IEM Daily Feature
Wednesday, 13 January 2021

Changing Climatologies

Posted: 13 Jan 2021 05:34 AM

Every ten years, the National Centers for Environmental Information (NCEI) publishes an updated 30 year climatology. The update is scheduled to be released in May to include the 1991 through 2020 period, which will replace the present climatology covering the 1981 through 2010 period. The sausage making process for these climatologies is complex. The featured chart presents one aspect of this process, which is a comparison of average computed for Des Moines over the 1991-2020 period vs the NCEI 1981-2010 climatology. The right two panels present smoothed daily differences and monthly aggregates. The difference shown for December is interesting and would hint that an upward adjustment for the month within the new climatologies would be warranted.

Good = 14
Bad = 2