CLARA-A2: 34-Year Global Cloud, Albedo, and Radiation Data from AVHRR Satellites

CLARA-A2 provides a 34-year record (1982-2015) of cloud, surface albedo, and radiation parameters derived from NOAA and METOP satellite AVHRR sensors. The dataset, created by the Swedish Meteorological and Hydrological Institute, features inter-calibrated and homogenized radiances using MODIS Collection 6 as a reference. It includes daily and monthly averages on a 0.25° global grid, with polar region data at 25 km resolution.

Use Cases

• Analyzing long-term trends in cloud cover and properties based on the 34-year time series.
• Modeling surface energy budgets based on downwelling shortwave and longwave radiation components.
• Studying polar climate dynamics based on surface albedo and cloud products in the dedicated equal-area grids.
• Developing improved cloud detection algorithms based on the probabilistic cloud mask experimental product.
• Investigating cloud microphysics based on joint frequency histograms of cloud optical thickness, cloud top pressure, and phase.

Strengths

• Covers a 34-year time period (1982-2015), enabling long-term climate studies.
• Features inter-calibration and homogenization using MODIS Collection 6 as a reference, likely improving consistency.
• Provides data on multiple spatial grids, including a global 0.25° grid and a 25 km polar grid.
• Includes an extended product portfolio with daily resampled Level 2b cloud products compared to the previous edition.

Limitations

• Column-level documentation is absent; field semantics must be inferred after download.
• Last update date is unknown; freshness unverified.
• Data may reflect temporal bias inherent to the specific 1982-2015 satellite record.

Provenance

Source

Swedish Meteorological and Hydrological Institute (SMHI).

Collection Method

Derived from AVHRR sensor data onboard polar orbiting NOAA and METOP satellites, with inter-calibration against MODIS.

Time Range

1982-2015.

Freshness

Edition 2 covers data up to 2015; last update date for the dataset record is unknown.

Geography

Global, with specific polar region grids.