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cemac / SWIFT-Synoptic

SWIFT Automated synoptic plotting
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Trial improvements for locating ITD #25

Open tdjames1 opened 3 years ago

tdjames1 commented 3 years ago

Using 15deg dewpoint temp to identify ITD is not correct over western regions e.g. Senegal, need to additionally take account of winds.

Doug's suggestion for identifying ITD / Congo Air Boundary as confluence lines:

I think I have a neat solution for this, which emerged from thinking about velocity potential. Because these features are geographically defined to be E-W (ITD) and N-S (CAB), you should be able to identify them by analysing velocity fields across the domain in the lat-lon directions separately.

For the ITD I am suggesting you can integrate the equation d\phi / dy = v by finite differences, starting with \phi=const (e.g. \phi=0) at a fixed latitude comfortably south of the ITD. Then the convergence-based ITD will by where \phi is maximum in y (by definition, v=0 at this maximum).

Then, for the CAB the process can be repeated, for latitudes south of the ITD (south of min latitude of ITD), solving d\phi / dx = u.

I think this should work, and because it's an integral, it should be robust. The only problem will come if there is a jump in the latitude (of ITD) from latitude to latitude. In that case maybe the ITD can be broken if it jumps more than a couple of gridboxes?

tdjames1 commented 2 years ago

Notes from SWIFT Science meeting 2/11/2021 (during EA TB3). Strong signal CAB 11am Plot confluence line - ITCZ/CAB Integrate in wind and find min (min advection in one direction)