[thredds] Question about NARR-A Monthly Complete PoR Aggregation NetcdfSubset

Dear THREDDS user group,

I?m unsure whether or not this is the right place to send these questions.
If not, I?d love some advice on who to direct them to.

I?ve been getting North American Regional Reanalysis (NARR) data from
http://nomads.ncdc.noaa.gov/thredds/narr.html using the netCDFSubset tool.
I am running some analysis on these netCDF files with focus on
Precipitation, Evaporation, Runoff, Vegetation and Surface Air Temperature.
I have therefore downloaded the following variables:

·         Evaporation (time, y, x)

·         Subsurface_runoff_baseflow (time, y, x) 

·         Surface_runoff_non-infiltrating (time, y, x) 

·         Total_precipitation (time, y, x)

·         Vegetation  (time1, y, x)

·         Temperature_height_above_ground (time1, height_above_ground, y, x)

 

I?m interested in a 20-year average of these fields (from 1980-01-01-0000 to
2000-12-31-2100) so I figured I?d use the ?NARR-A Monthly Complete PoR
Aggregation? and download monthly averages in one unique file which I?d then
use to compute a 20-year average.  The process ran fine but I?m curious
about the netCDF file that I was able to download.  The first four variables
(Evaporation, Subsurface_runoff_baseflow, Surface_runoff_non-infiltrating
and Total_precipitation) indeed have several monthly grids.  However the
last two variables (Vegetation and Temperature_height_above_ground) only
have one unique grid each.  

 

So I downloaded several 3-hourly NARR-A files from the NetcdfSubset tool
that I picked randomly from the entire dataset:

·         narr-a_221_19790101_0000_000.grb.nc 

·         narr-a_221_19800101_0000_000.grb.nc

·         narr-a_221_20001231_2100_000.grb.nc

·         narr-a_221_20100101_0000_000.grb.nc

·         narr-a_221_20111031_2100_000.grb.nc

 

I realized that the Vegetation variable had the same exact grid for all
these files.  So it makes sense to only have one grid in the aggregation.
However, the Temperature_height_above_ground grid varies with time.

 

So here are my two questions:

1)      Is the NARR Vegetation variable static?

2)      How is the Temperature_height_above_ground grid in the NARR-A
Monthly Complete PoR Aggregation computed?

 

Any help and advice would be greatly appreciated!!!

Many thanks,

Cedric