An Overview of Reanalysis-2
Masao Kanamitsu, Wesley Ebisuzaki
Climate Prediction Center, NCEP
Environmental Modeling Center, NCEP
Jerry Potter, Michael Fiorino
PCMDI, Lawrence Livermore National Laboratory
Attempt to correct known errors
in the NCEP/NCAR reanalysis.
Monthly average data available on:
Computational resource was
for Climate Model Diagnosis and Intercomparison) at Lawrence Livermore
Computations were done at the DOE's National Energy Research
Supercomputing Center (NERSC)
Based on NCEP/NCAR Reanalysis
system with portabilityexpanded.
Very small effort.
Production and monitoring by 2.5 person. Less
than 1 hour total per day spent.
Model resolution, data and period:
Same resolution as N/N Reanalysis:
Same raw observed data
Same dependence of satellite
Global 1979-1999 for the
first phase. Plan exits to go back to 1950's.
New system components:
Fix S. H. PAOBs problem (79-92)
Fix snow cover analysis error
Removed spectral snow problem
Fixed oceanic albedo (entire
Fixed discontinuities in radiation
fluxes at date line due to cloud tuning (entire period)
Improvements to the model:
Simple rainfall assimilation for soil wetness
Improved fixed fields:
New boundary layer (non-local
scheme by Hong and Pan)
New short wave radiation
Updated convective parameterization
Fix "cloud top cooling" in radiation
Updated cloud parameterization
and RH-cloud relationship
Run radiation code more
frequently (1 hr vs 3 hrs)
Run radiation code on full
Nudging of deep layer soil
Improvement to the diagnostics:
Improved desert albedo (Briegleb 1982)
Improved sea-ice SST fields (AMIP-II, Mike Fiorino)
New ozone climatology
Observed snow mask interpolation to daily
CO2(350ppmv) AMIP-II constants
Archive and Distribution:
Fixed snow/water budget diagnostics
Fixed snow melt term
Better cloud diagnostics field
Data kept in the NERSC mass storage
and no CD-ROMs (time
Distribute analysis through internet
NCAR will distribute the
analysis in future
Updated Reanalysis for
the satellite era.
errors in N/N Reanalysis
Some improvements in the
Demonstrated that the systemcan
be ported to other sites.
Some diagnostics has been done outside.
About 1000 download, 2.5GB transfer
per month from ftp site.
Soil wetness, especially
the interannual variations better
Winter time precipitation,
temp and fluxes
in high latitudes better.
Tropical precipitation looks
better (still with some problems)
Oceanic albedo more reasonable
Short wave radiation fluxes
Snow cover and surface
temperature are better
Major differences between R-1 and R-2:
R-2 overestimates OLR over
pool (poster by S-K Yang)
Equatorial upper level moisture
R-2 much drier (over convection area)
Long term spin-down of soil
wetness in polar latitudes.
Other minor but notable differences:
Soil temperature and 2m temperature.
tend to be warmer.
Precipitable water in the
tropics. R-2 larger.
Cloud amount R-2
surface downward shortwave flux
over equatorial ocean.
Some difference of height
and temperature in the N.H. oceans
Stratospheric temperature difference.
circulation. Lower in R-2.
jet located slight to the north.
divergent winds different.
Reanalysis and Reanalysis-2
Two analyses should go
together. They have same resolution, similar output, and files making
of two analyses provide important information on the sensitivity
the analysis to change in analysis systems.
It also provides some measure of the analysis error.
should be used by user affected by
errors in the N/N Reanalysis.
Analysis of transients
(particularly case studies) in S. H. mid-high latitudes
Use of near
surface temperature and snow cover over the N. H. continents in
will provide more accurate
wetness and near
budgetin polar regions
may not be better than
N/N Reanalysis in some fields.
should not be regarded as a next generation N/N Reanalysis
difference maps between R1, R2 (and ERA40).
Albedo over ocean : Error fix in radiation
Note that R1 has unrealistic albedo
over south America : Effect of smoothed orography in R2.
Note that R1 preciptation is noisy over Amazon basin.
Albedo over Africa : Improved desert albedo
Note that R2 has higher albedo over Sahara desert.
Land area averaged 2 m temperature
(30N-60N) : Effect of corrected snow cover analysis.
Note the peak difference in fall seasons.
Soil moisture comparisons : Effect of using observed pentad precipitation
Note much larger interannual variability in R2
5.1 Soil moisture over North America
Dry condition in some of the years may not be accurate due
to possible problems in observed pentad precipitation.
5.2 Soil moisture over Africa
5.3 Soil moisture over South America
5.4 Soil moisture over Eurasia polar
Note the very slow spin down in soil wetness over this region
at 100 hPa at the equator : Difference due to parameterization
Note that difference between R1 and R2 is much smaller than
the difference between R1, R2 and ERA. This may be
due to difference in model as well as to the way satellite data was used
(NESDIS retrieval for R1, R2 and 1-D variational
analysis for ERA).