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.