Simulating the Impacts of Snow Cover Boundaries on Synoptic Circulations
Abstract
The presence or absence of snow cover on the surface is a highly variable, seasonal component of weather and climate in the middle and high latitudes. In the Northern Hemisphere, the nature of mid-latitude cyclone trajectories leads to consistent snow cover north of a seasonal cyclone track and the absence of snow to the south, creating strong temperature, moisture, and albedo gradients that have been shown to induce mesoscale circulations around the boundary. However, it is not known whether these boundaries also generate larger-scale modifications to the free-atmosphere and on mid-latitude cyclones themselves. Better understanding the interactions of the snow boundaries can reduce uncertainty in forecast models as well as in climate predictions involving synoptic storm track changes. Previously, we showed a statistical relationship between location anomalies of mid-latitude disturbances and snow boundaries (Rydzik and Desai, 2014), but the physical mechanism remains less well understood. Here, we tested two competing mechanisms in the Weather Research and Forecasting (WRF) model with case studies of cyclones that track along snow boundaries. We hypothesized that low-level potential vorticity generated over the snow can modify synoptic circulations, strengthening and weakening passing systems as the potential vorticity is advected into the system. We also tested whether the snow boundary can alter the trajectories of synoptic circulations by creating and reinforcing a low level baroclinic region. In WRF, we strategically modified existing snow cover across the domain at optimal locations for interaction, mainly within 100km of the absolute vorticity minima, in addition to a control case and a no-snow case. Here, we present our findings from the model output of the potential mechanisms driving changes in intensity and trajectory of modelled cyclones.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFM.C31A0732B
- Keywords:
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- 3349 Polar meteorology;
- ATMOSPHERIC PROCESSESDE: 0794 Instruments and techniques;
- CRYOSPHEREDE: 0798 Modeling;
- CRYOSPHEREDE: 1863 Snow and ice;
- HYDROLOGY