Presenting Author: Mr. Jimmy Booth

To isolate baroclinic wave activity, time filtering is applied to the meridional winds at 10 meters (m) and 850 millibars (mb) over the Northern Hemisphere Atlantic and Pacific Oceans, and the Southern Ocean. The standard deviation of the time filtered winds is calculated for the winter months during the QuikSCAT period using ECMWF winds. After verifying that the ECMWF model yields an adequate representation of the variability in the surface winds for this time period, ECMWF fields are used to allow examination of atmospheric fields away from the surface. At 850 mb, the standard deviation of meridional winds yields the atmospheric storm tracks. The spatial structure can be reproduced using other atmospheric variables aloft, such as the 300 mb height field. These patterns capture the regions of large baroclinic wave activity, and correspond to the regions of heavy occurrence of midlatitude storms. At 10 m, the pattern differs from the storm track aloft. The standard deviation of the time filtered 10m meridional wind has a maximum south of the maximum aloft. These differences can be explained by the preferential mixing down of momentum in regions in which atmospheric boundary layer (ABL) instability is large. The region of strong ABL instability corresponds to the region of the storm track entrance. The mixing down of strong winds enhances the surface fluxes in these regions, seeding the storm tracks with warm moist air.

2025 International OVWST Meeting May 5th - 8th Darmstadt, Germany

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