Vector arrows for primary wave direction

[Nathan Cool]

Thanks Matthias. I sure do appreciate the help. That produced some
interesting results, but it didn't seem accurate (arrows pointing in some
rather bizarre directions). Perhaps though this is a data problem, and I
need to grab different GRIB files? Currently, I'm using GRIBs from the NCEP
server:
ftp://polar.ncep.noaa.gov/pub/waves/latest_run/

-Nathan


On Wed, Nov 4, 2009 at 7:53 AM, Matthias Fripp
<matthias.fripp at eci.ox.ac.uk>wrote:

> How about this:
>
> set gxout vector
> display cos(DIRPWsfc * 3.14159/180); sin(DIRPWsfc * 3.14159/180)
>
> This converts the wave direction from degrees to radians, and then
> calculates its u and v components.
>
> Matthias
>
> On Nov 4, 2009, at 2:38 PM, Nathan Cool wrote:
>
> Thanks, but I'm not trying to display "wind" vector arrows; instead, I'm
> trying to display the primary wave direction.
>
> The vars in the Grib are:
> ------------------------
> DIRPWsfc  0 107,1,1  ** surface Primary wave direction [deg]
> DIRSWsfc  0 109,1,1  ** surface Secondary wave direction [deg]
> HTSGWsfc  0 100,1,1  ** surface Sig height of wind waves and swell [m]
> PERPWsfc  0 108,1,1  ** surface Primary wave mean period [s]
> PERSWsfc  0 110,1,1  ** surface Secondary wave mean period [s]
> UGRDsfc  0 33,1,1  ** surface u wind [m/s]
> VGRDsfc  0 34,1,1  ** surface v wind [m/s]
> WDIRsfc  0 31,1,1  ** surface Wind direction [deg]
> WINDsfc  0 32,1,1  ** surface Wind speed [m/s]
> WVDIRsfc  0 101,1,1  ** surface Direction of wind waves [deg]
> WVPERsfc  0 103,1,1  ** surface Mean period of wind waves [s]
>
> ...and I can see that others have been able to show the primary wave
> direction (DIRPWsfc) using vector arrows, as is the case on the FNMOC models
> like this one:
> https://www.fnmoc.navy.mil/ww3_cgi/dynamic/ww3.w.npac.sig_wav_ht.000.gif
>
> Do you know how this can be done?
>
> Thanks,
>
> -Nathan
>
>
> On Tue, Nov 3, 2009 at 9:58 PM, sushant puranik <sushantpuranik at gmail.com>wrote:
>
>> Hi
>> I am able to generate wind direction. try his
>> 'set arrscl 1 30'
>> 'set cthick 5'
>> 'set arrowhead 0.10'
>> 'set clevs 3 5 10 15 20 25'
>> 'set ccols 0 4 1 2 3 5 12'
>> 'set gxout vector'
>> 'd
>> skip(UGRDsfc,2,2);skip(VGRDsfc,2,2);skip(sqrt(UGRDsfc*UGRDsfc+VGRDsfc*VGRDsfc),2,2)'
>> 'run cbar.gs'
>> 'printim wind(m/s)'
>>
>> with the help of such script i am able to generate output which is
>> attached with this mail.
>>
>> all the best.
>>
>>
>> On Tue, Nov 3, 2009 at 9:45 PM, Nathan Cool <nathan at nathancool.com>wrote:
>>
>>> Good morning everyone,
>>>
>>> I'm generating wave analysis models, but I'm having a tough time showing
>>> the mean-wave (or primary) wave direction arrows.
>>>
>>> The vars in the Grib are:
>>> -------------------------------------------------
>>> DIRPWsfc  0 107,1,1  ** surface Primary wave direction [deg]
>>> DIRSWsfc  0 109,1,1  ** surface Secondary wave direction [deg]
>>> HTSGWsfc  0 100,1,1  ** surface Sig height of wind waves and swell [m]
>>> PERPWsfc  0 108,1,1  ** surface Primary wave mean period [s]
>>> PERSWsfc  0 110,1,1  ** surface Secondary wave mean period [s]
>>> UGRDsfc  0 33,1,1  ** surface u wind [m/s]
>>> VGRDsfc  0 34,1,1  ** surface v wind [m/s]
>>> WDIRsfc  0 31,1,1  ** surface Wind direction [deg]
>>> WINDsfc  0 32,1,1  ** surface Wind speed [m/s]
>>> WVDIRsfc  0 101,1,1  ** surface Direction of wind waves [deg]
>>> WVPERsfc  0 103,1,1  ** surface Mean period of wind waves [s]
>>>
>>> For displaying wind vector arrows it's straightforward as there are U and
>>> V variables (UGRDsfc and VGRDsfc) for the zonal and meridional components.
>>> Displaying primary wave direction though seems more elusive, yet I see it
>>> done on many models such as the following:
>>> https://www.fnmoc.navy.mil/ww3_cgi/dynamic/ww3.w.npac.sig_wav_ht.000.gif
>>>
>>> ...which was generated using GrADS by FNMOC.
>>>
>>> Any help you can provide would be greatly appreciated, and thank you for
>>> your time.
>>>
>>> --
>>> Nathan Cool
>>> nathan at nathancool.com
>>>
>>
>>
>>
>> --
>> Sushant Puranik
>> Junior Research Fellow
>> Dept. of Atmospheric & Space Sciences,
>> University of Pune,
>> Pune-07,
>> India.
>>
>
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://gradsusr.org/pipermail/gradsusr/attachments/20091104/89958daf/attachment.html