Dynamical processes for descriptive ocean circulation
Example 7B: Dynamic Topography Maps
DPO Chapter 7 (website supplement) includes this map of the dynamic topography of Pacific Ocean, 0/1000 decibars (Figure S7.21).
We will next use JOA to make a similar map from a custom subset of the WOA05 data set. This data set was made with somewhat reduced grid resolution (= larger grid size) in order to make a smaller data set that will work well with more computers.
Files that may be needed or created in this example:
Exercise 7B-01: Making a Dynamic Topography Map
- Start JOA
- File → Open
If your computer cannot handle the large WOA05_decimated_Pacific.joa file, then try using the smaller WOA09_heavydeci_Pacific.joa data file instead.
- Calculations → Parameters
- From the Parameter Calculations dialog box select Geopotential anomaly and click OK
- Plots → Map
- Set up a whole-Pacific Mollweide-projection map plot as follows:
- Use the Bathymetry tab of the Configure Map Plot dialog box to select the etopo20.nc bathymetry file and use the Colorbar “ROSE-black_cbr.xml” (like with other map plots where the stations are in a grid covering the map)
- Select the Iso-surface value sub-panel of the Station Colors tab to make an Iso-surface value plot of GPOT referenced to 1000 decibars:
- Choose GPOT under Parameter:
- Use PRES-0-1000_srf.xml for Surface:
- We have made a custom color bar for GPOT. To do this:
- Choose the Blue-White_Red-32 color palette
- Click on the linear ramp Create autoscale colorbar choice (the left-most one)
- Double-click on the default autoscale color bar to bring up the Colorbar Editor dialog box
- Enter -41 for the Start value: and 0 for the End value: and click the linear (left-most) Create with shape: choice
- Click OK to return to the Configure Map Plot dialog box
- In the Surface Value section of the Configure Map Plot dialog box:
- Enter Initial surface value: as 1000
- Select Reference Level: and enter PRES = 1000
- Click Plot to get this map, which is similar to the DPO Chapter 7 map of the dynamic topography of the Pacific Ocean, 0/1000 decibars:
Using this technique, you can now map dynamic topography for other ocean regions.