Technical Note Phase II WP1200: SMOS Report on data thinning

Technical Note Phase II WP1200: SMOS Report on data thinning
Date Published
ESA/ESRIN Contract 4000101703/10/NL/FF/fk
J.M. Sabater
Tomas Wilhelmsson
Patricia de Rosnay
L. Isaksen
Abstract Contracted by the European Space Agency (ESA), the European Centre for Medium-Range Weather Forecasts (ECMWF) is involved in global monitoring and data assimilation of the Soil Moisture and Ocean Salinity (SMOS) mission data. SMOS is the second Earth's Explorer mission of the ESA Living Planet Programme. ECMWF is receiving the Near Real Time (NRT) product, which is currently used to monitor SMOS brightness temperatures in NRT. This product collects several dozens of multi-angular and multi-polarized measurements of the same target at a relatively global fine spatial resolution. A consequence is that the data product handled at ECMWF has a very high volume. The current operational capabilities of the ECMWF Integrated Forecasting System (IFS) do not make it possible to use the whole SMOS dataset within the monitoring suite or in an assimilation experiment. On the contrary (as it happens for any other source of satellite data), only a reduced subset of observations can be used within the IFS. Therefore, a strong data thinning filter needs to be applied to the data before it is ingested in the IFS. This report discusses several options to thin SMOS data and make it compatible with the IFS structure, while keeping a subsample of representative and good quality data for monitoring and assimilation purposes. This is the technical note, phase II, workpackage number 1200 of the ESA Request for Quotation RfQ 3-13053/09/NL/FF/FvK. It is produced as part of the second phase of the monitoring and data assimilation study with SMOS data at ECMWF, and it is complimentary of reports TN-PII-WP1300 and TN-PII-WP1400 as described in the contract document number 4000101703/10/NL/FF/fk (Oct 2010 - Jan 2013).