Potential vorticity and strat-trop exchange

[duderstadtk@gmail_com]

We are looking at stratosphere-troposphere exchange (STE) in our WACCM runs. Is there a way include potential vorticity (Ertel's Potential Vorticity) in our history files?

There appears to be a subroutine in the cam dynamics code "epvd.F90" that calculates "absolute potential vorticity (epv)". However, there doesn't seem to be a variable for potential vorticity in the Master Field List. I also can't find the location from which "epvd" is called. Can we use the "epvd" subroutine to calculate and record potential vorticity in order to study strat-trop exchange? How would we go about calling this subroutine and then adding "epv" as a field to the Master Field List for the history files?

Alternative approaches from the literature for identifying tropopause and strat-trop exchange include:

Lapse rate decrease to 2 K/km
Ertel's Potential Vorticity
O3-CO correlations
Water vapor distributions
Artificial tracers (e.g., Prather et al., 2012 -- "e90" tracer)
Ratio of cosmogenic radionuclides Beryllium-10 to Beryllium-7

Do you have any suggestions on which of these methods is the best approach for identifying STE on the basis of WACCM's current and future capabilities? [Are there plans to include cosmic rays and radionuclides like Be-7 in future releases of WACCM?]

Thanks!

 

[santos]

I can't comment about the best way to examine STE, but I have a couple of observations:

1. The subroutine in epvd.F90 is actually not called from anywhere in CAM right now, and hasn't been updated since 2007. It still compiles/links within CAM, so it may still work, but it seems like no one is using it in the current code.

2. The subroutine "addfld" in cam_history is responsible for adding entries to the master field list. Then the subroutine "outfld" can be used to add the actual data.

 

[zhangjkstrato@hotmail_com]

Hi, K. Duderstadt. I am not sure whether you are still focusing on STE in WACCM, since the poster is old. Actually, I make some modifications in WACCM and achieve the release of regional tracer at any pressure level. I suppose the artificial tracers might help to diagnose STE. Jiankai