DComb wet tropospheric correction for CryoSat-2 over open and coastal ocean

M. Joana Fernandes (Universidade do Porto, Faculdade de Ciências; CIIMAR, Portugal)

CoAuthors

Clara Lazaro (Universidade do Porto, Faculdade de Ciências; CIIMAR, Portugal); Alexandra L. Nunes (Instituto Politécnico do Porto - ISEP; CIIMAR, Portugal); Nelson Pires (Universidade do Porto, Faculdade de Ciências; CIIMAR, Portugal)

Event: 2014 Ocean Surface Topography Science Team Meeting

Session: Instrument Processing: Corrections

Presentation type: Type Oral

In the scope of the CryoSat Plus for Oceans (CP4O) project, supported by the European Space Agency, a data combination (DComb) algorithm has been developed for the computation of the wet tropospheric correction (WTC) for CryoSat-2 (CS-2), which does not possess an on-board microwave radiometer (MWR), thus relying on a model-based WTC provided by the European Centre for Medium-Range Weather Forecasts (ECMWF). The DComb WTC is based on the data combination through objective analysis (OA) of three wet path delay data sources: scanning imaging MWR (SI MWR) on board remote sensing satellites; Global Navigation Satellite Systems (GNSS) measurements at coastal stations and ECMWF operational model fields.

This presentation gives a description of the DComb algorithm and its application to the full CS-2 mission, using the data available in the Radar Altimeter Database System (RADS).

The DComb WTC was first computed for Jason-2 and compared with the correction from the Jason-2 advanced microwave radiometer (AMR) present on the version D of the Geophysical Data Records (GDR-D), known to be a well calibrated and accurate correction, with improved performance in coastal regions. The comparison shows that for epochs and locations for which SI-MWR or GNSS measurements are available, the DComb WTC is very similar to that of AMR. The SI-MWR water vapour products, previously calibrated with respect to AMR, revealed to be an extremely valuable data set for the estimation of the WTC for any altimeter mission. The GNSS data, in spite of its sparseness, play an important role in the coastal regions, of major importance for the full exploitation of CryoSat-2 data, in particular those acquired in the Synthetic Aperture Radar (SAR) mode. Since the SI-MWR coverage varies with time, the DComb correction computed for Jason-2 is globally less accurate than that from AMR, but consistently an improvement with respect to that from ECMWF.

To remove the discontinuities in the OA WTC resulting from the transition between zones with and without GNSS and/or SI-MWR measurements, a dynamically linked model (DLM) type of algorithm was further applied.

For both Jason-2 and CryoSat-2 the new correction was validated through a set of statistical analyses such as along-track sea level anomaly (SLA) variance at crossovers and SLA variance function of distance from the coast and latitude. The results of this validation are presented showing the impact of the correction both on open-ocean and in the coastal regions.
 

Oral presentation show times:

RoomStart DateEnd Date
Ballroom Tue, Oct 28 2014,14:15 Tue, Oct 28 2014,14:30
M. Joana Fernandes
Universidade do Porto, Faculdade de Ciências; CIIMAR
Portugal
mjfernan@fc.up.pt