[5-1] Invited

The 20th Century Reanalysis Version 3 Ensemble Data Assimilation System

Jeffrey S. Whitaker (NOAA/ESRL) and Gilbert Compo (University of Colorado/CIRES)

The Twentieth Century Reanalysis version 2 dataset is a comprehensive global atmospheric circulation dataset spanning 1871-2012, using only surface pressure observations and monthly Hadley Centre SST and sea ice distributions (HadISST1.1) as input. The upcoming version 3 dataset improves upon version 2 by using an updated, higher resolution version of the NOAA/NCEP global forecast model, newly digitized surface pressure observations and improved data assimilation. In this talk I will describe improvements to the ensemble Kalman filter assimilation system, including an observation quality control procedure that accounts for non-gaussian observation errors, and an adaptive covariance localization scheme that calculates the localization radius based upon the predicted ensemble variance reduction in observation space. Experiments with the version 3 system show that produces 500 hPa height analyses that are 20-30% closer to the ERA-Interim reanalysis over the year 2000.