Sequence patterns of 1000 hPa and 500 hPa geopotential height fields associated with cold surges over Central Argentina

摘要

An objective classification of sequence patterns of 1000 hPa and 500 hPa geopotential heights associated with cold surges over Central Argentina was carried out. Polar Outbreaks during wintertime in Central Argentina (May to September) cause important damage to the regional agriculture and sometimes affect the energy supply. In particular, the consumption of natural gas is strongly dependent on significant temperature descents. The rotated Principal Components Analysis (PCA) was used to obtain the basic patterns of sequence of 1000 hPa and 500 hPa geopotential heights. The winter cold surges during the 1979-1993 period occur in seven patterns at 1000 hPa and three modes at 500 hPa. The combination of both levels shows three typical situations related to cold surges over Central Argentina. The most classic pattern shows an important ridge west of the Pacific coast of the continent at its upper level and a postfrontal anticyclone at its lower level producing cold air advection over Central Argentina. The other two patterns present a long wave trough at upper levels affecting the continent, one of them with the postfrontal anticyclone moving over middle and low latitudes, and the other with the migratory anticyclone affecting lower latitudes.