Air motion intercomparison flights during Transport and Chemical Evolution in the Pacific (TRACE‐P)/ACE‐ASIA

Thornhill, K. L.; Anderson, B. E.; Barrick, J. D.; Bagwell, Donald R.; Friesen, R. B.; Lenschow, Donald H.

doi:10.1029/2002jd003108

Cited by 33 publications

(29 citation statements)

References 17 publications

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“…Almost one-third of annual global biomass burning emissions originate from regional fires across the savanna and woodlands of sub-Saharan Africa, and one-fourth originate from southern Africa (van der Werf et al, 2010). From ap-proximately June until October, these intense BB emissions are subsequently transported over the southeast Atlantic (SEA) region (Adebiyi and Zuidema, 2016;Garstang et al, 1996), greatly elevating CCN levels above background concentrations (Ross, et al, 2003) and interacting with low-level marine-boundary-layer clouds that are abundant in the SEA (e.g., Seager et al, 2003;Grosvenor et al, 2018;Zuidema et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

Biomass burning aerosol as a modulator of the droplet number in the southeast Atlantic region

et al. 2020

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Abstract. The southeastern Atlantic (SEA) and its associated cloud deck, off the west coast of central Africa, is an area where aerosol–cloud interactions can have a strong radiative impact. Seasonally, extensive biomass burning (BB) aerosol plumes from southern Africa reach this area. The NASA ObseRvations of Aerosols above CLouds and their intEractionS (ORACLES) study focused on quantitatively understanding these interactions and their importance. Here we present measurements of cloud condensation nuclei (CCN) concentration, aerosol size distribution, and characteristic vertical updraft velocity (w∗) in and around the marine boundary layer (MBL) collected by the NASA P-3B aircraft during the August 2017 ORACLES deployment. BB aerosol levels vary considerably but systematically with time; high aerosol concentrations were observed in the MBL (800–1000 cm−3) early on, decreasing midcampaign to concentrations between 500 and 800 cm−3. By late August and early September, relatively clean MBL conditions were sampled (<500 cm−3). These data then drive a state-of-the-art droplet formation parameterization from which the predicted cloud droplet number and its sensitivity to aerosol and dynamical parameters are derived. Droplet closure was achieved to within 20 %. Droplet formation sensitivity to aerosol concentration, w∗, and the hygroscopicity parameter, κ, vary and contribute to the total droplet response in the MBL clouds. When aerosol concentrations exceed ∼900 cm−3 and maximum supersaturation approaches 0.1 %, droplet formation in the MBL enters a velocity-limited droplet activation regime, where the cloud droplet number responds weakly to CCN concentration increases. Below ∼500 cm−3, in a clean MBL, droplet formation is much more sensitive to changes in aerosol concentration than to changes in vertical updraft. In the competitive regime, where the MBL has intermediate pollution (500–800 cm−3), droplet formation becomes much more sensitive to hygroscopicity (κ) variations than it does in clean and polluted conditions. Higher concentrations increase the sensitivity to vertical velocity by more than 10-fold. We also find that characteristic vertical velocity plays a very important role in driving droplet formation in a more polluted MBL regime, in which even a small shift in w∗ may make a significant difference in droplet concentrations. Identifying regimes where droplet number variability is driven primarily by updraft velocity and not by aerosol concentration is key for interpreting aerosol indirect effects, especially with remote sensing. The droplet number responds proportionally to changes in characteristic velocity, offering the possibility of remote sensing of w∗ under velocity-limited conditions.

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Section: Introductionmentioning

confidence: 99%

Biomass burning aerosol as a modulator of the droplet number in the southeast Atlantic region

et al. 2020

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“…Winds are derived from five pitot static-pressure ports mounted on the radome (nose) of the aircraft (Brown et al, 1983;Thornhill et al, 2003). In essence, these sensors provide the velocity of air with respect to the aircraft.…”

Section: Meteorology and Telemetrymentioning

confidence: 99%

The NASA Carbon Airborne Flux Experiment (CARAFE): instrumentation and methodology

et al. 2018

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Abstract. The exchange of trace gases between the Earth's surface and atmosphere strongly influences atmospheric composition. Airborne eddy covariance can quantify surface fluxes at local to regional scales (1-1000 km), potentially helping to bridge gaps between top-down and bottomup flux estimates and offering novel insights into biophysical and biogeochemical processes. The NASA Carbon Airborne Flux Experiment (CARAFE) utilizes the NASA C-23 Sherpa aircraft with a suite of commercial and custom instrumentation to acquire fluxes of carbon dioxide, methane, sensible heat, and latent heat at high spatial resolution. Key components of the CARAFE payload are described, including the meteorological, greenhouse gas, water vapor, and surface imaging systems. Continuous wavelet transforms deliver spatially resolved fluxes along aircraft flight tracks. Flux analysis methodology is discussed in depth, with special emphasis on quantification of uncertainties. Typical uncertainties in derived surface fluxes are 40-90 % for a nominal resolution of 2 km or 16-35 % when averaged over a full leg (typically 30-40 km). CARAFE has successfully flown two missions in the eastern US in 2016 and 2017, quantifying fluxes over forest, cropland, wetlands, and water. Preliminary results from these campaigns are presented to highlight the performance of this system.

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“…The turbulent air motion measurement system (TAMMS) [ Thornhill et al , 2003] provided 25 Hz data for the u , v , w components of the wind, water vapor mixing ratio (MR) from a Lyman α absorption sensor, static temperature, and pressure. The SO 2 counts data were recorded by the TAMMS data system to insure that the time recorded for the SO 2 counts would be identical to the time recorded for the three component wind data.…”

Section: Methodsmentioning

confidence: 99%

Long‐range transport of sulfur dioxide in the central Pacific

Thornton

Bandy

et al. 2004

J. Geophys. Res.

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Long‐range transport of sulfur dioxide (SO2) from east Asia to the central North Pacific troposphere was observed on transit flights during the NASA Transport and Chemical Evolution over the Pacific mission. A series of SO2‐enhanced layers above the boundary layer was observed during these flights. The significant features included enhanced SO2 layers associated with low water vapor and low turbulence that were usually dynamically isolated from the marine boundary layer. This study shows that atmospheric dynamics were very important in determining the SO2 distributions in the central Pacific during March and April 2001. Trajectory studies revealed that SO2‐enhanced layers could be connected to both volcanic and anthropogenic sources in east Asia. These trajectory studies also showed that the air parcels usually were lifted 2 km above the source regions and then progressed to the east in the midlatitudes (30°–60°N). The air parcels arrived in the central Pacific within 2–3 days. Sulfur dioxide transported at altitudes of 2–4 km dominated the SO2 distribution in the central Pacific. A comparison of SO2 observations and results of chemical transport models indicated that SO2 was removed primarily by cloud processes. Therefore, in the absence of cloud, SO2 can be transported long distances if the trajectory is decoupled from the boundary layer. Another important observation was that the Miyake‐jima volcano made a major contribution to the SO2 concentrations in the central Pacific troposphere during March and April 2001. At times, the volcanic SO2 had more influence in the central Pacific than the six largest anthropogenic SO2 source regions in east Asia.

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Air motion intercomparison flights during Transport and Chemical Evolution in the Pacific (TRACE‐P)/ACE‐ASIA

Cited by 33 publications

References 17 publications

Biomass burning aerosol as a modulator of the droplet number in the southeast Atlantic region

Biomass burning aerosol as a modulator of the droplet number in the southeast Atlantic region

The NASA Carbon Airborne Flux Experiment (CARAFE): instrumentation and methodology

Long‐range transport of sulfur dioxide in the central Pacific

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