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%