12-MONTH RUNNING MEAN
-5 -4 -3 -2 -1 0 1 2 3 40
0.5
1
1.5
2
2.512-Month Runnning Mean Precipitation vs. SOI
SOI data
Pre
cipi
tatio
n (in
.)
R=-0.3614Pvalue=0-permissible
PERIODICITIES
10-1
100
101
102
103
0
5
10
15
years/cycle
SOI index
10-1
100
101
102
103
0
20
40
60
80
years/cycle
Precipitation
•El Nino occurs roughly every 3-7 years•No significant cycle in increased rainfall
CPSD
0 2 4 6 8 10 120
0.2
0.4
0.6
0.8
1
1.2
1.4
•Significant peak at 2 years, lesser so at 4,6,7•Still no concreteness in trend
COHERENCE
0 2 4 6 8 10 120
0.1
0.2
0.3
0.4
0.5
0.6
0.7
Frequency
Mag
nitu
de S
quar
ed C
oher
ence
Coherence Estimate via Welch •Incoherent in frequency, random signals
CONCLUSION
El Nino occurs roughly every 3-6 years Some years in San Diego are wetter
than others, with or without El Nino Not many years with extreme
precipitation Should take data at more regional scale There are other reasons for spike in
precipitation (winter Pacific storms coming in from Alaska)