preliminary results of assimilation of asar wave spectra level 2b products in wam
DESCRIPTION
Preliminary results of assimilation of ASAR wave spectra level 2b products in WAM. L. Aouf (1) , J.M. Lefevre (1) and D. Hauser (2) (1) Meteo France; (2) CETP/CNRS. 1. Introduction. Assimilation of directional spectra in wave model in Meteo France. Better estimate of the wave parameters - PowerPoint PPT PresentationTRANSCRIPT
Preliminary results of assimilation of ASAR wave spectra level 2b products in WAM
L. Aouf (1), J.M. Lefevre (1) and D. Hauser (2)
(1) Meteo France; (2) CETP/CNRS1. Introduction
Assimilation of directional spectra in wave model in Meteo France
Better estimate of the wave parameters(Synthetic directional spectra)
2. Description of the assimilation scheme
Partitioning of the wave spectrum (first guess and observed)
Cross-assignement between equivalent wave systems (fg and obs)
Optimal interpolation for the selected partitions
Reconstitution of the analysed wave spectrum
Data set 1 data set 2 data set 3 data set 4
May 3 at 6:00 may 3 at 12:00 may 4 at 0:00 may 8 at 12:00
3. Case studies
ASAR-ENVISAT wave spectra
Wave model WAM (global scale 1x1 degrees)Discretization 24 frequency (0.044-0.22 Hz) and 36 directions
4. Limitation for the observed ASAR wave spectrum
Two versions of the assimilation scheme :1- all wave spectrum2- limited wave spectrum (cut-off fc=0.1 Hz)
0 100 200 3000.05
0.1
0.15
0.2
wave direction (degrees)
frequ
ency
(H
z)WAM-FG
0
10
20
30
0 100 200 3000.05
0.1
0.15
0.2
wave direction (degrees)
frequ
ency
(H
z)
ASSIMILATED
0
5
10
15
20
0 100 200 3000.05
0.1
0.15
0.2
wave direction (degrees)
frequ
ency
(H
z)
ASAR-ENVISAT
0
5
10
15
0 0.1 0.2 0.3 0.40
5
10
15
20
frequency (Hz)
ener
gy d
ensi
ty (
m2 /H
z)
long=282 deg; lat=-26 deg
WAMASSIASAR
Comparison between wave spectra:Without limitation in the scheme (may 3 at 6:00)Long=282 deg; lat=-26 deg
Comparison between wave spectra:Without limitation in the scheme (f=0.1 Hz)Long=282 deg;lat=-26 deg
0 100 200 3000.05
0.1
0.15
0.2
wave direction (degrees)
frequ
ency
(H
z)
WAM-FG
0
10
20
30
0 100 200 3000.05
0.1
0.15
0.2
wave direction (degrees)
frequ
ency
(H
z)
ASSIMILATED
0
5
10
15
20
0 100 200 3000.05
0.1
0.15
0.2
wave direction (degrees)
frequ
ency
(H
z)
ASAR-ENVISAT
0
5
10
15
0 0.1 0.2 0.3 0.40
5
10
15
20
frequency (Hz)
ener
gy d
ensi
ty (
m2 /H
z)
long=282 deg; lat=-26 deg
WAMASSIASAR
0 100 200 3000.05
0.1
0.15
0.2
wave direction (degrees)
frequ
ency
(H
z)
WAM-FG
0
2
4
6
8
10
0 100 200 3000.05
0.1
0.15
0.2
wave direction (degrees)
frequ
ency
(H
z)
ASSIMILATED
0
5
10
15
0 100 200 3000.05
0.1
0.15
0.2
wave direction (degrees)
frequ
ency
(H
z)
ASAR-ENVISAT
0
5
10
0 0.1 0.2 0.3 0.40
2
4
6
8
10
frequency (Hz)
ener
gy d
ensi
ty (
m2 /H
z)
long=278 deg; lat=-11 deg
WAMASSIASAR
Comparison between wave spectra:Without limitation in the scheme Long=278 deg; lat=-11 deg
0 100 200 3000.05
0.1
0.15
0.2
wave direction (degrees)
frequ
ency
(H
z)WAM-FG
0
2
4
6
8
10
0 100 200 3000.05
0.1
0.15
0.2
wave direction (degrees)
frequ
ency
(H
z)
ASSIMILATED
0
5
10
0 100 200 3000.05
0.1
0.15
0.2
wave direction (degrees)
frequ
ency
(H
z)
ASAR-ENVISAT
0
5
10
0 0.1 0.2 0.3 0.40
2
4
6
8
10
frequency (Hz)
ener
gy d
ensi
ty (
m2 /H
z)
long=278 deg; lat=-11 deg
WAMASSIASAR
Comparison between wave spectra:Without limitation in the scheme (f=0.1 Hz)Long=278 deg; lat=-11 deg
0 10 20 30 40 500
0.5
1
1.5
2
2.5
3
3.5
4
observation index
low
fre
qu
en
cy w
ave
he
igh
t (m
)
may 3, 2002 at 6:00
assi-totalasar-envisatnoassiassi-limit10
Bias(m) RMS(m) STD(m)Assi total spectrum
Assi spectrum cut-off0.1 Hz
Without assim
-0.102 0.292 0.277
0.037 0.243 0.245
-0.369 0.648 0.539 Statistic analysis for low frequency wave height Hs>10s(set 1)Date : may 3 at 6:00
240 250 260 270 280 290-80
-60
-40
-20
0
20
40
longitude (degrees)
lati
tud
e (
de
gre
es)
locations of observations; may 3 at 6:00
0 20 40 60 800
1
2
3
4
5
observation index
low
fre
qu
en
cy w
ave
he
igh
t (m
)
may 3, 2002 at 12:00
assi-totalasar-envisatnoassiassi-limit10
Statistic analysis for low frequency wave height Hs>10s(set 2)Date : may 3 at 12:00
Assi total spectrum
Assi spectrum cut-off0.1 Hz
Without assim
-0.057 0.475 0.475
-0.092 0.341 0.329
-0.461 0.688 0.513
100 150 200 250 300 350-80
-60
-40
-20
0
20
40
60
80
longitude (degrees)
lati
tud
e (
de
gre
es)
total spectrum; may 3 at 12:00
Bias(m) RMS(m) STD(m)
1 2 3 4 50
0.5
1
1.5
2
2.5
3
3.5
4
observation index
low
fre
qu
en
cy w
ave
he
igh
t (m
)
may 4, 2002 at 0:00
assi-totalasar-envisatnoassiassi-limit10
Statistic analysis for low frequency wave height Hs>10s (set 3)Date : may 4 at 0:00
Assi total spectrum
Assi spectrum cut-off0.1 Hz
Without assim
0.010 0.592 0.596
-0.077 0.349 0.342
-0.438 0.7 0.548
0 100 200 300 4000
10
20
30
40
50
60
70
80
longitude (degrees)
lati
tud
e (
de
gre
es)
obs locations; may 4 at 0:00
Bias(m) RMS(m) STD(m)
0 10 20 30 40 50 60 700
1
2
3
4
5
6
observation index
may 3, 2002 at 6:00, limited
SW
H in
me
ters
NOASSIERS-ALTIASAR-ENVISATASSI=SPEC
Bias (m) RMS (m)ERS2alti-asar-level2 1.18 1.35ERS2alti-wam 0.28 0.89ERS2alti-assi-cutoff 0.47 0.87
Results on significant Wave height may 3 at 6:00
Comparison to ERS2 Altimeter significant wave height
0 20 40 60 80 1000
1
2
3
4
5
6
7
8
observation index
may 3, 2002 at 12:00, limited
SW
H in
me
ters
NOASSIERS-ALTIASAR-ENVISATASSI=SPEC
Bias (m) RMS (m)Ers2alti-asar-level2 0.58 1.24Ers2alti-wam -0.75 1.37Ers2alti-assi-cutoff -0.42 1.25
Results on significant Wave height may 3 at 12:00
Comparison to ERS2 Altimeter significant wave height
0 1 2 3 4 5 6 7 80
1
2
3
4
5
observation index
may 4, 2002 at 0:00, limited
SW
H in
me
ters
NOASSIERS-ALTIASAR-ENVISATASSI=SPEC
Bias (m) RMS (m)Ers2alti-asar-level2 0.62 0.73Ers2alti-wam -0.66 0.68Ers2alti-assi-cutoff -0.52 0.55
Results on significant Wave height may 4 at 0:00
Comparison to ERS2 Altimeter significant wave height
Assimilation impact on SWH may 3 at 12:00
Assimilation impact on mean Frequency may 3 at 12:00
Assimilation index : (%) SWH 53
mean period 41.6 mean direction 51.3
RMS with assi without assiSWH (m) 0.385 0.817Period (s) 1.56 2.6Direction(deg) 32.7 49.4
Assimilation impact on SWH may 8 at 12:00
Assimilation mpact on mean frequency may 8 at 12:00
Concluding remarks and future works
Assimilation scheme in wave model is efficient and works correctlyperformance will be improved
The limitation of the spectral information (frequency cut-off) is very important for the wave forecast otherwise the analysed wave parameters will be deteriorated
Long period assimilation for validation and analyse of the Impact on the wave forecast (one week complete data, if Nick can provide us)
Combined assimilation ASAR and RA2
Financial support to continue this study and to have more conclusiveInterpretations (ESA, CNES)