Aerosol size distributions during the Atmospheric Tomography (ATom) mission: methods, uncertainties, and data products

Abstract

Abstract. From 2016–2018 a DC-8 aircraft operated by the U.S. National Aeronautics and Space Administration (NASA) made four series of flights, profiling the atmosphere from 150 m to ~ 12 km above sea level from the Arctic to the Antarctic over both the Pacific and Atlantic Oceans. This program, the Atmospheric Tomography (ATom) mission, sought to sample the troposphere in a representative manner, making measurements of atmospheric composition in each season. This paper describes the aerosol microphysical measurements and derived quantities obtained during this mission. Dry size distributions from 2.7 nm to 4.8 µm in diameter were measured in-situ at 1 Hz using a battery of instruments: 10 condensation particle counters with different nucleation diameters, two ultra-high sensitivity aerosol size spectrometers (UHSAS), one of which measured particles surviving heating to 300 °C, and a laser aerosol spectrometer (LAS). The dry aerosol measurements were complemented by size distribution measurements from 0.5–930 µm diameter at near-ambient conditions using a cloud, aerosol, and precipitation spectrometer (CAPS) mounted under the wing of the DC-8. Dry aerosol number, surface area, and volume, and optical scattering and asymmetry parameter at several wavelengths from the near-UV to the near-IR were calculated from the measured dry size distributions (2.7 nm to 4.8 µm). Dry aerosol mass was estimated by combining the size distribution data with particle density estimated from independent measurements of aerosol composition with a high-resolution aerosol mass spectrometer and a single particle soot photometer. This paper briefly describes the instrumentation and fully documents the aircraft inlet and flow distribution system, the derivation of uncertainties, and the calculation of data products from combined size distributions. Comparisons between the instruments and direct measurements of some aerosol properties confirm that in-flight performance was consistent with calibrations and within stated uncertainties for the two deployments analyzed. The unique ATom dataset contains accurate, precise, high-resolution in-situ measurements of dry aerosol size distributions, and integral parameters, and estimates and measurements of optical properties, for particles

Sea spray aerosol concentration modulated by sea surface temperature

“…Dry particles were measured during all flights. In addition to POPS, the dry aerosol number size distribution was also measured by an aerosol microphysical properties (AMP) package ( 37 , 38 ), which consists of a Laser Aerosol Spectrometer, two nucleation-mode aerosol size spectrometers, and two Ultra-High Sensitivity Aerosol Spectrometers. The ambient size distribution was measured using an externally mounted second-generation Cloud, Aerosol, and Precipitation Spectrometer (CAPS [ 39 ]).…”

Interferences on Aerosol Acidity Quantification due to Gas-phase Ammonia Uptake onto Acidic Sulfate Filter Samples

“…The laser aerosol spectrometer (from TSI), which measured aerosol from geometric diameter 100 nm to 6.3 µm, is used here for volume distribution. For the ATom missions, the measurements have been described elsewhere (Kupc et al, 2018;Williamson et al, 2018;Brock et al, 2019) . Briefly, the dry particle size distribution, from geometric diameter of 2.7 nm to 4.8 µm, were measured by a series of optical particle spectrometers, including the Nucleation Model Aerosol Size Spectrometer (3 nm to 60 nm, custom built (Williamson et al, 2018) ), an Ultra-High Sensitivity Aerosol Spectrometer (60 nm to 1 µm) from Droplet Measurement Technologies (Kupc et al, 2018) ), and Laser Aerosol Spectrometer (120 nm to 4.8 µm) from TSI).…”

Supplementary material to "The Importance of Size Ranges in Aerosol Instrument Intercomparisons: A Case Study for the ATom Mission"

“…It also shows that the AMS cutoff size in dta depends on aerosol density (also altitude, see Table S1 for examples) and the MOUDI impactor cut size depends on altitude. Spectrometer, CAPS) (Brock et al, 2019;Spanu et al, 2020), and submicron dust volume fraction (Fig. S19), respectively.…”

“…Also shown is the line to the LARGE inlet operated by the AMP team that was used at times instead of the HIMIL to check performance (see the comparison inFig. S4)(Brock et al, 2019). Right: Total residence time from the tip of the secondary diffuser inside the HIMIL to the AMS, as a function of altitude, color-coded by the different parts of the inlet assembly.Fig.…”