Surface Meteorological includes the GAPP surface meteorological data sets and includes links to many national, regional, state and local meteorolgical networks.

Precipitation and Radar includes the GAPP precipitation and radar data sets and includes links to a variety of precipitation and radar specific data sources (many of the Surface Meteorological Data Sources also provide precipitation data).

Snow and Ice includes the GAPP snow and ice data sets and includes links to a variety of snow and ice specific data sources including the NSIDC, NRCS SNOTEL and snow surveys and others.

Hydrological includes the GAPP hydrology data sets and includes links to a variety of agencies and their internal organizations that provide hydrological data. These include the US Bureau of Reclamation and the US Geological Survey.

Flux and Carbon Cycle includes the GAPP flux and carbon cycle data sets and includes links to sources for flux and carbon cycle data (including Ameriflux).

Upper Air includes the GAPP upper air data sets and includes links to data and information on the radiosonde network as well as profilers and others.

Land and Soils includes the GAPP land and soils data sets and includes links to a variety of agencies that provide land and soils data and information. These include the USGS, EROS Data Center, NRCS, and others.

Climatological Data includes the GAPP climatological data sets and includes links to a variety of agencies that provide climatological data and information.

Federal Agencies includes general links to federal agencies including NOAA, NASA, among others.