Towards Advanced Sentinel-3 Near Real Time (NRT) L2 synergy capabilities for enhanced atmospheric imagery characterisation

As an operational user-driven Earth observation satellite agency, EUMETSAT is the reference European provider of Near Real Time (NRT - < 3h from the sensing time) Level 2 (L2) atmospheric imagery satellite observations from a constellation combining both Low Earth Orbit (LEO), with Metop / Sentinel-3 and EPS-SG, and GEOstationary (MSG & MTG). Primary users are operational air quality, meteorology and climate services from the Copernicus program and its own member states.

Notably, for several years, EUMETSAT has closely interacted with the Copernicus Atmospheric Monitoring Service (CAMS) and provided expertise to support the uptake of all its observations into the modelling and assimilation processes.

With two multi-spectral optical sensors and observations acquired at a high spatial resolution at 10:00, Sentinel-3 is the main Copernicus mission entrusted to EUMETSAT by the European Commission to provide a high quality of L2 NRT aerosols, fires, water vapour and cloud products at global coverage during morning overpass time for the long future. Current (pre)-existing operational processors are for now solely based on one of the optical sensors. For example:

• The L2 NRT Aerosol Optical Depth (AOD) and Fire Radiative Power (FRP) are retrieved from the Sea and Land Surface Temperature Radiometer (SLSTR) sensor.
• The L2 Total Column Water Vapour, Cloud Top pressure (CTP), and Aerosol Layer Heigh (ALH) are retrieved from the Ocean and Land Colour Imager (OLCI) sensor.

Based on lessons learned, EUMETSAT is now leading a major set of activities to extend the current S3 L2 NRT atmosphere portfolio towards atmospheric imagery with enhanced information and characterization of our atmosphere by combining the measurements from these two optical sensors in an optimal way, accounting for both the operational timeliness requirements and the gridding needs for L2. Such a fundamental work relies on multi-optical spectral synergy and redesign of the L2 operational algorithms. Expected benefits are multiple, such as:

• enhanced aerosol typing (via Fine Mode retrieval, and dust & Single Scattering Albedo determination).
• improved water vapour estimation over both lands and aquatic surfaces.
• more accurate cloud detection, cloud and aerosol discrimination, and cloud obstruction estimation of Top Of Atmosphere (TOA) per spectral channel.

In this presentation, EUMETSAT will summarise the status of all S3 L2 NRT atmosphere products, and illustrate the preliminary progress of the corresponding L2 synergy developments in progress for the purpose of enhanced atmospheric imagery characterisation. Also, the expectations in terms of bridging closer air quality models and observations will be illustrated in the case of aerosol components, early fire warning & impact on smoke forecast, and assimilation.