Changes Made to DSS's ECMWF Supplemental Data Archive (DS111.3)

On September 11, 2000 ECMWF changed the manner in which this data is archived. Previously, the archive consisted of 6 hour forecast fields from the 00,06, 12 and 18 hour model runs. The model run times and valid times of the data were :
Model Run TimeP1Valid Time of Data
00Z606Z
06Z612Z
12Z618Z
18Z600Z next day

model run time = Initialization time of the model
P1 = GRIB Period of Time field, which you add to the model run time to get the valid time
valid time of data= Actual time the field is valid for


Starting on September 12, 2000 the model run times and valid times changed to :
Model Run TimeP1Valid Time of Data
00Z606Z
00Z1212Z
12Z0618Z
12Z1200Z next day


So the output has changed from daily 4x a day 6 hourly forecast fields from the 00z,06z,12z and 18z model runs to daily 4x a day 6 and 12 hourly forecast fields based on only the 00Z and 12Z model runs. As noted in the table, you have to look at the GRIB reference time (the hour of the model run ) and the Period of Time (P1) to decode the time period for the grid. You only have to add the P1 parameter to the reference time to obtain the valid hour for the field. For more information on the GRIB format, please see our GRIB web page and more specifically the Prodict Definitions Section of the GRIB web page.

ECMWF also changed the manner in which they archive the data. Prior to the Sept 12, 2000 change, ECMWF used the date of the valid time of the fields to archive the data. Starting September 12, 2000 they now use the actual analysis time. This only affects the first and last time period of each file.

Please contact Joey Comeaux if you have any questions