the visible portion. More precise work requires the use of spectral albedos, referenced to specific wavelengths. Visible albedos of natural surfaces range from low values of 0.04 for calm, deep water and overhead Sun, to 0.8 for fresh snow or thick clouds. Many surfaces show an increase in albedo with increasing solar zenith angle. (AMS)

ALE

Atmospheric Lifetime Experiment

AMIP

Atmospheric Model Intercomparison Project

Amphiphilic

Of, relating to, or being a compound (as a surfactant) consisting of molecules having a polar, water-soluble group attached to a water-insoluble hydrocarbon chain; also: being a molecule of such a compound.

AO

Arctic Oscillation

AOGCM

Atmosphere-Ocean General Circulation Model

ARGO

A global array that will eventually include approximately 3000 free-drifting profiling floats that measure the temperature and salinity of the upper 2000 m of the ocean.

ARM

Atmospheric Radiation Measurement

ASF Model

Atmospheric Stabilization Framework Model

A-Train

A planned satellite formation consisting of two of the major EOS missions, three Earth System Science Pathfinder missions, and a French Centre National d’Etudes Spatiales (CNES) mission flying along the same orbit track and separated by only a few minutes.

AVHRR

Advanced Very High Resolution Radiometer


Black carbon (BC)

Light-absorbing carbonaceous aerosol, including elemental carbon and low-volatility organic compounds.

BLAG (Berner/Lasaga/Garrels) hypothesis

Variations in seafloor spreading rates lead to variations in volcanic outgassing and, thus, atmospheric CO2 concentrations.

Bowen ratio

The ratio of sensible to latent heat fluxes from the Earth’s surface up into the atmosphere. Typical values are 5 over semiarid regions, 0.5 over grasslands and forests, 0.2 over irrigated orchards or grass, 0.1 over the sea, and negative in some advective situations such as over oases where sensible heat flux can be downward while latent heat flux is upward. (AMS)

BSRN

Baseline Surface Radiation Network



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