[Wrf-users] Confused about model height

[sparling at umbc.edu]

Oops - you're right!  I process the wrfout* files myself, so was in native
vertical coordinate mode. Sorry, John!  -  Lynn

> Hello Lynn,
>
> The lowest model level is a surface of constant sigma (native hybrid
> terrain-following vertical coordinate) so near the ground, the height of
> model level surfaces will follow the surface topography. However, John was
> referring to the geopotential height on constant pressure surfaces, not on
> native model coordinate surfaces. The raw WRF history files (wrfout*)
> contain fields on native model coordinate surfaces, which is probably what
> you are looking at. But ARWpost vertically interpolates the WRF history
> output to constant pressure surfaces.
>
> Best regards,
>
> Eric L. Altshuler
> Assistant Research Scientist
> Center for Ocean-Land-Atmosphere Studies
> 4041 Powder Mill Road, Suite 302
> Calverton, MD 20705-3106
> USA
>
> E-mail: ela at cola.iges.org
> Phone: (301) 902-1257
> Fax: (301) 595-9793
>
> ----- Original Message -----
> From: sparling at umbc.edu
> To: "Eric Altshuler" <ela at cola.iges.org>
> Cc: "John Krasting" <krasting at envsci.rutgers.edu>, wrf-users at ucar.edu
> Sent: Tuesday, March 10, 2009 10:54:01 PM GMT -05:00 US/Canada Eastern
> Subject: Re: [Wrf-users] Confused about model height
>
> Also,if you do a line plot of elevation vs lat (or lon) and overplot the
> geopotential height of the lowest model level and you can see that it
> follows the topography.
> Cheers,
>
> Lynn
>
>> Hello John,
>>
>> Geopotential heights are always given as height above sea level (I think
>> the definition is more rigorous than this, but the effects of the
>> non-spherical earth and non-uniform gravitiational fields are
>> second-order
>> effects). Otherwise, if height fields were computed as the height above
>> the ground level, height fields would be distorted by the pattern of
>> surface topography, and could not be used for calculating geostrophic
>> winds, for example.
>>
>> Best regards,
>>
>> Eric L. Altshuler
>> Assistant Research Scientist
>> Center for Ocean-Land-Atmosphere Studies
>> 4041 Powder Mill Road, Suite 302
>> Calverton, MD 20705-3106
>> USA
>>
>> E-mail: ela at cola.iges.org
>> Phone: (301) 902-1257
>> Fax: (301) 595-9793
>>
>> ----- Original Message -----
>> From: "John Krasting" <krasting at envsci.rutgers.edu>
>> To: wrf-users at ucar.edu, "WRF Help" <wrfhelp at ucar.edu>
>> Sent: Tuesday, March 10, 2009 3:01:14 PM GMT -05:00 US/Canada Eastern
>> Subject: [Wrf-users] Confused about model height
>>
>> Hi Users -
>>
>> Just want to confirm exactly how height is calculated using ARWpost.
>>
>> Is this the height above ground level or above sea level?  I'm
>> assuming that since WRF is using a terrain-following hydrostatic
>> coordinate, that these values are above ground level.
>>
>>
>> Thanks,
>> John
>>
>> -----------------------------
>>
>> more module_calc_height.f90
>> !! Diagnostics: Height
>>
>> MODULE module_calc_height
>>
>>   CONTAINS
>>   SUBROUTINE calc_height(SCR, cname, cdesc, cunits)
>>
>>   USE constants_module
>>   USE module_model_basics
>>
>>   !Arguments
>>   real, pointer, dimension(:,:,:)       :: SCR
>>   character (len=128)                   :: cname, cdesc, cunits
>>
>>
>>   SCR      = ( (PH+PHB) / G ) / 1000.
>>   cname    = "height"
>>   cdesc    = "Model height"
>>   cunits   = "KM"
>>
>>   END SUBROUTINE calc_height
>>
>> END MODULE module_calc_height
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>>
>
>
>
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> Lynn Sparling			sparling at umbc.edu
> Associate Professor		PH:   410-455-6231
> Department of Physics		FAX: 410-455-1072
> University of Maryland, Baltimore County
> 1000 Hilltop Circle
> Baltimore, MD 21250
>
> "One can measure to test the ruler." -Wittgenstein
>
>
>



^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Lynn Sparling			sparling at umbc.edu
Associate Professor		PH:   410-455-6231
Department of Physics		FAX: 410-455-1072
University of Maryland, Baltimore County
1000 Hilltop Circle
Baltimore, MD 21250

"One can measure to test the ruler." -Wittgenstein