[Narccap-announce] Data updates: snow and HRM3-hadcm3 times

[Seth McGinnis]

Greetings NARCCAP Users,

We have recently published two major updates to the data on ESG.

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1) Snow variables 'snd' and 'snw' replaced with 'swe'

There was some confusion within the NARCCAP team about the meaning of
the snow variable (snd), and whether it was supposed to record the
depth of snowpack or the amount of water contained in the snow.  Some
modeling teams submitted snd in thickness units, and others submitted
it with units of kg/m^2 (in which case it was published as snw).

Upon further investigation we determined that, regardless of units,
ALL of the submitted snow data was recording the amount of water in
the snow, not the depth of snowpack.

To resolve this confusion and make the meaning of snow unambiguous, we
have retracted both snd and snw variables and in their place we have
published snow-water-equivalent as the variable swe, which is the
thickness of a uniform layer of water with the same water content as
the snowpack.

The lone exception to this change is the MM5I-ncep run, whose snd
variable contained depth of snowpack that could not be converted to
swe, and which has been left as-is.

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2) Fixed time coordinates in HRM3-hadcm3 2-D data

We found an error in the time coordinates of the originally published
HRM3-hadcm3 files.  There was a single timestep that was repeated
at midnight, January 1st, 1970, which threw off the file boundaries
for the rest of the simulation.  This problem affected only the
3-hourly 2-D data (so Tables 2 and 3), and was not totally consistent
from variable to variable.

To fix the problem, the Hadley Centre team reprocessed all the 2-D
data from the hadcm3-driven runs, and we have replaced all the
previously published data with the new data.  We have checked the data
in these files (that is, the contents of the data variable) and they
are identical from the old version to the new versions.

ONLY THE TIME COORDINATES AND SOME METADATA HAVE CHANGED IN THE NEW
FILES.  If you are not concerned with the timing of the diurnal cycle,
it is likely that this update will have no effect on you.

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Our apologies for any confusion.

Cheers,

--Seth