Atmospheric Reanalyses Update Mike Bosilovich

ReanalysisHoriz.ResDatesVintageStatus NCEP/NCAR R1T present1995ongoing NCEP-DOE R2T present2001ongoing CFSR (NCEP)T382=0.5  1979-present2010thru 2009, ongoing 20CR (ESRL)22 Complete, in progress ERA-40T done ERA-InterimT present2009ongoing JRA-25T present2006ongoing JRA-55T In Preparation MERRA (NASA)0.5  1979-present2009thru 2009, ongoing Summary of the main atmospheric reanalyses that are current or underway, with the horizontal resolution (latitude; T159 is equivalent to about 0.8  ), the starting and ending dates, the approximate vintage of the model and analysis system, and current status.

Atmospheric Reanalyses Four new global reanalyses available recently – CFSR (NCEP), ERA Interim (ECMWF), 20CR (NOAA ESRL), MERRA (NASA) – JRA55 in preparation – Resolutions, systems and data QC improving Several Regional Reanalyses under development Issues: – Proliferation or unique contributions? – Direction and organization (save till 7.6)

NCEP Climate Forecasting System Reanalysis (CFSR) Resolution: T382 (~38Km, 64 levels to.26 hPa) Duration: 1979-present Objectives: Reforecasts, Climate for forecast statistics, Operational climate products Includes coupled ocean and land data assimilation WWW:

ECMWF ERA Interim Resolution: T255 Duration: 1989-present Objectives – A checkpoint to the next generation, weather statistics but also climate monitoring ERA-Interim compared to ERA-40 – 12 hour 4D-Var – Better formulation of background error constraint, New humidity analysis, Improved model physics – Data quality control that draws on experience from ERA-40 and JRA-25 – Variational bias correction of satellite radiance data, and other improvements in bias handling – More extensive use of radiances

NASA/GMAO – Modern Era Retrospective- analysis for Research and Applications (MERRA) Resolution: ½° lat × ⅔° lon, 72 levels (0.01 hPa) Duration: 1979-present Objectives: Improve on the representation of water and energy budgets; Put new and research satellite data into a climate context; provide the base for coupled analyses – Also designed to support Chemistry Transport Modeling community – Collaboration with NCEP on conventional observations and GSI Analysis, Haimberger sonde corrections, Intercalibrated MSU channels

NOAA/ESRL 20 th Century Reanalysis (20CR) Resolution T62 (28 levels, 56 Ens. Members) Duration: (Version 2) Objectives: Using ensemble spread and surface pressure assimilation, analyze climate over the 20 th century Uncertainty estimates for states and derived quantities

Proliferation: Variability among reanalyses Dynamics fields are generally consistent in the presence of observations at any time – However, even time variations of the Hadley and Walker circulations can differ (e.g. Chen et al. 2008) Physics fields are closely connected to model components of reanalyses (Kalnay et al 1996) Changes in the observing system affect the climate of a reanalysis (e.g. Onogi et al. 2007) Despite assimilating much the same observations, uncertainty among reanalyses persists

Regional Reanalyses Generally same principles as global with benefit from: – Higher spatial resolution, targeted physical processes, testing/development focuses on regional priorities – Rely on some global reanalysis for lateral boundary conditions NARR first and widely used (~32 Km) Japan regional reanalysis (JRA55, but also NCEP) Arctic Reanalysis (ARS) – into testing (30Km WRF), planning higher resolution, and integrated system; model development (e.g. NOAH land processes) EURO4M – High resolution, regional observations, climate and variability including extreme events Others in consideration for development for South America and South Asia

The Next Global Reanalyses: On the horizon for a 2012 Conference JRA55 – In Preparation, Significant model improvements, 4DVAR, VAR BC, resolution ERA 75- Starting in 1938, Production ~2013 GMAO – Phased Integrated Earth System Analyses - in testing, working from MERRA – Partial coupling of the ocean (aerosols and land/sea ice also progressing) 20CR – Higher resolution, possibly multi-model, uncertainty in forcings Redundancy may be an issue if progress slows and/or objectives and quality converge

Proliferation? CFS – NCEP Climate Forecast System GEOS – NASA Goddard Earth Observing System Courtesy Paul Dirmeyer