Satellite-Based Ocean Surface Turbulent Fluxes - Satellite-based Applications on Climate Change - page 166

11.4.3 GSSTF
GSSTF is produced by NASA's Goddard Space Flight Center. The latest version 2c
or (GSSTF2c) was released in November 2011. In the prior version 2b (GSSTF2b),
Q a is derived from SSM/I V6 total columnar precipitable water and bottom-layer
precipitable water as described in Chou et al. ( 1995 , 1997 ). U is obtained from
SSM/I V6 retrievals. T a and SST are taken from NCEP/DOE reanalysis. Chou et al.
( 2003 ) bulk algorithm is used to calculate turbulent flux. The GSSFT2b turbulent
fluxes cover the time period from July 1987 to December 2008. Daily and monthly
data sets with 1 resolution are available via the anonymous FTP ( ftp://measures.
gsfc.nasa.gov/data/s4pa/GSSTF/ ) through the Goddard Earth Sciences Data and
Information Services Center (GES DISC). There are two sets of GSSTF2b data: sets
1 and 2 (Shie et al. 2010 ; Shie 2010 ). Set 1 was found to show a spurious increasing
global LHF, especially after 2000. Noting the large trends in set 1, set 2 is produced
by removing satellite products that have a relatively larger trend in LHF. The
satellites not included in set 2 are the DMSP F13 and F15 SSM/Is. Analyses of
LHF showed linear trends of 23.1 and 15% over the period 1987-2008, with the
surface sea-air humidity difference ( Q s Q a ) accounting for 20 and 12.3%, for set
1 and set 2, respectively, and wind change contributing to 3.1% for both sets (Chiu
et al. 2012 ). Hilburn and Shie ( 2011 ) noted a drift in the Earth incidence angle
(EIA), and a correction algorithm which incorporates the satellites' attitude has
been developed to account for the drift in EIA. The EIA is the angle between the
line of sight of the satellite sensor and the zenith at the Earth's surface. This
correction has been applied to the SSM/I brightness temperature ( T b ), and the latest
version, GSSTF2c (Shie et al. 2011 ;Shie 2011 ), is now available from the same
GES DISC anonymous FTP. The EIA corrected T b 's in GSSTF2c has reduced the
trends, especially in the latent heat flux (Shie and Hilburn 2011 ;Shie 2011 ).
11.4.4 Combined Approach
Surface turbulent fluxes can also be derived from global model results that are
constrained by surface and rawinsonde observations and satellite measurements.
Such products are called reanalyses, which include NCEP's older reanalysis
(NCEP/NCAR and NCEP/DOE) and the latest Climate Forecast System Reanal-
ysis (CFSR), ECMWF's 40-year reanalysis (ERA-40) and interim reanalysis
(ERA-Interim), JMA's Japanese 25-year ReAnalysis (JRA-25), and the most
recent NASA GMAO's Modern Era Retrospective Analysis for Research and
Applications (MERRA).
The Woods Hole Oceanographic Institution produced the Objectively Analyzed
Air-Sea Fluxes (OAFlux) by combining bulk variables derived from satellites and
those from reanalysis (Yu et al. 2008 ). Satellite inputs include U from SSM/I,
AMSR-E, and QuikSCAT; SST from NOAA OI analysis by Reynolds et al. ( 2007 );