2010年夏のロシアブロッキングのメカニズムと予測可能性

Abstract

We investigate the mechanism and predictability of a strong and persistent blocking residing over Russia from late-July to mid-August of 2010 using a reanalysis dataset and two kinds of forecast datasets. It is found that the following different mechanisms contributed to the enhancement of the blocking: During a maintenance period of the blocking in the end of July, when the predictability of the blocking was much reduced in comparison with the adjacent periods, an anticyclonic vorticity forcing associated with horizontal divergence in the upper troposphere due to a deepening trough upstream of the blocking was a predominantly important factor for the blocking formation; during another maintenance period in early-August, an anticyclonic vorticity forcing produced by the interaction between the climatological horizontal convergence and the coexisting anticyclonic anomaly in the upper troposphere over the western part of the Eurasian continent was a key to maintain the blocking. These maintenance mechanisms are also found to be inherent to the Russian blocking in the summer of 2010.