185 High-Resolution Doppler Radar and Radiometer Analysis of a Cold Front Topped with Atmospheric Waves

Thursday, 31 August 2017
Zurich DEFG (Swissotel Chicago)
Timothy A. Coleman, Univ. of Alabama, Huntsville, AL; and K. Knupp and P. N. Gatlin

Doppler radar data, in addition to time-height sections of temperature and water vapor from a microwave profiling radiometer, are used to observe the structure of a shallow cold front. The cold front examined in this presentation was associated with light precipitation and clouds, allowing for extensive and detailed radar observations of the cold front at very close range (within 5 km), using both PPI and RHI scans.

Distinct Kelvin-Helmholtz waves were observed by Doppler radar at very high resolution along the frontal surface, and are most visibly dramatic in RHI scans. The front also exhibited some characteristics of a density current, including a raised head, an elevated nose, and a rear-to-front feeder flow.

Utilizing radar data to determine vertical wind shear along the cold front surface, then combining this with a time-to-space conversion of potential temperature derived from microwave profiling radiometer data, a vertical cross-section of the Richardson number along the front was produced. Values of the Richardson number less than 0.25 corresponded well with the area where waves were observed.

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