Model ALADIN as regional climate model for Central and Eastern Europe   总被引：4，自引：0，他引：4  

Aleš Farda  Michel Déué  Samuel Somot  András Horányi  Valery Spiridonov  Helga Tóth 《Studia Geophysica et Geodaetica》2010,54(2):313-332

Results obtained with two versions of the Limited Area Model (LAM) ALADIN over differently sized integration domains (large, intermediate and small) in the European area are presented in order to investigate both the general model performance and the influence of domain choice on the quality of obtained results. The aim is also to illustrate the issues related to the strategy of selection of the optimal integration domain. Each of these studies has been performed with two versions of the ALADIN model: the first one is ALADIN-CLIMATE developed at CNRM/Météo-France, the second one is ALADIN-CLIMATE/CZ prepared at the Czech Hydrometeorological Institute (CHMI). This leaves us with total of six experiments forced by the European Centre for Medium-Range Weather Forecasts (ECMWF) ERA-40 reanalysis data. The west Balkan domain covering Bulgaria is used as an evaluation region for investigation of the temporal and spatial properties of simulated precipitation and temperature fields. This region has been selected for its challenging orography making the results obtained here a valuable source for studies leading to further developments in climate modeling. It was found that size of the domain strongly affects the quality of obtained results. We have found that the largest domain reproduces the spatial characteristics of climate (such as bias) very well, but its use results in a poor representation of temporal aspects, which are however captured very well in experiments over both smaller domains. Our findings suggest that there is no optimal choice of domain size, securing the best results for both spatial and temporal evaluation.  相似文献   

Mikulino and Valdai palaeoenvironments in the Vologda area, NW Russia     

Valery Gey  Matti Saarnisto  Juha Pekka Lunkka  Igor Demidov 《Global and Planetary Change》2001,31(1-4)

Nine representative sediment sequences and pollen diagrams obtained during the Quaternary mapping programme carried out by the Geological Expedition (St. Petersburg, Russia) between 1960s and 1980s are presented from the Vologda area, NW Russian Plain, covering the time span from the Moscow cold (Saale) stage into the Late Valdai (Weichsel) substage. This work was done in order to shed light on the evolution of palaeoenvironments, vegetation and climate in the area. The results suggest that two major depressions in the Vologda area, namely the Mologa–Sheksnian and Prisukhonian basins, witnessed lake level fluctuations that were most likely closely linked to climatic fluctuations. It is suggested that during the Mikulino (Eem) thermal optimum most of the lowland areas were dry land. However, during the Early and Middle Valdai, the large depressions started to flood as a result of wet and cold climate. This caused the accumulation of lacustrine and also lacustrine–alluvial and lacustrine–bog sediments into the basins. The Valdai forest composition varied between closed spruce–birch forests and treeless tundra. Lakes persisted throughout the Valdai stage including the extremely dry last glacial maximum (LGM)-time when the Scandinavian Ice Sheet dammed the northbound rivers in the Vologda area.  相似文献   

The extent of the Late Weichselian ice sheet in the southeastern Barents Sea     

Valery Gataullin  Jan Mangerud  John Inge Svendsen   《Global and Planetary Change》2001,31(1-4)

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Perceived effects of climate change on profit efficiency among small scale chili pepper marketers in Benue State,Nigeria     

Djomo  Choumbou Raoul Fani  Ukpe  Henrietta Udeme  Ngo  Ngo Valery  Mohamadou  Sani  Adedze  Miranda  Pemunta  Ngambouk Vitalis 《GeoJournal》2021,86(4):1849-1862

GeoJournal - In the determination of the level of efficiency of an enterprise, the role of climate change cannot be overemphasized. However, some scholars are of the view that climate change might...  相似文献   

Distribution of ejecta from small impact craters     

Valery Shuvalov  Henning Dypvik 《Meteoritics & planetary science》2013,48(6):1034-1042

The present study focuses both on the influence of impact scale on ejecta expansion and on specific features of ejecta deposits around relatively small craters (i.e., those a few kilometers in width). The numerical model is based on the SOVA multimaterial multidimensional hydrocode, considering subaerial vertical impacts only, applying a 2‐D version of the code to projectiles of 100, 300, and 1000 m diameter. Ejecta can roughly be divided into two categories: “ballistic” ejecta and “convective” ejecta; the ballistic ejecta are the ejecta with which the air interacts only slightly, while the convective ejecta motion is entirely defined by the air flow. The degree of particle/air interaction can be defined by the time/length of particle travel before deceleration. Ejecta size‐distributions for the impacts modeled can be described by the same power law, but the size of maximum fragment increases with scale. There is no qualitative difference between the 100 m diameter projectile case and the 300 m diameter projectile impact. In both cases, fine ejecta decelerate in the air at a small distance from launching point and then rise to the stratosphere by air flows induced by the impacts. In the 1000 m‐scale impact, the mass of ejecta is so large that it moves the atmosphere itself to high altitudes. Thus, the atmosphere cannot decelerate even the fine ejecta and they consequently expand to the rarefied upper atmosphere. In the upper atmosphere, even fine ejecta move more or less ballistically and therefore may travel to high altitudes.  相似文献   

Spectra of the spreading layers on the neutron star surface and constraints on the neutron star equation of state     

Valery Suleimanov  Juri Poutanen 《Monthly notices of the Royal Astronomical Society》2006,369(4):2036-2048

Spectra of the spreading layers on the neutron star surface are calculated on the basis of the Inogamov–Sunyaev model taking into account general relativity correction to the surface gravity and considering various chemical composition of the accreting matter. Local (at a given latitude) spectra are similar to the X-ray burst spectra and are described by a diluted blackbody. Total spreading layer spectra are integrated accounting for the light bending, gravitational redshift and the relativistic Doppler effect and aberration. They depend slightly on the inclination angle and on the luminosity. These spectra also can be fitted by a diluted blackbody with the colour temperature depending mainly on a neutron star compactness. Owing to the fact that the flux from the spreading layer is close to the critical Eddington, we can put constraints on a neutron star radius without the need to know precisely the emitting region area or the distance to the source. The boundary layer spectra observed in the luminous low-mass X-ray binaries, and described by a blackbody of colour temperature   T _c= 2.4 ± 0.1 keV  , restrict the neutron star radii to   R = 14.8 ± 1.5 km  (for a  1.4-M_⊙  star and solar composition of the accreting matter), which corresponds to the hard equation of state.  相似文献