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: tomas.halenka@mff.cuni.cz
*************************************************
-----Original Message-----
From: regcnet-bounces@lists.ictp.it
[mailto:regcnet-bounces@lists.ictp.it] On Behalf Of BI XUNQIANG
Sent: Wednesday, November 16, 2005 9:48 AM
To: Wm. J. Gutowski
Cc: Gao Xuejie; regcnet@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
kueppers@pmc.ucsc.edu
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
William J. Gutowski, Jr.
3021 Agronomy Hall
Dept. of Geological and
Atmospheric Sciences
Iowa State University
Dept. of Agronomy
Ames, Iowa 50011-1010
gutowski@iastate.edu
Tel:1-515-294-5632
Fax:1-515-294-2619
http://www.ge-at.iastate.edu/
http://rcmlab.agron.iastate.edu/
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Group ~
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~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*
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@pmc.ucsc.edu
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
William J. Gutowski, Jr.
3021 Agronomy Hall
Dept. of Geological and
Atmospheric Sciences
Iowa State University