The NASA Aerosol Cloud meTeorology Interactions oVer the western ATlantic Experiment (ACTIVATE) produced a unique dataset for research into aerosol–cloud–meteorology interactions, with applications ...extending from process-based studies to multi-scale model intercomparison and improvement as well as to remote-sensing algorithm assessments and advancements. ACTIVATE used two NASA Langley Research Center aircraft, a HU-25 Falcon and King Air, to conduct systematic and spatially coordinated flights over the northwest Atlantic Ocean, resulting in 162 joint flights and 17 other single-aircraft flights between 2020 and 2022 across all seasons. Data cover 574 and 592 cumulative flights hours for the HU-25 Falcon and King Air, respectively. The HU-25 Falcon conducted profiling at different level legs below, in, and just above boundary layer clouds (< 3 km) and obtained in situ measurements of trace gases, aerosol particles, clouds, and atmospheric state parameters. Under cloud-free conditions, the HU-25 Falcon similarly conducted profiling at different level legs within and immediately above the boundary layer. The King Air (the high-flying aircraft) flew at approximately ∼ 9 km and conducted remote sensing with a lidar and polarimeter while also launching dropsondes (785 in total). Collectively, simultaneous data from both aircraft help to characterize the same vertical column of the atmosphere. In addition to individual instrument files, data from the HU-25 Falcon aircraft are combined into “merge files” on the publicly available data archive that are created at different time resolutions of interest (e.g., 1, 5, 10, 15, 30, 60 s, or matching an individual data product's start and stop times). This paper describes the ACTIVATE flight strategy, instrument and complementary dataset products, data access and usage details, and data application notes. The data are publicly accessible through https://doi.org/10.5067/SUBORBITAL/ACTIVATE/DATA001 (ACTIVATE Science Team, 2020).
Although many regulations have been enacted with the goal of improving air quality, many parts of the U.S. are still classified as “non-attainment areas” because they frequently violate federal air ...quality standards. Adequately monitoring the spatial distribution of pollutants both within and outside of non-attainment areas has been an ongoing challenge for regulators. Observations of near-surface pollution from space-based platforms would provide an unprecedented view of the spatial distribution of pollution and there are plans for launching satellites to broaden the view of air quality. Among the challenges in interpreting satellite observations will be to understand the expected gradients in pollution at scales smaller than the satellite footprint. NASA’s DISCOVER-AQ observations offer the opportunity to examine small-scale spatial gradients for footprints similar to that expected for future satellites, and a metric for identifying those gradients and examining their size and frequency was developed. This analysis is applied to the DISCOVER-AQ spiral profiles, which were designed to provide vertical profiles of pollution in the lower atmosphere. The spirals were approximately 5 km in diameter, meaning that the vertical gradients were sometimes influence by horizontal gradients as well. To identify instances of these horizontal gradients, spirals were divided into octants, and averages of a given species were calculated, with certain points being flagged when its value compared to adjacent octants indicated departure from a natural vertical gradient. This technique showed that a spatial heterogeneity is present in the data, but is not very pervasive, except over certain locations with persistent pollution sources.