Changing height of lowest hybrid level

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l.vankampenhout@...
Changing height of lowest hybrid level

In CAM6, the midpoint of the lowest atmosphere layer sits at about 60 metres. This can be seen as follows:

double lev(lev) ;
lev:long_name = "hybrid level at midpoints (1000*(A+B))" ;
lev(-1) = 992.556095123291 hPa

The reference pressure is 100,000 Pa. Filling in the calculator (T = 0 degC) at https://www.mide.com/pages/air-pressure-at-altitude-calculatoryields a midpoint height of 59.75m.

I am wondering, is there a standard procedure to change atmospheric levels? I would like to move the lowest midpoint closer to the surface, say 12 m. Is this at all possible? What are potential caveats?

Cheers,Leo van Kampenhout
rneale

Hi Leo,

First of all I would advise very strongly against doing this in CAM6. The model is not ready yet and has the potential for significant changes ahead.

For the most part the procedure is a matter of interpolating initial files to your required vertical levels. The model takes the vertical levels for the simulation from this file.

The consequences of doing this could be substantial. Simulations with a 20m lowest level centerpoint changes the tropical precipitation quite dramatically due to the sensitivity of the deep convection. Contact me separately if you want more details on this. Good luck!

Rich

Richard Neale CESM AMWG Co-chair eval(unescape('%64%6f%63%75%6d%65%6e%74%2e%77%72%69%74%65%28%27%3c%61%20%68%72%65%66%3d%22%6d%61%69%6c%74%6f%3a%72%6e%65%61%6c%65%40%75%63%61%72%2e%65%64%75%22%20%63%6c%61%73%73%3d%22%62%62%2d%65%6d%61%69%6c%22%3e%72%6e%65%61%6c%65%40%75%63%61%72%2e%65%64%75%3c%2f%61%3e%27%29%3b')) http://www.cgd.ucar.edu/cms/rneale Atmosphere Modeling and Predictability Section, AMP, NCAR Tel (303) 497-1380 Fax (303) 497-1324