Title: Delay-mode quality control of Argo float salinity data in the Tyrrhenian Sea
1Delay-mode quality control of Argo float salinity
data in the Tyrrhenian Sea
- Giulio Notarstefano
- OGS Trieste - Italy
Third Argo Delay-Mode Quality Control Workshop
(DMQC-3) University of Washington Seattle,
Washington USA - September 10-12, 2008
2Contents
- Argo Profilers
- Float and historical data
- Application of DMQC in the Tyrrhenian Sea
- Results
- Conclusions
3ARGO profilers
- APEX ( Webb Research Corporation, USA)
SBE-CTD sensor (model 41 pumped
MicroCAT) Accuracies 0.002C 0.005 PSU 2.4 dbar
4ARGO profilers
- Configuration
- Parking depth 350 m (LIW).
- Profiling depths700 m and 2000 m (every 10
cycles). - Cycles 5-10 days.
5Float data
- Float data extracted from CORIOLIS in NetCDF
format - Float data from August 2004 to March 2008
- ftp//ftp.ifremer.fr/ifremer/argo/dac/coriolis/
Tyrrhenian Sea
6Float data
50 floats (16 active) in the Mediterranean Sea
7Float data
- two APEX floats (WMO number 6900280 and 6900281)
- deployed in the Tyrrhenian Sea in August 2004
- float 6900280 228 cycles, the last one in
November 2007 - float 6900281 still active with 280 cycles in
August 2008
8Historical data
- Two types of historical CTD data were used
- MEDAR/MEDATLAS climatology (1975-1997)
- Data kindly made available by Borghini and
Santoleri (2004)
Tyrrhenian Sea
9Historical data
- Mean profile (black line) of salinity vs
pressure standard deviation (red bars) is an
indicator of the large variability along the
water column of the Tyrrhenian Sea. The green
points are the number of data used to compute the
statistics.
10DMQC method in the Tyrrhenian Sea
- apply the DMQC method in the various sub-basin of
the Mediteranean Sea separately - Two Argo floats in the Tyrrhenian WMO numbers
6900280 and 6900281
11DMQC method in the Tyrrhenian Sea
- Parameters used
- CONFIG_MAX_CAST 300
- MAP_USE_PV yes (0.5 and 0.1)
- MAPSCALE 6, 2 (longitude), 5, 1.67
(latitude) - MAPSCALE_AGE 10 years
- MAP_P_EXCLUDE 200 dbar
- MAP_P_DELTA 250 dbar
- Theta/pres range default values
12Results for Argo float 6900280
- More than 3 years of data, from August 2004 and
November 2007, were collected by float 6900280
that performed 228 cycles - The black line represents the mean profile of
the salinity from float versus pressure. In the
first 150-200 meters the highly variability of
the shallower water is shown by the amplitude of
the standard deviation
13Results for Argo float 6900280
- The conductivity sensor worked quite well
during its life but it seems that the salinity
measurements from the float are almost always a
bit fresher than the climatology (r gt 1) - The application of the calibration method
proposed a correction of less than 0.02 PSU to
the float salinity measurements
14Results for Argo float 6900281
- Deployed in August 2004, the float 6900281 is
still active and performed more than 250 cycles - The black line represents the mean profile of
the salinity from float versus pressure
15Results for Argo float 6900281
- The conductivity sensor seems to be stable and
r is close to 1 for more than 150 cycles after
the deployment - The application of the calibration method
proposed a correction that is smaller than the
Argo accuracy (0.01 PSU)
16Conclusions
- There is quite a good agreement between the
historical and float measurements, given the
natural variability of both datasets - Despite the long operational floats life (gt 3
years), the conductivity sensor worked well and
demonstrated to be quite stable in time - The corrections proposed by the DMQC method are
small (less than 0.02 PSU) and, over long
periods, less than the Argo accuracy (0.01 PSU) - The corrections proposed by the DMQC method are
smaller than the variability of the climatology,
so we do not think that any correction is needed
at the moment
17Future work
- Increase climatology historical data until 2006
for the Tyrrhenian sea. More recent data for
other areas of the Mediterranean Sea - Apply the DMQC method to other sub-basins of the
Mediterranean Sea - Use other available floats