Ageostrophic Wind and Thermal Wind. Assignment 8. Due March 4

Review the information on the ageostrophic wind in the Djuric text.

Model forecast guidance from the Eta model initialized at 12z 26 February will be used.

Use Garp to access the model forecast sequence.

1. Describe the evolution of the 500 mb height field during the 60 h period. Where/when did the Eta model forecast troughs and ridges to amplify or decay?

2. Overlay geopotential height, wind vectors, and streamlines at 500 mb. Identify locations at the initial time where the flow crosses height contours. At a couple of locations where the flow crosses height contours, indicate whether the flow is accelerating or decelerating.

3. Now add the geostrophic wind at 500 mb. Identify locations at the initial time where the flow is nearly geostrophic and where it is not. Are there locations where the flow is ageostrophic but parallel to the height contours? If so, indicate the direction and relative magnitude of the forces that are acting perpendicular to the direction of the wind at a couple of representative points.

4. Clear the screen. Start with the height at 500 mb again and add the ageostrophic wind. Where at the initial time is the actual wind clearly subgeostrophic? Supergeostrophic?