TROPO Product

The OPERA Level-4 Troposphere Zenith Radar Delays (TROPO) product provides global estimates of atmospheric delay that can help correct atmospheric signal errors from any Synthetic Aperture Radar (SAR) mission. Radar signals slow down as they pass through Earth’s atmosphere, especially due to variations in temperature, pressure, and water vapor. These effects—collectively known as tropospheric delay—are one of the largest sources of noise in InSAR measurements of ground motion. TROPO quantifies this delay by providing zenith-integrated hydrostatic and wet components, derived from the European Centre for Medium-Range Weather Forecasts (ECMWF) High-Resolution Forecast (HRES) model.

The OPERA TROPO product is fully sensor-agnostic, TROPO supports corrections for OPERA’s SAR-based products (CSLC, DISP, and VLM) and other external products derived from existing and future SAR missions such as Sentinel-1, NISAR, ALOS, RADARSAT, TerraSAR-X, and more.

Each TROPO dataset delivers:

• Global coverage on a ~8 km (0.07°) latitude/longitude grid
• Four observations per day (00, 06, 12, 18 UTC)
• Delay profiles from the surface to ~81 km altitude
• Hydrostatic and wet delay fields needed to correct radar measurements
• CF-1.8–compliant NetCDF format with complete geolocation and metadata

These layers are designed so users can easily combine them with a digital elevation model (DEM) and project the delays into any radar viewing geometry, enabling accurate tropospheric corrections for SAR data. TROPO therefore helps reveal true surface deformation signals—for example, subsidence, uplift, tectonic motion, or changes related to groundwater or ice—by removing atmosphere-related distortions.

The TROPO record begins in July 2016, providing a long, consistent archive suitable for both operational and research applications. All TROPO products are openly distributed through the Alaska Satellite Facility Distributed Active Archive Center (ASF DAAC).

To contact us or give feedback: opera.sep@jpl.nasa.gov