Relationship between Vertical Reflectivity and Vertical Motion Gradients in Winter Storms Observed during IMPACTS

This study uses airborne vertically pointing radar data to diagnose layers of turbulence and shear within extratropical cyclones sampled during the Investigation of Microphysics and Precipitation for Atlantic Coast Threatening Snowstorms (IMPACTS) field campaign. During IMPACTS, the ER-2 had a suite of vertically pointing radars (CRS, HIWRAP, and EXRAD) that sampled the fine scale vertical structure of extratropical cyclones over the Midwest and Northeast United States. Vertical reflectivity gradients were often found coinciding with fine scale gravity waves and turbulence. Gradients formed because ice crystals mixed out of the wave/turbulence layer creating a positive reflectivity gradient near the top and bottom of the wave/turbulence layer and a negative reflectivity gradient within the wave/turbulence layer. Laminar, nonturbulent layers of rising motion along warm fronts were also observed during several flight legs (manifesting as layers of positive vertical motion gradient). These layers have the effect of slowing particle descent causing a positive vertical reflectivity gradient above them and negative reflectivity gradient below them (particles falling slower and collecting and then faster beneath the layer) fall out of the positive layer. Vertical reflectivity gradients were also observed associated with fall streaks from elevated convection and cloud top generating cells. The goal is to relate vertical reflectivity gradients to changes in vertical motion and cloud microphysics data. Occasionally higher concentrations or larger particles were present when the P-3 aircraft (which was flying in situ during IMPACTS) sampled positive reflectivity gradients. We also hope to apply this work to Dual Frequency Ratio measurements in the future to better diagnose regions of riming and aggregation within extratropical cyclones.