Clustering Analysis of Precipitation Sized Particles in Various Synoptic Regimes Using In Situ Observations

It is widely assumed that hydrometeors are spatially distributed in a random and uncorrelated fashion (a Poissonian distribution); however, previous studies using airborne observations have shown this is not true for small hydrometeors such as cloud droplets. Previous work using rain gauges and disdrometer networks have also found this to be true for precipitation size particles, but little research has been done using airborne observations to study such phenomena. Thus, a question to be addressed in this study is whether clustering of precipitation size particles can be examined using airborne observations.

In situ microphysical data collected on the University of North Dakota Citation II research aircraft during the Olympic Mountains Experiment (OLYMPEX) using a High Volume Precipitation Spectrometer (HVPS-3) are analyzed. The HVPS-3 captures shadow images of precipitation size particles, which can be used to examine clustering signatures on meter to kilometer size scales. Flight data are also stratified by the synoptic classifications used in OLYMPEX to determine if clustering changes with synoptic forcing. Overall, preliminary results indicate that clustering can be examined using airborne observations and that differences do occur between synoptic regimes. Results from this study also emphasize that non-Poissonian statistics should be incorporated into the current radar framework, as a considerable amount of research has indicated that particles are not uniformly distributed in space.