[gradsusr] GFS total cloud cover

Thu Nov 3 08:59:48 EDT 2016

Sam,

  You can get the "0-1 hour ave fcst", "1-2 hour ave fcst", etc
by using the -ncep_norm option of wgrib2.

   http://www.cpc.ncep.noaa.gov/products/wesley/wgrib2/ncep_norm.html

Here is a simple script that takes a list of gfs forecast files in order

#!/bin/sh
#
# usage $0 (list of gfs grib2 forecast files in order)
#
A=":TCDC:entire atmosphere:"
B=":TCDC:low cloud layer:"
C=":TCDC:middle cloud layer:"
D=":TCDC:high cloud layer:"

cat $* | wgrib2 - -match "($A|$B|$C|$D)" -set_grib_type c3 \
   -if "$A" -ncep_norm $stmp/junk \
   -if "$B" -ncep_norm $stmp/junk \
   -if "$C" -ncep_norm $stmp/junk \
   -if "$D" -ncep_norm $stmp/junk

Wesley

On Thu, Nov 3, 2016 at 6:59 AM, Shrinivas Moorthi <
shrinivas.moorthi at noaa.gov> wrote:

> The grib header is correct.
> Let us denote the data from 6 hourly output as C1, C2, C3, C4, C5, C6.
>
> To get hourly mean, then
> for hour 1, the mean is C1,
> for hour 2, the mean is 2C2-C1
> for hour 3, the mean is 3C3-2C2
> for hour 4, the mean is 4C4-3C2
> for hour 5, the mean is 5C5-4C4
> and for hour 6, it is 6C6-5C5
>
> This pattern repeats every six ours.
> I hope this helps.
> Moorthi
> On 11/02/2016 07:41 PM, Sam Wilson wrote:
>
> Hi Jeff,
>
> I plotted a quick and dirty cloud animation using the data - each step is
> 1 hour from f001 through f015 in the attached.
>
> It appears that they are averages over time - you can see the bigger jumps
> at steps 8 and 14 (the transition from 0-6hr avg to 6-7hr and from 6-12hr
> avg to 12-13hr).
>
> Marian - thank you for the feedback.  Sounds like using the hourly data
> for cloud cover may not be a good idea, unless someone else has a solution.
>
> Thanks,
> Sam
>
> From: <gradsusr-bounces at gradsusr.org> on behalf of Jeff Duda <
> jeffduda319 at gmail.com>
> Reply-To: GrADS Users Forum <gradsusr at gradsusr.org>
> Date: Wednesday, November 2, 2016 at 3:21 PM
> To: GrADS Users Forum <gradsusr at gradsusr.org>
> Subject: Re: [gradsusr] GFS total cloud cover
>
> Sam,
> That might just be a wgrib table thing. Have you actually plotted the
> field over those times? If it's truly an averaged field, you should be able
> to see some indication of that in the texture and smoothness of the fields
> as you progress through increasing averaged times.
>
> My guess is that this is just some arbitrary setting in wgrib and does not
> reflect the true nature of the field. But I could be wrong. If there are
> any NCEP folks who work on the GFS on this forum, perhaps one of them could
> set the record straight.
>
> Jeff
>
> On Wed, Nov 2, 2016 at 4:54 PM, Sam Wilson <sam at surfline.com> wrote:
>
>> Thanks for the response Jeff - it’s strange to me as well!
>>
>> Running wgrib2 on the data files for forecast hours 001 through 007 gives
>> the following for TCDCclm:
>>
>> *f001:*
>> 17:7991683:d=2016110212:TCDC:entire atmosphere:*0-1* hour ave fcst:
>> *f002:*
>> 17:8082626:d=2016110212:TCDC:entire atmosphere:*0-2* hour ave fcst:
>> *f003:*
>> 17:8059826:d=2016110212:TCDC:entire atmosphere:*0-3 *hour ave fcst:
>> *f004:*
>> 17:8057865:d=2016110212:TCDC:entire atmosphere:*0-4* hour ave fcst:
>> *f005:*
>> 17:8119289:d=2016110212:TCDC:entire atmosphere:*0-5* hour ave fcst:
>> *f006:*
>> 17:8172510:d=2016110212:TCDC:entire atmosphere:*0-6* hour ave fcst:
>> *f007:*
>> 17:8013825:d=2016110212:TCDC:entire atmosphere:*6-7* hour ave fcst:
>>
>> And it continues on..once the files go to 3 hourly (after hour 120), we
>> have:
>>
>> *f123:*
>> 17:7687687:d=2016110212:TCDC:entire atmosphere:*120-123* hour ave fcst:
>> *f126:*
>> 17:7778871:d=2016110212:TCDC:entire atmosphere:*120-126* hour ave fcst:
>> *f129:*
>> 17:7728042:d=2016110212:TCDC:entire atmosphere:*126-129* hour ave fcst:
>>
>> And finally the 12 hourly files (past hour 240) are all just 12 hour
>> average forecasts:
>>
>> *f252:*
>> 17:6845416:d=2016110212:TCDC:entire atmosphere:*240-252* hour ave fcst:
>>
>> I did think about the method you suggested (tcdcclm - tcdcclm(t-1)) but
>> stopped there for the reason you mentioned..
>>
>> Strange indeed - unless I’m missing something..
>>
>> Thanks,
>> Sam
>>
>> From: <gradsusr-bounces at gradsusr.org> on behalf of Jeff Duda <
>> jeffduda319 at gmail.com>
>> Reply-To: GrADS Users Forum <gradsusr at gradsusr.org>
>> Date: Wednesday, November 2, 2016 at 2:08 PM
>> To: GrADS Users Forum <gradsusr at gradsusr.org>
>> Subject: Re: [gradsusr] GFS total cloud cover
>>
>> It seems a little strange to me that the total cloud cover product would
>> be averaged over time. Is that really the case?
>>
>> Anyway, if you really do have an average over overlapping and increasing
>> windows, with nothing else to go on and without applying the equations of
>> motion in reverse, you'd have to assume a linear averaging, so subtraction
>> of subsequent slices of the field (i.e., tcdcclm - tcdcclm(t-1)) would give
>> you piecewise temporal averages. However, that method would give you
>> negative cloud cover values which is clearly nonsensical, which again is
>> why I question whether or not that array contains a temporal average. That
>> just doesn't make a lot of sense.
>>
>> Jeff Duda
>>
>> On Wed, Nov 2, 2016 at 3:27 PM, Sam Wilson <sam at surfline.com> wrote:
>>
>>> Hi,
>>>
>>> I’m working with hourly GFS total cloud cover (TCDCclm) and I’m a bit
>>> stumped on the following..
>>>
>>> Given TCDCclm for hours 0-1, 0-2, 0-3, 0-4, 0-5, and 0-6, what is the
>>> proper way to determine TCDCclm for hours 1-2, 2-3, 3-4, 4-5, and 5-6?
>>>
>>> I may be making the problem more difficult than it is..but wanted to
>>> ping this group to be sure.
>>>
>>> Is there an existing grads script that handles this already and if not,
>>> does anyone here have any insight?
>>>
>>> Thanks so much for your time.
>>>
>>> Best,
>>> Sam
>>>
>>> _______________________________________________
>>> gradsusr mailing list
>>> gradsusr at gradsusr.org
>>> http://gradsusr.org/mailman/listinfo/gradsusr
>>>
>>>
>>
>>
>> --
>> Jeff Duda
>> Post-doctoral research associate
>> University of Oklahoma School of Meteorology
>>
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>>
>>
>
>
> --
> Jeff Duda
> Post-doctoral research associate
> University of Oklahoma School of Meteorology
>
>
> _______________________________________________
> gradsusr mailing listgradsusr at gradsusr.orghttp://gradsusr.org/mailman/listinfo/gradsusr
>
>
>
> --
> Dr. Shrinivas Moorthi
> Research Meteorologist
> Global Climate and Weather Modeling Branch
> Environmental Modeling Center / National Centers for Environmental Prediction
> 5830 University Research Court - (W/NP23), College Park MD 20740 USA
> Tel:(301)683-3718
>
>
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>
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