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Volume 11, issue 7 | Copyright
Atmos. Meas. Tech., 11, 3969-3985, 2018
https://doi.org/10.5194/amt-11-3969-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 06 Jul 2018

Research article | 06 Jul 2018

HOVERCAT: a novel aerial system for evaluation of aerosol–cloud interactions

Jessie M. Creamean1,2, Katherine M. Primm1, Margaret A. Tolbert1, Emrys G. Hall1,3, Jim Wendell3, Allen Jordan1,3, Patrick J. Sheridan3, Jedediah Smith4, and Russell C. Schnell3 Jessie M. Creamean et al.
  • 1Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO 80309, USA
  • 2Physical Sciences Division, National Oceanic and Atmospheric Administration, Boulder, CO 80305, USA
  • 3Global Monitoring Division, National Oceanic and Atmospheric Administration, Boulder, CO 80305, USA
  • 4Smith & Williamson, Corvallis, OR 97330, USA

Abstract. Aerosols have a profound impact on cloud microphysics through their ability to serve as ice nucleating particles (INPs). As a result, cloud radiative properties and precipitation processes can be modulated by such aerosol–cloud interactions. However, one of the largest uncertainties associated with atmospheric processes is the indirect effect of aerosols on clouds. The need for more advanced observations of INPs in the atmospheric vertical profile is apparent, yet most ice nucleation measurements are conducted on the ground or during infrequent and intensive airborne field campaigns. Here, we describe a novel measurement platform that is less expensive and smaller (<5kg) when compared to traditional aircraft and tethered balloon platforms and that can be used for evaluating two modes of ice nucleation (i.e., immersion and deposition). HOVERCAT (Honing On VERtical Cloud and Aerosol properTies) flew during a pilot study in Colorado, USA, up to 2.6km above mean sea level (1.1km above ground level) and consists of an aerosol module that includes an optical particle counter for size distributions (0.38–17µm in diameter) and a new sampler that collects up to 10 filter samples for offline ice nucleation and aerosol analyses on a launched balloon platform. During the May 2017 test flight, total particle concentrations were highest closest to the ground (up to 50cm−3 at <50m above ground level) and up to 2 in 102 particles were ice nucleation active in the immersion mode (at −23°C). The warmest temperature immersion and deposition mode INPs (observed up to −6 and −40.4°C, respectively) were observed closest to the ground, but overall INP concentrations did not exhibit an inverse correlation with increasing altitude. HOVERCAT is a prototype that can be further modified for other airborne platforms, including tethered balloon and unmanned aircraft systems. The versatility of HOVERCAT affords future opportunities to profile the atmospheric column for more comprehensive evaluations of aerosol–cloud interactions. Based on our test flight experiences, we provide a set of recommendations for future deployments of similar measurement systems and platforms.

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A new balloon-borne system has been developed to measure the properties of aerosol particles that form cloud ice in the lower troposphere, called HOVERCAT (Honing On VERtical Cloud and Aerosol properTies). Test flights in Colorado demonstrated the utility of HOVERCAT for profiling these ice nucleating particles (INPs), where we found higher numbers of INPs from agricultural sources. Measurements by HOVERCAT can help improve understanding of how aerosols impact clouds in the atmosphere.
A new balloon-borne system has been developed to measure the properties of aerosol particles...
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