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How were the maps created?
This climatology is derived from reanalysis fields available from the National Centers for Environmental Prediction (NCEP) and the National Center for Atmospheric Research (NCAR). The NCEP/NCAR reanalysis is based on a wide range of observations of the atmosphere and short-range forecasts. It is a global data set with a spatial resolution of 2.5 latitude by 2.5 longitude and includes temperature and humidity (along with several other variables) at the needed pressure levels. Although the reanalysis fields extend back to 1948, only the period from 1961-2000 was used because a considerably larger number of observations, particularly satellite and aircraft observations, were included in the later period. The climatology is limited to 0000 UTC, and bounded by 10 o and 85N latitude and by 60 and 145W longitude.
Haines originally divided the lower 48 United States along climatological divisions into three regions (low, mid, and high) according to general surface elevation. This climatology extended those boundaries into Canada and Mexico, by first overlaying the Haines boundaries for the United States onto the generalized terrain field for the NCEP/NCAR reanalysis. This revealed that the 300 and 1000 meter elevation contours coincide best with Haines’ original boundaries between the low and mid regions and between the mid and high regions, respectively. These contours define the regional boundaries for Canada and Mexico on the maps in this climatology. |
Single Map
