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UC Santa Cruz @ VOCALS?

The Phase-Doppler interferometer measures cloud drop size, velocity, and spacing on a single drop basis (3 to 150 µm). Pre-flight testing on the CIRPAS TwinOtter for the Marine Stratocumulus Experiment (MASE) revealed bimodal distributions, likely due to collision-coalescence process. Comparisons with Gerber-derived Liquid Water Content (LWC) were conducted.

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UC Santa Cruz @ VOCALS?

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  1. UC Santa Cruz @ VOCALS? • PI: Patrick Chuang • Instrument: Phase-Doppler interferometer • Measures cloud drop • size • velocity • inter-drop spacing on a single drop basis. • Size range: 3 to 150 um PDI mounted on the CIRPAS TwinOtter

  2. Pre-flight testing of the PDI

  3. Sample data from the Marine Stratocumulus Experiment (MASE). Note the occurence of bi-modal distributions most likely caused by collision-coalescence, a key process in drizzle formation.

  4. Example of bimodal distribution in stratocumulus clouds.

  5. Comparison of view volume diameter derived from in situ measurements and theoretically-derived curve. The theoretical curve uses two parameters: 1. The laser beam waist diameter 2. The minimum scattered light intensity required for detection by photodetectors. Fitting data to theoretical curve retrieves (1), leaving (2) as the only free parameter.

  6. Comparisons of PDI and Gerber derived LWC. (A) No roll-off correction applied to Gerber data. (B) Normal roll-off correction. (C) Roll-off shifted by 7 um (towards smaller sizes) (D) PDF of 1 Hz LWC data during MASE.

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