During 1983-2001, NASA conducted a collection of field campaigns as part of the Global Tropospheric Experiment (GTE) for developing advanced instrumentation to quantify atmospheric trace gases’ sources, sinks, and distribution as well as gain a better understanding of atmospheric chemical processes throughout the troposphere. Among those field campaigns were the Atmospheric Boundary Layer Experiment (ABLE) campaigns. The ABLE expeditions were separated into three campaigns to study different ecosystems whose biosphere-atmosphere interaction strongly influence global tropospheric chemistry. The Arctic Boundary Layer Expedition (ABLE 3) was designed to survey two different high-latitude ecosystems over summer months, focusing on understanding the “early warning” response of a near-surface, organic active layer to climate variability (Harriss et al., 1992).

ABLE 3A took place in the Arctic and subarctic regions of North America during July-August 1988. The primary objectives of ABLE 3A were to investigate the magnitude and variability of methane emissions from the tundra ecosystem and to elucidate factors controlling ozone production and destruction in the Arctic atmosphere (Harriss et al., 1992). Observations from Able 3A showed that climate variability in soil moisture and temperature changes were linked to methane emissions and that while nitrous oxide (NOx) concentrations were low enough to still contribute to ozone (O3) destruction, the increase in NOx levels had already reduced the capacity of the region to act as an O3 sink.

The follow-on to ABLE 3A, ABLE 3B, occurred in the north central and northeastern boreal forest regions of Canada during July-August 1990. ABLE 3B’s focus was 3 parts: (1) influence of regional biosphere-atmosphere interactions on the atmospheric biogeochemical cycles; (2) importance of long-range transport as a source of airborne pollutants; and (3) atmospheric photochemical conditions related to the production and/or destruction of tropospheric ozone (Harriss et al., 1994).

To accomplish its objectives, the ABLE 3 science team deployed the NASA Lockheed Electra aircraft on both sub-campaigns. With over 50 total flights, ABLE 3 utilized the Electra aircraft to take measurements of methane (CH4), carbon monoxide (CO), carbon dioxide (CO2), nonmethane hydrocarbons (NMHC), acetic acid (HA), formic acid (HFo), nitric oxide (NO), nitrogen dioxide (NO2), total “reactive” nitrogen gas (NOy), nitric acid (HNO3), peroxyacetyl nitrate (PAN), peroxypropionyl nitrate (PPN), O3, and aerosol chemical composition and size distribution. Onboard the Electra, the airborne UV Differential Absorption Lidar (DIAL) provided remotely sensed data on the two-dimensional distribution of aerosols and O3.

The results of ABLE 3 indicated that atmospheric chemical changes in arctic and subarctic regions may serve as unique early warning indicators of global changes. The expeditions characterized five factors that influenced summertime O3 concentrations and processes: (1) stratosphere-troposphere exchange, (2) emissions from biomass burning, (3) emissions and transport of industrial pollutants, (4) biospheric effects on production/destruction processes, and (5) long range transport of tropical air to northern high latitudes (Harriss et al., 1994). ABLE 3 also provided the first comprehensive observational data to assess the importance of stratosphere-troposphere exchange on midsummer tropospheric O3 concentrations in the North American Arctic and Subarctic using the DIAL lidar (Harriss et al., 1994). Detailed descriptions related to the motivation, implementation, and instrument payloads are available in the ABLE 3A overview paper and the ABLE 3B overview paper.