GSICS Microwave SNO/Vicarious Calibration Focus Group meeting 2025-06-24

1. Lukas Muser (DWD): Analysis of inhomogeneities within satellite footprints
   • Investigating the effects of inhomogeneities within satellite footprints using synthetic observations with a high-resolution NWP model
   • (fov_operator currently does not account for Gaussian antenna pattern of microwave instruments - but this is planned)
   • This project aims to enhance the accuracy of satellite-based data assimilation by understanding and characterizing observation errors
   • Potentially valuable input to SNO uncertainty budgets
   • Analysis could potentially be extended to characterise uncertainties when comparing imperfectly matched observations from two satellites - to be discussed offline
   • to be considered with SNO uncertainties from Variograms and Synthetic Random Fields - presented in SNO Focus Group meeting 2024-08-08
   • Method relies on NWP model ability to characterise spatial variability on grid scale
     • Would be interesting to repeat analysis with high resolution NWP model - and compare over equivalent domains
       
       
2. Shannon Brown (NASA-JPL): Vicarious Calibration algorithms applied to Sentinel-6 AMR/HRMR
   • Vicarious techniques are now considered secondary and used for validating the calibration of altimetry radiometers
   • Newer systems have redundant external calibration (BB + DS) viewed through a secondary reflector and use spacecraft manoeuvres to view deep space
   • Long-term calibration drifts would map 1:1 into sea level height trends
   • Vicarious cold relies on fitting line to cold end of histogram to predict brightness temperature with a zero probability of occuring
   • Amazon hot references, identify areas of dense vegetation: Modelled frequency-dependent emissivity + canopy physical temperature
     • found influence of El Nino years - so developed
   • Calibration Validation against coastal tide gauge records (via L2 products)
     • found dependence on temperature of cold sky switch in older radiometers
   • RFI experience
     • 34GHz limited mostly to continents (debris tracking radars),
     • 18GHz increasingly problematic;
     • no RFI found at HRMR frequencies
     • topic of future T&T Focus Group meeting
       
       
3. Tim Hewison (EUMETSAT) – EPS-Sterna Inter-calibration Constellation Implementation Plan
   • How to roll-out inter-calibration algorithms to constellation of small satellites
   • Planning for operational implementation of algorithms under development, as presented at 2025 Annual GSICS Meeting
   • Should aim to ensure consistent results (within uncertainties) from different methods - including NWP double-differencing
   • Inter-calibration of 325GHz channels expected to be problematic
     • only reliable reference is ICI, which is conically-scanning and has significantly different passbands
     • AWS may be a potential reference if it is still operational and stable, as it will be well-characterised by then
   • GSICS to be invited to final presentation of Inter-calibration study Jan 2026

Attendees