[NARCCAP-discuss] Consistency between tas, tasmax and tasmin.

[Gauvin St-Denis, Blaise]

Hi,

There seems to be inconsistent behaviour between tas, tasmax and tasmin in some narccap simulations.

To frame the problem, we have 3-hourly temperatures (tas) and daily minimum and maximum temperatures (tasmin,tasmax). One would expect that:
tasmin <= tas <= tasmax
during a given day. Now, some models might have their 'day' start at a different hour and compute tasmin/tasmax with respect to the previous 24h, but still, this relationship should be valid within at most a 24h offset.


Here are the problems I have:

WRFG-CCSM: Offset of multiple days between tas and (tasmin,tasmax). Could this be linked to the missing timesteps problems?
example in attached figure (tasmm_wrfg_ccsm.png): we can see that there is an offset of more than 48h.

Note that I did not see this problem in the WRFG-CGCM3 run.



RCM3: 3-hourly temperatures often overshoot/undershoot the (tasmin,tasmax) envelope.
example in attached figure (tasmm_rcm3_gfdl.png): a few points where the 3-hourly temperature is well below/over 3 deg. C of tasmin/tasmax

Note that this is present in both RCM3-GFDL and RCM3-CGCM3.



Any confirmation/comment on those issues would be appreciated,

Thanks,

Blaise Gauvin St-Denis
Groupe Scénarios Climatiques
Ouranos

st-denis.blaise at ouranos.ca
Tel. 514-282-6464 #302
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