Waves breaking on sea wall. Credit: Zacarias da Mata

EPS/ASCAT ocean wind assessment

 

Waves breaking on sea wall. Credit: Zacarias da Mata
Waves breaking on sea wall. Credit: Zacarias da Mata

The objective of the study is the assessment of the impact and further development of the assimilation strategy of ASCAT products on the Metop satellites at the European Centre for Medium-Range Weather Forecasts (ECMWF).

Last Updated

30 January 2023

Published on

30 October 2018

The study also aims to take into account the EPS-SG scatterometer (SCA) features, in particular the better representation of high winds and the higher spatial resolution.

Objectives

The main goals of this study are:

  • To better understand how to handle and take maximum benefit of very high wind speeds, this study aims to improve the QC to allow an inclusion of extreme observations.
  • To investigate the optimal observation sampling strategies by testing different thinning procedures and observation errors.
  • To assess the impact on tropical cyclones (TC) based on the swath coverage and on TC cyclogenesis.
  • To test the sensitivity of the NWP system to different products resolutions.
  • To assess the impact of ASCAT winds on the modeled ocean parameters by using a coupled ocean-atmosphere system.

Overview

The European Centre for Medium-Range Weather Forecasts (ECMWF) conducted this study to provide support for the assessment and further development of ASCAT related products from the Advanced Scatterometer on board the METOP satellites for the EUMETSAT Polar System (EPS). Specifically, the study addressed:

  • The characterisation of the ASCAT wind error, the wind speed distribution and the analysis and background departures. The use of the current ‘Gaussian plus flat’ VarQC distribution for variational quality control within 4D-Var was compared to different settings of the Huber norm VarQC distribution.
  • Sensitivity tests on the use of a reduced thinning and an inflated observation error standard deviation were performed (see Figure 1).
  • The impact of scatterometer winds on the TC developing stage and on the impact of a partial storm coverage by the ASCAT swath were evaluated.
  • An analysis on the use of the ASCAT 12.5 km products, replacing the current 25 km ones used in operations, was carried out.
  • Another analysis, related to the sensitivity of the system to product resolutions, was performed on the assimilation of experimental ASCAT products providing wind observations at low resolutions of 50 km, 62.5 km and 100 km. These products were generated by ICM-CSIS in the framework of a NWP SAF project.
  • The impact of ASCAT winds assimilation on a coupled atmosphere ocean system was evaluated over 2014.
ASCAT-A wind used observations for a case study on TC Kilo for the cycle 8 September 2015 12UTC for the experiments on Huber norm (HN) and reduced thinning (Thin): “CTRL” (a), “VarQC/Thin=2” (b), “HN” (c), “NH/Thin=2” (d).
Figure 1: ASCAT-A wind used observations for a case study on TC Kilo for the cycle 8 September 2015 12UTC for the experiments on Huber norm (HN) and reduced thinning (Thin): “CTRL” (a), “VarQC/Thin=2” (b), “HN” (c), “NH/Thin=2” (d).
Phase Details
Kick-Off 09/03/2015
Duration 24 months
Status Completed: 26/07/2018
WP1 Handling high winds and appropriate observations resolution
WP2 Coupled ocean-atmosphere OSEs
Phase Date and location
Kick-Off 09/03/2015, EUMETSAT
PM 03/06/2016, Telecon
PM 12/07/2016, ECMWF
Work Package 2 KO 10/10/2016, Telecon
Final meeting 26/07/2018, ECMWF

Conference and/or workshop

International Ocean Vector Winds Science Team Meeting (IOVWST), 2016, Sapporo, Japan
13th International Winds Workshop (IWW13), 2016, Monterey, US
International workshop on measuring high-wind speeds over the ocean, 2016, Met Office, Exeter, UK
International Ocean Vector Winds Science Team Meeting (IOVWST), 2017, San Diego, US
EUMETSAT Meteorological Satellite Conference, 2017, Rome, IT

EUMETSAT Project Manager
Dr Stefanie Linow
Remote Sensing Scientist - Scatterometry
Remote Sensing and Products Division
EUMETSAT
Email		 Dr Stephen English
Head of the Earth System Assimilation Section
ECMWF
Email

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