Supplementary Material: Machine Learning Nowcasting of GNSS-Derived Tropospheric Turbulence Parameters
Authors: Gaël Kermarrec, [co-authors]
Journal: [Journal name]
DOI: [to be added upon publication]
Overview
This repository contains supplementary animations accompanying the manuscript "Machine Learning Nowcasting of GNSS-Derived Tropospheric Turbulence Parameters over the United Kingdom."
The animations show the spatiotemporal evolution of two turbulence parameters — the cutoff frequency λ (s⁻¹) and the fluctuation amplitude σ (mm) — estimated from high-rate Zenith Wet Delay (ZWD) observations at approximately 100 GNSS stations across the United Kingdom. Fields are interpolated using natural neighbor interpolation with Gaussian smoothing for visualization.
Files
| File | Movie | Event | Parameter | Description |
|------|-------|-------|-----------|-------------|
| lambda_2021_214_evolution_HD.mp4 | S1 | 2 Aug 2021 (DOY 214) | λ | Organized frontal passage |
| sigma_2021_214_evolution_HD.mp4 | S2 | 2 Aug 2021 (DOY 214) | σ | Organized frontal passage |
| lambda_2021_221_evolution_HD.mp4 | S3 | 9 Aug 2021 (DOY 221) | λ | Fragmented air-mass convection |
| sigma_2021_221_evolution_HD.mp4 | S4 | 9 Aug 2021 (DOY 221) | σ | Fragmented air-mass convection |
| lambda_2021_304_evolution_HD.mp4 | S5 | 31 Oct 2021 (DOY 304) | λ | Halloween windstorm (organized frontal) |
| sigma_2021_304_evolution_HD.mp4 | S6 | 31 Oct 2021 (DOY 304) | σ | Halloween windstorm (organized frontal) |
Event Descriptions
Movies S1–S2: Organized Frontal Event (2 August 2021)
A frontal system associated with an upper-level trough crosses the UK from southwest to northeast. The λ and σ fields display coherent maxima propagating systematically across the network at approximately 40 km h⁻¹, consistent with the documented frontal speed from ERA5 reanalysis. The southwest-to-northeast progression is clearly visible in both parameters.
Movies S3–S4: Fragmented Convection (9 August 2021)
Air-mass convection develops in an environment of moderate CAPE with weak synoptic forcing. Multiple isolated cells appear and decay asynchronously across the domain. The λ and σ fields show scattered hotspots without coherent spatial organization or systematic propagation, illustrating the fundamental contrast with organized frontal events.
Movies S5–S6: Halloween Windstorm (31 October 2021)
An intense frontal system with a secondary mesolow produces the strongest turbulence signals in the dataset. Sharp gradients in both λ and σ propagate rapidly across the domain, with the frontal band clearly visible as a coherent band of elevated values extending from southwestern England to northeastern Scotland.
Technical Details
- Temporal resolution: 25-minute intervals (corresponding to the sliding window step of the Matérn parameter estimation)
- Spatial resolution: ~100 GNSS stations across the UK, interpolated to a 0.1° grid
- Video format: MP4 (H.264), 1920×1080, 1 fps
- Parameter estimation: Von Kármán / Matérn spectral model fitted to ZWD residuals using weighted maximum likelihood estimation (see manuscript Section 2)
Data Availability
Raw GNSS observations are available from the British Isles continuous GNSS Facility (BIGF; http://www.bigf.ac.uk). The processed turbulence parameter dataset and trained Random Forest models are available from the corresponding author upon reasonable request.
Citation
If you use these materials, please cite:
[Full citation to be added upon publication]
License
This supplementary material is provided under CC BY 4.0.