Mesoscale Improved Data Assimilations of Scatterometer winds (MIDAS)

MIDAS is a collaborative project between The Portuguese Institute for Sea and Atmosphere (IPMA) and The Royal Netherlands Meteorological Institute (KNMI) that aims to provide EUMETSAT users and the NWP community with relevant information on the use of scatterometers in data assimilation.

Objectives

The main objectives of the study are to:

1. Assess the impact of scatterometer data assimilation in mesoscale NWP.
2. Investigate strategies to take optimal benefit from denser space-time scatterometer wind observations in mesoscale data assimilation.
3. Learn about the optimal spatial-temporal coverage of scatterometes data assimilation in mesoscale NWP.

Through the benefits in regional mesoscale NWP, optimal use of scatterometer winds will benefit marine alert advisories in the off-shore economy (transport, energy, tourism). In addition, it will provide improved high-resolution winds to force ocean, wave and surge models. Moreover, lessons learned from this study may contribute to the future transition to Metop-SG.

Overview

IPMA and KNMI will conduct this study using the HARMONIE-AROME 4D-Var DA system for a domain over southwestern Europe. See the detailed description of the HARMONIE-AROME forecast model setup.

The domain includes a large area covered by the Atlantic where initialization through observations, such as ocean winds from scatterometers, is critical. A 4D-Var DA method will allow to overcome the time mismatch between observations and analysis time, which is a major limitation of scatterometer winds assimilation in current mesoscale convective scale NWP models using the 3D-Var technique.

Specifically, the study will address:

• The preparation of the HARMONIE-AROME 4D-Var system for a domain over the Iberian Peninsula.
• Adaptation of the interface and code for adding different scatterometer observations in the assimilation system.
• Tuning settings for scatterometer use in the data assimilation system.
• The impact of the scatterometer’s improved spatial coverage in the observation system, taking advantage of 3 operational Metop missions in orbit during the project time frame.
• The impact of improved temporal coverage provided by HY-2B (into a 6:00 LTAN) and CFOSAT (into a 7:00 LTDN) scatterometers, measuring at different local times in the observation system. Note that further improvements of temporal/spatial coverage can potentially be obtained if during the time frame of MIDAS, well-calibrated data from OSCAT-3 (launch schedule is into a noon LTAN orbit in July 2020), HY-2C (scheduled in a regressive orbit by July 2020) and from WindRad on the Feng Yun-3E satellite (into a 6:00 LTAN by December 2020), become available.
• Testing different approaches to data thinning, superobbing (averaging in observation space) and supermodding (averaging in model space).
• Experiments to infer the validity of the scatterometer implementation in 4D-Var.