El Niño Effects on Goleta Coast Wave Climate
By Tina Nguyen
Summary• Research question: How does El Nino affect frequency
and magnitude of large swell events on Goleta coast during December, January, February
• Preliminary work – investigate relationship between large swell events and El Nino
• Following previous study of Seymour et al 1984• Data did not support Seymour’s correlation of large swells
with Oceanic Nino Index (ONI) – Seymour used data from Harvest buoy– This study used Goleta Point buoy
• Study did showed annual increase of frequency of waves during January – possible change in EN or wave climate
Methodology
• El Nino can increase large swell events in two
ways:– 1. number of storms remains constant but magnitude
of each storm increases = overall increase of large swell events (over 2m).
– 2. magnitude of storms remains constant but frequency of storms increase = increased probability of large swell events given the same distribution of swell heights.
Methodology cont’d
• Downloaded Goleta buoy data from Coastal Data Information Project (CDIP)
• Histogram of daily max wave heights (Hs) showed 74% of measurements below 2 m
• Defined large swell event as over 2 m threshold• Summarized number of days over 2 m to
measure frequency of large swell events• Graphed frequency against sea surface
temperature anomalies (SST) from ONI to investigate correlation
Results
• No consistent pattern between anomalous sea surface temperature and frequency of high waves was evident
• The 2009/2010 El Nino showed a correlation with increased magnitude and frequency of waves
• The 2005-2008 period does not show any consistent relationship
• Recognized increasing pattern in frequency of maximum wave heights during the month of January
2002-03 2003-04 2004-05 2005-06 2006-07 2007-08 2008-09 2009-100
2
4
6
8
10
12
14
16
18
20
-2
-1.5
-1
-0.5
0
0.5
1
1.5
2
Goleta Buoy Wave Height > 2m and Oceanic Nino Index
December January February +/- 0.5 °C SST Anomally
Num
ber o
f Day
s > 2
m
+/- 0
.5° C
(Se
a Su
rfac
e Te
mpe
ratu
re A
nom
aly)
Discussion and Future DirectionsThe Goleta buoy is affected by wave shadowing from Channel
Islands and Point Conception, possibly obscuring El Nino effects
• Further research should use Harvest Platform buoy data since it is more exposed to all North Pacific storm activity
• longer time series including strong El Nino events (1982-83 or 1997-98) is necessary to understand decadal impacts of El Nino
• Data from multiple buoys is needed – one location is not representative of entire region
• Parameters such as wave period and swell direction should also be analyzed
• The annual increase during January presents an opportunity to assess possible climate change effects
Wave shadowing