This shows our study basins, the 2° buffer used for
selecting weather stations, and the 5° used for selecting radiosonde stations.
The rectangle indicates the size of the data grids being passed on the the VIC
model.
For January ,1997 through September, 2000, we downloaded the daily records from the
National Climatic Data Center
1254 stations fall within 2 degrees of our study area. The number of stations with
data on any given day is:
The initial phase of our processing is done in geographic coordinates.
This gives a bias to the weights of stations to the east or west of a point,
but the effect is small at these latitudes. Subsequent calculations involving
areas all use corrected values.
Max temperature, min temperature, wind, and precip, were extracted from the NCDC
ASCII files and placed in 1056 daily files. These files were converted to
ARC/INFO "coverage" format.
Quarter-degree grids of wind speed were created for each day by using an inverse-distance-weighted algorithm built into ARC/INFO. The algorithm averages all stations within 0.4 degrees of the grid center, but extending the search until at least 3 stations are found.
Precipitation grids were made in a similar manner, but with less confidence. We judged the NCDC GPCP (Gloabal Precipitation Climatology Project) one-degree rainfall to be superior to any product we could devise, so we created our grids only for comparison. ...
zcat 3B42.990101.5.HDF.Z | cutout 320 54 48 112 85414 4 90 > 990101 OR foreach month (01 02 03 04 05 06 07 08 09 10 11 12) foreach fil (3B42.??${month}*) zcat $fil | cutout 320 54 48 112 85414 4 90 > `echo $fil | cut -d '.' -f2` end endComparing 990101 to the NCDC 1dd data (after multiplying by 25.4), the mean difference is 0.22 mm, with a with abs(diff) of 3.33 mm, while all rainfall patterns are maintained.
Questions:
Harvey Greenberg