relative magnitude of PTTEND components (CESM2.1.3): DTV+TTGW much weaker than DTCOND, QRL, QRS?

[hhzhang]

Hi,

I am looking at the various physics tendency terms in CESM2.1.3, a basic F2000CLIMO control simulation. I found that the DTV and TTGW terms are about four orders of magnitude weaker than DTCOND, QRL and QRS even near the surface where they all should be comparable based on reanalysis products. In CESM, I derived DTV+TTGW from PTTEND-DTCOND-QRS-QRL (since I did not save them in history files).

As an example, below are two figures showing a zonal-vertical cross section averaged 0N-10S in my f2000climo control simulation (top 4 panels, vertical pressure coordinate) and in the NCEP-NCAR reanalysis 2 product (bottom 4 panels, vertical sigma coordinate). PTTEND, COND (ie. DTCOND), RAD (i.e., QRL+QRS) are similar between CESM and reanalysis (despite comparing CESM annual mean with a monthly mean reanalysis), but VD (i.e., DTV+TTGW) is negligible in CESM (derived as PTTEND-DTCOND-QRS-QRL) even near the surface (where it's comparable to other terms in reanalysis).
----------------------------CESM----------------------------


----------------------------NCEP-NCAR reanalysis ----------------------------



The weak DTV+TTGW in CESM appear to be wrong. Can someone explain this?

Thanks.
Honghai

 

[cacraig]

I'm sorry no one has answered this question yet. Do you still need an answer, or have you figured it out on your own? I'll try to find someone to answer this if you still have the question.

 

[hhzhang]

Thanks for the reply. I have some qualitative ideas, but would like to hear some more quantitative answer if possible from an expert. thanks.

 

[juliob]

Dear Hongzhai,
Apologies for the very delayed reply: The temperature tendency from vertical diffusion (DTV) in CAM5 *should* have been much larger than it is now in CAM6. Turbulent vertical transport of heat in CAM6 is carried out by the CLUBB scheme, not by vertical diffusion. In CAM6, the only temperature tendency that remains in DTV is that from kinetic energy dissipation resulting from the Beljaars form drag scheme. This should be much smaller (by orders-of-magnitude) than that from turbulent transport. You can check the static energy (cpair*T) tendency from CLUBB by looking at the output variable STEND _CLUBB. This should resemble (after division by cpair) the DTV from CAM5.

I would also expect TTGW to be much smaller than either DTV in CAM5 or STEND_CLUBB/cpair in CAM6. TTGW is heating by gravity wave drag induced KE conversion (in CAM5/CESM1) and KE conversion+diffusion by breaking waves in CAM6/CESM2. In both CAM5 and CAM6 this should be much smaller than the tendencies from vertical turbulent transport (STEND_CLUBB or DTV). In any event, I think it would be good to check STEND_CLUBB and TTGW in CAM6 independently against DTV and TTGW in CAM5. If your result still does not make sense please let me know.
-Julio

 

[hhzhang]

Hi Juliob,

Thank you for the explanation. The temperature tendency from vertical turbulent transport in CAM6 is included in DTCOND, as opposed to DTV in CAM5. These changes have not been reflected in the CAM6 user documentation yet, which causes my confusion. I agree that the tendencies from KE related processes should also be small, since KE in the atmosphere is a small term compared to MSE. thanks again.

Honghai

 

[QINKONG]

Dear Hongzhai,
Apologies for the very delayed reply: The temperature tendency from vertical diffusion (DTV) in CAM5 *should* have been much larger than it is now in CAM6. Turbulent vertical transport of heat in CAM6 is carried out by the CLUBB scheme, not by vertical diffusion. In CAM6, the only temperature tendency that remains in DTV is that from kinetic energy dissipation resulting from the Beljaars form drag scheme. This should be much smaller (by orders-of-magnitude) than that from turbulent transport. You can check the static energy (cpair*T) tendency from CLUBB by looking at the output variable STEND _CLUBB. This should resemble (after division by cpair) the DTV from CAM5.

I would also expect TTGW to be much smaller than either DTV in CAM5 or STEND_CLUBB/cpair in CAM6. TTGW is heating by gravity wave drag induced KE conversion (in CAM5/CESM1) and KE conversion+diffusion by breaking waves in CAM6/CESM2. In both CAM5 and CAM6 this should be much smaller than the tendencies from vertical turbulent transport (STEND_CLUBB or DTV). In any event, I think it would be good to check STEND_CLUBB and TTGW in CAM6 independently against DTV and TTGW in CAM5. If your result still does not make sense please let me know.
-Julio

Hi Julio,
Thanks for your answer. Does it mean that in CAM6, the balance equation of temperature tendency due to physical process should be:
PTTEND=DTCOND+QRS+QRL+DTV+TTGW+STEND_CLUBB/cpair

Is that correct?
In the last reply of Honghai, he seems to think that vertical turbulent transport in CAM6 is included in DTCOND. Is that true? If it is, does that mean there is a overlapping between DTCOND and STEND_CLUBB/cpair?

Thanks for your help!
-Qin

 

[khartig]

Seconding Qin's question, I am also hoping someone can confirm (or correct) the temperature tendency PTTEND =? DTCOND + QRS + QRL + DTV + TTGW + STEND_CLUBB/cpair for CAM6.

In CAM5, I usually saw TTGWORO instead of TTGW used in the temperature tendency budget (in this post, for example). If they are not the same, which one is used in the temperature tendency budget for CAM6?