Session 12A.7 Airborne Radar and Dropsonde Analysis of an Oceanic Cold Front

Friday, 10 August 2007: 9:45 AM
Hall A (Cairns Convention Center)
Roger M. Wakimoto, NCAR, Boulder, CO; and H. V. Murphey

Presentation PDF (1.1 MB)

Analysis of an oceanic cold front using airborne Doppler radar and dropsonde data is presented. The aircraft equipped with a Doppler radar flew several legs (~200 km in length) in the cross-frontal direction providing a detailed vertical cross section of its kinematic structure. This synthesized windfield was significantly enhanced by a series of dropsondes released by a second aircraft flying a parallel track at a higher altitude. The average spacing between drops in the present case was ~30 km. This combination of kinematic and thermodynamic data, both in areal extent and finescale resolution, collected on a cold front is believed to be unprecedented. In addition, the total elapsed time for the dropsonde flight leg was 1 h (while covering a distance of >450 km), which is not a restrictive time interval to assume stationarity. The horizontal temperature gradient defining the frontal zone was most intense aloft contrary to the classical models of surface cold fronts. The ageostrophic and geostrophic components of the wind parallel to the front were calculated. The diabatic effect (often ignored in past cases) was included in the frontogenesis calculations. Although the discontinuity associated with the frontal boundary was abrupt, the analysis reveals that it was undergoing frontolysis. Comparisons with other cases will be shown.
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