Publication Date:
2016-01-01
Description:
Ice storms are an infrequent but significant hazard in the U.S southern Great Plains. Common synoptic profiles for freezing precipitation reveal advection of low-level warm moist air from the Gulf of Mexico (GOM), above a shallow Arctic air mass ahead of a midlevel trough. Because the GOM is the proximal basin and major moisture source, this study investigates impacts of varying GOM sea surface temperature (SST) on the thermodynamic evolution of a winter storm that occurred during 28–30 January 2010, with particular emphasis on the modulation of freezing precipitation. A high-resolution, nested ARW sensitivity study with a 3.3-km inner domain is performed, using six representations of GOM SST, including control, climatological mean, uniform ±2°C from control, and physically constrained upper- and lower-bound basin-average anomalies from a 30-yr dataset. The simulations reveal discernable impacts of SST on the warm-layer inversion, precipitation intensity, and low-level dynamics. Whereas total precipitation for the storm increased monotonically with SST, the freezing-precipitation response was more varied and nonlinear, with the greatest accumulation decreases occurring for the coolest SST perturbation, particularly at moderate precipitation rates. Enhanced precipitation and warm-layer intensity promoted by warmer SST were offset for the highest perturbations by deepening of the weak 850-hPa low circulation and faster eastward progression associated with enhanced baroclinicity and diabatic generation of potential vorticity. Air-parcel trajectories terminating within the freezing-precipitation region were examined to identify airmass sources and modification. These results suggest that GOM SST can affect the severity of concurrent ice-storm events in the southern Great Plains, with warmer basin SST potentially exacerbating the risk of damaging ice accumulations.
Print ISSN:
1558-8424
Electronic ISSN:
1558-8432
Topics:
Geography
,
Physics
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