ALBERT

Description: Results are reported on the performance of (1) denuder-tube/chemiluminescent, (2) nylon-filter/ion-chromatography, and (3) tunable-diode-laser/multipath-absorption HNO3 measurement instruments during the NASA Global Tropospheric Experiment Chemical Instrumentation Test and Evaluation 2 (CITE 2) program in summer 1986. The instrument designs, test protocols, and CITE 2 flights are described, and the results are presented in extensive graphs and discussed in detail. The data obtained with the three instruments are shown to be in very poor agreement at mixing ratios below 150 parts per trillion by volume (pptv), with significant discrepancies even at higher levels. Instrument (3) gave systematically higher values than (1) and (2). It is concluded that none of the instruments is accurate enough for reliable use at normal atmospheric HNO3 levels (around 100 pptv).

Description: Results on NO2 instruments are reported from the NASA Global Tropospheric Experiment Chemical Instrumentation Test and Evaluation 2 (CITE 2) program in summer 1986. The instruments tested were (1) a two-photon LIF system using a laser for NO2-NO photolysis, (2) a chemiluminescence (CL) detector using FeSO4 for NO2-NO conversion, (3) a CL detector using an arc lamp for NO2-NO photolysis, and (4) a tunable-laser-diode multipath-absorption system. The procedures for the CITE 2 ground-based and flight tests are described in detail, and the results are presented in extensive graphs. Instrument (2) was eliminated because the FeSO4 converted atmospheric PAN to NO, resulting in spuriously high NO2 values. The remaining instruments gave readings in 30-40-percent agreement at NO2 mixing ratios of 100-200 parts per trillion by volume (pptv). At ratios below 50 pptv, the correlation among the measurements was very poor, with a tendency for system (4) to give higher values than (1) or (3).

Description: The Arctic Boundary Layer Expedition (ABLE) 3B used data from ground-based, aircraft, and satellite platforms to characterize the chemistry and dynamics of the troposphere in subarctic and Arctic regions of midcontinent and eastern Canada during July - August 1990. This paper reports the experimental design for ABLE 3B and a brief overview of results. The detailed results are presented in a series of papers in this issue. The chemical composition of the atmospheric mixed layer over remote tundra, boreal wetland, and forested environments was influenced by emissions of CH4 and nonmethane hydrocarbons from biogenic sources, emissions of gases and aerosols from local biomass burning, and transport of pollutants into the study areas from urban/industrial sources. Minimum concentrations of both trace gas and aerosol species in boundary layer air were associated with Arctic source areas. In the free troposphere the biospheric influence was undetectable, and major sources of chemical variability were related to long-range transport of pollutants into the study areas from biomass burning and industrial sources in Alaska and the Great Lakes regions, respectively. Minimum concentrations of both trace gas and aerosol species in the free troposphere were associated with a persistent, widespread air mass which both chemistry and air mass trajectory analyses suggested had originated in the tropical Pacific. Subsidence of air from the upper troposphere and lower stratosphere frequently enhanced ozone and influenced other trace gas and aerosol species at midtropospheric altitudes. The North American Arctic is a complex dynamical and chemical environment with considerable spatial and temporal variability in aerosol and trace gas concentrations. The use of atmospheric chemical indicators for climate change detection will require a much more comprehensive Arctic monitoring program than currently exists.

Description: The Arctic Boundary Layer Expedition (ABLE 3A), conducted in Arctic and sub-Arctic regions of North America and Greenland during July and August 1988, was the first comprehensive investigation of the sources, sinks, and distribution of trace gas and aerosol chemical species in a northern high-latitude region during summer months. The experimental design emphasized the role of biosphere-atmosphere interactions in determining the chemical composition of the troposphere and in processes which influence the tropospheric O3 budget. This paper reports the overall experimental design of ABLE 3A and includes a brief overview of results.

Description: This paper describes the overall experimental design for the Amazon Boundary Layer Experiment (ABLE 2B), which used data from aircraft, ground-based, and satellite platforms to characterize the chemistry and dynamics of the lower atmosphere over the Amazon Basin during wet season conditions in April-May 1987. The ABLE 2B focused on determining the spatial and temporal scales of variability in trace gases and aerosols in the lower and midtroposphere over the Amazonian rain forest during wet season conditions, and assessing the role of local-to-regional atmospheric scales of motion on determining the distribution of atmospheric chemical species and their photochemical environment. A summary of the results from the combined ABLE 2A and ABLE 2B are presented.