Atmospheric Reanalyses Update
Mike Bosilovich
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.
Reanalysis
Horiz.Res
Dates
Vintage
Status
NCEP/NCAR R1
T62
1948-present
1995
ongoing
NCEP-DOE R2
T62
1979-present
2001
ongoing
CFSR (NCEP)
T382=0.5 1979-present
2010
thru 2009, ongoing
20CR (ESRL)
2
1891-2008
2010
Complete, in progress
ERA-40
T159
1957-2002
2004
done
ERA-Interim
T255
1989-present
2009
ongoing
JRA-25
T106
1979-present
2006
ongoing
JRA-55
T319
1958-2012
2010+
In Preparation
1979-present
2009
thru 2009, ongoing
MERRA (NASA) 0.5
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: http://cfs.ncep.noaa.gov/cfsr/
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
• http://www.ecmwf.int/research/era/do/get/era-interim
NASA/GMAO – Modern Era Retrospectiveanalysis 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
• http://gmao.gsfc.nasa.gov/merra/
NOAA/ESRL 20th Century Reanalysis (20CR)
• Resolution T62 (28 levels, 56 Ens. Members)
• Duration: 1871-2008 (Version 2)
• Objectives: Using ensemble spread and surface
pressure assimilation, analyze climate over the
20th century
• Uncertainty estimates for states and derived
quantities
• http://www.esrl.noaa.gov/psd/data/20thC_Rean/
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