Decadal evolution of the coastal
temperature from satellite and in situ
data sets : case of the English Channel
by Francis Gohin and Bertrand Saulquin,
Ifremer Brest
DYNECO/PELAGOS
Why a SST climatology ?
A request of the community of biologists in the
context of the global change (the GMES spirit)
A huge effort in coastal operational
oceanography
A support from different European projects
(MarCoast/ESA, ECOOP/FP6)
The SST climatologies available
Faugères et al. (SAF)
CASEY (NODC)
SST mid-September
!
"
#
#
!
%
%
&
'0&
'( %
)*
%
$
$
&& +* 0 & '
+
& ,-. /'
067 7.8-66*
(1 2100
" 3
" 3
% 4&
% 4&
5
5
%
%
9
78:((
!
"
Parameters P0, P1 of the seasonal curves
derived from AVHRR data (1986-2005).
P0, mean sst.
P1, warming slope.
!
"
Parameters P2, P3, parameters of the first of the first
harmonic of the seasonal curves
P2, first harmonic amplitude
P3, first harmonic phase
!
"
Parameters P4, P5, parameters of the second harmonic of the
seasonal curves
P4, second harmonic amplitude
P5, second harmonic phase
!
"
Total variance of the satellite SST residuals over the
period 1986-2005.
The kriging method
#
$
%
Firstly, the space-time covariance is estimated
γ(∆
∆x,∆
∆t) = 1/2E[SST(x+∆
∆x,t+∆
∆t) - SST(x,t)]2
! #$
#$
#$
#$
Secondly, SST is estimated by kriging
on a 5km and weekly grid
;
#$
#$
#$
! #$
The Kriging Matrix
The interpolator is linear & ' =
No bias :
α
α
λα (α
λα =
Optimal ; minimization of Var[Y*(x) – Y(x)]
Inversion of the kriging matrix (covariance matrix)
%
%
The variograms
%
% !
&'# ( )* +
/0#(
#(
, #+ #+ )
! #$
.
!
!
!
32 #(#2 #($
32 #(
1 + #2 #($
4
R/S versus In situ SST
)
+
*
" *
*
The kriging applied to the coastal
stations : The coastal gradient
)
,
-
.
,"
.
0&
&
&
ROSCOFF
The cross-shore
effect at Roscoff
4
)) # #
5 # #2
62
The temporal variability :
The Marel buoy, La Carosse, in the plume
of the river Seine
X
Mineral SPM
X
Chlorophyll
7# #
( !&
+
&
' !&
+9 <9 = " '
The 19031927 mean
SST
9°5
10°
10°5
11°
5
From Atlas de
Temperature de
Salinité de l’Eau de
Surface
ICES 1933,
Kopenhagen
11°5
12°
12°5
(SST of the English
Channel estimated
by Lumby)
( !& >
+9 <9 = " '
10°5
The 19031927 mean
SST
11°
12°
12°5
13°5
13°
13°
12°5
13°
From Atlas de
Temperature de
Salinité de l’Eau de
Surface
ICES 1933,
Kopenhagen
(SST of the English
Channel estimated
by Lumby)
2
%&
!
#(
( #2 2 5 ### 2+
8
#+
# #( # 2 6 ((
2
#
)) *
1 "
*
.
"
*1
/
-234& ,+
1
*
"
*3
"
,/ 0.
5
*1
35