Analysis of possible geomagnetic effects on the precipitation over Northwestern Argentina

TERESITA HEREDIA; ANA G. ELIAS

Buenos Aires

Workshop; WCRP/SPARC Workshop with focus on the Southern Hemisphere and South America; 2012

CIMA - UBA

The precipitation time series over Tucuman (26.8° S; 65.2° W), which is representative of the Northwestern region of Argentina, is analyzed in search of an association with geomagnetic activity, with the purpose of contributing to the controversial issue on the connection between climate variation and anthropogenic vs. natural forcing. Monthly time series of precipitation and aa index were used for the period 1884-2010. A correlation analysis reveals a type of associations prior to 1940 and another afterwards. To explain this we consider two mechanisms which imply opposite associations between geomagnetic activity and precipitation. The first one is through cosmic ray effects which are modulated directly by the solar wind. This mechanism supports the negative correlation found for the period previous to 1940. The second mechanism consists of a link of processes beginning in the upper atmosphere, which indirectly induce shifts in the atmospheric circulation patterns in the troposphere and would support the positive correlation found after the 1940s.