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[en] Daily snow depth (SD) and snow cover extent around 820 stations are used to analyse variations in snow cover characteristics in Northern Eurasia, a region that encompasses the Russian Federation. These analyses employ nearly five times more stations than in the previous studies and temporally span forty years. A representative judgement on the changes of snow depth over most of Russia is presented here for the first time. The number of days with greater than 50% of the near-station territory covered with snow, and the number of days with the snow depth greater than 1.0 cm, are used to characterize the duration of snow cover (SCD) season. Linear trends of the number of days and snow depth are calculated for each station from 1966 to 2007. This investigation reveals regional features in the change of snow cover characteristics. A decrease in the duration of snow cover is demonstrated in the northern regions of European Russia and in the mountainous regions of southern Siberia. An increase in SCD is found in Yakutia and in the Far East. In the western half of the Russian Federation, the winter-averaged SD is shown to increase, with the maximum trends being observed in Northern West Siberia. In contrast, in the mountainous regions of southern Siberia, the maximum SD decreases as the SCD decreases. While both snow cover characteristics (SCD and SD) play an important role in the hydrological cycle, ecosystems dynamics and societal wellbeing are quite different roles and the differences in their systematic changes (up to differences in the signs of changes) deserve further attention.
[en] The temperature sensitivity of the snowfall season (start, end, duration) over northern Eurasia (the former USSR) is analyzed from synoptic records of 547 stations from 1966 to 2000. The results find significant correlations between temperature and snowfall season at approximately 56% of stations (61% for the starting date and 56% for the ending date) with a mean snowfall season duration temperature sensitivity of −6.2 days °C−1 split over the start (2.8 days) and end periods (−3.4 days). Temperature sensitivity was observed to increase with stations’ mean seasonal air temperature, with the strongest relationships at locations of around 6 °C temperature. This implies that increasing air temperature in fall and spring will delay the onset and hasten the end of snowfall events, and reduces the snowfall season length by 6.2 days for each degree of increase. This study also clarifies that the increasing trend in snowfall season length during 1936/37–1994 over northern European Russia and central Siberia revealed in an earlier study is unlikely to be associated with warming in spring and fall seasons. (letter)
[en] Northern Eurasia is one of the largest terrestrial carbon reservoirs on the Earth’s surface. However, since the coverage of surface CO2 observations is still limited, the response to the climate variability remains uncertain. We estimated monthly CO2 fluxes for three sub-regions in Northern Eurasia (north of ∼60°N), Northeastern Europe, Western Siberia and Eastern Siberia, using CO2 retrievals from the Japanese Greenhouse Gases Observing SATellite (GOSAT). The variations of estimated CO2 fluxes were examined in terms of the regional climate variability, for the three consecutive growing seasons of 2009–2011. The CO2 fluxes estimated using GOSAT data are highly correlated with the surface temperature anomalies in July and August ( r > 0.8) while no correlation is found in the CO2 fluxes estimated only using surface observations. The estimated fluxes from GOSAT data exhibit high negative correlations with one-month lagged positive precipitation anomalies in late summer ( r > −0.7) through surface temperature and the Normalized Difference Vegetation Index (NDVI). The results indicate that GOSAT data reflects the changes in terrestrial biospheric processes responding to climate anomalies. In 2010, a large part of Eurasia experienced an extremely hot and dry summer, while cold and wet weather conditions were recorded in Western Siberia. The CO2 fluxes estimated from GOSAT data showed a reduction of net CO2 uptake in Northeastern Europe and Eastern Siberia, but the enhancement of net CO2 uptake in Western Siberia. These opposite sub-regional flux anomalies can be explained by the different climate anomalies on a sub-regional scale in Northern Eurasia. Thus, this study demonstrates that space-based observations by GOSAT compensate for the lack of ground-based observational coverage so as to better capture the inter-annually varying atmosphere-terrestrial biosphere CO2 exchange on a regional scale. (letter)
[en] Cloudina-morph fossils in Siberia have been traditionally regarded as a taphonomic mode of Anabarites tests inserted one into another under specific hydrodynamic conditions. Clusters of telescoped conical tests are ubiquitous in the Kessyusa Group and coeval strata across Siberia and not all of them can be easily interpreted as a result of simple mechanical stacking. It remains to be confirmed whether any of these clusters actually represents a life association of a Cloudina-morph structure.
[es]En Siberia los morfotipos de Cloudina han sido tradicionalmente considerados como una variedad tafonómica de conchas de Anabarites, insertadas una dentro de otra, bajo condiciones hidrodinámicas específicas. Las asociaciones de conchas cónicas telescópicas son omnipresentes en el Grupode Kessyusa y en estratos contemporáneos a lo largo de Siberia, y no todos ellos pueden ser fácilmente interpretados como resultado de un simple apilamiento mecánico. Queda por ver si alguna de estas bioacumulaciones representa una asociación de vida de una estructura morfotípica de tipo Cloudina.
[en] If the 1908 Tunguska cosmic body (TCB) explosion involved a comet, compressional heating of the comet was expected to create hydrogen and deuterium plasma. The velocity distribution of protons and deuterons in this plasma is not expected to be the Maxwell-Boltzmann distribution. It is shown that the use of a generalized momentum distribution leads to substantial increases of deuteron fusion rates and that a thermonuclear explosion may compete with a thermo-chemical explosion. Therefore, it may be possible that a thermo-chemical explosion induced a hydrogen thermonuclear explosion and both the thermo-chemical and thermonuclear explosions occurred in the 1908 Tunguska event. Experimental tests of this hypothesis are proposed. Presented at the 20th Few-Body Conference, Pisa, Italy, 10-14 September 2007. (author)