Documentation of NJ average temperatures
Bill Sacks
November 29, 2011
I obtained monthly averages of the NARR reanalysis from
ftp://nomads.ncdc.noaa.gov/NARR_monthly, for the years 1979 - 2010.
I then created weighted averages over NJ, using the following weighting map:
These weights are not exactly right, and should probably be created more rigorously if, say,
these analyses will be used for publication. However, this was a close approximation of the
correct weights, which I was able to generate using a political map that I had readily available.
The purpose of these weights is to give partial weights (between 0 and 1) to grid cells that fall
partly inside and partly outside of NJ.
I computed weighted averages of three temperature fields (here I give their names in the excel
spreadsheet):
 temp_2m: Temperature 2m above the ground. This is probably the variable that
corresponds most closely to direct temperature measurements, as would be reported
by the state climatology office, for example.
 temp_lev1: Temperature of the lowest atmospheric level (this is probably somewhere
around 30m above the ground, though I have not been able to determine this height
definitively)
 temp_sfc: Temperature of the ground surface; I believe that this corresponds to the
temperature of the soil / pavement / water / etc. (sometimes referred to as the "skin
temperature"), though I have been unable to confirm that definitively
For convenience, I also copied monthly data from the NJ state climatology office
(http://climate.rutgers.edu/stateclim_v1/data/njhisttemp.html) into the same spreadsheet. I also
report the difference between the 2m temperature field that I calculated from NARR and these
data from the state climatology office.
Here is a summary of the differences (in degrees C):
Min. 1st Qu. Median
Mean 3rd Qu.
-1.7380 -0.6441 -0.2576 -0.2519 0.1036
Max.
5.2440
Positive values indicate higher temperatures in my analysis compared to the state climatology's
office. The max value of 5.244 is a single outlier (Sept. 1992); removing this outlier, the max
difference is 0.916 deg C.
So, while there are some differences between the two sources, they are generally less than 1 - 2
degrees C.