Evaluation of satellite-derived agro-climate variables in the Northern Great Plains of the United States     

Rebecca Lemons  Andrea Hewitt  Gehendra Kharel  Cherie New  Andrei Kirilenko  Xiaodong Zhang 《国际地球制图》2013,28(8):613-626

The climate of the United States Northern Great Plains region is highly variable. Modelling of agriculture in this region and similar locations depends on the availability and quality of satellite and ground data for agro-climate variables. We evaluated tropical rainfall measuring mission (TRMM) multi-satellite preparation analysis (TMPA) precipitation, atmospheric infrared sounder (AIRS) surface air temperature, and AIRS relative air humidity (RH). A significant bias was found within the temperature and RH products and no bias but an insufficient rain event detection skill in the precipitation product (probability of detection ～0.3). A linear correction of the temperature product removed the bias as well as lowered the root mean square deviation (RMSD). The bias-corrections for RH led to increased RMSD or worse correlation. For precipitation, the correlation between the satellite product and ground data improved if cumulative precipitation or only precipitation during the growing season was used.  相似文献   

The dynamic response of a fluid‐filled borehole under a normal point load on the free surface     

Andrei M. Ionov 《Geophysical Prospecting》2013,61(1):104-119

The dynamic response of a semi‐infinite fluid‐filled borehole embedded in an elastic half‐space under a concentrated normal surface load is analysed in the long‐wavelength limit. The solution of the problem is obtained with integral transforms in the form of a double integral with respect to the slowness and frequency. The partial P‐ and SV‐wave responses are further transformed to path integrals along Cagniard paths in the complex slowness plane. Unlike the traditional Cagniard‐de Hoop technique based on the Laplace transform of time dependence, this paper is based on the Fourier transform. The tube‐wave response is presented as a causal integral over a slowness range. The resultant representation in the time‐domain is suitable for the numerical evaluation of the complete response in the fluid‐filled borehole, especially at large distances. Asymptotic analysis of seismic phases arising in the borehole is performed on the basis of the obtained solution. The complete asymptotic wavefield consists in P‐ and SV‐waves, the Rayleigh wave and the low‐frequency Stoneley (tube) wave. Pressure synthetics obtained by the use of the asymptotic formulas are shown to be in good agreement with straightforward calculations.  相似文献   

Deglaciation history of Lake Ladoga (northwestern Russia) based on varved sediments     

Raphael Gromig  Bernd Wagner  Volker Wennrich  Grigory Fedorov  Larisa Savelieva  Elodie  Lebas  Sebastian Krastel  Dominik Brill  Andrei Andreev  Dmitry Subetto  Martin Melles 《Boreas: An International Journal of Quaternary Research》2019,48(2):330-348

Lake Ladoga in northwestern Russia is Europe's largest lake. The postglacial history of the Ladoga basin is for the first time documented continuously with high temporal resolution in the upper 13.3 m of a sediment core (Co1309) from the northwestern part of the lake. We applied a multiproxy approach including radiographic imaging, (bio‐)geochemical and granulometric analyses. Age control was established combining radiocarbon dating with varve chronology, the latter anchored to a correlated radiocarbon age from a lake close by. The age‐depth model reveals the onset of glacial varve sedimentation at 13 910±140 cal. a BP, when Lake Ladoga was part of the Baltic Ice Lake. Linear extrapolation of published retreat rates of the Scandinavian Ice Sheet provides a formation age of the Luga moraine close to Lake Ladoga's southern shore of 14.5–15.9 cal. ka BP, older than previously assumed. Varve sedimentation covers the Bølling/Allerød interstadial, the Younger Dryas stadial and the Early Holocene. Varve‐thickness variations, conjoined with grain‐size and geochemical variations, inform about the relative position of the Scandinavian Ice Sheet and the climate during the deglaciation phase. The upper limit of the varved succession marks the change from glaciolacustrine to normal lacustrine sedimentation and post‐dates the drainage of the Baltic Ice Lake as well as the formation of the Salpausselkä II moraine north of Lake Ladoga, by c. 250 years. The Holocene sediment record is divided into three periods in the following order: (i) a lower transition zone between the Holocene boundary and c. 9.5 cal. ka BP, characterized by mostly massive sediments with low organic content, (ii) a phase with increased organic content from c. 9.5 to 4.5 cal. ka BP corresponding to the Holocene Thermal Maximum, and (iii) a phase with relatively stable sedimentation in a lacustrine environment from c. 4.5 cal. ka BP until present.  相似文献   

Reply to “Discussion 1 on ‘Introspection on improper seismic retrofit of Basilica Santa Maria di Collemaggio after 2009 Italian earthquake’ by G.P. Cimellaro, A.M. Reinhorn and A.De Stefano” by Vincenzo Ciampi     

Gian Paolo Cimellaro  Andrei M. Reinhorn  Alessandro De Stefano 《地震工程与工程振动(英文版)》2012,11(2):283-288

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Twinning control of magnetic properties of multidomain magnetite below the Verwey transition revealed by measurements on individual particles     

Andrei Kosterov  Karl Fabian 《Geophysical Journal International》2008,174(1):93-106

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Bi-normalized response spectra and seismic intensity in Bucharest for 1986 and 1990 Vrancea seismic events     

Florin Pavel  Radu Vacareanu  Cristian Neagu  Andrei Pricopie 《地震工程与工程振动(英文版)》2014,13(1):125-135

The Vrancea subcrustal earthquakes of August 30,1986 and May 30,1990 are the two most recent seismic events that have occurred in Romania with moment magnitudes M W ≥ 6.9.The spectral analysis of the strong ground motions recorded in Bucharest reveals that despite small differences in magnitude between the 1986 and 1990 earthquakes,their frequency contents are very different,sometimes even opposing.The main focus of this study is to conduct a comparative analysis of the response spectra in terms of the bi-normalized response spectra(BNRS) proposed by Xu and Xie(2004 and 2007) for strong ground motions recorded in Bucharest during these two seismic events.The mean absolute acceleration and relative velocity response spectra for the two earthquakes are discussed and compared.Furthermore,the mean bi-normalized absolute acceleration and normalized relative velocity response spectra with respect to the control period T C are computed for the ground motions recorded in Bucharest in 1986 and 1990.The predominant period T P is also used in this study for the normalization of the spectral period axis.Subsequently,the methodology proposed by Martinez-Perreira and Bommer(1998) is applied in order to estimate the seismic intensity of the two events.The results are discussed and several conclusions regarding the possibility of using the bi-normalized response spectra(BNRS) are given.  相似文献   

The ionizing background at the end of reionization     

Steven R. Furlanetto  Andrei Mesinger† 《Monthly notices of the Royal Astronomical Society》2009,394(3):1667-1673

One of the most sought-after signatures of reionization is a rapid increase in the ionizing background (usually measured through the Lyα optical depth towards distant quasars). Conventional wisdom associates this with the 'overlap' phase when ionized bubbles merge, allowing each source to affect a much larger volume. We argue that this picture fails to describe the transition to the post-overlap Universe, where Lyman-limit systems (LLSs) absorb ionizing photons over moderate length-scales  (≲20–100   Mpc)  . Using an analytic model, we compute the probability distribution of the amplitude of the ionizing background throughout reionization, including both discrete ionized bubbles and LLSs (parametrized by an attenuation length, which we impose rather than attempt to model self-consistently). We show that the overlap does not by itself cause a rapid increase in the ionizing background or a rapid decrease in the mean Lyα transmission towards distant quasars. More detailed seminumeric models support these conclusions. We argue that the rapid changes should instead be interpreted as evolution in the attenuation length itself, which may or may not be directly related to overlap.  相似文献   

Climate change and food stress in Russia: what if the market transforms as it did during the past century?     

Nikolai Dronin  Andrei Kirilenko 《Climatic change》2008,86(1-2):123-150

It is expected that a warmer climate would be beneficial for agriculture in high latitudes. However, this general tendency is not necessarily true for all northern countries, as a short growing period is not the only factor limiting agriculture. For Russia, our model shows that the remarkable increase in potential yield in central and northern-forested regions would not compensate for a sharp drop in yields due to increasing frequency of droughts in the currently most productive southern European regions. If this scenario is indeed realized, the majority of Russian regions will continue to rely on import of agricultural products from a few regions with the best soils, and a system of interregional grain trade will remain critical for food security. However, the basic rules of interregional food market have varied widely over the past century. We have attempted an analysis of the potential impact of these basic rules on regional food security by describing four basic historical market scenarios and applying these scenarios to our results for climate change impact on agriculture in the 2020s and 2070s. We show that the current system, if it continues, would bring the worst results. We also show that the traditionally effective planned adaptation measures would help little in future climate conditions if the current market system were still in place.  相似文献   

Flood hazard and risk assessment in Russia     

Andrei Shalikovskiy  Konstantin Kurganovich 《Natural Hazards》2017,88(1):133-147

Flood risk assessment is usually performed by application of sophisticated mathematical models of river flow. However, there are cases when it is required to assess the risk in the lack of data conditions or a limited time available. In such cases, it is advisable to use some simplifications, which provide reliable results faster. This study proposes a hybrid approach to the flood risk assessment combining quantitative and qualitative indicators. The article describes various methods to assess the flood risk, such as likelihood of flooding, magnitude of the flood, average annual damage, maximum damage and expectation of damage. The authors examined special cases of calculation of the mathematical expectation of harm and zoning in the corresponding indicators. This approach is designed for the conditions of the Russian Federation, but it can be adapted for other regions. It is based on the use of two types of risk maps. The first type of maps is intended to define the mathematical expectation of damage zones for reference building with possibility of risk calculation for other buildings using multiple factors. The second type of maps is designed for the purposes of land use regulation for floodplains based on a priori statistical estimates of flood risk.  相似文献   

Analysis of Cassini/CIRS limb spectra of Titan acquired during the nominal mission: I. Hydrocarbons, nitriles and CO₂ vertical mixing ratio profiles     

Sandrine Vinatier  Bruno Bézard  Andrei Mamoutkine  Ronald C. Carlson  Donald E. Jennings  Nick A. Teanby  F. Michael Flasar 《Icarus》2010,205(2):559-570

Observations of the Composite InfraRed Spectrometer (CIRS) during the entire nominal Cassini mission (2004-2008) provide us with an accurate global view of composition and temperature in the middle atmosphere of Titan (between 100 and 500 km). We investigated limb spectra acquired at resolution at nine different latitudes between 56°S and 80°N, with a better sampling in the northern hemisphere where molecular abundances and temperature present strong latitudinal variations. From this limb data acquired between February 2005 and May 2008, we retrieved the vertical mixing ratio profiles of C₂H₂, C₂H₄, C₂H₆, C₃H₈, CH₃C₂H, C₄H₂, C₆H₆, HCN, HC₃N and CO₂. We present here for the first time, the latitudinal variations of the C₂H₆, C₃H₈, CO₂, C₂H₄ and C₆H₆ vertical mixing ratios profiles. Some molecules, such as C₂H₆ or C₃H₈ present little variations above their condensation level. The other molecules (except CO₂) show a significant enhancement of their mixing ratios poleward of 50°N. C₂H₄ is the only molecule whose mixing ratio decreases with height at latitudes below 46°N. Regions depleted in C₂H₂, HCN and C₄H₂ are observed around 400 km (0.01 mbar) and 55°N. We also inferred a region enriched in CO₂ located between 30 and 40°N in the 2-0.7 mbar pressure range. At 80°N, almost all molecules studied here present a local minimum of their mixing ratio profiles near 300 km (∼0.07 mbar), which is in contradiction with Global Circulation Models that predict constant-with-height vertical profiles due to subsidence at the north pole.  相似文献