During the summer of 2010, an unusually persistent blocking episode resulted in anomalously warm dry weather over the European part of Russia. The excessive heat resulted in forest and peat fires, impacted terrestrial ecosystems, greatly increased pollution in urban areas, and increased mortality rates in the region. Using the National Centers for Atmospheric Research (NCAR), National Centers for Environmental Prediction (NCEP) reanalysis datasets, the climatological and dynamic character of blocking events for summer 2010 and a precursor May blocking event were examined. We found that these events were stronger and longer lived than typical warm season events. Using dynamic methods, we demonstrate that the July 2010 event was a synoptic-scale dominant blocking event; unusual in the summer season. An analysis of phase diagrams demonstrated that the planetary-scale did not become stable until almost one week after block onset. For all other blocking events studied here and previously, the planetary-scale became stable around onset. Analysis using area integrated regional enstrophy (IRE) demonstrated that for the July 2010 event, synoptic-scale IRE increased at block onset. This was similar for the May 2010 event, but different from case studies examined previously that demonstrated the planetary-scale IRE was prominent at block onset. 1. Introduction Blocking events are generally thought of as quiescent phenomena that bring warmer and drier conditions to the areas that they impact and colder, wetter conditions in the upstream and downstream [1–7]. Their influence on the weather upstream and downstream of the main event, however, is well documented (e.g., [1–7]). They often bring anomalously stable weather conditions (high pressure), and this can result in air pollution events over the regions where they occur (e.g., [8–12]). During the cold season, it is the upstream and downstream regions that are more adversely affected by strong cold waves induced by the blocking event (e.g., [2, 7]). During the warm season, the regions were covered by the block suffer excessive heat (e.g., [11, 12]). The blocking episode that occurred over the European part of Russia during the summer of 2010 was devastating, especially over the western part of the country. It is estimated that more than 50,000 Russian inhabitants perished due to the weather conditions associated with the blocking events (see http://ifaran.ru/science/seminars/Summer2010.html). The mortality rates due to the unprecedented summer heat and air pollution associated with the forest and peat fires were
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