An Ensemble Mean and Evaluation of Third Generation Global Climate Reanalysis Models

Jeffrey Auger,Keah Schuenemann,Paul Mayewski,Sean Birkel,Kirk Maasch

doi:10.3390/atmos9060236

Abstract

We have produced a global ensemble mean of the four third-generation climate reanalysis models for the years 1981–2010. The reanalysis system models used in this study are National Centers for Environmental Prediction (NCEP) Climate Forecast System Reanalysis (CFSR), European Centre for Medium-Range Weather Forecasts (ECMWF) Reanalysis Interim (ERA-I), Japan Meteorological Agency (JMA) 55-year Reanalysis (JRA-55), and National Aeronautics and Space Administration (NASA) Modern-Era Retrospective Analysis for Research and Applications (MERRA). Two gridded datasets are used as a baseline, for temperature the Global Historical Climatology Network (GHCN), and for precipitation the Global Precipitation Climatology Centre (GPCC). The reanalysis ensemble mean is used here as a comparison tool of the four reanalysis members. Meteorological fields investigated within the reanalysis models include 2-m air temperature, precipitation, and 500-hPa geopotential heights. Comparing the individual reanalysis models to the ensemble mean, we find that each perform similarly over large domains but exhibit significant differences over particular regions.

Highlights

Reanalysis models are numerical frameworks from which gridded solutions for past atmospheric states are obtained from the assimilation of historical meteorological observations
Interannual variability correlations for T2m are strong on the global mean, we find significant differences in T2m between the reanalyses over many arid regions
For the T2m (Figure 1) baseline we show each reanalysis and the ensemble mean subtract Global Historical Climatology Network (GHCN)

Summary

Introduction

Reanalysis models are numerical frameworks from which gridded solutions for past atmospheric states are obtained from the assimilation of historical meteorological observations The first such model National Center for Environmental Prediction and National Center for Atmospheric Research (NCEP, NCAR, respectively) Reanalysis (R1) [1] provides meteorological outputs on a global domain, over the period of 1948–present, on a coarse 2.5◦ × 2.5◦ horizontal grid. A third generation of global reanalysis models made significant advances in data assimilation and internal physics, computed at resolutions finer than 1◦ × 1◦ These models are NCEP Climate Forecast System Reanalysis (CFSR) [4], ECMWF Reanalysis Interim (ERA-I) [5], JMA 55-year Reanalysis (JRA-55) [6], and NASA Modern-Era Retrospective Analysis for Research and Applications (MERRA) [7]. Since the beginning of this analysis, a new version of National Aeronautics and Space Administration (NASA) MERRA has been released, MERRA-2 [8]

Methods

Results

Conclusion