Spatial feeding patterns of herring (Clupea harengus L.), sprat (Sprattus sprattus L.), and the three-spined stickleback (Gasterosteus aculeatus L.) in the Gulf of Finland, Baltic Sea     

Peltonen  Heikki; Vinni  Mika; Lappalainen  Antti; Ponni  Jukka 《ICES Journal of Marine Science》2004,61(6):966-971

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Emissions, Concentrations, & Temperature: A Time Series Analysis     

Robert K. Kaufmann  Heikki Kauppi  James H. Stock 《Climatic change》2006,77(3-4):249-278

We use recent advances in time series econometrics to estimate the relation among emissions of CO₂ and CH₄, the concentration of these gases, and global surface temperature. These models are estimated and specified to answer two questions; (1) does human activity affect global surface temperature and; (2) does global surface temperature affect the atmospheric concentration of carbon dioxide and/or methane. Regression results provide direct evidence for a statistically meaningful relation between radiative forcing and global surface temperature. A simple model based on these results indicates that greenhouse gases and anthropogenic sulfur emissions are largely responsible for the change in temperature over the last 130 years. The regression results also indicate that increases in surface temperature since 1870 have changed the flow of carbon dioxide to and from the atmosphere in a way that increases its atmospheric concentration. Finally, the regression results for methane hint that higher temperatures may increase its atmospheric concentration, but this effect is not estimated precisely.  相似文献   

The triggered origin of the solar system     

Harri A. T. Vanhala 《Journal of Earth System Science》1998,107(4):391-400

The scenario of the triggered origin of the solar system suggests that the formation of our planetary system was initiated by the impact of an interstellar shock wave on a molecular cloud core. The strength of this scenario lies in its ability to explain the presence of short-lived radionuclides in the early solar system. According to the proposal, the radioactivities were produced in a stellar source, transported into the molecular cloud core by a shock wave and mixed into the collapsing system during the interaction between the shock wave and the core. We examine the viability of the scenario by presenting results from recent numerical simulations. The calculations show that molecular cloud cores can be triggered into collapse by the impact of a shock wave propagating at the velocity of 10–45 km s⁻¹. Some of the shock wave material incident on the core, typically 10–20%, can be injected into the collapsing system. The time scale of the process is ∼10⁴–10⁵ years, sufficiently short for the survival of the short-lived radioactivities. The simulations therefore confirm the viability of the scenario of the triggered origin of the solar system.  相似文献   

Potential forest fire danger over Northern Eurasia: Changes during the 20th century   总被引：4，自引：1，他引：3  

Pavel Ya. Groisman  Boris G. Sherstyukov  Vyacheslav N. Razuvaev  Richard W. Knight  Jesse G. Enloe  Nina S. Stroumentova  Paul H. Whitfield  Eirik Frland  Inger Hannsen-Bauer  Heikki Tuomenvirta  Hans Aleksandersson  Anna V. Mescherskaya  Thomas R. Karl 《Global and Planetary Change》2007,56(3-4):371

Significant climatic changes over Northern Eurasia during the 20th century have been reflected in numerous variables of economic, social, and ecological interest, including the natural frequency of forest fires. For the former USSR, we are now using the Global Daily Climatology Network and a new Global Synoptic Data Network archive, GSDN, created jointly by U.S. National Climatic Data Center and Russian Research Institute for Hydrometeorological Information. Data from these archives (approximately 1500 of them having sufficiently long meteorological time series suitable for participation in our analyses) are employed to estimate systematic changes in indices used in the United States and Russia to assess potential forest fire danger. We use four indices: (1) Keetch–Byram Drought Index, (KBDI; this index was developed and widely used in the United States); (2) Nesterov, (3) Modified Nesterov, and (4) Zhdanko Indices (these indices were developed and widely used in Russia). Analyses show that after calibration, time series of the days with increased potential forest fire danger constructed using each of these three indices (a) are well correlated and (b) deliver similar conclusions about systematic changes in the weather conditions conducive to forest fires. Specifically, over the Eastern half of Northern Eurasia (Siberia and the Russian Far East) statistically significant increases in indices that characterize the weather conditions conducive to forest fires were found. These areas coincide with the areas of most significant warming during the past several decades south of the Arctic Circle. West of the Ural Mountains, the same indices show a steady decrease in the frequency of “dry weather summer days” during the past 60 yr. This study is corroborated with available statistics of forest fires and with observed changes in drought statistics in agricultural regions of Northern Eurasia.  相似文献