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Steven was our west-coast intern this year coming to us from the University of Washington where he was a junior in Atmospheric Science and Applied Mathematics. Steve studied mid-latitudes and the tropics as they are characterized by Rossby numbers to better understand and distinguish tropical and extratropical dynamical regimes. His mentors were Professor Thomas Birner and graduate student Nick Davis.

Mid-latitudes are usually characterized by Rossby numbers ~.1 (consistent with geostrophic balance) where as the tropics are characterized by Rossby numbers ~1. Gaining an understanding of the structure of the Rossby number could be useful in determining the meridional extent of the tropical belt, which determines the locations of subtropical dry zones and their changing positions with climate change. In his study, Steve analyzed scale dependencies of the Rossby number as a function of latitude using global coverage reanalysis data.

Steve found that the geostrophic wind approximation has a consistently high bias for predicting large wind speeds. The geostrophic approximation holds very high accuracy to very low latitudes. He found there is no obvious connection between the Rossby number and the breakdown of the geostrophic wind approximation at low latitudes and that the Rossby number has a distinct structure. Significant transitions in the Rossby number show potential for locating subtropical dry zones. The Rossby number has a strong dependence on the horizontal scale of the wind field used to calculate it. This dependence varies with latitude and can tell us the different distances of large scale dynamics as a function of latitude.

Steven's summer research poster, Distinguishing Tropical and Extratropical Dynamical Regimes Based on Rossby Number Statistics, is available here.

Steve is from Woddinville, WA where he is very active climbing, freediving, skiing, white water rafting and eating so a summer in Colorado was a nice fit! His research interests include mountain weather, cloud microphysics, ensemble forecasting and numerical weather prediction.

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