School of Meteorology

Observations of a Cold Front at High Spatiotemporal Resolution using Imaging Radar

Andrew Mahre

School of Meteorology

19 July 2016, 11:00 AM

National Weather Center, Room 5600
120 David L. Boren Blvd.
University of Oklahoma
Norman, OK

Over the past 40+ years, the structure of cold fronts has been studied for a variety of reasons, including convection initiation and aviation safety. It has been noted that many traditionally scanning radars are not well-suited to observe small-scale cold front phenomena. One reason for this is low spatial and temporal resolution, as the evolution of small-scale phenomena is not well-captured. Additionally, nonsimultaneous elevations within a given vertical cross-section can lead to errors in analysis, as differential vertical advection cannot be distinguished from temporal evolution while the radar is in plan-position indicator (PPI) mode. In this study, a cold front from 19 September 2015 is analyzed using the Atmospheric Imaging Radar (AIR). This mobile, X-band, phased-array radar offers relatively high spatial (0.5 degrees in elevation, 30 m in range) and temporal (300 ms) resolution. Because the AIR is an imaging radar, electromagnetic energy is transmitted in a 20-degree fan beam in elevation, and digital beamforming is used on receive to generate simultaneous receive beams. The ability of the AIR to obtain simultaneous range-height indicators (RHIs) at sub-second temporal resolution without any mechanical movement allows for unique analysis of the vertical structure of a cold front that would otherwise not be possible. Features such as Kelvin-Helmholtz Instabilities, low-level mass transport (feeder flow), longitudinal and transverse jet oscillations, and regions of heightened spectrum width will be shown and discussed in this seminar.

School of Meteorology Seminar Series website