The differences and causes of European climate between 2008and 2012winter

There are huge differences in the European climate between 2008and 2012 winter(January and February),and La Nina occurred in both winters.The surface temperature was above normal during 2008winter,and was below normal during 2012winter.The atmospheric circulation anomalies are the direct reasons for the different climate.In 2008winter,the North Atlantic Oscillation anomaly was in positive phase,benefited the Europe warming.During 2012 winter,the blocking over the North Atlantic and high-latitude Eurasia benefited the extreme cold event in Europe.The role of sea surface temperature(SST)and sea ice concentration anomalies were investigated by one atmospheric general circulation model.The SST anomalies over the North Atlantic can explain the atmospheric circulation over Atlantic in Europe in a certain extent separately for these two years,so they are important for the climate differences.While thetropical SST anomalies can just simulate similar atmospheric responses over the North Atlantic in 2012winter,while they seemed play a negative role in 2008winter.The loss of sea ice over Arctic adjoined Europe lead to cold conditions over Europe,so it played a negative role during 2008winter,while a positive role during 2012winter.