A Dynamic Analysis of the Role of the Planetary- and Synoptic-Scale in the Summer of 2010 Blocking Episodes over the European Part of Russia

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

Special issue: 10th anniversary of atmosphere: climatology and meteorology

During the last decade, the number of open access science journals has increased, and these have become an avenue for publishing quality science in a relatively fast and economical way [...

Hydrological Changes: Historical Analysis, Contemporary Status, and Future Projections

This chapter looks at several aspects of the hydrological regime across Siberia using long-term historical data and model simulation results to provide a better understanding of ongoing changes and future directions. It begins with a survey of the major components of water balance: river flow, precipitation, and evapotranspiration. This is followed by the primary focus on the Siberian river systems with emphasis on annual variability and the anomalously high river discharge in 2007, the seasonality of river flow with increases in winter discharge, and changes in magnitude of minimum river flow and the temporal shifts in maximum river flow. Other components related to the river systems are also explored, including the thermal regime showing a lack of widespread evidence for increasing river temperature while the ice cover over the major rivers is decreasing in terms of both the duration of ice cover and ice thickness. Related hydrological conditions (e.g., groundwater hydrology) demonstrate an increase in both levels and temperatures; however, there is evidence for some local decreases in groundwater level. Additionally, increases in groundwater runoff from the taiga zone are observed. Total thermokarst lake area is changing, depending on the landscape zone. Northern zones of tundra are gaining lake area, while the southern tundra and taiga regions are losing lake area. This chapter concludes with a look at possible future changes in the region’s hydrology. River discharge in the major Siberian watersheds is expected to rise, and this result is consistent across a majority of the global climate models’ projections for the twenty-first century

Crucial role of Black Sea warming in amplifying the 2012 Krymsk precipitation extreme

Over the past 60 years, both average daily precipitation intensity and extreme precipitation have increased in many regions1, 2, 3. Part of these changes, or even individual events4, 5, have been attributed to anthropogenic warming6, 7. Over the Black Sea and Mediterranean region, the potential for extreme summertime convective precipitation has grown8 alongside substantial sea surface temperature increase. A particularly devastating convective event experienced in that region was the July 2012 precipitation extreme near the Black Sea town of Krymsk9. Here we study the effect of sea surface temperature (SST) increase on convective extremes within the region, taking the Krymsk event as a showcase example. We carry out ensemble sensitivity simulations with a convection-permitting atmospheric model and show the crucial role of SST increase in the extremeness of the event. The enhancement of lower tropospheric instability due to the current warmer Black Sea allows deep convection to be triggered, increasing simulated precipitation by more than 300% relative to simulations with SSTs characteristic of the early 1980s. A highly nonlinear precipitation response to incremental SST increase suggests that the Black Sea has exceeded a regional threshold for the intensification of convective extremes. The physical mechanism we identify indicates that Black Sea and Mediterranean coastal regions may face abrupt amplifications of convective precipitation under continued SST increase, and illustrates the limitations of thermodynamical bounds for estimating the temperature scaling of convective extremes