Post on 01-Apr-2015
transcript
Verification ofRA-2 Wind and Wave
andMWR Water Content
Products
Peter Janssen and Saleh Abdalla
ECMWF, Reading, UK
Time series of Means and Standard Deviations
for the period18 July – 22 Nov. 2002
0
5000
10000
15000
20000
25000
15-Jul 25-Jul 4-Aug 14-Aug 24-Aug 3-Sep 13-Sep 23-Sep 3-Oct 13-Oct 23-Oct 2-Nov 12-Nov 22-Nov
Nu
mb
er
of
En
trie
s
Ku-Band Altimeter
Note the drop in Backscatter on the 23rd of October and the consequences for mean wind
speed.
0.00
2.00
4.00
6.00
8.00
10.00
12.00
14.00
15-Jul 25-Jul 4-Aug 14-Aug 24-Aug 3-Sep 13-Sep 23-Sep 3-Oct 13-Oct 23-Oct 2-Nov 12-Nov 22-Nov
Ku
-Ban
d B
acks
catt
er (
dB
)
MeanStd. Deviation
0.00
2.00
4.00
6.00
8.00
10.00
12.00
14.00
16.00
15-Jul 25-Jul 4-Aug 14-Aug 24-Aug 3-Sep 13-Sep 23-Sep 3-Oct 13-Oct 23-Oct 2-Nov 12-Nov 22-Nov
Win
d S
pe
ed
(m
/s)
Mean
Std. Deviation
0.00
0.50
1.00
1.50
2.00
2.50
3.00
3.50
15-Jul 25-Jul 4-Aug 14-Aug 24-Aug 3-Sep 13-Sep 23-Sep 3-Oct 13-Oct 23-Oct 2-Nov 12-Nov 22-Nov
Ku
-Ba
nd
SW
H
(m)
Mean
Std. Deviation
S-Band Altimeter
In the early period S-band was erratic but since the 2nd of November appears to be
stable.
0.00
5.00
10.00
15.00
20.00
25.00
30.00
35.00
15-Jul 25-Jul 4-Aug 14-Aug 24-Aug 3-Sep 13-Sep 23-Sep 3-Oct 13-Oct 23-Oct 2-Nov 12-Nov 22-Nov
S-B
and
Bac
ksca
tter
(d
B)
MeanStd. Deviation
0.00
1.00
2.00
3.00
4.00
5.00
6.00
7.00
8.00
9.00
10.00
15-Jul 25-Jul 4-Aug 14-Aug 24-Aug 3-Sep 13-Sep 23-Sep 3-Oct 13-Oct 23-Oct 2-Nov 12-Nov 22-Nov
S-B
and
SW
H (
m)
MeanStd. Deviation
MWR Total Column Water Vapour
There is a large variability on a daily time scale
0.00
10.00
20.00
30.00
40.00
50.00
60.00
70.00
80.00
90.00
100.00
15-Jul 25-Jul 4-Aug 14-Aug 24-Aug 3-Sep 13-Sep 23-Sep 3-Oct 13-Oct 23-Oct 2-Nov 12-Nov 22-Nov
To
tal C
olu
mn
Wat
er V
apo
ur
(kg
/m2)
MeanStd. Deviation
Statistics for October 2002
. Ku-band winds against modeland against buoys . Ku-band waves . S-band waves . TCWV from MWRagainst model
Atmospheric model shows saturation in TCWV but MWR
observations not.Thermodynamics of the moist adiabat tells you, however, that for given SST there is an upper
limit to the amount of water vapour the atmosphere can
contain.
RA2 – ERS-2 – Buoy - ModelCollocations
(18 July - 17 Nov. 2002)
Results of Triple Collocation of HS > 1 m and a collocation error
of 1.5% are:
# of collocations: 723Envisat error: 6.3%ERS-2 error: 7.1%Buoy error: 9.3%
Analysis error: 4.6%
The collocation method also provides corrections with respect to an arbitrarily chosen standard,
say the buoys.The results are:
Envisat is too high by 3.0%ERS-2 is too low by 4.4%
Analysis is too low by 5.5%