Meteorology 415/715

Spring 2011

 

 

 

Lab 3 Key (Parts 1, 2 and 3)

 

Basic Satellite Analysis Techniques for Oceanographers

Due Beginning of Class, Wednesday 2 April, 2008

(Parts 1, 2 and 3) 300 points
(Part 4) 100 points

 

 

 
  1. It's best if all your work for this class is kept in a three hole binder. Turn in the binder when you have finished the Lab.
  2. Show all work in mathematical problems. No credit given if only answer is provided.
  3. Questions requiring a written answer should be completed thoughtfully. Sentences should be complete with a subject, a verb and an object. One word, or one phrase answers will be penalized.

Using Satellite Information to Infer Thermal Structure, Position of Eddies and Current Systems in the Oceans

 

Current gyres

Figure 1:  Global map of geostrophic currents.

Sea-surface Temperatures

Figure 2:  Thermal infrared image of the Gulf Stream. Colors are false colors representing various sea surface temperatures (Table 1).

Table 1:  False colors and temperatures for Figure 2.

Color Temperature (Celsius)

Text Box: Reds and Oranges 	24° to 28° Yellows and Greens 	17° to 23° Light Blues 	10° to 16° Dark Blues	  2° to 9°

Exercises:

Part 1

1.  (26 points) Examine at the thermal infrared satellite image [Fig. 2]. (13 pts each)
(a) Identify the Gulf Stream on the image by placing a "GS" right on the map
; (b) how does comparing Fig. 2 to Fig. 1 show that the common representation of the Gulf Stream on maps/diagrams such as Fig. 1 is a gross simplification.

 

Annotated gulf stream

 

The geostrophic currents shown in Fig. 1 represent an oversimplification and a time average that smooth out mesoscale and microscale features evident in current representations on any given day.

 

2. (40 points) Locate the following: (10 pts each)

(a.) a warm eddy on the warm water side (WW) of the Gulf Stream; (b.) a warm eddy on the cold water side (WC) of the Gulf Stream; (c.) a cold water eddy on the warm water side (CW) of the Gulf Stream; and, (d.) a cold water eddy on cold water side (CC) of the Gulf Sream.

 

See map.

 

3. (45 points) (a) Use the temperature scale [Table 1] to label the eddies you found in (2) with different values (create isotherms) (here is a zoomed portion of Fig. 2); (b) with respect to the eddies you identified in (2), which are liable to have upwelling or downwelling at their center; and, (c) with respect to the eddies you identified in (2), which are liable to have ocean surface divergence or or ocean surface convergence at their centers.

 

temps]\

 

The warm eddies are most liable to be associated with downwelling and surface convergence. The cold eddies are liable to be associated with upwelling and surface divergence.

 

4. (65 pts) Get into this website: http://argo.colorado.edu/~realtime/gom-real-time_velmag/

 

(a) (30 pts) Plot a map of the ocean currents (velocity vectors) and sea-surface heights (SSH) in the Gulf of Mexico for August 26, 2005 (apart from the date and time, leave all choices as their defaults. (This will depict the conditions in the Gulf of Mexico a few days before Katrina explosively intensified when it moved over warmer water). Print your images (in color, preferably).

 

Altimetry

vectors

 

(b) (15 pts) The most obvious circulation feature extends from the western tip of Cuba northwestward to about 92W longitude. Using the evidence you can see in the two plots, discuss why this would be a warm eddy.

 

This is a meander of the Loop Current that has formed a ridge. The ridge should sequester a region south of the current that is warm. It's probably a warm eddy.

 

(c) (20 pts) Using the evidence you can see in the two plots, discuss why these two charts in tandem can be used to illustrate geostrophy in the oceans.)

 

The current vectors are tangent to the altimetry contours, are flowing clockwise around altimetry highs and counterclockwise around altimetry lows, and with a speed in proportion to the altimetry gradient. This is consistent with a geostrophic current.

 

5. Get into this website: http://argo.colorado.edu/%7Erealtime/global-sst/

 

(a) Create a map of SST's for the West Coast of the U.S. for July 4, 2007. Use the Global High Resolution Sea Surface Temperature (GHRSST) data set. Use the following formatting options: Geographical Area....East Longitude Minimum 227; Maximum 245; Latitude Minimum 30; Maximum 45. Contours--Radio Buttons Checked: Show Contours; Annotate Contours; Contour Interval 2; Annotation Interval 5; Range of Data Values 8 to 25C; Tick Mark Interval 1. Print the map in color.(30 points)

 

July SST

 

(b) Indicate with the letter "U" the most dramatic upwelling plumes. (10 points)

 

(c) Indicate with a long arrow, the rough position of the California Current. (9 points)

 

6. Get into this website: http://www.cdc.noaa.gov/HistData/

 

(a) Create a map of sea-level pressure for the West Coast of the U.S. for July 4, 2007. Use the following options: start and end date are both 20070704; Variable is sea level pressure; Plot Type is mean; Map Domain is Custom; Latitude Range is 25 to 55; Longitude Range is 217 to 255; Color is Black/White; Shading Type is Contours Only; Contour Interval is 2, Range is 998 to 1024; Plot Size is 150%. Print the map. (30 points).

 

July Wind

 

(b) Indicate the sense of the winds with schematic short vectors along the California Coast. (10 points)

 

(c) Briefly discuss the relationship between (b) here and your answer in 5 (b). (15 points)

 

The afternoon winds suggested here would accelerate the surface flow in the California current out of geostrophic balance by increasing their speed. Since Coriolis acceleration is directly proportional to the currnt speed, an additional deflection to the right would occur in the surface current, creating flow away from the coast and, roughly, at 45 degrees to the wind. The blue arrows on the SST map indicte the net effect.The afternoon winds suggested here would accelerate the surface flow in the California current out of geostrophic balance by increasing their speed. Since Coriolis acceleration is directly proportional to the current speed, an additional deflection to the right would occur in the surface current, creating flow away from the coast and, roughly, at 45 degrees to the wind. The blue arrows on the SST map indicte the net effect.

Part II: Satellite Meteorology

The visible, enhanced infrared and water vapor GOES-10 satellite images for approximately 1200 UTC 18 February 2003 are provided below. (60 points in this section)

 Satellite 3

Image A: Visible

 Satellite 1

Image B: 16 km Enhanced IR

 Satellite 2

Image C: Water Vapor

Satellite 4

Image D: 28 km Enhanced IR

he visible, enhanced infrared and water vapor GOES-10 satellite images for approximately 1200 UTC 18 February 2003 are provided below. (174 points in this section)

images

 

1. On the blank map provided, sketch the upper tropospheric flow (streamlines) for the entire north Pacific (use Images B and D primarily for this). (30 points)

2. To the best of your ability, on a second blank map, do a frontal analysis for the north Pacific (use Images A, B and D for this). (30 points)

3. Note on the infrared image (conventional notation):

  1. Two long wave trough axes (black) (10 pts)
  2. Two long wave ridge axes (blue) (10 pts)
  3. A short wave trough axis. (purple) (10 pts)
  4. a sharp (green) and a broad (red) ridge axis (could be the same one/s you used in B. above). (10 pts)