Verification of RA-2 Wind and Wave and MWR Water Content Products Peter Janssen and Saleh Abdalla ECMWF, Reading, UK

Time series of Means and Standard Deviations for the period 18 July – 22 Nov. 2002

Jul25-Jul4-Aug14-Aug24-Aug3-Sep13-Sep23-Sep3-Oct13-Oct23-Oct2-Nov12-Nov22-Nov Number of Entries

Ku-Band Altimeter Note the drop in Backscatter on the 23 rd of October and the consequences for mean wind speed.

Jul25-Jul4-Aug14-Aug24-Aug3-Sep13-Sep23-Sep3-Oct13-Oct23-Oct2-Nov12-Nov22-Nov Ku-Band Backscatter (dB) Mean Std. Deviation

Mean Std. Deviation

Jul25-Jul4-Aug14-Aug24-Aug3-Sep13-Sep23-Sep3-Oct13-Oct23-Oct2-Nov12-Nov22-Nov Ku-Band SWH (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.

Jul25-Jul4-Aug14-Aug24-Aug3-Sep13-Sep23-Sep3-Oct13-Oct23-Oct2-Nov12-Nov22-Nov S-Band Backscatter (dB) Mean Std. Deviation

Jul25-Jul4-Aug14-Aug24-Aug3-Sep13-Sep23-Sep3-Oct13-Oct23-Oct2-Nov12-Nov22-Nov S-Band SWH (m) Mean Std. Deviation

MWR Total Column Water Vapour There is a large variability on a daily time scale

Jul25-Jul4-Aug14-Aug24-Aug3-Sep13-Sep23-Sep3-Oct13-Oct23-Oct2-Nov12-Nov22-Nov Total Column Water Vapour (kg/m2) Mean Std. Deviation

Statistics for October Ku-band winds against model and against buoys. Ku-band waves. S-band waves. TCWV from MWR against 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 - Model Collocations (18 July - 17 Nov. 2002)

Results of Triple Collocation of H S > 1 m and a collocation error of 1.5% are: # of collocations: 723 Envisat 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%