Reliable ETA80 Grib data containing dewpoint data

[Daniel Leins]

Matt,

This file works, however it seems to be much like the others.  While it
has dewpoint data included, it's only at 6 levels.  Do any of those nam
files contain dewpoint data for every level?  RH is there for each
level, but not dewpoint.  Like I said before, if it's not possible to
find such data, can I derive dewpoint at every level?  And if I can, how
accurate is it?

Dan

Matt Alonso wrote:

> Hey Dan,
>
> I use the NAM 212 (nam.t**z.awip3d**.tm00) from the NCEP ftp site and
> it has relative humidity on all of the layers in the data file.  Give
> those a try.  Let me know how this works out for you.
>
> Regards,
> Matt



Daniel Leins wrote:

> List,
>
> I'm attempting to download and plot eta80km model data in skew-t and
> plan view format.  I don't have any problems getting the data or
> plotting what I want to, however I've noticed that the grib files
> don't contain dewpoint data for all the levels available, or
> sometimes, the grib file doesn't contain dewpoint data at all.  I've
> been downloading from ftpprd.ncep.noaa.gov, and pulling in the
> nam.tXXz.awp211ZZ.tm00 files (the eta80km), but this doesn't contain
> dewpoint data.  Or, when I download the grbgrd##.tm00, which I think
> is the eta40km, it contains dewpoint data, but only at 6 levels.
> Likewise, when I move away from downloading entire data sets, and
> "'sdfopen
> http://nomads.ncdc.noaa.gov:9090/dods/NCDC_NOAAPort_ETA/200504/20050414/meso-eta_212_20050414_1200_fff'",
> no dewpoint data exists here either.
>
> Does anyone know of a location where I can either download a full set
> of grib data, one that contains as much dewpoint data at as many
> levels as possible, or might anyone know of a dods server where I can
> get this information?
>
> I had another thought, since RH and temperature are available at every
> level.  Would it be possible to derive dewpoint at every level using
> an extremely re-arranged form or RH=100*(e/es).  Does anyone have an
> equation spelled out in Grads that would solve for Td in this
> equation?  Is this even a reliable method though, does vapor pressure
> vary with height?
>
> Any help would be appreciated,
>
> Thanks,
> Dan Leins
>