Enhanced Use of Altimeter Wind and Wave Products at ECMWF

Author:

Abdallah Saleh - (ECMWF)

Co-Investigator(s):

Giovanna De Chiarai (ECMWF)

Abstract:

ECMWF has been using altimeter wind and wave data since the early 1990’s (see for example Abdalla and Janssen, 2018). The data has been used for monitoring the quality of model wind and wave fields. Furthermore, altimeter data are used to assess the model development. The most important use is the assimilation of significant wave height to improve the current state (analysis) and forecasts. At the same time, the model fields have been used to monitor and assess the altimeter wind and wave products.

This work has three major aims: The first is to maintain the currently ongoing work done using wind and wave data from current altimeters. Altimeter data are verified against each other as well as ECMWF model, in-situ data and possibly other instruments like scatterometers. The second aim is to monitor, assess and make use of the wind and wave data from the forthcoming satellites like Sentinel-6 and Sentinel-3C & D. The third aim is to investigate the possibility of improving the assimilation of altimeter data in the ECMWF model.

For the purpose of this work the global near real time (NRT; usually referred to as OGDR) ocean wind and wave products from various altimeters like Jason-3, Sentinel-3 and Sentinel-6. This involves extensive assessment of the altimeter products to explore their characteristics like availability, accuracy, consistency and reliability. It also involves the assimilation of NRT significant wave height information in the wind wave model ECWAM that is run operationally at ECMWF. All altimetry wind and wave data products available in NRT pass a monitoring and validation process to check their quality. The tools that were developed in-house and used for the monitoring and validation of data from earlier altimetry missions like ERS, ENVISAT are adapted to monitor and validate the quality of the wind and wave products from new satellites (e.g. Sentinel-6). Model fields, in-situ observations and scatterometer data will be used for the validation purpose. Once the quality of altimeter significant wave height (SWH) products is determined, their assimilation in the ECMWF ocean wave model will be tested by conducting numerical experiments and assessing their impact on the wave model predictions. If they proved to be beneficial, they will be assimilated in ECMWF wave model on operational basis.

Altimeter SWH and surface wind speed products are used as a diagnostic tool to assess the potential model changes and they are also used to make statements regarding the model performance. Furthermore, nonconventional techniques, e.g. triple collocation and spectral analysis, will be used to characterise the quality of the altimeter products as well as those of the model.

The work specified here is done using the resources made available through various funded projects. If some of those resources do not materialise, some of the tasks will not be carried out.