[NARCCAP-discuss] Questions on data for our project.

[Seth McGinnis]

Hi Ping,

All the NARCCAP data is 3-hourly, so if you want daily and monthly averages,
you'll have to do the averaging yourself.  The only exceptions are the four
variables in Table 1, which are inherently daily values.  (We do have plans to
make a number of monthly and seasonal averages and climatologies available, but
they're not ready yet.)

If you're an NCL user, I wrote a script ("aggregate.ncl") for creating various
time-averages that you may find useful.  You can find it here:
http://narccap.ucar.edu/contrib/tools/ncl/  It's also pretty easy to create
those time-averages using the NCO command "ncrcat" and the multislab feature.
 (Especially if you have NCO installed with udunits support, and can use date
ranges for subsetting the time coordinate -- see my post to the narccap-discuss
mailing list of about a week ago for more details.)

To get the variables that you list, you'll need either to change units or
calculate them from other variables, depending. The published data includes:

* tas = surface air temperature in degK
* pr = precipitation in flux units (kg/m^2/s)
* ps = surface air pressure (in Pa)
* clt = cloud cover (fraction from 0 to 1 -- look in Table 3 for this one)

I wrote a couple shellscripts that use NCO commands to change units for
temperature and precipitation.  You can find them here:
http://narccap.ucar.edu/contrib/tools/util/  The "tas2temp" script converts
degK to degC, and "pr2prec" converts precip from kg/m^2/s to mm/day.  The
commands to convert ps files from Pa to mbar would be entirely analogous.

Relative humidity can be calculated from specific humidity, temperature, and
pressure (variables huss, tas, and ps).  There's an NCL script
("calc_humid.ncl", which also calculates dewpoint) in that contrib/tools/ncl
directory on the website.

I haven't had cause to calculate wet bulb temperatures yet, so I can't offer
any tools to help with that yet, sorry.

Cheers,

--Seth


On Sun, 11 Mar 2012 11:19:00 -0600
 ping yang <pingyang.whu at gmail.com> wrote:
>Dear NARCCAP users,
>
>I need data for the following items with daily step and monthly step:
>
>•Precipitation –Units (mm)
>
>•Surface Air temperature –Units (°C)
>
>•Surface Air pressure –Units (mbars)
>
>•Humidity (relative )
>
>•Wet bulb temperature –Units (°C)
>
>•Cloud Cover
>
>I looked into the NARCCAP data tables, actually there are so much
>information that I am a little confusing,  e.g., I found the Max/Min
>Surface air temperature data in daily but the instantaneous surface
>air temperature data in 3 hours, and some data like Wet bulb
>temperature I don't know how it was classified or named in the NARCCAP
>dataset.  Is here someone has the same experiences who can give me
>some instructiona on how to get those data or some suggestion on how
>to process the available data?
>
>All the Best,
>
>Ping
>--
>Ping Yang, Ph.D.
>Postdoctoral Research Associate
>CUNY Environmental Crossroads Initiative
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