From c43f38066e9e2e2a169e65552f5d5ebd1ebdccb7 Mon Sep 17 00:00:00 2001
From: ctroupin <charles.troupin@gmail.com>
Date: Fri, 21 Dec 2018 13:40:53 +0100
Subject: [PATCH] ADCP QC described
---
latex/AlborexData_ESSD.tex | 17 +++++++++--------
1 file changed, 9 insertions(+), 8 deletions(-)
diff --git a/latex/AlborexData_ESSD.tex b/latex/AlborexData_ESSD.tex
index 0f19e31..fb8dc57 100644
--- a/latex/AlborexData_ESSD.tex
+++ b/latex/AlborexData_ESSD.tex
@@ -370,9 +370,9 @@ The velocities exhibit a dominant eastward current with speed locally larger tha
\subsubsection{Configuration}
-The current profiler is an Ocean Surveyor ADCP, manufactured by Teledyne RD Instruments and operating at a frequency of 150~KH. This instrument was configured with a 8-m depth bin and a total of 50 bins. Final velocity profiles were averaged in 10-minute intervals.
+The current profiler is an Ocean Surveyor ADCP, manufactured by Teledyne RD Instruments and operating at a frequency of 150~KH. This instrument was configured with 8-m depth bins and a total of 50 bins. Final velocity profiles were averaged in 10-minute intervals. The transducer depth is approximatively 2~m.
-The position and behavior (heading, pitch and roll) of the research vessel is obtained with an Ashtec 3D GPS 800 ADU positioning system that provides provide geographical positions with a 10-20 cm accuracy and heading, pitch and roll with an accuracy on the order of 1$^{\circ}$.
+The position and behavior (heading, pitch and roll) of the research vessel is obtained with an Ashtec 3D GPS 800 ADU positioning system that provides provide geographical positions with a 10-20 cm accuracy and heading, pitch and roll with an accuracy on the order of 1$^{\circ}$. The technical report referring to this platform is available in the Annex~II of \cite{RUIZ2015}.
\subsubsection{Quality checks}
@@ -382,21 +382,22 @@ The position and behavior (heading, pitch and roll) of the research vessel is ob
\caption{Velocity field obtained with the ADCP at a 40~m depth (left panel) and sections of zonal velocity on May 26 (S1) and 27 (S2). The locations of the sections are indicated by dashed rectangles on the map. Only data with a quality flag equal to 1 (good data) are represented\label{fig9a:adcp}}
\end{figure*}
-The vessel's velocity is one or two order or magnitudes greater than the currents that have to be measured, hence this type of current measurements requires a careful processing in order to get meaningful velocities from the raw signal. The QC procedure for the VM-ADCP is complex as it involves tests on more than 40 technical and geophysical variables. The different tests are based on the technical reports of \citet{COWLEY2009} and \citet{BENDER2009}, which aim primarily at ADCP mounted on moorings.
+The vessel's velocity is one or two order or magnitudes greater than the currents that have to be measured, hence this type of current measurements requires a careful processing in order to get meaningful velocities from the raw signal. The QC procedure for the VM-ADCP is complex as it involves tests on more than 40 technical and geophysical variables \citep{SOCIBQC2018}. The different tests are based on the technical reports of \citet{COWLEY2009} and \citet{BENDER2009}, which aim primarily at ADCP mounted on moorings. The procedure can be summarised as follows:
\begin{enumerate}
-\item Velocities:
-\item Vessel behaviour:
+\item Technical variables: valid ranges are checked for each of these variables: if the measurement is outside the range, the QF is set to 4 (bad data). Example of technical variables are: bottom track depth, sea water noise amplitude, correlation magnitude.
+\item Vessel behaviour: its pitch, roll and and orientation angles are checked and QF are assigned based on specific ranges. In addition the vessel velocity is checked and anomalously high values are also flagged as bad.
+\item Velocities: valid ranges are provided for the computed current velocities: up to 2~m/s, velocities considered as good; between 2 and 3~m/s, probably good, and above 3~m/s, bad.
\end{enumerate}
+The application of all these tests lead to Fig~\ref{fig9b:adcpQC}, which illustrates the QF during the whole mission. The 3 main periods during which the ADCP was turned off are shown as grey areas. In addition, no measurements are available in the first meters of the water column, due to the position of the ADCP on the ship, at a depth of approximately 2~m.
-Figure~\ref{fig9b:adcpQC} shows the QF during the whole mission. The 3 main periods during which the ADCP was turned off are shown as grey areas. In addition, no measurements are available in the first meters of the water column, due to the position of the ADCP on the ship.
\begin{figure}[ht]
\includegraphics[width=.95\textwidth]{fig12.png}
-\caption{Quality flags for the velocity measurements.\label{fig9b:adcpQC}}
+\caption{Quality flags for the velocity measurements. The areas marked with a $\times$ are those during which the VM-ADCP was no acquiring measurements.\label{fig9b:adcpQC}}
\end{figure}
-Overall the quality of the data tends to deteriorate when the depth increases, as reflected by the bad and missing values. In the first 200~m, about 95\% of the measurements are considered as good. Below 200~m, the ratio drops to 57\% with more than 21\% of missing values. Note that the flags 5, 7 and 8 were not used in this case but kept in the plot.
+Overall the quality of the data tends to deteriorate when the depth increases, as reflected by the bad and missing values. In the first 200~m, about 95\% of the measurements are considered as good. Below 200~m, the ratio drops to 57\% with more than 21\% of missing values. Note that the flags 5 (, 7 and 8 were not used in this case but kept in the plot.
\subsection{Nutrients}
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