Changeset 181 for altifloat/doc

Timestamp:

10/05/15 11:11:24 (9 years ago)

Author:

jbrlod

Message:

nemed exp

Location:

altifloat/doc/ocean_modelling

Files:

• Draft1.tex (modified) (3 diffs)
• mybib.bib (modified) (1 diff)

altifloat/doc/ocean_modelling/Draft1.tex

@@ -159 +159 @@
 All the data detailed in this section were extracted for two target period : first from 25 August 2009 to 3 September 2009, and second from 28 August 2013 to 4 September 2013.
 \subsection {Altimetry data}
-Geostrophic surface velocity fields used as a background in the study were produced by Ssalt/\textit{Duacs} and distributed by \textit{Aviso}. Altimetric mission used were  Saral, Cryosat-2, Jason-1\&2. Data were mapped daily at a resolution of 1/8$^o$ over Mediterranean Sea. Data were linearly interpolated every hour at the advection model time step.
+Geostrophic surface velocity fields used as a background in the study were produced by Ssalt/\textit{Duacs} and distributed by \textit{Aviso}. Altimetric mission used were  Saral, Cryosat-2, Jason-1\&2. The geostrophic absolute velocity fields were deduced from Maps of Absolute Dynamic Topography (MADT) using the regional Mediteranean Sea product.
+
+Data were mapped daily at a resolution of 1/8$^o$. Data were linearly interpolated every hour at the advection model time step.
 
 \subsection{\label{sec:drifters}Drifters data}
@@ -165 +167 @@
 \begin{table}
 \centering
-\begin{tabular}{|c|c|c|c|c|c|}
-\hline
-Deploy Date & Lat & Lon & Last Date & Lat & Lon \\
-\hline
-29 Jul. 2009 & 31.90 & 34.42 & 28 Oct. 2009 & 34.1 & 31.77 \\
-\hline
-03 Aug. 2009 & 32.59 & 32.63 & 26 Dec. 2009 & 32.92 & 34.28 \\
-\hline
-27 Aug. 2013 & 33.28 & 34.95 & 22 Sep. 2013 & 36.77 & 35.94 \\
-\hline
-27 Aug. 2013 & 33.28 & 34.98 & 04 Sep. 2013 & 34.13 & 35.64 \\
-\hline
-27. Aug. 2013 & 33.28 & 35.03 & 17 Sep. 2013 & 34.88 & 35.88 \\
+\begin{tabular}{|c|c|c|c|c|c|c|}
+\hline
+Project & Deploy Date & Lat & Lon & Last Date & Lat & Lon \\
+\hline
+NEMED & 29 Jul. 2009 & 31.90 & 34.42 & 28 Oct. 2009 & 34.1 & 31.77 \\
+\hline
+NEMED & 03 Aug. 2009 & 32.59 & 32.63 & 26 Dec. 2009 & 32.92 & 34.28 \\
+\hline
+Altifloat & 27 Aug. 2013 & 33.28 & 34.95 & 22 Sep. 2013 & 36.77 & 35.94 \\
+\hline
+Altifloat & 27 Aug. 2013 & 33.28 & 34.98 & 04 Sep. 2013 & 34.13 & 35.64 \\
+\hline
+Altifloat & 27. Aug. 2013 & 33.28 & 35.03 & 17 Sep. 2013 & 34.88 & 35.88 \\
 \hline
 \end{tabular}
@@ -436 +438 @@
 In the context of the Nemed deployment (see section ~\ref{sec:drifters}), we selected two drifters trajectories from 25 August 2009 to 3 September 2009. Assimilating the successive positions of the drifters every six hours, the AVISO velocity field was corrected.
 
-In Fig.~\ref{fig:eddy-velocity}, the trajectory of the drifters were represented in gray, the AVISO surface geostrophic velocity field in blue and the corrected geostrophic field in red. In this case, it can be seen that the drifter trajectories were situated in an eddy. The AVISO field is produced by an interpolation method which tends to overestimate the spatial extent of the eddy and underestimate the intensity.
+In Fig.~\ref{fig:eddy-velocity}, the trajectory of the drifters were represented in gray, the mean AVISO surface geostrophic velocity field in blue and the mean corrected geostrophic field in red. 
+
+The real trajectory of the drifters and the simulated trajectory using the total corrected field (sum of corrected field in red and the wind-indeuced velocity) are very close. 
+The mean position error (expressed in arc length) is $8.6\times 10^{-3}$ degrees with a maximum of $0.06$ degrees. The real trajectory and simulated trajectory would be indescernible in Fig.~\ref{fig:eddy-velocity}. 
+
+
+
 \begin{figure}[h]
 \centering
 \includegraphics[scale =0.6]{./fig/Eddy_velocity.png}
-\caption{\label{fig:eddy-velocity} Corrected field (in red) compared to AVISO background fields (in blue). The assimilated drifter trajectories are represented in gray. The North-West coast in the figure is Cyprus.}
+\caption{\label{fig:eddy-velocity} Corrected surface velocity field (in red) compared to AVISO background field (in blue). The assimilated drifter trajectories are represented in gray. The North-West coast in the figure is Cyprus.}
+\end{figure}
+
+
+In this case, it can be seen that the drifter trajectories were situated in an eddy. The AVISO field is produced by an interpolation method which tends to overestimate the spatial extent of the eddy and underestimate the intensity. In order to estimate the effect of the assimilation on the eddy characterics, we computed the Okubo-Weiss parameter~\citep{isern2004} on the mean velocity fields before correction (background) and after correction. Eddies are characterized by a negative Okubo-Weiss parameter, the value of the parameter is an indicator of the intensity of the eddy. Results are shown in Fig.~\ref{fig:okubo-weiss}. As exected, it can be noticed that the Okubo-Weiss parameter had greater absolute values and a slighlty smaller spatial extent which indicated a improvement of the Aviso processing bias. This results constitutes a validation of the assimilation method presented in this paper showing that eddies were better resolved after assimilating drifter trajectories.
+
+\begin{figure}[h]
+\centering
+\includegraphics[scale=0.5]{./fig/okubo_weiss_aviso.png}
+\includegraphics[scale=0.5]{./fig/okubo_weiss_analyse.png}
+\caption{\label{fig:okubo-weiss} Okubo-Weiss parameter calculated on background field (upper panel) and corrected field (lower panel). The negativity of this parameter characterised eddies, and the absolute value corresponds to the intensity of the eddy. It can be noticed that eddy is smaller in size and more intense after the correction process.}
 \end{figure}
 

altifloat/doc/ocean_modelling/mybib.bib

@@ -33 +33 @@
 year = {2011},
 }
+
+@article{isern2004,
+  title={Spatial structure of anticyclonic eddies in the Algerian basin (Mediterranean Sea) analyzed using the Okubo--Weiss parameter},
+  author={Isern-Fontanet, Jordi and Font, Jordi and Garc{\'\i}a-Ladona, Emilio and Emelianov, Mikhail and Millot, Claude and Taupier-Letage, Isabelle},
+  journal={Deep Sea Research Part II: Topical Studies in Oceanography},
+  volume={51},
+  number={25},
+  pages={3009--3028},
+  year={2004},
+  publisher={Elsevier}
+}