An assessment of the surface climate in CFSR Wanqiu Wang, Pingping Xie, and Soo-Hyun Yoo Climate Prediction Center, NCEP/NOAA, Camp Springs, MD-20746

1
An Examination of the Radiative Fluxes in Various
Reanalyses with an Emphasis on the Global
Budget Wesley Ebisuzaki1, S. K. Yang 1,2, Li
Zhang1,2, Arun Kumar1 1NOAA Climate Prediction
Center, Camp Springs, Maryland 2Wyle Science
Technology and Engineering, McLean, Virginia
OSR climatologies
Introduction
Most of the reanalysis projects are based on the
forecast models and data assimilation systems
used in the numerical forecasting of weather. In
the data assimilation, there are no constraints
on the annual global energy balance at the top of
the atmosphere. However, if there were a net
imbalance in the energy budget, the observations
or the lower boundary condition would have to
adding or removing the thermal energy. This
study will show the top-of-atmosphere radiative
fluxes from various reanalyses CFSR,
ERA-interim, JRA-25, MERRA, NCEP/NCAR Reanalysis
(R1) and NCEP/DOE Reanalysis (R2). For these
reanalyses, the global outgoing long-wave
radiation (OLR) ranges from 237 W/m/m (R1) to 255
W/m/m (JRA-25). Most of the reanalyses have more
OLR than the 239 W/m/m that was estimated by
Trenberth et al (BAMS, 2001). The outgoing
short-wave radiation flux (OSR) at the top of the
atmosphere was estimated to be 109 W/m/m by
Trenberth et al. and was within the range of the
various reanalyses estimates (94 W/m/m of JRA-25
to 117 W/m/m of R1). The net global imbalance
ranged from -6 W/m/m to 13 W/m/m.

• Data Monthly mean data converted to a 192x94
  Gaussian grid. The reanalyses used
• CFSR Reanalysis from Climate Forecast System
  version 2 (Saha et al. 2010)
• ERA-Interim Reanalysis from ECMWF (Dee et al.
  2011)
• JRA Japanese 25-year Reanalysis Project (Onogi
  2007)
• MERRA Reanalysis (Rienecker et al 2009)
• R1 NCEP/NCAR reanalysis (Kalnay et al 1996)
• R2 NCEP/DOE reanalysis (Kanamitsu et al. 2002)
• The climatologies were calculated from 1979-2008.

OLR climatologies
Global 12-month running mean OLR. Consistent
results except for R1 and JRA-25. Other
reanlayses range between 242 and 246 W/m/m. No
secular trends.
Global 12-month running mean of net radiative
flux. (Upwards is positive). ERA-interim is
within 3 W/m/m of radiative balance. CFSR and
MERRA are close to be being balanced but show
secular trends.
Global 12-month running mean OSR. R1 is an
outlier, larger range for other reanalyses. Drop
in CFSR recent years. More trends than in OLR
time series.
The uncertainty in the January OLR is situated
over subtropical belt and in particular South
America. Outside of the sub-tropics, the spread
is small, about 10 W/m/m. The ERA-interim and
CFSR climatologies are in agreement with
themselves and the ensemble mean. Both of these
reanalyses are within 5 W/m/m over much of the
globe. MERRA was in more disagree-ment with the
newer reanalyses especially in the extratropics.
Summary
The uncertainty in the July OLR shifted north and
with peak uncertainty in the Caribbean. The
CFSR and ERA-interim are again in close agreement
with each other and the ensemble mean. The MERRA
shows much more convention over the Caribbean
and the Northern Indian ocean and subtropical
Western Pacific. The agreement in the OLR
climatologies between the newer reanalyses is
sign that the con-vective clouds are more
con-sistent that in the older models.
One expects that the models used by the
reanalyses to improve. Signs of improvement are
the reanalyses becoming consistent and the
systems becoming more in balance. We examined
the OLR and OSR and found that the newwer
reanalyses are producing more consistent OLR (4
W/m/m with the new systems). However, the OSR is
a different story. The OSR estimates show a
larger variability than the OLR and the new
reanalyses dont show a strong evidence of
converging. The global incoming radiation must
be balanced by the outgoing radiation and the
heat storage term. Averaging over one or more
years should reduce the size of storage term and
one would expect a near balance of the incoming
and outgoing radiation. The ERA-interim has an
imbalance of 3 W/m/m. MERRA has an imbalance of
4 W/m/m in the early period and approaches zero
in the later period. The CFSR has an imbalance
of 2 W/m/m until something happens (around 2010).