[RegCNET] tmax and tmin
Anji Seth
seth at iri.columbia.edu
Thu Nov 17 13:39:05 CET 2005
Hello All,
This is a great discussion, and very important for obvious reasons.
Keeping Tmin/Tmax for each SRF output interval will permit more
flexibility and reduce the problems the Jeremy has mentioned. I
completely agree with this approach.
Jeremy, can you refresh my memory - is surface air temperature for tall
vegetation computed for 2 m above the vegetation?
-Anji
On Nov 17, 2005, at 4:42 AM, Jeremy Pal wrote:
> Hi Bill,
>
> If it is OK for others, I agree that we should use 00UTC. But, I
> foresee potential problems with this approach. For example, if you
> have a day that is very hot followed by a cooler day, you may end up
> counting the maximum temperature twice for the hot day depending on
> locally what time 00UTC is. A similar scenario could be thought of
> for minimum temperature. For this reason, I suggested the max/min of
> the SRF output interval, so that the user could decide at the
> postprocessing stage what time to use. Anyway, if you think that
> these potential problems are negligible, we can use 00UTC.
>
> Regarding the 2m temperature, do you think there is a need to rethink
> our approach for computing it in the presence of tall vegetation? If
> so, do you have any suggestions?
>
> A small clarification... In the default version, I pretty sure that
> the midpoint of the lowest model level generally about 35 to 40
> meters.
>
> Thanks for the comments. It is nice to see so much interaction for
> so many different RegCNETers!
>
> Jeremy
>
> Wm. J. Gutowski wrote:Lara:
>> I'm not sure that using the lowest ATM level is the best
>> choice, although we do want an air temperature. What most models
>> that I know about typically do is use the near-surface air
>> temperature that the land-surface model determines, perhaps in
>> conjunction with the PBL model This is the temperature that
>> corresponds to what the observing stations are measuring. The lowest
>> ATM level may be many meters above the surface. For example, RegCM's
>> lowest layer's delta sigma = 0.05 implies a lowest-layer thickness of
>> about 500 m, that the nominal middle of the layer is at about 250 m.
>> There may be a further issue here though (and I need help
>> from the ICTP people on this!): is the near-surface air temperature
>> computed in RegCM3 at 2 m? I thought some observation stations used
>> other heights above the surface.
>>
>> Also, how well do we know that Tmin/Tmax stations adhere to
>> WMO standards? I know if the U.S. they don't, simply because of the
>> disparate reset times used. If that is the case elsewhere, then I
>> suggest doing the reset at a default time of 00 UTC (so that the
>> values are for the calendar day ending at that time). This could be
>> a parameter that the user can change in the input files, though that
>> might cause confusion about what day to associate the values with.
>> (Arguably, that potential for confusion will always be there relative
>> to the local clock.)
>>
>> Bill
>>
>> At 11:02 AM -0800 05.11.16, Lara Kueppers wrote:
>>> Jeremy-
>>> A couple of things:
>>> * Mark and I were discussing that it would be best if Tmin and Tmax
>>> were calculated from air temperature (lowest ATM level) so that they
>>> are consistent with the average T values. If you output this in the
>>> SRF file, that's fine, just so it's clear we're talking atmospheric
>>> min and max.
>>> * Also, calculating min and max from 00 to 00 UTC seems the most
>>> workable option. Unless there is some argument for having sub-daily
>>> min and max (as opposed to average) temperature, we'd say limit the
>>> file size!
>>>
>>> One other thought... Would anyone else find it useful to have the
>>> combined surface albedo values available from BATS? (i.e. the total
>>> vis and ir albedos calculated from veg, soil, snow etc.) This would
>>> be helpful for interpreting seasonal cycle results from land cover
>>> change experiments. Of course this would increase the file size...
>>>
>>> Lara
>>>
>>> Jeremy Pal wrote:
>>>> Hi,
>>>> Having it done based on local time may be a bit tricky to code
>>>> up. As an alternative, we could consider storing the max/min
>>>> temperature and wind for every output interval (e.g. 3 hours).
>>>> This way, the user can decide the reset time at the postproc
>>>> stage... Of course, this increases the SRF output file size by
>>>> about 15% as opposed to just a couple percent.
>>>> What do you think of this idea?
>>>> Jeremy
>>>>
>>>> Tomá” Halenka wrote:
>>>>> Dear All,
>>>>>
>>>>> Not bad hearing Tmax and Tmin will be included properly in new
>>>>> edition
>>>>> of RegCM. But I would recommend to use WMO definition and reset
>>>>> time,
>>>>> moreover, keep in mind it has to be done in local time as my
>>>>> opinion.
>>>>>
>>>>> Best regards,
>>>>>
>>>>> Tomas
>>>>>
>>>>> *************************************************
>>>>> RNDr. Tomas Halenka, CSc.
>>>>> Charles University in Prague,
>>>>> Faculty of Mathematics and Physics,
>>>>> Department of Meteorology and Environment Protection,
>>>>> V Holesovickach 2, 180 00 Prague 8,
>>>>> Prague, Czech Republic,
>>>>> Phone: +420 2 21912514
>>>>> Fax: +420 2 21912533
>>>>> E-mail: tomas.halenka at mff.cuni.cz
>>>>> *************************************************
>>>>>
>>>>> -----Original Message-----
>>>>> From: regcnet-bounces at lists.ictp.it
>>>>> [mailto:regcnet-bounces at lists.ictp.it] On Behalf Of BI XUNQIANG
>>>>> Sent: Wednesday, November 16, 2005 9:48 AM
>>>>> To: Wm. J. Gutowski
>>>>> Cc: Gao Xuejie; regcnet at lists.ictp.it
>>>>> Subject: Re: [RegCNET] tmax and tmin
>>>>>
>>>>>
>>>>> Dear Bill, Lara, and Gao:
>>>>>
>>>>> In the next public released RegCM3 version, we will add Tmax, Tmin
>>>>> and vertital velocity (for pressure level) as the standard output.
>>>>>
>>>>> We will calculated Tmax and Tmin as the way Bill suggested (for
>>>>> every land surface step, and reset at 00 UTC).
>>>>> Any other fields are also necessary to be included ?
>>>>>
>>>>> Thanks and best regards,
>>>>>
>>>>> On Tue, 15 Nov 2005, Wm. J. Gutowski wrote:
>>>>>
>>>>> Dear Lara:
>>>>>> I am not the expert on this, but I am pretty sure that
>>>>>> observed
>>>>>>
>>>>>> and Tmax are obtained primarily from min/max thermometers, which
>>>>>>
>>>>>> highest and lowest temperature attained since the last time they
>>>>>> were
>>>>>>
>>>>>> They are almost always reset every 24 hours, though they don't
>>>>>> all get
>>>>>>
>>>>>> at the same time. That is, different stations, even in the same
>>>>>>
>>>>>> in the US, the same state) may reset their thermometers at
>>>>>> different
>>>>>>
>>>>>> the day. This can induce a small bias in one station's
>>>>>> climatological
>>>>>>
>>>>>
>>>>> averages compared to what it would get if it reset at another
>>>>> time.
>>>>>>
>>>>>> documented in the literature somewhere, though I don't have the
>>>>>>
>>>>>> myself.
>>>>>> Using the 3-hourly output will tend to reduce the diurnal
>>>>>>
>>>>>> range you get because that is probably not sampling the extremes
>>>>>> of
>>>>>>
>>>>>> though I have not seen this reduction tabulated by anyone, and it
>>>>>>
>>>>>> depends on location and season. Including a computation of the
>>>>>> true
>>>>>>
>>>>>> min/max temperature would be just a few lines of code, and some
>>>>>> of us RegCNETers have undoubtedly done it for their version of
>>>>>> the code - we
>>>>>>
>>>>>> should have it as part of the standard model, I think. There
>>>>>> would
>>>>>>
>>>>>> the question of what time of day to "reset the thermometer", but
>>>>>> in
>>>>>>
>>>>>> intercomparisons I've been part of, we typically agree to go from
>>>>>> 00
>>>>>>
>>>>>> UTC.
>>>>>>
>>>>>> Bill
>>>>>>
>>>>>> At 11:32 AM -0800 05.11.14, Lara Kueppers wrote:
>>>>>>
>>>>>>> Hi-
>>>>>>> Awhile back I asked how Tmin and Tmax in the SRF output file
>>>>>>> were calculated. Here is Nellie's recent reply, in case anyone
>>>>>>> else is interested.:
>>>>>>>
>>>>>>> "Hi Lara,
>>>>>>>
>>>>>>> I just verified this with Bi...Tmin and Tmax are calculated
>>>>>>> from the
>>>>>>>
>>>>>>> output, so if you have the model output to the SRF file every 3
>>>>>>>
>>>>>>> that is what the min and max are calculated from. Bi thinks
>>>>>>> this is
>>>>>>>
>>>>>>> better way to do it since min and max temp observations are
>>>>>>> generally
>>>>>>>
>>>>>>> from 3 or 6 hourly obs. You can increase the frequency of the
>>>>>>> srf
>>>>>>>
>>>>>>> variables (in the regcm.in file) to see how much of difference it
>>>>>>>
>>>>>>> make in the diurnal temp range. "
>>>>>>>
>>>>>>> --
>>>>>>> ~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*
>>>>>>> Lara M. Kueppers, PhD
>>>>>>> Postgraduate Researcher
>>>>>>> Department of Earth Sciences
>>>>>>> University of California, Santa Cruz
>>>>>>> 1156 High Street
>>>>>>> Santa Cruz, CA 95064
>>>>>>> USA
>>>>>>>
>>>>>>> 831.459.3504 ph
>>>>>>> 831.459.3074 fax
>>>>>>> kueppers at pmc.ucsc.edu
>>>>>>>
>>>>>>> _______________________________________________
>>>>>>> RegCNET mailing list
>>>>>>> RegCNET at lists.ictp.it
>>>>>>> https://lists.ictp.it/mailman/listinfo/regcnet
>>>>>>>
>>>>>> --
>>>>>> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>>>>> William J. Gutowski, Jr.
>>>>>> 3021 Agronomy Hall
>>>>>> Dept. of Geological and
>>>>>> Atmospheric Sciences
>>>>>> Iowa State University
>>>>>> Dept. of Agronomy
>>>>>> Ames, Iowa 50011-1010
>>>>>>
>>>>>> gutowski at iastate.edu
>>>>>> Tel:1-515-294-5632
>>>>>> Fax:1-515-294-2619
>>>>>> http://www.ge-at.iastate.edu/
>>>>>> http://rcmlab.agron.iastate.edu/
>>>>>> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>>>>>
>>>>>> _______________________________________________
>>>>>> RegCNET mailing list
>>>>>> RegCNET at lists.ictp.it
>>>>>> https://lists.ictp.it/mailman/listinfo/regcnet
>>>>>>
>>>>>>
>>>>>
>>>>> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>>>> ~ Dr. Xunqiang Bi email:bixq at ictp.it ~ ~ Physics of
>>>>> Weather and Climate Group ~
>>>>> ~ The Abdus Salam ICTP ~
>>>>> ~ Strada Costiera, 11 ~
>>>>> ~ P.O. BOX 586, 34100 Trieste, ITALY ~
>>>>> ~ Tel: +39-040-2240302 Fax: +39-040-2240449 ~
>>>>> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>>>> _______________________________________________
>>>>> RegCNET mailing list
>>>>> RegCNET at lists.ictp.it
>>>>> https://lists.ictp.it/mailman/listinfo/regcnet
>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> RegCNET mailing list
>>>>> RegCNET at lists.ictp.it
>>>>> https://lists.ictp.it/mailman/listinfo/regcnet
>>>>>
>>>> --
>>>> The Abdus Salam International Centre for Theoretical Physics
>>>> Strada Costiera 11; 34100 Trieste, ITALY
>>>> Phone: +39 040 2240579; Fax: +39 040 2240449
>>>>
>>>>
>>>> --------------------------------------------------------------------
>>>> ----
>>>> _______________________________________________
>>>> RegCNET mailing list
>>>> RegCNET at lists.ictp.it
>>>> https://lists.ictp.it/mailman/listinfo/regcnet
>>>>
>>> --
>>> ~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*
>>> Lara M. Kueppers, PhD
>>> Postgraduate Researcher
>>> Department of Earth Sciences
>>> University of California, Santa Cruz
>>> 1156 High Street
>>> Santa Cruz, CA 95064
>>> USA
>>>
>>> 831.459.3504 ph
>>> 831.459.3074 fax
>>> kueppers at pmc.ucsc.edu
>>>
>>> _______________________________________________
>>> RegCNET mailing list
>>> RegCNET at lists.ictp.it
>>> https://lists.ictp.it/mailman/listinfo/regcnet
>>
>>
>> --
>>
>> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>> William J. Gutowski, Jr.
>> 3021 Agronomy Hall
>> Dept. of Geological and
>> Atmospheric Sciences
>> Iowa State University
>> Dept. of Agronomy
>> Ames, Iowa 50011-1010
>>
>> gutowski at iastate.edu
>> Tel:1-515-294-5632
>> Fax:1-515-294-2619
>> http://www.ge-at.iastate.edu/
>> http://rcmlab.agron.iastate.edu/
>> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> --
> The Abdus Salam International Centre for Theoretical Physics
> Strada Costiera 11; 34100 Trieste, ITALY
> Phone: +39 040 2240579; Fax: +39 040 2240449
>
> _______________________________________________
> RegCNET mailing list
> RegCNET at lists.ictp.it
> https://lists.ictp.it/mailman/listinfo/regcnet
>
Anji Seth, Geography, University of Connecticut
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