S172 A Climatology of Andean South American Cold Surges and their Continental Effect

Sunday, 7 January 2018
Exhibit Hall 5 (ACC) (Austin, Texas)
Kevin C. Prince, Univ. of Wisconsin–Milwaukee, Milwaukee, WI

Cold surge occurrence in northern South America not only poses an economic issue through crop destruction, but also may represent a pathway by which South Pacific synoptic-scale patterns can have influences that reach to tropical latitudes in the Northern Hemisphere. It has been noted that the structure of these cold surges is similar to that of cold surges in North American winters. Research has also been done on cold surge structure and dynamics throughout the world, including along the Andes and Brazilian Highlands in South America, along the Rocky Mountains in North America, and to the east of the Ethiopian highlands in Africa.

Cold surges have been described as shallow features (up to 850hPa) that involve a sharp decline in temperature, an increase in pressure, and a shift in winds to an equatorward-directed component. For South America in particular, these cold surge events are typically associated with the passing of an upper-tropospheric ridge over the Andes that distorts the climatological lee trough east of the Andes and causes a sudden reversal of winds at 850hPa. A climatology of South American Austral winter cold surges that follow along the Andean pathway will be obtained utilizing dynamic and thermodynamic variables. Intensities are classified utilizing standardized anomalies of relevant fields (850-925hPa temperature, 850-925hPa v-wind, etc.), with composites of these relevant fields being created for days leading up to, and following, the start day of the surge events. It is found that on average these events modulate the atmosphere over majority of the Amazon basin, into the extreme south of The Caribbean. Present future works are comparison between stronger and weaker cold surges, also looking for any potential impacts on tropical weather.

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