A Balloonborne Particle Size, Imaging, and Velocity Probe for in Situ Microphysical Measurements

Abstract

A balloonborne instrument known as the Particle Size, Image, and Velocity (PASIV) probe has been developed at the National Severe Storms Laboratory to provide in situ microphysical measurements in storms. These observations represent a critical need of microphysics observations for use in lightning studies, cloud microphysics simulations, and dual-polarization radar validation. The instrument weighs approximately 2.72 kg and consists of a high-definition (HD) video camera, a camera viewing chamber, and a modified Particle Size and Velocity (Parsivel) laser disdrometer mounted above the camera viewing chamber. Precipitation particles fall through the Parsivel sampling area and then into the camera viewing chamber, effectively allowing both devices to sample the same particles. The data are collected on board for analysis after retrieval. Taken together, these two instruments are capable of providing a vertical profile of the size, shape, velocity, orientation, and composition of particles along the balloon path within severe weather. The PASIV probe has been deployed across several types of weather environments, including thunderstorms, supercells, and winter storms. Initial results from two cases in the Deep Convective Clouds and Chemistry Experiment are shown that demonstrate the ability of the instrument to obtain high-spatiotemporal- resolution observations of the particle size distributions within convection.

Electrical discharges in the overshooting tops of thunderstorms

“…In this scenario, the relatively small size of the charge regions involved in the discharges could be due to variations in updraft speeds over horizontal distances of roughly1–2 km or less or could be due to large gradients in particle number density. Recent balloon‐borne soundings of hydrometeor size and number in two storms found number densities of small ice particles varying by 1–2 orders of magnitude from one 50 m interval of height to the next and large variations occurred also over larger intervals of height [ Waugh , ].…”

In Situ Microphysical Observations of the 29–30 May 2012 Kingfisher, OK, Supercell With a Balloon‐Borne Video Disdrometer

“…The PASIV design and operation were previously described by Waugh et al (, hereafter referred to as W15) and in more detail by Waugh (); however, a brief summary is presented here with some additions over W15. The PASIV is a hybrid instrument system that combines a videosonde employing an HD camcorder with a Parsivel laser disdrometer (Löffler‐Mang & Joss, ) to provide redundant in situ measurements of the PSD (Figure ).…”

“…These regular ice crystals are typically less than 2 mm in diameter and have highly elliptical shapes. Additional details on the particle classifications are covered in Waugh ().…”

“…Preliminary tests of the automated classification on the 29–30 May 2012 case yield results that are consistent with visual identification and physical expectations. More details on the random forest classification method, as well as an appendix of identified particle examples, can be found in Waugh ().…”

“…In fact, several of these areas have unique challenges that have made validation and advancement difficult. Toward that end, a balloon‐borne particle imaging device known as the PArticle Size, Image, and Velocity (PASIV) probe has been under development at the National Severe Storms Laboratory (NSSL) to advance our observational data sets of in situ microphysical storm properties (Waugh et al, ).…”