Abstract
While the vertical structure of cold fronts has been studied using various methods, previous research has shown that traditional methods of observing meteorological phenomena (such as pencil-beam radars in PPI/volumetric mode) are not well-suited for resolving small-scale cold front phenomena, due to relatively low spatiotemporal resolution. Additionally, non-simultaneous elevation sampling within a vertical cross-section can lead to errors in analysis, as differential vertical advection cannot be distinguished from temporal evolution. In this study, a cold front from 19 September 2015 is analyzed using the Atmospheric Imaging Radar (AIR). The AIR transmits a 20-degree fan beam in elevation, and digital beamforming is used on receive to generate simultaneous receive beams. This mobile, X-band, phased-array radar offers temporal sampling on the order of 1 s (while in RHI mode), range sampling of 30 m (37.5 m native resolution), and continuous, arbitrarily oversampled data in the vertical dimension. Here, 0.5-degree sampling is used in elevation (1-degree native resolution). This study is the first in which a cold front has been studied via imaging radar. The ability of the AIR to obtain simultaneous RHIs at high temporal sampling rates without mechanical steering allows for analysis of features such as Kelvin-Helmholtz instabilities and feeder flow.
Highlights
Study of the vertical structure of cold fronts dates back over 40 years, during which time primary interest has been placed on the impact of cold fronts on convection initiation (CI) [1,2]
As seen with applications to gust front detection, radar systems that operate in plan position indicator (PPI) mode do not offer sufficient temporal resolution along a given radial to observe the evolution of small-scale features in the vertical dimension
This lack of knowledge regarding the vertical structure of a cold front and its evolution in time serves as the primary motivation for this study; the methods used allow for cold front analysis that would not be possible via traditional scanning radars in PPI/volumetric mode
Summary
Study of the vertical structure of cold fronts dates back over 40 years, during which time primary interest has been placed on the impact of cold fronts on convection initiation (CI) [1,2]. As seen with applications to gust front detection, radar systems that operate in plan position indicator (PPI) mode do not offer sufficient temporal resolution along a given radial to observe the evolution of small-scale features in the vertical dimension. This lack of knowledge regarding the vertical structure of a cold front and its evolution in time serves as the primary motivation for this study; the methods used allow for cold front analysis that would not be possible via traditional scanning radars in PPI/volumetric mode.
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