[gradsusr] GFS total cloud cover
Shrinivas Moorthi
shrinivas.moorthi at noaa.gov
Thu Nov 3 06:59:13 EDT 2016
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
> <mailto:gradsusr-bounces at gradsusr.org>> on behalf of Jeff Duda
> <jeffduda319 at gmail.com <mailto:jeffduda319 at gmail.com>>
> Reply-To: GrADS Users Forum <gradsusr at gradsusr.org
> <mailto:gradsusr at gradsusr.org>>
> Date: Wednesday, November 2, 2016 at 3:21 PM
> To: GrADS Users Forum <gradsusr at gradsusr.org
> <mailto: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
> <mailto: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
> <mailto:gradsusr-bounces at gradsusr.org>> on behalf of Jeff Duda
> <jeffduda319 at gmail.com <mailto:jeffduda319 at gmail.com>>
> Reply-To: GrADS Users Forum <gradsusr at gradsusr.org
> <mailto:gradsusr at gradsusr.org>>
> Date: Wednesday, November 2, 2016 at 2:08 PM
> To: GrADS Users Forum <gradsusr at gradsusr.org
> <mailto: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
> <mailto: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
>
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>
> --
> 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
>
>
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--
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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