Russian Summer Heat Wave 2010: Climatological Background and Intraseasonal Evolution Igor Zveryaev, Yulia Zyulyaeva Sergey Gulev, Klaus Peter Koltermann P.P. Shirshov Institute of Oceanology, RAS Moscow State University

H500 height – Polland, SE Germany, Czech Rep. Central Russia Pakistan Long-lasting and stable blocking over the Central and Western Eurasia resulted in disastrous heat wave in European Russia, anomalous precipitation and associated flooding in Western Europe and in Pakistan Impacts of anomalous summer 2010

Questions: - The extent to which Russian Heat Wave 2010 was similar/different compared to the past anomalous summers of the last century. - Whether the circulation conditions over the Northern Hemisphere and SST anomalies in the Atlantic were different. - If the intraseasonal evolution of the Russian Heat Wave 2010 was different from other similar events. Approach: To select cases of strong positive temperature anomalies over European Russia during the last century and to analyze associated quasi-time series of SLP and SST in order to retrieve the leading modes in these potentially provoking hot summers. To compare the key features of the Russian summer heat waves of 2010 and 1972.

2010 Monthly Air Temperature Anomalies over European Russia NASA-GISSNCEP/NCAR July Aug

Normalized AT Anomalies over European Russia (35-45E, 50-60N) 2010 anomaly is the strongest in the record (6.93 K) The macrostructure of the anomaly was different from the other years At the same time, regional structure of the anomaly in European Russia was comparable to that in earlier years AUG anomalies JUL anomalies

Northern Hemisphere SLP Anomalies Associated with Hot Summers over European Russia

Leading EOF Modes of the Summer SLP over the Atlantic-Eurasian Sector

Leading EOF Modes of the Summer Atlantic SST

Pre-selection of warm (+) and hot (1σ) years and building virtual space-time series of SLP and SST EOF analysis of the pre-selected times series: considerations of only SLP and SST patterns associated with warm and hot months

EOFs of SLP obtained for pre-selected Russian Warm and Hot summers Warm Hot PC1 PC2

EOFs of Atlantic SST obtained for pre-selected Russian Warm and Hot summers Warm Hot PC1 PC2

JJA SLP anomalies for 2010 (a), for 1972 (b) and 500 hPa heights anomalies for 2010 (c) and for 1972 (d).

Summer (JJA) daily air temperature anomalies (red curve) and NAO index (blue curve) for 2010 (a) and 1972 (b).

Correlations between AT over European Russia and SLP for 2010 (a) and for 1972 (b). The same for 500 hPa for 2010 (c) and for 1972 (d).

EOF-1(18%) and EOF-2 (11%) of the daily JJA SLP for 2010 (a, b respectively). EOF-1(19%) and EOF-2 (11%) of the daily JJA SLP for 1972 (c, d respectively).

Correlations between AT anomalies over European Russia (50N-60N, 35E-45E), the NAO index and the leading principal components (PC-1 and PC-2) of SLP.

CONCLUSIONS -While the regional (over European Russia) structure of the surface AT anomalies during 2010 summer was similar to the previous anomalous events of e.g. 1972, 1981, 2002, large scale AT anomaly patterns during those summers were quite different. - EOF analysis applied to the SLP and SST for the pre-selected warm and hot Russian summers allowed for identification of the circulation modes and SST patterns associated with anomalously warm cases. - SLP pattern, although retrieves the blocking conditions, does not provide insights on the mechanisms leading to the AT anomaly. SST patterns show a clear association of the AT anomaly either with the EOF-1 (like in 2010) or with the EOF-2 (like in 1972) of pre-selected time series. - During the two hottest summers of 2010 and 1972 intraseasonal evolution of the AT anomalies over European Russia was quite different. Moreover, their relation to the NAO was also different. Overall, results of the present analysis suggest that there are at least two (probably more) different mechanisms that drive Russian summer heat waves.