P1.4 The effects of splash artifacts on aerosol measurements in clouds

Monday, 28 June 2010
Exhibit Hall (DoubleTree by Hilton Portland)
Lucas W. Craig, Clarkson University, Potsdam, NY; and A. Schanot, A. Moharerri, P. Dubey, S. Dhaniyala, D. C. Rogers, and D. W. Toohey

Splash/breakup artifacts are generated when cloud particles hit the upstream edges of instruments and air sample inlets, causing them to fracture into numerous satellite particles. These particles contaminate the air sample. They lead to incorrect measurements of the cloud particles and aerosols, and the aerosol measurements are often discarded for samples inside of clouds. This study uses measurements from several airborne research projects with cloud physics and aerosol measurements to document the magnitude of this effect and to characterize the production of splash/breakup artifacts. The measurements include those parameters that are most relevant to the splash/breakup process: cloud particle size distribution, phase (liquid, solid, or mixed), particle concentration, air speed, geometry of the sampling probe, and its location on the aircraft. Data sources for the study come from six different airborne projects. In total, they represent 90 research flights or approximately 650 hours of flight time in a wide variety of clouds and meteorological conditions. Different types of inlets and sampling methods were used, including: aft-facing, forward facing, sharp-edge diffuser, goose-neck, counter-flow virtual impactor, and a low turbulence inlet. The goal of this study is to quantify the splash-artifact generation characteristics of different inlet types and the dependence on droplet size, concentration, and other aircraft parameters. The results will provide guidance for interpreting cloud physics and aerosol measurements and for designing inlets and probes that are less affected by this contamination. The plot shows one example of splash artifact particle production when the aircraft climbed through marine stratocumulus clouds. (left panel) The boundary layer was well-mixed from ocean surface up through cloud top at 960 m. (right panel) Of the various aerosol data, only the forward-facing cone inlet (RED) correctly shows this well-mixed nature. The others show enhancement by splash artifacts, by as much as a factor 20X.

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