Mechanism of formation of long-term directional climate changes in the past and current centuries     

A. V. Dzyuba  G. N. Panin 《Russian Meteorology and Hydrology》2007,32(5):287-300

Climatic changes of the past century are diagnosed based on the generalized empirical data. Considered is a forcing impact of interannual inhomogeneity of the angular velocity of the Earth on the pressure field, atmospheric circulation, and radiation balance of the climate system. A physical mechanism of formation of global climate change tendencies as a response to the composition of greenhouse and rotational effects is described. Possible climate changes in the current century are assessed.  相似文献   

Flow and sediment processes in a cutoff meander of the Danube Delta during episodic flooding     

Laura Jugaru Tiron  Jrme Le Coz  Mireille Provansal  Nicolae Panin  Guillaume Raccasi  Guillaume Dramais  Philippe Dussouillez 《Geomorphology》2009,106(3-4):186-197

This article analyzes the water and suspended solid fluxes through a straightened meander of the southern branch of the Danube Delta (the St. George branch) during episodic flooding. The Mahmudia study site corresponds to a vast natural meander which was cut off in 1984–1988 by an artificial canal opened to shipping. The meander correction accelerated fluxes through the artificial canal and dramatically enhanced deposition in the former meander. After his formation, the cutoff meander acted as sediment storage locations, essentially removing channel and point bar sediments from the active sediment budget of the main channel. Increases in slope and stream power in reaches upstream and downstream have also occurred, but to a lesser degree. During the one-hundred-year recurrent flood in April 2006, bathymetry, flow velocity and discharge data were acquired across several sections of both natural and artificial channels with an acoustic Doppler current profiler (aDcp Workhorse Sentinel 600 kHz, Teledyne RDI) in order to investigate the distribution of the flow and sediment and his impact on sedimentation in a channelized reach and its adjacent cutoff. The contrasting hydro-sedimentary processes at work in both channels and bifurcation/confluence nodal points are analyzed from the measured flux distribution, morphological profiles and velocity and concentration patterns. In the cutoff, a diminishing of the intensity of the flow velocity (c. 50%) and of the SSC was observed correlated with the aggradation of the river bed. In the bifurcation/confluence nodal points and in the artificial canal were observed the most intensive hydrodynamic activity (high flow velocity, SSC concentration, degradation of the river bad). Both the event-scale and long-term morphological trends of the alluvial system are discussed analyzing the boundary shear stress and SSC variability. Excess boundary shear stress in the sub-reaches directly affected by cutoffs resulted in scour that increased downstream bed material load. These high sediment loads play a key role in driving morphological adjustments towards equilibrium in the cutoff channel.The approach followed in this paper combines detailed episodic in-situ aDcp measurements and robust numerical 1D modeling in order to provide a practical comprehension of the relevant morphodynamical processes. The 1D model reproduces robustly the continuity of hydrodynamical variables along the streamwise axes of the two-channel network. The simulated are used in the paper for highlighting reach-scale morphological processes, at both event and long-term scales.  相似文献   

Climate-induced changes in surface runoff on the North-Eurasian plains during the late glacial and Holocene     

A. Yu. Sidorchuk  A. V. Panin  O. K. Borisova 《Water Resources》2008,35(4):386-396

Abandoned rivers (large paleochannels and meanders) are common on river floodplains and low terraces on the East European and West Siberian plains. They are 10–15 times greater in size than the present-day river channels. The large paleochannels are dated back to 11–15 thousand radiocarbon years B.P. (the Late Glacial period). Based on the hydraulic and morphometric relationships for present-day rivers and the method of paleogeographic analogs, the surface runoff during the Late Glacial period was quantitatively reconstructed by the morphometric parameters of large paleochannels. The reconstructed surface runoff exceeded the present values by 1.4 times on the northern mega-slope of the East European Plain (the Northern Dvina, Mezen, and Pechora river basins), by 2.3 times on its southern mega-slope (the Volga, Don, and Dnepr basins), and twofold in West Siberia (the Ob basin). The large surface runoff volumes can be explained by the landscape and climate conditions, including the high coefficients of runoff (due to the permafrost), the increased proportion (and, conceivably, the amount) of snowfall, and, hence, the respective increased intensity of spring floods. The transformation of large Late-Glacial paleorivers due to climate warming at the beginning of the Holocene is a likely scenario of the surface runoff development within the present-day permafrost zone at the ongoing human-induced climate warming. A general decrease in surface runoff and its more uniform intra-annual distribution would result in the reduced size of rivers in the middle Siberia, Yakutia, and northeastern Russia.  相似文献   

A Measure of Inhomogeneity of the Land Surface and Parametrization of Turbulent Fluxes under Natural Conditions   总被引：1，自引：0，他引：1  

G. N. Panin  G. Tetzlaff 《Theoretical and Applied Climatology》1999,62(1-2):3-8

Summary The effects of surface heterogeneity and nonstationarity on turbulent fluxes are parametrized by introducing an additional roughness length that corrects for deviations from Stationarity and Horizontal Homogeneity (SHH). Using data from the experiments of FIFE, KUREX, TARTEX and SADE, a relationship was detected between the underestimation of turbulent fluxes (the lack of balance in the surface energy budget) and terrain inhomogeneity. Based on the assumption that the parametrization obtained from these data is applicable for complex terrain surfaces in general, the paper presents some simple relationships for surface turbulent fluxes, bulk transfer coefficients, and roughness lengths. Received August 8, 1997 Revised March 9, 1998  相似文献   

Treatment of Crystal Violet from Synthetic Solution Using Membranes Doped with Natural Fruit Extract          下载免费PDF全文

Simona Caprarescu  Alexandra R. Miron  Violeta Purcar  Anita‐Laura Radu  Andrei Sarbu  Cristian Andi Nicolae  Mihaela Pascu  Daniela Ion‐Ebrasu  Valentin Raditoiu 《洁净——土壤、空气、水》2018,46(7)

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Adapting a model of heat and mass exchange between a water body and the atmosphere taking into account the effect of shallows: Case study of the Ivankovo Reservoir     

G. N. Panin  M. G. Grechushnikova  V. V. Puklakov 《Water Resources》2011,38(6):818-826

The paper is based on a box model of heat and mass exchange with the incorporation of a block for calculating latent heat flux, supplemented by parameterization of heat and mass exchange between shallow water area and the atmosphere. The results of calculation of evaporation from the water area of the Ivankovo Reservoir, with allowance made for more intense evaporation from shallows, are given. The latent heat fluxes from shallow and deep-water zones of the water body are shown to differ, depending on weather conditions and water level; the increase in the evaporated-water volume due to taking into account the shallow-water effect is evaluated.  相似文献   

On climate changes in polar zones of the Earth in the twentieth and twenty-first centuries     

Panin  G. N. 《Doklady Earth Sciences》2009,427(2):988-992

Doklady Earth Sciences -  相似文献   

Thermal regime of the near-surface layer of a water body and its effect on the state of aquatic ecosystem     

G. N. Panin  S. G. Sarkisyan  A. M. Nikanorov  N. M. Trunov 《Water Resources》2007,34(6):663-675

The thermal regime of the surface water layer in a water body is studied, and its effect on the mass and gas exchange in the water body-atmosphere system is examined by using a mesocosm as a microecosystem model.  相似文献   

A numerical analysis of the foot-floor interaction in long wall workings     

Nicolae Cristescu  Ioan R. Ionescu  I. Rosca 《国际地质力学数值与分析法杂志》1994,18(9):641-652

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The masses in a symmetric solution of the four body problem     

Florin Nicolae Diacu 《Celestial Mechanics and Dynamical Astronomy》1989,46(1):27-30

It is proved that if a non-collinear motion of the four body problem has a symmetry axis (or plane), then the center of mass lies on this axis (plane) and the symmetric masses are equal. We also remark that this result is true for the generalized attraction law given by the inverse (α+1)-power of the distance, with α > 0.  相似文献