Developing NSSL PodRads: Low-cost, pod-style radars for measuring vertical profiles of vertical velocities in tornadoes and convective storms

Mobile weather radars have been used for several decades to study the structure and evolution of tornadoes and severe convective storms. While some mobile radars have been able to collect very high-resolution observations of tornadoes, nearly all datasets collected by such radars consist of data along quasi-horizontal surfaces (e.g., at elevation angles generally below 20-30 deg). As a result, Doppler velocity data are primarily estimates of the radial component of the quasi-horizontal flow (particularly at very low altitudes near the ground), although dual- and multi-Doppler retrievals have been able to provide estimates of the complete three-dimensional flow in limited situations. Owing to logistical and safety concerns, among other reasons, data used in these retrievals are almost exclusively from radars that are positioned such that the spatiotemporal resolution of the retrievals is too coarse to resolve any sampled tornadoes. Consequently, we have little in the way of direct radar measurements of the vertical profile of vertical winds in any tornado.

Past modeling, theory, and photogrammetry-focused work has indicated that the vertical velocities in some tornadoes may be very large; in some cases, the vertical component of the flow may exceed the horizontal component (which is generally what mobile radars have measured). The dearth of observations of vertical velocities in tornadoes to validate prior research and our understanding of tornadoes affects the work done by communities that study tornadoes and their impacts (e.g., structural engineering). In a first attempt to provide a more comprehensive understanding of the vertical structure of vertical velocities in tornadoes, we have begun to design and prototype PodRads, small, low-cost, low-power, X-band, FM-CW radars that are being built to observe vertical velocities in phenomena such as tornadoes. This presentation will introduce the primary motivations and design considerations that are driving PodRad development. Some very preliminary testing data and an outline of future plans for development will also be discussed.