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

[David Bronaugh]

Hmm; I took another look at your graph, and while the plotting methodology
is making more of those data points look problematic than actually are,
there are still definitely some that exceed the tasmin/tasmax bounds by a
wide margin. So I can't chalk it all up to a plotting methodology problem;
though it would be nice to see the plots redone.

David

On Tue, Feb 7, 2012 at 1:07 PM, David Bronaugh <bronaugh at uvic.ca> wrote:

> Hi Gauvin,
>
> I think you have a methodological problem with your plotting. If you want
> to display tasmax/tasmin for a day, the lines for tasmin and tasmax should
> always be flat, but yours are on angles. Can you replot using independent
> line segments for each day for each of tasmax/tasmin? I believe this will
> probably "resolve" the second problem. The first one does sound like a real
> data issue; I can't speak to it.
>
> David
>
>
> On Tue, Feb 7, 2012 at 11:59 AM, Gauvin St-Denis, Blaise <
> GauvinSt-Denis.Blaise at ouranos.ca> wrote:
>
>> 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
>
>
>