The main challenge to automated systems was
the selection, siting around the ship and maintenance of the sensor suite. In order to achieve good
exposure for any relative wind direction, two or
three sensors for each variable are required. Calibration and maintenance of the sensors is required
at frequent intervals.
The introduction of high-quality automated data
systems meant that many ships were now acquiring
and reporting meteorological data for the first
time: IMET systems were installed on numerous
(six to eight) US research vessels, and are now
being installed on some US Voluntary Observing
Ships. A comprehensive account of the status of
shipboard meteorology measurements and the
associated surface flux calculations at the end of
the 1990s can be found in the Final Report of the
Joint WCRP/SCOR Working Group on Air–Sea
Fluxes (WGASF, 2000).
3.1.4.2 Data assembly and quality control
The Data Assembly Centre for surface meteorology is at the Center for Ocean-Atmosphere Prediction Studies (COAPS) in Florida State University.
Data are assembled, reviewed for quality using an
automatic system, have quality flags attached, and
are made available to the user community (Smith
et al., 1996). (Note in passing that while QC flags
are set, data are not changed. Thus the end user is
responsible for determining the action taken with
flagged data.) Data assembled via this route are
particularly valuable because of the quality of the
instrumentation, continuous data collection and
documentation efforts. At the time of writing, the
DAC has data from 454 WOCE cruises, which
they estimate to be 74% of the completed total.
The distribution of data held at the DAC is shown
in Fig. 3.1.8 (see Plate 3.1.8, p. 172).
3.1.4.3 Uses for shipboard meteorological data
In addition to the high quality, there are a number
of other characteristics that make these data particularly valuable:
¥ Coverage is obtained from data-sparse regions,
particularly the Southern Ocean, which is rarely
visited by ships of opportunity.
¥ Many of the automated data are not reported
via the GTS. This means they are not included
in Numerical Weather Prediction products and
can be used as an independent check.
¥ Some ships report standard bridge observations
at synoptic hours, but also have independent
automated systems. This allows an intercomparison between the two data streams.
The high quality of research vessel data also makes
them suitable for evaluating flux products. While
this can be done on short time scales, i.e. synoptic
rather than climatological or other longer-averaged time scales, spatial and temporal coverage is
limited. Cruises are not typically repeated to a particular region, and coincidence of ships with, for
example, satellite overpasses may not be exact.
3.1.5 Summary and conclusions
The one-time survey was a success in achieving global coverage, meeting its requirements on
sampling accuracy of the basic hydrography,
documenting methods used at sea and ashore and
educating a generation of hydrographers to achieve
the above in the face of a heavy seagoing schedule,
which strained personnel and logistics.
Advances in the use and exploitation of ADCPs
during the WOCE observational period were
enormous. Data quality from shipboard ADCPs
improved by an order of magnitude, although this
was due to improvements in external navigation
rather than enhancements to the instrument itself.
Lowering of self-contained ADCPs with CTD packages progressed from being an innovative development to a routine exercise wherever the hardware
could be made available. While the deployment of
LADCPs is now routine, there remains much to
be done in understanding and reducing the errors
and uncertainties associated with LADCP data.
Although the WHP has been an obvious beneficiary
of ADCP developments, it is likely that they would
have taken place even without the existence of the
programme.
The full scientific payoff of the programme
remains to be realized as up until now, few attempts
have been made to incorporate these measurements
(including transient tracers) with other data (for
example from float trajectories and ADCPs) or
models of the circulation.
While not all taken at the same instant of time,
sufficient WHP measurements were repeats of
earlier (e.g. IGY) sections or have been made
multiple times (24°N in the Atlantic has been
re-occupied now four times since the IGY) to begin
3.1 Shipboard Observations during WOCE
121
King, Firing and Joyce
the selection, siting around the ship and maintenance of the sensor suite. In order to achieve good
exposure for any relative wind direction, two or
three sensors for each variable are required. Calibration and maintenance of the sensors is required
at frequent intervals.
The introduction of high-quality automated data
systems meant that many ships were now acquiring
and reporting meteorological data for the first
time: IMET systems were installed on numerous
(six to eight) US research vessels, and are now
being installed on some US Voluntary Observing
Ships. A comprehensive account of the status of
shipboard meteorology measurements and the
associated surface flux calculations at the end of
the 1990s can be found in the Final Report of the
Joint WCRP/SCOR Working Group on Air–Sea
Fluxes (WGASF, 2000).
3.1.4.2 Data assembly and quality control
The Data Assembly Centre for surface meteorology is at the Center for Ocean-Atmosphere Prediction Studies (COAPS) in Florida State University.
Data are assembled, reviewed for quality using an
automatic system, have quality flags attached, and
are made available to the user community (Smith
et al., 1996). (Note in passing that while QC flags
are set, data are not changed. Thus the end user is
responsible for determining the action taken with
flagged data.) Data assembled via this route are
particularly valuable because of the quality of the
instrumentation, continuous data collection and
documentation efforts. At the time of writing, the
DAC has data from 454 WOCE cruises, which
they estimate to be 74% of the completed total.
The distribution of data held at the DAC is shown
in Fig. 3.1.8 (see Plate 3.1.8, p. 172).
3.1.4.3 Uses for shipboard meteorological data
In addition to the high quality, there are a number
of other characteristics that make these data particularly valuable:
¥ Coverage is obtained from data-sparse regions,
particularly the Southern Ocean, which is rarely
visited by ships of opportunity.
¥ Many of the automated data are not reported
via the GTS. This means they are not included
in Numerical Weather Prediction products and
can be used as an independent check.
¥ Some ships report standard bridge observations
at synoptic hours, but also have independent
automated systems. This allows an intercomparison between the two data streams.
The high quality of research vessel data also makes
them suitable for evaluating flux products. While
this can be done on short time scales, i.e. synoptic
rather than climatological or other longer-averaged time scales, spatial and temporal coverage is
limited. Cruises are not typically repeated to a particular region, and coincidence of ships with, for
example, satellite overpasses may not be exact.
3.1.5 Summary and conclusions
The one-time survey was a success in achieving global coverage, meeting its requirements on
sampling accuracy of the basic hydrography,
documenting methods used at sea and ashore and
educating a generation of hydrographers to achieve
the above in the face of a heavy seagoing schedule,
which strained personnel and logistics.
Advances in the use and exploitation of ADCPs
during the WOCE observational period were
enormous. Data quality from shipboard ADCPs
improved by an order of magnitude, although this
was due to improvements in external navigation
rather than enhancements to the instrument itself.
Lowering of self-contained ADCPs with CTD packages progressed from being an innovative development to a routine exercise wherever the hardware
could be made available. While the deployment of
LADCPs is now routine, there remains much to
be done in understanding and reducing the errors
and uncertainties associated with LADCP data.
Although the WHP has been an obvious beneficiary
of ADCP developments, it is likely that they would
have taken place even without the existence of the
programme.
The full scientific payoff of the programme
remains to be realized as up until now, few attempts
have been made to incorporate these measurements
(including transient tracers) with other data (for
example from float trajectories and ADCPs) or
models of the circulation.
While not all taken at the same instant of time,
sufficient WHP measurements were repeats of
earlier (e.g. IGY) sections or have been made
multiple times (24°N in the Atlantic has been
re-occupied now four times since the IGY) to begin
3.1 Shipboard Observations during WOCE
121
King, Firing and Joyce