[RegCNET] tmax and tmin
William J. Gutowski
gutowski at iastate.edu
Thu Nov 17 19:47:46 CET 2005
Jeremy:
You have given a nice, succinct example
of the bias that can occur depending on the time
of day that the clock resets. This can happen at
any time, though probably some times have larger
bias due to this than others. Something similar
of course happens with Tmin, esp. if the clock is
reset around local sunrise.
I think putting this output in the SRF
file, and at 3 hour intervals is a good idea, and
then users can decide for themselves what matches
their obs. sources best or other needs. It also
takes advantage of the existing output file
structure for RegCM. For multi-model
comparisons, esp. in extratropical domains that
stretch over several time zones, it will probably
be best to stick to 00 UTC.
I have the nearly same question as Anji -
is the "2-m" temperature computed relative to the
zero-plane displacement level for the vegetation
under consideration? The zero-plane displacement
level is not the top of the vegetation, but it is
a function typically of the vegetation's
roughness length.
I must have lost a factor of 10 somewhere
in my estimate of the lowest level's midpoint -
thanks for the correction.
Bill
At 10:42 AM +0100 2005.11.17, 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:
>
>>Re: [RegCNET] tmax and tmin
>>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: <mailto:tomas.halenka at mff.cuni.cz>tomas.halenka at mff.cuni.cz
>>>>>*************************************************
>>>>>
>>>>>-----Original Message-----
>>>>>From: <mailto:regcnet-bounces at lists.ictp.it>regcnet-bounces at lists.ictp.it
>>>>>[<mailto: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; <mailto:regcnet at lists.ictp.it>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
>>>>>>
>>>>>>
>>>>>Tmin
>>>>>
>>>>>>and Tmax are obtained primarily from min/max thermometers, which
>>>>>>
>>>>>>
>>>>>record the
>>>>>
>>>>>>highest and lowest temperature attained since the last time they were
>>>>>>
>>>>>>
>>>>>reset.
>>>>>
>>>>>>They are almost always reset every 24 hours, though they don't all get
>>>>>>
>>>>>>
>>>>>reset
>>>>>
>>>>>>at the same time. That is, different stations, even in the same
>>>>>>
>>>>>>
>>>>>country (or
>>>>>
>>>>>>in the US, the same state) may reset their thermometers at different
>>>>>>
>>>>>>
>>>>>times of
>>>>>
>>>>>>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.
>>>>>>
>>>>>>
>>>>>This is
>>>>>
>>>>>>documented in the literature somewhere, though I don't have the
>>>>>>
>>>>>>
>>>>>reference
>>>>>
>>>>>>myself.
>>>>>> Using the 3-hourly output will tend to reduce the diurnal
>>>>>>
>>>>>>
>>>>>temperature
>>>>>
>>>>>>range you get because that is probably not sampling the extremes of
>>>>>>
>>>>>>
>>>>>the day,
>>>>>
>>>>>>though I have not seen this reduction tabulated by anyone, and it
>>>>>>
>>>>>>
>>>>>probably
>>>>>
>>>>>>depends on location and season. Including a computation of the true
>>>>>>
>>>>>>
>>>>>daily
>>>>>
>>>>>>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
>>>>>>
>>>>>>
>>>>>really
>>>>>
>>>>>>should have it as part of the standard model, I think. There would
>>>>>>
>>>>>>
>>>>>still be
>>>>>
>>>>>>the question of what time of day to "reset the thermometer", but in
>>>>>>
>>>>>>
>>>>>model
>>>>>
>>>>>>intercomparisons I've been part of, we typically agree to go from 00
>>>>>>
>>>>>>
>>>>>UTC - 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
>>>>>>>
>>>>>>>
>>>>>BATS
>>>>>
>>>>>>>output, so if you have the model output to the SRF file every 3
>>>>>>>
>>>>>>>
>>>>>hours, then
>>>>>
>>>>>>>that is what the min and max are calculated from. Bi thinks this is
>>>>>>>
>>>>>>>
>>>>>a
>>>>>
>>>>>>>better way to do it since min and max temp observations are generally
>>>>>>>
>>>>>>>
>>>>>taken
>>>>>
>>>>>>>from 3 or 6 hourly obs. You can increase the frequency of the srf
>>>>>>>
>>>>>>>
>>>>>output
>>>>>
>>>>>>>variables (in the regcm.in file) to see how much of difference it
>>>>>>>
>>>>>>>
>>>>>would
>>>>>
>>>>>>>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
>>>>>>><mailto:kueppers at pmc.ucsc.edu>kueppers at pmc.ucsc.edu
>>>>>>>
>>>>>>>_______________________________________________
>>>>>>>RegCNET mailing list
>>>>>>><mailto:RegCNET at lists.ictp.it>RegCNET at lists.ictp.it
>>>>>>><https://lists.ictp.it/mailman/listinfo/regcnet>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
>>>>>>
>>>>>><mailto:gutowski at iastate.edu>gutowski at iastate.edu
>>>>>>Tel:1-515-294-5632
>>>>>>Fax:1-515-294-2619
>>>>>><http://www.ge-at.iastate.edu/>http://www.ge-at.iastate.edu/
>>>>>><http://rcmlab.agron.iastate.edu/>http://rcmlab.agron.iastate.edu/
>>>>>>~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>>>>>
>>>>>>_______________________________________________
>>>>>>RegCNET mailing list
>>>>>><mailto:RegCNET at lists.ictp.it>RegCNET at lists.ictp.it
>>>>>><https://lists.ictp.it/mailman/listinfo/regcnet>https://lists.ictp.it/mailman/listinfo/regcnet
>>>>>>
>>>>>>
>>>>>>
>>>>>
>>>>>~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>>>>~ Dr. Xunqiang Bi
>>>>><email:bixq at ictp.it>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
>>>>><mailto:RegCNET at lists.ictp.it>RegCNET at lists.ictp.it
>>>>><https://lists.ictp.it/mailman/listinfo/regcnet>https://lists.ictp.it/mailman/listinfo/regcnet
>>>>>
>>>>>
>>>>>_______________________________________________
>>>>>RegCNET mailing list
>>>>><mailto:RegCNET at lists.ictp.it>RegCNET at lists.ictp.it
>>>>><https://lists.ictp.it/mailman/listinfo/regcnet>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
>>>><mailto:RegCNET at lists.ictp.it>RegCNET at lists.ictp.it
>>>><https://lists.ictp.it/mailman/listinfo/regcnet>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
>>><mailto:kueppers at pmc.ucsc.edu>kueppers at pmc.ucsc.edu
>>>
>>>_______________________________________________
>>>RegCNET mailing list
>>><mailto:RegCNET at lists.ictp.it>RegCNET at lists.ictp.it
>>><https://lists.ictp.it/mailman/listinfo/regcnet>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
>>
>><mailto:gutowski at iastate.edu>gutowski at iastate.edu
>>Tel:1-515-294-5632
>>Fax:1-515-294-2619
>><http://www.ge-at.iastate.edu/>http://www.ge-at.iastate.edu/
>><http://rcmlab.agron.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
--
*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*
William J. Gutowski
3021 Agronomy
Dept. of Geological and
Atmospheric Sciences gutowski at iastate.edu
Dept. of Agronomy Tel: +1-515-294-5632
Iowa State University Fax: +1-515-294-2619
Ames, Iowa 50011-1010
http://www.ge-at.iastate.edu
http://rcmlab.agron.iastate.edu/
*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*
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