Atmospheric blockings and associated climate extremes in the Northern Hemisphere detection of change and attribution of causes

Strong regional climate anomalies associated with atmospheric blockings have been noted during the last few years. The impact of blocking is exhibited in such extremes as heat and cold waves, droughts, and forest fires. In order to detect changes in blocking activity characteristics, the analayis of different data for the Northern Hemispehre with the use of various methods for blocking detection was carried out. In particular, the data for 500 hPa geopotential from the NCEP/NCAR reanalyses (1948-2010) and the NOAA-CIRES 20th century reanalyses version 2 (1871 - 2008) have been used as well as climate model simulations (1900 - 2100) with anthropogenic forcing. Different indicies for drough conditions are analyzed with an assessment of the relationship to the impact of El Nino/La Nina phenomena. Special attention is paid to the summer climate anomaly in the European part of Russia in 20010 ("Russian Heat Wave"). Causes of this anomaly and the possibility of intensification of blocking associatied impacts under global warming are discussed. Changes in blocking characteristics in the Northern Hemisphere and associated regional climate anomalies in the 21st century relative to the end of the 20th century are analyzed on the basis of model simulations with athropogenic forcing.