SEA SURFACE TEMPERATURE ANOMALIES / EL NIÑO AIR-SEA INTERACTION
DEFINITIONS:
Sea Surface Temperature (SST) = the absolute temperature recorded at (or within 5-10
meters of) the surface of the ocean
Sea Surface Temperature Anomaly (SSTA) = the measure of temperature variably
(deviation from normal) from the mean SST recorded for a given interval
El Niño / Southern Oscillation (ENSO) = a coupled atmosphere-ocean phenomenon, the
negative phase of which causes higher-than-normal SST’s in the equatorial
Pacific Ocean and changes in atmospheric circulation and precipitation patters at
various locations around the globe, with a recurrence period of 2-7 years
SEA SURFACE TEMPERATURE EXERCISE
Owing to the extensive media coverage and the very real importance of the El Niño / Southern
Oscillation (ENSO) coupled atmosphere-ocean system, the second part of today's exercise is to
examine sea surface temperature anomalies (SSTA’s) recorded from the equatorial Pacific and
attempt to identify a strong El Niño event. We will use data supplied by the International
Research Institute (IRI) of the Lamont Doherty Earth Observatory (LDEO) to prepare a summary
of SSTA’s from January 1996 to December 1999, a time period that encompasses the last
pronounced El Niño event (1997-1998). To better manage the data, we will select only those
months that record seasonal celestial events (summer/winter solstices in June/December and
vernal/autumnal equinoxes in March/September).
Data Collection
We will organize into groups of two. Each group will be responsible for one or two months
(March, June, September, or December) of the years 1996-1999 and will acquire SSTA data from
the LAMONT CLIMATE DATA SERVER. (You can also access this link from the left menu bar
on the Lab Exercise 9 web page and simply follow the instructions given below.) Once your
group has successfully retrieved the data for a particular month, reveal that month on the matrix
poster in the lab and make sure your plot matches the plot on the poster. When the poster is
completely uncovered, we will spend a few minutes observing and discussing some general
trends in the data. Try to quantify the temperature ranges on the contour maps.
These data are real and were collected using oceanographic instrumentation spanning the past
several decades. The description of the methodology is outlined in Reynolds and Smith (1994).
The attached handout outlines the parameters used for the LDEO/IRI SSTA database.
Animations (Eastern Equatorial Pacific)
Next, investigate the animations on the website. The first is a comparison between time-averaged
monthly SST’s, or CLIMATOLOGY, VS. ACTUAL SST’S for 1996-1999. The second shows
SSTA’s in PLAN VIEW (OVERHEAD), and the third shows Pacific Ocean temperatures in a
CROSS SECTIONAL PROFILE on the equator. Also examine the animations for ZONAL
(EAST-WEST) WINDS and PRECIPITATION ANOMALY DATA and consider how these
trends relate to the SSTA data.
Collection of SSTA Data Online:
Log on to the LAMONT DOHERTY DATA SERVER from our home web page in the
Oceanography Lab (Select: Week 9 - Interactive El Nino -- Exploring Online Data. Then
select the Lamont Data Server link to the climate data server. If you see a colored map of the
ocean, you're on!
1) In the Time box at the top, type the abbreviated month and year (e.g., Mar 2000) you
wish to retrieve.
2) Click Redraw on the lower left and your data will be contoured automatically! You also
have the option of viewing the raw temperature values recorded for any given month.
3) Reveal the data corresponding to that month on the SSTA Matrix Poster in the lab.
4) When all the data revealed, address the following questions.
Questions to Consider:
1) Which months of the year do the greatest SSTA’s occur? Can you identify El Niño
events? Can you identify La Niña events? What are the maximum and minimum
temperature anomalies for each period?
2) What are the latitudinal boundaries of the SSTA’s? What are the topographic and
atmospheric circulation characteristics of the eastern Pacific and the adjacent landmass?
Considering both solar insolation and Coriolis effects (think Ekman transport, or lack
thereof), can you provide an explanation as to what might cause and/or contribute to
these observed phenomena?
3) Do ENSO conditions influence regional climates elsewhere on the globe? If so, can you
provide an explanation for why? Do these SST perturbations influence natural
ecosystems in the ocean? (See attached brief summary of El Niño and supporting data
tables, figures, etc.)
Assignment:
Prepare a 1 page report to synthesize your SSTA observations made in the laboratory today.
Include your printed copy of the March SSTA contour map. Try to address as many of the
questions presented above. Due at our next laboratory meeting.
LIST OF ONLINE CLIMATE RESOURCES (REAL CLIMATE DATA)
A) Lamont Doherty Earth Observatory Climate Data
1) Igoss Nmc Monthly Ssta: Sea Surface Temperature Anomaly Data
http://ingrid.ldgo.columbia.edu/SOURCES/.IGOSS/.nmc/.monthly/.ssta/
Monthly Sea Surface Temperature Anomaly from IGOSS nmc: sea surface temperature fields
blended from ship, buoy and bias-corrected satellite data (Reynolds and Smith, 1994).
Time grid: /T (months since 1960-01-01) ordered Nov 1981 to Feb 2000 by 1. N= 220 pts
Longitude grid: /X (degree_east) periodic 179.5W to 179.5E by 1. N= 360 pts
Latitude grid: /Y (degree_north) ordered 89.5S to 89.5N by 1. N= 180 pts
Other Info:
CE 4.2
CS -4.2
PLOTCOAST 1
Units: degree_Celsius standard units* degree_Kelvin
History: IGOSS nmc monthly ssta Monthly mean sea surface temperature anomaly (blended from
ship, buoy, and bias-corrected satellite data). USA
Colorscale:
2) NOAA NCEP EMC CMB Pacific weekly temperature data
http://ingrid.ldeo.columbia.edu/SOURCES/.NOAA/.NCEP/.EMC/.CMB/.Pacific/.weekly/.temp/
Time grid: /T (julian_day) ordered 31 Dec 1997 to 14 Mar 2001 by 7. N= 168 pts :grid
Longitude grid: /X (degree_east) ordered 122.25E to 71.25W by 1.5 N= 112 pts :grid
Latitude grid: /Y (degree_north) ordered [ 0] :grid
Depth grid: /Z (m) ordered [ 967.5 720. 550. 430. 345. 285. 240. 205. 177.5 155. 136.25 120.
106.25 95. 85. 75. 65. 55. 45. 35. 25. 15. 5.] :grid
Other Info:
CE 35 colorscalename sstcolorscale
CS –2 missing_value NaN
Units: degree_Celsius -- standard units* degrees_Kelvin
Colorscale:
Reference:
R. W. Reynolds and T. M. Smith, 1994, Improved global sea surface temperature analyses:
Journal of Climate, v. 7, p. 929-948.
B) NOAA Ferret Climate Server
http://ferret.wrc.noaa.gov/fbin/climate_server/
1) Levitus (1982) Climatological Atlas of the World Ocean
Grid: 1x1 degree, global, 33 levels from surface to 5500 m, annual climatology.
Author: Sydney Levitus
This data set is the annual climatology prepared by Sydney Levitus and published in 1982, of
temperature, salinity and oxygen in the world ocean.
The following is from the reference below.
This atlas represents a synthesis of all temperature, salinity and oxygen data available from the
National Oceanographic Data Center (NODC). These parameters have been analyzed in a
consistent, objective manner at standard oceanographic analysis levels on a one-degree latitudelongitude grid between the surface and ocean bottom with a maximum depth of 5500 m.
The analyses and statistical information presented are intended primarily for use in the study of
the role of the oceans in controlling the earth's climate, but they can be used for other scientific
investigations also. The objective analyses shown in this atlas have certain limitations owing to
the nature of the database (non-synoptic, scattered in space) and to the characteristics of the
objective analysis techniques and the particular grid which we used. These limitations and
characteristics are discussed in the text. The analyses presented are viewed as another tool for
studying the world ocean. Preliminary results have been used in a variety of ways.
Reference:
Levitus, S., 1982, Climatological Atlas of the World Ocean, NOAA/ERL GFDL: Professional
Paper 13, Princeton, N.J., p. 173.
2) Rasmusson and Carpenter El Nino 3-year composite
Grid: 2x2 degree, extending from 100E to 70W, and 30S to 30N; monthly points
in a three year composite of an El Nino cycle
Authors: E.M. Rasmusson and T.H. Carpenter of the Climate Analysis Center
The Rasmusson and Carpenter tropical Pacific analysis consists of two separate data sets, a longterm monthly mean, and a composited El Nino. Both are derived from surface marine
observations; both extend from 100E to 70W, and 30S to 30N, on a 2x2 degree grid.
This data set is a composite of six recent El Niño events -- those of 1951, 1953, 1957, 1965, 1969,
and 1972. The set is three years long, spanning the years before, during, and after the peak of an
event; values given are three-month running averages, sequentially centered on each month of the
three-year period. The set reports sea surface and air temperature, zonal and meridional wind
speed and pseudo-stress, and the product of the sea/air temperature difference and the wind speed.
Reference:
Rasmusson, E.M., and T.H. Carpenter, 1982, Variations in tropical sea surface temperature and
surface wind fields associated with the Southern Oscillation/El Niño: Monthly Weather Review,
v. 110, p. 354-384.