Quasi-Lagrangian Sampling of Air Pollution by Aircraft during the Intercontinental Chemical Transport Experiment Phase B

One of the goals of NASA's Intercontinental Chemical Transport Experiment Phase B (INTEX-B) was to perform quasi-Lagrangian (q-L) sampling of air pollution as it is transported across the Pacific Ocean from Asia toward North America. We define q-L as air pollution sampled by one aircraft that is later sampled at another location. Iterative procedures are required to determine q-L segments along aircraft flight paths during the INTEX-B sampling. We set meteorological criteria and ran backward trajectories from the C-130 aircraft to determine if q-L connections were made with the DC-8 flights. National Centers for Environmental Prediction (NCEP) reanalyses and GOES satellite imagery help provide a meteorological overview for each case and verify air flow calculations from the trajectory model. In-situ chemical data are used to adjust and confirm the q-L segments. Four case studies are examined. Backward trajectories from the DC-8 q-L segments show that the polluted air masses mostly have Asian origins. Between aircraft sampling, chemical aging rates calculated from a photochemical model show some differences between in-situ-derived aging and model-derived aging. These differences can be attributed to factors such as mixing, dilution, and surface deposition. Carbon Monoxide (CO) from the Atmospheric InfraRed Sounder (AIRS) and from the Goddard Earth Observatory System (GEOS) chemical model shows the spatial extent and locations of the plume features being sampled.