AVISO L4: Satellite Altimetry Observation Counts for Ocean Topography

Observation counts underpin the AVISO Level 4 Absolute Dynamic Topography dataset, a key input for climate model intercomparison. The data, provided by the French space agency AVISO, are derived from sea surface height measurements by the Envisat, TOPEX/Poseidon, Jason-1, and OSTM/Jason-2 satellites. It is designed to support the CMIP5 (Coupled Model Intercomparison Project Phase 5) portion of the PCMDI (Program for Climate Model Diagnosis and Intercomparison).

Use Cases

• Assessing data density and quality for satellite altimetry products based on the number of observations.
• Supporting the validation of ocean circulation models within the CMIP5 framework.
• Analyzing global ocean surface dynamics referenced to the geoid.
• Providing ancillary metadata for the primary Absolute Dynamic Topography dataset.

Strengths

• Derived from multiple established satellite missions: Envisat, TOPEX/Poseidon, Jason-1, and OSTM/Jason-2.
• Explicitly created to support a major international climate science initiative (CMIP5/PCMDI).
• Hosted and maintained by NASA's Physical Oceanography Distributed Active Archive Center (PO.DAAC).

Limitations

• Column names and data structure are not described in the provided metadata.
• The dataset is not intended for standalone use, requiring the primary Absolute Dynamic Topography data for context.
• Update dates conflict between sources (2010 on NASA Earthdata vs. 2026 on Data.gov), suggesting potential metadata staleness.

Provenance

Source

AVISO (French space agency data provider), processed and distributed by NASA/PO.DAAC.

Collection Method

Generated from sea surface height measurements by satellite altimetry.

Freshness

Last updated date conflicts: 2026-03-13 (Data.gov) vs. 2010-12-30 (NASA Earthdata).

Geography

Global ocean coverage.