MARS 452/512 Lab
  Oceanography from space
sea surface color, sea surface temparature, height variability
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Objectives:

          1) to become familiar with satellite-derived data sets that are useful for oceanography
          2)  to become familiar with simple image management software
          3)  to use sea surface temperature and color data to infer surface circulation patterns
                in the California Bight

  I. Getting started using WimLE, Windows Image Manager:  

A.  To open WimLE
    1.  Under Start, then Programs,  find the Wim software, then click on the WimLE  icon
             (pink W, looks like a butterfly).
    2.  Click on File Open then go to the CD to find the images you want to examine.  The numbered
             folders 1-9 hold various image sets.  For illustration purposes, let’s use the images in Folder 5.
    3.  Click on Folder 5, then click on image 9433403, wait for 94334503 to open.
    4.  Go to the menu bar again, click on File Open, then open image 9433502.
    5. Note that you can open and manipulate as many images as you want.  They will stack as tiles on
            the monitor.   You can rotate through the various opened images by clicking on the image
            number in the List of Images box.  If the List of Images box does not automatically appear, you
            can open it  using the View command on the menu, and clicking on List of Images.

 

B.  To manipulate color contrast and access pixel information: 

      1.  View Color  OK  or click on the color icon on the menu bar
           Move slide bars to set best color contrast and show greatest detail.
           Set all opened images to similar settings.
     2.  View settings:
            to view sea surface temperature click on dot that chooses X 10 OK

 

C. Information available in the header bar:
    1. Image designation and image size (number of pixels on a side).   We have chosen to name our files
            using a 7-digit number giving the year, Julian day and GMT hour.  For example image 9433403
                                       94 = 1994
                                       334 = Julian day = 334th  day of the year = Nov 30
                                       03 =  0300 hours Greenwich Mean Time = 3 a.m. GMT
        link to Julian date table
    2.  If you hold the right mouse button down and move the cursor around on the image the numbers in
            the header bar change.  Some of those numbers are housekeeping numbers and are irrelevant to
            this exercise.  Others are useful. Watch the numbers within the two sets of parentheses.
                          (XXX.XXX;YY.YYY) where  XXX.XXX = longitude
                                                                               YY.YYY = latitude
                                                                       (ZZ.Z)    ZZ.Z = temperature, oC

 

D. You can choose an area within the image by placing the cursor in the upper left of the area of interest,
            holding the left mouse button down, moving the cursor to the lower right of the area of interest. 
            Then you can ask the software to calculate a histogram (among other choices) of the data shown
            within the designated box by using the menu bar:   Examine  histogram calculate OK 


E.  For general practice answer the following questions;
             1.  What the the sea surface temperature in the area near Point Conception?
             2.  What is the sea surface temperature near San Diego?
             3.  What is the sea surface temperature in the southwesterly area of the images?
             4.  What  is the time difference in hours between the these two images?
             5.   In what general direction is the upwelling filament south of Point Conception moving?

 

II.  Distribution of sea surface temperature as an indicator of surface current properties

These AVHRR images show the California coastal region.  The purpose of this exercise is to use sea
surface temperature to infer where currents affecting the California Bight.  The California and Davidson
Currents and coastal upwelling, are likely to be present.  Use these images to get a general idea of
how these three currents interact with each other.

A). Open images in WIM folder 9.     images  9300322
                                                                      9303115
                                                                      9309223
                                                                      9310915
                                                                      9313000
                                                                      9317323
Check the View menu Settings to be sure you have X10 and rainbow pallet. Adjust the colors for best
contrast.  Examine the header bar to be sure you can read Lat, Lon and temperature data.

1. In order to be sure we know where we are, what is the longitude and latitude of:
                            a. Point Conception?
                            b. San Diego?

2. In order to be sure we know when these sea surface temperatures were imaged, on what year, day
and hour were these images recorded?  (link to Julian date table).
       a. 9300322    b. 9303115    c. 9309223  d. 9310915  e. 9313000   f. 9317323

 

3. In order to gain some insight into the geographical area shown in these images note the following
dimensions and compare them to the physiographic map of the California Bight.  Assume
that in this region 1o longitude  ~100 km and 1o latitude ~ 120 km
    a)  What is the distance from Monterey Bay seaward to the western edge of the images?

                b)  What is the distance from Point Conception to the western edge of the images?

                c)  What is the distance from San Diego to the western edge of the images?
    d)  What is the width of the continental shelf shown on the physiographic map off San Diego? 
    e)  What is the width of the continental shelf off Point Conception?

                e)  Note where the edge of the continental shelf would be on the AVHRR images
    f)  Look carefully at the upwelling filament show in image 9309223 that extends southwesterly
            from Point Conception.   How far off shore is the elbow or bend in the filament.  Explain
            why the filament has an elbow.  Explain why the elbow occurs off shore?
     g) Compare the upwelling filament shape in 9309223 to the filaments in 9310915. 
            Why do the filaments in 9310915 curl northward? 


4.  The six images you have opened can be used to gain some general insights about seasurface temperature
distribution.  Construct a table showing data for the six scenes listed above:
    a)   year, month and date of the scene
    b)  representative temperature and general locations of  upwelling filaments
    c)  representative temperature and general location of surface water likely to be California Current
    d)  representative and general location of surface water likely to be Davidson Current 

                e)Write a paragraph describing the distribution of sea surface temperature in the Bight and how
        SST is influenced by the three currents.

  

5.    Link into Coast Watch web page  http://coastwatch.pfel.noaa.gov/ 
            click on Access CoastWatch satellite data
        A.  Open  New Visual Catalog:  click on WS (west coast south).  This shows recent scenes
                    of the California Bight region.  Click on one scene.  Examine the SST data for
                    today.  Note that gray regions are masked regions (continental land mass or clouds).
                    Briefly describe the distribution of sea surface temperatre.  In what region does SST
                    reflect the presence of the California Current, the Davidson Current and/or upwelling. 
                    If today's scene is too cloud-covered to reveal SST, choose a prior scene.
          B.  Go back to the CoastWatch Data Brouser page.  Click on High Resolution Composites.  Enter the
                year, month, region, data type, then click on Submitt.  For example, enter year 2005, February,
                Region L, month composite, submit.  Examine images for each of the following:  2004, 2003,
                2002, 2001, 2000;  Region L;  Sept 16th-end composite.  Using these images, describe typical
                patterns for the Califronia and Davidson Currents and coastal upwelling.  Include in your
                description general  geographical area and temperature range of each water mass and the direction
                of water flow.   Describe the portion of the water column (depth, breadth) influenced by the
                movement of these water masses.   Is the satellite-derived data from the Coastwatch images
                consistent with the Sproul  shipboard seawater temperature data (CTD near surface data)? 
                Why or why not?

III.  Sea surface height variability
1.  Link to Jet Propulsion Laboratory showing sea surface height variability from Topex data
                    http://topex-www.jpl.nasa.gov/science/jason1-quick-look/
                    scroll down to Image Archive, click on All Images.
                    Examine sea surface height in the Pacific shown in as many images as you can find near the
                    dates of the Sproul cuises (late September, early October  2003, 2004, 2005).  Describe
                    relative differences is sea surface height in the Pacific in general and  along the west coast
                    of the US and southern California in particular. 

IV.   SEA SURFACE BIO-OPTICAL PROPERTIES

Link to the NASA SeaWiFS web page    http://oceancolor.gsfc.nasa.gov/SeaWiFS/

Click on the main title SeaWiFS Project at the top of the page
Scroll down to SeaWiFS Data, click on Browsing SeaWiFS Data

        a)  In the SeaWiFS browser page, you can select a year and month from the table.  Once the global

                map for the year/month selected appears, you can choose an area using the box on the right or

                simply click on the area of the map you want to view.  Then click on OK

         b)    10 or so swath panels will appear.  You can enlarge an individual swath by clicking on it.  The
      enlarged images shows both ture color and chlorophyll-a concentration.  Where do you see
      the highest chlorophyll a concentrations along the entire west coast of the United States? 
      Describe the distribution of chlorophyll a in the California Bight.  Is chlorophyll a higher or lower
      in the California Bight than along other areas of the west coast?  Based on your knowledge and
      upwelling patterns and the sea floor topography of the California Borderland, why might
      chlorophyll a be different in the California Bight than other areas along the west coast? 
c)  Look at September and October 2001, 2002, 2003 and 2004.

            d)  Compare chlorophyll a distribution at the time of the Sproul Cruise over the years.  Was the
        time of the Sproul cruise “typical” for that space and time or different than one would expect?




V.  Buoy data in the eastern Pacific

  1. Link to the NOAA Pacific Marine Environmental Laboratory page:  http://www.pmel.noaa.gov/home/data.shtml 
  2. Scroll down, click on North Pacific Float Data.  This link provides data generated by environmental profiling floats in the North Pacific.   
    1. Float 2573 is presently in a region of the California Current north of Point Conception
    2. Floats 2050 and 2049 are in the eastern tropical Pacific
    3. Float 1829 is in a region of California Current off Washington State
  3. The menu bar across the top of the page provides links to the various data sets you can examine.  Click on Float Trajectories, then click on 2573.  Scroll down to see the most recent path and location maps.
  4. Go back to the page showing the menu bar, click on Vertical Sections, then select 2573.  Examine and note:
    1. Range and distribution of temperature; shape of isotherms.
    2. Range and distribution of salinity; shape of isohalines.
    3. Range and distribution of isopycnals.
  5. Go up to the float table, click on float 2050 and then on float 2049 and then float 1829.  Note the same information as you did for float 2573
  6. Go back to main menu page, click on T & S Profiles.  Examine the temperature/depth and salinity/depth profiles and T-S diagram for all three floats.
  7. Compare and contrast the data for the two general locations, California Current region and the eastern tropical Pacific.  Speculate about the following if near surface water from the two regions approach and encounter each other near the California Bight:
    1. Which water mass is likely to remain at the surface? Why?
    2. Which water mass is likely to slide under the surface?  Why?
    3. Given a generally northward flow path for the ETP water and a generally southward flow path for California Current water, how might Coriolis force influence their relative motion in the region of the California Bight?
    4. How does the float data support (or not support) the conclusions you are able to draw from the satellite-derived data?