The scientific objectives of the ALE/GAGE/AGAGE programs are several in number and of considerable importance in furthering our understanding of a number of important global chemical and climatic phenomena. They are:
- To optimally determine from observations, the rate of emission and/or chemical destruction (i.e. lifetime) of the anthropogenic chemicals (e.g. chlorofluorocarbons (CFCs), halons, hydrofluorocarbons (HFCs), hydrochlorofluorocarbons (HCFCs), perfluorocarbons (PFCs), other fluorinated compounds, chlorocarbons and bromocarbons) that contribute most of the reactive chlorine and bromine released into the stratosphere (ozone depleting substances) and/or are strong infrared absorbers (greenhouse gases).
- To accurately document the global distributions and temporal behavior of the biogenic/anthropogenic gases N2O, CH4, CO, H2, CH3Cl, CH3Br, CH2Cl2, and CHCl3.
- To optimally determine the average concentrations and trends of OH radicals in the troposphere by determining the rates of destruction of atmospheric CH3CCl3 and other hydrohalocarbons from continuous measurements of their concentrations together with industrial estimates of their emissions.
- To optimally determine the magnitude and geographical distributions of sources of trace gases, using high frequency data and theoretical estimates of their rates of destruction.
- To provide an accurate data base on the rates of accumulation of trace gases over the globe which can be used to test the synoptic-, regional- and global-scale circulation predicted by three dimensional models and/or to determine characteristics of the sources of these gases near the stations.
- To provide routine measurements of CH4, CO and H2, and estimates of OH levels that can be used to test primary oxidation pathways in the atmosphere.