[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

19991115: quick hght ?

Matt,

hght will be in geopotential meters. That is, it is the
height above mean sea level of the sigma surface.

You should be able to calculate height above the sgma=1.0
level of any sgma surface, .8 sgma for example, with 

gvcord = sgma
glevel = 8000
gfunc = sub(hght,hght@0)

Steve Chiswell
Unidata User Support


>From: Matt Fearon <address@hidden>
>Organization: Desert Research Institute
>Keywords: 199911240149.SAA22167

>Steve,
>
>Sorry to be so repetitive with this question. I understand the
>calculation of sigma that it uses pres/pres@0, but the heights
>I attain from a supposed height of sigma level do not make
>sense to me. It seems that the hght@8000%sgma is not height
>of the sigma level above ground ? It appears to be geopotential
>height or height - I am not sure. When comparing hght@0%none
>to hght@9950%sgma over high terrain in the western US, the hght
>given at the sigma level is just barely greater than the hght@0%none.
>This does not make sense to me if hght@9950%sgma is height above
>ground. It seems to be correct though if hght@9950%sgma is height
>above sea level. For example, if
>
>hght@0%none is 1600 meters  hght@9950%sgma is ~1600 meters
>as well ?
>
>Again sorry to be repetitive and I hope I am not be bothersome,but
>there is something (that seems to be obvious) that I am missing.
>
>Please reply at your convenience. Thank you again in advance for all
>your help,
>
>-Matt Fearon
>address@hidden
>
>
>
>
>Unidata Support wrote:
>
>> Matt,
>>
>> hght@8000%sgma is height at the .80 sigma level.
>>
>> Sigma is defined as PRES / PSFC. Eg, .8 sigma is the
>> height at which the pressure of a point divided by the
>> surface pressure at the point is .80.
>>
>> Steve Chiswell
>>
>> >From: Matt Fearon <address@hidden>
>> >Organization: Desert Research Institute
>> >Keywords: 199911152257.PAA00309
>>
>> >Steve,
>> >
>> >hght@0%none is elevation of the grid point.
>> >
>> >hght@8000%sgma, would that be the height above
>> >ground or would it be the height above mean sea level;
>> >meaning to get the height above ground the following
>> >calculation would have to be performed:
>> >
>> >hght (agl) = hght@8000%sgma - hght@0%none ?
>> >
>> >Your advice would be greatly appreciated.
>> >Thank you,
>> >
>> >Matt Fearon
>> >address@hidden
>> >
>> >
>> >
>> >
>>
>> ****************************************************************************
>> Unidata User Support                                    UCAR Unidata Program
>> (303)497-8644                                                  P.O. Box 3000
>> address@hidden                                   Boulder, CO 80307
>> ----------------------------------------------------------------------------
>> Unidata WWW Service                        http://www.unidata.ucar.edu/     
>> ****************************************************************************
>