Airborne Phase Doppler Interferometry for Cloud Microphysical Measurements

Abstract

Conducting accurate cloud microphysical measurements from airborne platforms poses a number of challenges. The technique of phase Doppler interferometry (PDI) confers numerous advantages relative to traditional light-scattering techniques for measurement of the cloud drop size distribution, and, in addition, yields drop velocity information. Here, we describe PDI for the purposes of aiding atmospheric scientists in understanding the technique fundamentals, advantages, and limitations in measuring cloud microphysical properties. The performance of the Artium Flight PDI, an instrument specifically designed for airborne cloud measurements, is studied. Drop size distributions, liquid water content, and velocity distributions are compared with those measured by other airborne instruments.

Acknowledgments

This research was supported by NSF Physical Meteorology and Major Research Instrumentation (ATM-0320953, ATM-0535488, and ATM-0342651) and the ONR SBIR program. We thank Bob Bluth (CIRPAS) for his aid in funding the instrument development. We thank CIRPAS, Rick Flagan, and John Seinfeld (Caltech), and ONR for their efforts in making the MASE field mission a success. S. K. Cheah is acknowledged for his work in performing the Fluent calculations. We are grateful to Holger Siebert (Leibniz Institute for Tropospheric Research) for helpful discussions and for the ACTOS sonic anemometer data, and Zellman Warhaft for use of the Cornell wind tunnel for instrument testing. Jean-Louis Brenguier (Météo-France) is acknowledged for his helpful comments. Finally, we owe many thanks to Jim Smith (NCAR) for the discussions that initiated this project many years ago as well as those since then.

Notes

¹Note that PDI-based instruments are sometimes referred to with the name Phase Doppler Particle Analyzer, or PDPA.