Middle-latitude climates - The Global Climate System: Patterns, Processes, and Teleconnections - page 102

series (1946-96) (Schoof and Pryor 2003 ); global tropospheric temperatures
derived from satellite microwave sounding units and global surface air
temperatures (1979-90) (Sturaro 2003 ).
The second United States reanalysis project developed from the NASA/
DAO assimilated data set 1985-9, mentioned above, when it was expanded
to provide a 17-year reanalysis covering the period 1979-97. It was design-
ated as the NCEP/DOE (Department of Energy) AMIP-II Reanalysis or
Reanalysis 2 (note that by 2004 the organization had been renamed GMAO
or the Global Modeling and Assimilation Office of the Goddard Space Flight
Center). AMIP (Atmospheric Model Intercomparison Project) was inaugu-
rated in 1990 and is part of the World Climate Research Programme (see
www-pcmdi.llnl.gov/projects/amip) with offices at Lawrence Livermore
National Laboratory, California, USA. Reanalysis 2 has improved para-
meterizations of the physical properties and also fixed the errors discovered
in the original assimilation data set. It has been running in real-time since
2001 and now covers the period from 1979 to present. Details may be found
on wesley.wwb.noaa.gov/reanalysis2/index.html.
In February 1993 the European Centre for Medium-Range Weather
Forecasts (ECMWF) began a 15-year reanalysis programme (ERA-15) to
produce an assimilated data set for the period 1979-93. This project used its
own archive of observations received from the WMO, COADS, the Hadley
Centre (UK) sea ice and sea surface temperature (SST) data set as well as
the NCEP SST analyses, data from the First GARP (Global Atmospheric
Research Program) Global Experiment (FGGE) of 1978-9, the Alpine
Experiment (ALPEX) of 1982, Japanese and Australian data, TOGA
(Tropical Ocean Global Atmosphere) data, and the vertical sounder data
from the TIROS satellites. ECMWF had its own data assimilation system
and the project was completed in September 1996 (see www.ecmwf.int/
research/era/ERA-15/Project/). Although this was a useful experiment, the
documentation acknowledges that the reanalysis contained some problems
particularly with respect to changes in the amount and coverage of the
radiosonde data. In 2000 a new reanalysis was begun by ECMWF known
as ERA-40 to cover the period 1957-2001. This was completed in 2003. It
used the same data sources as ERA-15 but with the addition of a variety of
satellite radiances (from 1972 onwards), cloud photographs and cloud motion
winds, particularly those of the European Meteosat geostationary satellite
from 1982-8. The output is 6-hourly analyses on a grid with spacing of
about 125 km in the horizontal and with 60 levels in the vertical between
the surface and 65 km. (Simmons and Gibson 2000 ). The current availability
of ERA-40 analyses can be checked online at www.ecmwf.int/research/era/
Data_Services/section1.html. During the process of validation some defi-
ciencies in the reanalyses have been found so there was a rerun covering