GEOS 595e (ENSO: Past, Present, Future) Spring 2003
Data Exercise I: Tropical Atmosphere Ocean (TAO) Project
(last updated 6 February 2003)

To be discussed Feb 12th in class.  Questions? Send email or make an appointment to come see me. 

Hand in your summary and a photocopy of any transparencies you have made for discussion.

Purpose:
  1. To familiarize you with the observations and analysis available, practically in real time, for the tropical Pacific ocean-atmosphere system, from the TOGA-TAO buoy/satellite array.
  2. To explain the current observations in terms of the equatorial ocean-atmosphere dynamics we've been discussing.
  3. To discuss the question: how is the development of the current ENSO warm phase event (2002-2003) like/unlike recent events?
Assignment:

I suggest you begin by allowing me to lead you through the data views -- at first.  But then it's essential to think about what you've seen and put it all together.  Explore other data views if you like.  Finally, when you're satisfied you have a good picture of what's going on, write a summary (1-2 paragraphs) answering questions 1.0, 2.0 and 3.0 below.  Note any questions you have about other features you've observed, which you'd like to discuss in class.  Print out any plots you'd like to discuss on a transparency (talk to me if you can't do this easily). 

Be prepared to discuss these questions in class Feb. 12th along with the McPhaden (1999) paper.

Tools:

You'll need a networked computer with fast (e.g. University) Internet connection, and the largest display you can find.  A UNIX workstation with java-enabled Netscape browser would be my preferred system.  But I can do all what follows from a laptop.  Let me know if I can set you up on workstation here at the  Tree Ring Lab.

Tasks:

Browse to the Tropical Ocean Atmosphere Project's home page: (http://www.pmel.noaa.gov/tao/).  [You may want to have this assignment in a second window.]  Start by looking at the Project Overview; in particular, the Virtual Tour should give you an idea of the data and analysis which goes into the pictures you'll be examining.  Then go to Data Display where you'll have the choice of a number of different "slices" of the multidimensional TAO data.  
  1. How do the equatorial ocean dynamics we've discussed in class explain the current state of winds and SST in the equatorial Pacific Ocean?
  1. To address this question, I suggest you first examine the current 5-day conditions, latitude-longitude plot of SST/winds and SST/winds anomaly.  This you can look at by clicking on the color plot you see after choosing "Data Display" from the TAO menu.  (Or else: http://www.pmel.noaa.gov/tao/jsdisplay/.)  All of these plots pack a lot of information on a single color/contour/vector plot, so be sure you understand:
  1. What are the axes of the plot?
  2. What is the color scale?
  3. What is the contour scale?
  4. What is the vector scale?
  5. In all cases, what are the units?
  1. Now examine the monthly conditions in terms of the same plot: latitude-longitude plot of SST/winds and SST/winds anomaly.   To get to this plot, click on the "Lat-Lon Plots" button to get more display options.  Choose "sea surface temperature" plot and "monthly" time range, which gives you the latest month available (January 2003 currently).  Then click on "Make Plot!" which will open a new window with your requested plot.  Click on the plot to get a larger view.
  2. Does this plot change/broaden/reinforce what you've already observed?
Note that you can "download postscript" which will print on any postscript printer using Ghostview or other PS viewer.
  1. Now examine the evolution of SST and wind anomalies: Choose "section plots", first plot panel = SST anomaly, 2nd plot panel = zonal wind anomaly, default time ranges, make plot.
  2. Start by reminding yourself what the axes are and what the colors and contours represent.  Are the SST anomalies and zonal wind anomalies together consistent with what we've read about how and when ENSO events develop and decay?
  3. Now change the time interval and replot so you can examine the development of the 1997-8 ENSO warm phase event and the return to normal/cool conditions thereafter.  How does the current event resemble/not resemble the 1997-8 event?
  4. Now change the time interval and replot so you can examine the development of the 1986-7 ENSO warm phase event and the return to normal/cool conditions thereafter.  How does the current event resemble/not resemble the 1986-7 event?  Any thoughts about how the current event may continue to develop in the next several months?
  1. What is the relation of the subsurface thermal structure to the surface conditions?
  1. To look at the latest subsurface structure, choose Section plots, depth section, monthly mean conditions, equatorial section, variable = temp.  How does the western Pacific warm mixed layer differ from the eastern Pacific?  Given our brief discussion of Kelvin wave dynamics, how do you interpret the anomaly picture? (See also Zebiak and Cane, 1987, Figs. 12 and 13, p. 2269-70).
  1. How has the subsurface thermal structure evolved?  How do you expect conditions to evolve in the next several months?
  1. To look at how the subsurface structure has evolved over time,  choose time section, 20C isotherm depth mean, 20C isotherm depth anomaly, default start and end time, make plot.  How is the depth of the thermocline changing in time and longitude?  Given our understanding of ENSO theory, what does this imply for evolution of SST? zonal winds?  You may want to compare this to a similar plot, for the time period June 1996 - June 1998, or for the period June 1986-July 1988.  You may also want to compare the 20C isotherm depth anomaly to a plot of the SST anomaly and/or zonal wind anomaly.
Back to syllabus.