NCL Home> Application examples> Data Analysis || Data files for some examples

Example pages containing: tips | resources | functions/procedures

Data Analysis: Omega

NCL version 4.2.0.a033 is required to use omega_ccm_driver.
omega_1.ncl: This example shows how to compute omega from CCM output using the contributed.ncl function omega_ccm_driver. The CCM computed omega is also read in, and both omegas are overlaid on the plot. As one can see, they are identical. Due to the fact that the CCM model computes omega in double precision, and the default CCM model output precision is single precision, the omega output by the CCM model and omega_ccm_driver will agree to at least the 5th significant digit.

The special resource gsnXRefLine is used to draw a vertical line at x=0.0.

The contributed.ncl library must be loaded prior to the use of omega_ccm_driver:

load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/contributed.ncl"
omega_2.ncl: This example shows how to calculate omega using the kinematic method outlined in Atmospheric Science, An Introductory Survey by Wallace and Hobbs (eqn 8.20), as well as by using the O'Brian adjusted method outlined in Synoptic-Dynamic Meteorology in Midlatitudes by Bluestein (Volume I: pp315-316). The output from these two methods is compared to the omega calculated in the same fashion as in Example 1 above.

The main difference between the kinematic method and the O'Brian adjusted method is that the O'Brian method insures that omega goes to 0 at the top of the atmosphere.