The analysis increment for the NCEP/DOE AMIP-II reanalysis is six hours, and output
data are routinely reported every hour or six hours. In order to satisfy the ISLSCP-II requirement
for 3-hourly data, twice daily 36 hour forecasts were made and hourly output were obtained from
the 24-36 hour forecasts. The 24-36 hour forecasts were chosen to minimize "spin-up/spindown"
problems. The one-hour data were later combined to produce 3-hourly data. Time
averaging was performed on the native reanalysis grid. For the 3-hourly and the monthly-3-
hourly data, the hour in the file name refers to the end of the 3-hour period. For example, 03Z
refers to the value at 03Z (for instantaneous data) or the average over the preceding period 00Z-
03Z (for the flux fields and snow cover fraction).