data. Ultimately we hope that the best climatologies will become available from model–data combinations using the WOCE and historical data
sets. Most of the WOCE data sets and expected
climatologies are described here: hydrographic,
upper ocean thermal, velocity and surface fluxes.
Hydrographic data
Hydrographic climatologies are being produced by
a number of different groups; the principal efforts
are described here. The most widely used climatologies are from the National Oceanographic and
Atmosphere Administration (NOAA) (Levitus,
1982; Levitus et al., 1994b), utilizing the global
pre-WOCE hydrographic data set with quality
control; the 1994 version includes monthly and
annual climatologies of temperature and salinity
on a 1° latitude by 1° longitude grid at 33 standard depths. It is now understood that averaging
along isopycnals/isoneutral surfaces is superior to
averaging at standard depths, as the latter results
in spurious climatological features in the neighbourhood of the strong isopycnal slopes that occur
at major fronts (e.g. Lozier et al., 1995). New climatologies employing evolving methods and the
ever-enlarging hydrographic data set will continue
to be produced at NOAA.
Climatologies of the South Atlantic (without
WOCE data) and South Pacific (with WOCE and
historical data) have been produced by the WOCE
Hydrographic Programme Special Analysis Center
(WHP SAC) in Hamburg (Gouretski and Jancke,
1995, 1996), with a preliminary version for the
world ocean. The input data were subjected to
major quality control, and many data were adjusted
using regional average temperature–salinity relations. Along-isopycnal mapping was used, using
objective analysis, prior to interpolation to
standard depths for the output climatology. The
mapped fields are provided on a 1° grid at up to
43 standard depths in the vertical. The qualitycontrolled and adjusted data and the averaged
fields are available online.
The Lozier et al. (1995) climatology for the
North Atlantic is the basis for the first interactive
(electronic) climatology/atlas, which is being developed further as Hydrobase by R. G. Curry (personal
communication, 1999). The goal in this work is to
provide the most flexible access to the data sets,
allowing the investigator to construct whatever
average is most useful, along with error estimates.
This then allows comparison of fields from different
time periods more easily than does a single climatology (e.g. Curry et al., 1998). Rigorous quality
control of the input data sets is performed; this is
the step that requires the most time prior to making
the atlas available. The quality-controlled data sets
are available through the atlas. Averaging is along
isopycnals, although output can be at standard
depths as well as on isopycnals. Bin averaging is
used in the horizontal, but is being migrated to
optimal interpolation. The interactive atlas is available for the Atlantic Ocean, and is continually
updated with newly collected data sets. A North
Pacific version has been produced (Macdonald
et al., 2001). The remainder of the world ocean is
under construction and will be available in late
2000 (R. G. Curry, personal communication, 1999).
WOCE has produced the most comprehensive
hydrographic data set ever collected, both in terms
of global coverage and in types of observations.
To present both a quick, accessible view of the
data sets in cross-section and isopycnal maps of
properties, atlases of hydrographic data are being
constructed for each ocean basin (Pacific, Atlantic,
Indian and Southern), in both printed and interactive electronic formats. Atlases are being produced
by different groups for each ocean basin working
in close collaboration to produce uniform products. The WOCE one-time survey station sampling
strategy was optimized to resolve features along
sections with a minimum of spatial aliasing, including the all-important density field for geostrophic
calculations. The survey was intentionally not optimized for horizontal (along-isopycnal) coverage,
given the existence of historical data that provide
reasonable coverage of most regions for the basic
properties (temperature, salinity, oxygen and
nutrients). Therefore the isopycnal maps will
incorporate high-quality historical data as well as
WOCE data. The electronic atlases for the WOCE
hydrographic data set will include the information
in the printed atlases, links to the original data
sets, and interactive plotting capability.
Upper ocean thermal fields
Upper ocean thermal fields are constructed primarily from XBT observations collected by merchant
ships. This data set is much larger than the research
ship hydrographic data set. A new source of upper
ocean thermal data is profiles from profiling
subsurface floats, which collect temperature data
7.1 Towards a WOCE Synthesis
533
Talley, Stammer and Fukumori
sets. Most of the WOCE data sets and expected
climatologies are described here: hydrographic,
upper ocean thermal, velocity and surface fluxes.
Hydrographic data
Hydrographic climatologies are being produced by
a number of different groups; the principal efforts
are described here. The most widely used climatologies are from the National Oceanographic and
Atmosphere Administration (NOAA) (Levitus,
1982; Levitus et al., 1994b), utilizing the global
pre-WOCE hydrographic data set with quality
control; the 1994 version includes monthly and
annual climatologies of temperature and salinity
on a 1° latitude by 1° longitude grid at 33 standard depths. It is now understood that averaging
along isopycnals/isoneutral surfaces is superior to
averaging at standard depths, as the latter results
in spurious climatological features in the neighbourhood of the strong isopycnal slopes that occur
at major fronts (e.g. Lozier et al., 1995). New climatologies employing evolving methods and the
ever-enlarging hydrographic data set will continue
to be produced at NOAA.
Climatologies of the South Atlantic (without
WOCE data) and South Pacific (with WOCE and
historical data) have been produced by the WOCE
Hydrographic Programme Special Analysis Center
(WHP SAC) in Hamburg (Gouretski and Jancke,
1995, 1996), with a preliminary version for the
world ocean. The input data were subjected to
major quality control, and many data were adjusted
using regional average temperature–salinity relations. Along-isopycnal mapping was used, using
objective analysis, prior to interpolation to
standard depths for the output climatology. The
mapped fields are provided on a 1° grid at up to
43 standard depths in the vertical. The qualitycontrolled and adjusted data and the averaged
fields are available online.
The Lozier et al. (1995) climatology for the
North Atlantic is the basis for the first interactive
(electronic) climatology/atlas, which is being developed further as Hydrobase by R. G. Curry (personal
communication, 1999). The goal in this work is to
provide the most flexible access to the data sets,
allowing the investigator to construct whatever
average is most useful, along with error estimates.
This then allows comparison of fields from different
time periods more easily than does a single climatology (e.g. Curry et al., 1998). Rigorous quality
control of the input data sets is performed; this is
the step that requires the most time prior to making
the atlas available. The quality-controlled data sets
are available through the atlas. Averaging is along
isopycnals, although output can be at standard
depths as well as on isopycnals. Bin averaging is
used in the horizontal, but is being migrated to
optimal interpolation. The interactive atlas is available for the Atlantic Ocean, and is continually
updated with newly collected data sets. A North
Pacific version has been produced (Macdonald
et al., 2001). The remainder of the world ocean is
under construction and will be available in late
2000 (R. G. Curry, personal communication, 1999).
WOCE has produced the most comprehensive
hydrographic data set ever collected, both in terms
of global coverage and in types of observations.
To present both a quick, accessible view of the
data sets in cross-section and isopycnal maps of
properties, atlases of hydrographic data are being
constructed for each ocean basin (Pacific, Atlantic,
Indian and Southern), in both printed and interactive electronic formats. Atlases are being produced
by different groups for each ocean basin working
in close collaboration to produce uniform products. The WOCE one-time survey station sampling
strategy was optimized to resolve features along
sections with a minimum of spatial aliasing, including the all-important density field for geostrophic
calculations. The survey was intentionally not optimized for horizontal (along-isopycnal) coverage,
given the existence of historical data that provide
reasonable coverage of most regions for the basic
properties (temperature, salinity, oxygen and
nutrients). Therefore the isopycnal maps will
incorporate high-quality historical data as well as
WOCE data. The electronic atlases for the WOCE
hydrographic data set will include the information
in the printed atlases, links to the original data
sets, and interactive plotting capability.
Upper ocean thermal fields
Upper ocean thermal fields are constructed primarily from XBT observations collected by merchant
ships. This data set is much larger than the research
ship hydrographic data set. A new source of upper
ocean thermal data is profiles from profiling
subsurface floats, which collect temperature data
7.1 Towards a WOCE Synthesis
533
Talley, Stammer and Fukumori