From 8840879f7d1a1c1c8cd5f347d08c3138488922c2 Mon Sep 17 00:00:00 2001
From: ctroupin <charles.troupin@gmail.com>
Date: Wed, 19 Dec 2018 12:17:01 +0100
Subject: [PATCH] referee no.2 comments
---
latex/AlborexData.bib | 6 ++++--
latex/AlborexData_ESSD.tex | 39 ++++++++++++++++++++++++--------------
2 files changed, 29 insertions(+), 16 deletions(-)
diff --git a/latex/AlborexData.bib b/latex/AlborexData.bib
index 695bdc8..da09955 100644
--- a/latex/AlborexData.bib
+++ b/latex/AlborexData.bib
@@ -307,6 +307,7 @@ and Larnicol, G.},
Year = {2018},
Month = {Sep},
+ Pages = {1-8},
Volume = {5},
Doi = {10.3389/fmars.2018.00318},
@@ -336,9 +337,10 @@ and Larnicol, G.},
Url = {https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1002/2016JC012114}
}
-@InBook{,
- Title = {Observing the Oceans - A 2020 Vision for Ocean Science},
+@InBook{DELANEY2009,
+ Title = {{Observing the Oceans - A 2020 Vision for Ocean Science}},
Author = {Delaney, John R. and Barga, Roger S.},
+ Pages = {27-38},
Publisher = {Microsoft Research},
Year = {2009},
Month = {November},
diff --git a/latex/AlborexData_ESSD.tex b/latex/AlborexData_ESSD.tex
index 4436bdd..4b8a42c 100644
--- a/latex/AlborexData_ESSD.tex
+++ b/latex/AlborexData_ESSD.tex
@@ -81,7 +81,7 @@ The dataset presented in this paper can be used for the validation of high-resol
The variety of physical and biological processes occurring in the ocean at different spatial and temporal scales requires a combination of observing and modelling tools in order to properly understand the underlying mechanisms. Hydrodynamical models make it possible to design specific numerical experiments or simulate idealised situation that can reproduce some of these processes and assess the impacts of climate change. Despite the continuous progresses made in modeling (spatial resolution, parameterization, atmospheric coupling, \ldots), in situ observations remain an essential yet challenging ingredient when addressing the complexity of the ocean.
-The perfect observational system would consist in dense array of sensors present at many geographical locations, many depths and measuring almost continuously a wide range of parameters. Obviously such a system is not the reality: researchers have to rely on the combination of various platforms during a limited period of time, each platform measuring a given set of variables at different spatial and temporal resolutions, spatial coverage, accuracy and depth levels. We will refer to this as multi-platform systems, by opposition to experiments articulated only around the observations made using a research vessel. Further details can be found in \citet{TINTORE13}.
+To properly capture and understand these small-scale features, one cannot settle for only observations of temperature and salinity profiles acquired at different times and positions, but rather has to combine the information from diverse sensors and platforms acquiring data at different scales and at the same time, similarly to the approach described in \citet{DELANEY2009}. This also follows the recommendation for the Marine Observatory in \citet{CRISE2018}, especially the co-localization and synopticity of observations and the multi-platform, adaptive sampling strategy. We will refer to this as multi-platform systems, by opposition to experiments articulated only around the observations made using a research vessel. Further details can be found in \citet{TINTORE13}.
The western Mediterranean Sea is a particularly relevant region for multi-platform experiments, thanks to the wide range of processes taking place and intensively studied since the work of \cite{WUST61} on the vertical circulation: influence on climate \citep[e.g.,][]{GIORGI06,GIORGI08,ADLOFF15,GUIOT16,RAHMSTORF98} and sea-level change \citep[e.g.,][]{TSIMPLIS02,BONADUCE16,WOLFF18}, thermohaline circulation \citep[e.g.,][]{BERGAMASCO10,MILLOT87,MILLOT91,MILLOT99,SKLIRIS14,ROBINSON01}, water mass formation and convection process \citep[e.g.,][]{MEDOC70,STOMMEL72,SEND1999,MACIAS18}, mesoscale \citep[e.g.,][]{ALVAREZ96,PINOT95,PUJOL05,SANCHEZROMAN17} and submesoscale processes \citep[e.g.,][]{BOSSE15,DAMIEN17,MARGIRIER17,TESTOR03,TESTOR18}. Other recent instances of multi-platform experiments in the Mediterranean Sea were focused on the Northern Current \citep[December 2011,][]{BERTA18}, deep convection in the Northwestern Mediterranean sea \citep[July 2012--October 2013,][]{TESTOR18}, the Balearic Current system \citep[July and November 2007, April and June 2008,][]{BOUFFARD10} and coastal current off west of Ibiza island \citep[August 2013,][]{TROUPIN15}. Similar studies comparing almost synchronous glider and SARAL/AltiKa altimetric data on selected tracks have also been carried between the Balearic Islands and the Algerian coasts \citep{AULICINO18,COTRONEO16}.
@@ -108,16 +108,24 @@ The pair of images indicates that the front position slightly changed between Ma
\begin{figure}[t]
\includegraphics[width=.95\textwidth]{fig02.png}
-\caption{Sea surface temperature in the western Mediterranean Sea from MODIS sensor onboard Aqua satellite corresponding to May 25 and 30, 2014. The dashed black line indicates the approximative position of the front based on the temperature gradient for the period 25--30 May. Level-2, 11 $\mu m$, night-time images were selected. Only pixels with a quality flag equal to 1 (good data) were conserved and represented on the map. Note that the same front position is used in the subsequent figures.\label{fig2:SST}}
+\caption{Sea surface temperature in the western Mediterranean Sea from MODIS sensor onboard Aqua satellite corresponding to May 25 and 30, 2014. The dashed black line indicates the approximative position of the front based on the temperature gradient for the period 25--30 May. Level-2, 11 $\mu m$, night-time images were selected. Only pixels with a quality flag equal to 1 (good data) were conserved and represented on the map. The same front position is used in the subsequent figures.\label{fig2:SST}}
\end{figure}
+\subsection{Design of the experiment}
+
+The deployment of in situ systems was based on the remote-sensing observations described in the previous Section. Two high-resolution grids were sampled with the research vessel, covering an approximative region of 40~km $\times$ 40~km. At each station, one CTD cast and water samples for chlorophyll concentrations and nutrients analysis were collected. The thermosalinograph observations were also used in order to assess the front position.
+
+One deep glider and one coastal glider were deployed in the same area with the idea to have butterfly-like track across the front. These idealised trajectories turned out to be impossible considering the strong currents occurring in the region of interest at the time of the mission.
+
+The 25 drifters were released close to the frontal area with the objective to detect convergence and divergence zones. Their release locations were separated by a few kilometers.
+
\subsection{Data Reuse}
Three main types of data reuse are foreseen: 1.~model validation, 2.~data assimilation (DA) and 3.~planning of similar in situ experiments.
With the increase of spatial resolution in operational models, the validation at the smaller scales requires high-resolution observations. Remote-sensing measurements such as SST or chlorophyll-a concentration provides a valuable source of information but are limited to the surface layer. In the case of the present experiment, the position, intensity (gradients) and vertical structure of the front represent challenging features for numerical models, even when data assimilation is applied \citep{HERNANDEZ2018}.
-The AlborEx dataset can be used for DA experiments, for example assimilating the CTD measurements in the model and using the glider measurements as an independent observation dataset. The assimilation of glider observations has already been performed in different regions \citep[e.g.][]{MELET2012,MOURRE2014,PAN2014} and has been shown to improve the forecast skills. However the assimilation of high-resolution data is not trivial: the the background error covariances tends to smooth the small scale features present in the observations.
+The AlborEx dataset can be used for DA experiments, for example assimilating the CTD measurements in the model and using the glider measurements as an independent observation dataset. The assimilation of glider observations has already been performed in different regions \citep[e.g.][]{MELET2012,MOURRE2014,PAN2014} and has been shown to improve the forecast skills. However the assimilation of high-resolution data is not trivial: the the background error covariances tends to smooth the small scale features present in the observations and the high density of measurements may require the use of super-observations (averaging the observations in the model cells). Another complication arises from the fact that the observational errors are correlated, while data assimilation schemes often assume those errors are not correlated.
Finally, other observing and modeling programs in the Mediterranean Sea can also benefit from the present dataset, for instance the Coherent Lagrangian Pathways from the Surface Ocean to Interior (CALYPSO) in the Southwest Mediterranean Sea \citep{JOHNSTON2018}. Similarly to AlborEx, CALYPSO strives to study a strong ocean front front and the vertical exchanges taking place in the area of interest. For details on the mission objectives, see \url{https://www.onr.navy.mil/Science-Technology/Departments/Code-32/All-Programs/Atmosphere-Research-322/Physical-Oceanography/CALYPSO-DRI}, last accessed December 17, 2018.
@@ -125,16 +133,20 @@ Finally, other observing and modeling programs in the Mediterranean Sea can also
For each of the platform described in Sec.~\ref{sec:mission}, different processing are performed with the objective to turn raw data into quality-controlled, standardised data directly usable by scientists and experts. Specific conventions for data managed by SOCIB are explained below.
-All the data provided by SOCIB are available in different so-called processing levels, ranging from 0 (raw data) to 2 (gridded data). The files are organized by \textit{deployments}, where a deployment is defined as an event initiated when an instrument is put at sea and finished once the instrument is recovered from sea. Table~\ref{tab:deployment} summarizes the deployments performed during the experiment and the available processing levels.
+All the data provided by SOCIB are available in different, so-called processing levels, ranging from 0 (raw data) to 2 (gridded data). The files are organized by \textit{deployments}, a deployment being defined as an event initiated when an instrument is put at sea and finished once the instrument is recovered from sea. Table~\ref{tab:deployment} summarizes the deployments performed during the experiment and the available processing levels.
\begin{description}
-\item[Level 0 (L0)]: this is the level closest to the original measurements, as it contains exactly the same data as the raw files provided by the instruments, but in a single file.
+\item[Level 0 (L0)]: this is the level closest to the original measurements, as it is designed to contain exactly the same data as the raw files provided by the instruments. The goal is to deliver a single, standardised netCDF file, instead of one or several files in a platform-dependent format.
\item[Level 1 (L1)]: in this level, additional variables are derived from the existing ones (e.g., salinity, potential temperature). The attributes corresponding to each variable are stored in the netCDF file, with details of any modifications. Unit conversion are also applied if necessary.
-\item[Level 2 (L2)]: this level consists of regular, homogeneous and instantaneous profiles obtained by interpolating the L1 data. It is only provided for gliders, mostly for visualization and post-processing purposes: specific tools designed to read and display profiler data can then be used the same way for gliders.
+\item[Level 1 corrected (L1\_corr)]: this level is only available for the CTD: a corrective factor is obtained by a linear regression between the salinity measured by the CTD and that measured by the salinometer. The files corresponding to that processing levels contain new variables of conductivity and salinity to which the correction was applied. Additional metadata regarding the correction are also provided in the file.
+\item[Level 2 (L2)]: this level is only available for the gliders. It consists of regular, homogeneous and instantaneous profiles obtained by interpolating the L1 data. In other words, 3-dimensional trajectories are transformed into a time series of profiles.
+
+This level was created mostly for visualization and post-processing purposes: specific tools designed to read and display profiler data can then be used the same way for gliders.
\end{description}
-The glider data require a specific processing to ingest and convert the raw data files produced by the coastal and deep units. This is done within a toolbox designed for this purpose and extensively described in \citet{TROUPIN16}, the capabilities of which includes metadata aggregation, data download, advanced data processing and the generation of data products and figures. Of particular interest is the application of a thermal-lag correction for un-pumped Sea-Bird CTD sensors installed on Slocum gliders \citep{GARAU11}, which improves the quality of the glider data.
+The glider data require a specific processing to ingest and convert the raw data files produced by the coastal and deep units. This is done within a toolbox designed for this purpose and extensively described in \citet{TROUPIN16}, the capabilities of which includes metadata aggregation, data download, advanced data processing and the generation of data products and figures. Of particular interest is the application of a thermal-lag correction for un-pumped Sea-Bird CTD sensors \citep{GARAU11}, which improves the quality of the glider data.
-In order to go from L1 to L2, a spatial interpolation is performed into vertical depth levels with a resolution of 1~m.
+
+%%%%%%%%%%%%%
\begin{table*}[htpb]
\caption{Characteristics of the instrument deployments in AlborEx.\label{tab:deployment}}
@@ -181,7 +193,7 @@ Code & Meaning \\
\end{tabular}
\end{table}
-\subsubsection{QC tests}
+\subsubsection{QC tests\label{sec:qctests}}
The main tests performed on the data are:
\begin{description}
@@ -195,10 +207,7 @@ When the spike value is above the threshold (depending on the variable), the fla
\item[stationarity:] it aims to checks if measurements exhibit some variability over a period of time, by computing the difference between the extremal values over that period.
\end{description}
-Note that the tests described above are not yet applied on the glider data, since their processing is done outside of the general SOCIB processing chain, but the tests have been implemented in the glider toolbox \citep[][and available at \url{https://github.com/socib/glider_toolbox}]{TROUPIN16} and will be made operational once they have been properly tested and validated.
-
-
-\end{description}
+It is worth mentionning the tests described above are not yet applied on the glider data, since their processing is done outside of the general SOCIB processing chain, but the tests have been implemented in the glider toolbox \citep[][and available at \url{https://github.com/socib/glider_toolbox}]{TROUPIN16} and will be made operational once they have been properly tested and validated.
As the new files will not be available before a full reprocessing of all the historical missions, the decision was taken to provide the data files in their current state. A new version will be uploaded as soon as the processing has been performed.
@@ -233,7 +242,7 @@ In addition to the CTDs, the R/V thermosalinograph continuously acquired tempera
The CTD rosette was equipped with:
\begin{itemize}
-\item a SeaÂâ€Bird SBE 911Plus, 2 conductivity and temperature sensors and 1 pressure sensor units,
+\item a Sea-Bird SBE 911Plus, 2 conductivity and temperature sensors and 1 pressure sensor units,
\item a SBE 43 oxygen sensor,
\item a Seapoint [FTU] fluorescence and turbidity sensor.
\end{itemize}
@@ -242,6 +251,8 @@ The continuous, near-surface measurements of temperature and salinity are provid
\subsubsection{Quality checks}
+The general checks described in Sec.~\ref{sec:qctests} (i.e., ranges, spike, gradient and stationarity) are applied on the temperature, salinity, conductivity and turbidity. The threshold values are detailed in the corresponding tables in the QC procedure document \citep{SOCIBQC2018}.
+
--
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