A53A-0365
Aerosol-cloud closure study using RPAS measurements

Friday, 18 December 2015
Poster Hall (Moscone South)
Radiance Calmer1, Greg Roberts2, Kevin J Sanchez3, Keri Nicoll4, Jana Preissler5, Jurgita Ovadnevaite5, Jean Sciare6, Murat Bronz7, Gautier Hattenberger7, Daniel Rosenfeld8, Samuel Lauda3, Eyal Hashimshoni9 and BACCHUS science team, (1)Organization Not Listed, Washington, DC, United States, (2)Scripps Institution of Oceanography, La Jolla, CA, United States, (3)Météo-France Toulouse, Toulouse Cedex 01, France, (4)University of Reading, Reading, United Kingdom, (5)National University of Ireland, Galway, Ireland, (6)Cyprus Institute, Nicosia, Cyprus, (7)ENAC - École Nationale de l'Aviation Civile, Toulouse, France, (8)Hebrew University of Jerusalem, Jerusalem, Israel, (9)The Hebrew University of Jerusalem, Jerusalem, Israel
Abstract:
Enhancements in Remotely Piloted Aircraft Systems (RPAS) have increased their possible uses in many fields for the past two decades. For atmospheric research, ultra-light RPAS (< 2.5kg) are now able to fly at altitudes greater than 3 km and even in cloud, which opens new opportunities to understand aerosol-cloud interactions. We are deploying the RPAS as part of the European project BACCHUS (Impact of Biogenic versus Anthropogenic Emissions on Clouds and Climate: towards a Holistic Understanding).

Field experiments in Cyprus and Ireland have already been conducted to study aerosol-cloud interactions in climatically different environments. The RPAS are being utilized in this study with the purpose of complementing ground-based observations of cloud condensation nuclei (CCN) to conduct aerosol-cloud closure studies Cloud microphysical properties such as cloud drop number concentration and size can be predicted directly from the measured CCN spectrum and the observed updraft, the vertical component of the wind vector [e.g., Conant et al, 2004]. On the RPAS, updraft measurements are obtained from a 5-hole probe synchronized with an Inertial Measurement Unit (IMU). The RPA (remotely piloted aircraft) are programmed to fly at a level leg just below cloud base to measure updraft measurements while a scanning CCN counter is stationed at ground level. Vertical profiles confirm that CCN measurements on the ground are representative to those at cloud base. An aerosol-cloud parcel model is implemented to model the cloud droplet spectra associated with measured updraft velocities. The model represents the particle size domain with internally mixed chemical components, using a fixed-sectional approach [L. M. Russell and Seinfeld, 1998]. The model employs a dual moment (number and mass) algorithm to calculate growth of particles from one section to the next for non-evaporating species. Temperature profiles, cloud base, updraft velocities and aerosol size and composition, all measured during RPAS flights, constrain the parcel model. The measured thermodynamic and microphysical properties constrained the simulated droplet size distribution sufficiently to match the observed cloud microphysical properties.

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