Temporal behaviour of artificial small-scale ionospheric irregularities: Review of experimental results     

V.L. Frolov  L.M. Erukhimov  S.A. Metelev  E.N. Sergeev 《Journal of Atmospheric and Solar》1997,59(18):2317-2333

Features of artificial small-scale ionospheric irregularities (ASI) induced at F-region heights by powerful HF waves are discussed. The investigations presented here were performed during the past two decades at the Zimenki and Sura heating facilities, located at middle latitudes near Nizhniy Novgorod, Russia, as well as at the Gissar facility located at a lower latitude near Dushanbe, Tadzhikistan. The measurements were made by a variety of diagnostic methods employing artificial field-aligned scattering of HF and VHF radio waves, sounding of the disturbed region by means of low-power probing waves and testing of the artificial turbulence by means of stimulated electromagnetic emission (SEE). The dependence of ASI on such parameters as transverse scale length of the artificial irregularities, their location in the disturbed region, the power of the heating wave, the duration of HF radiation, geophysical conditions, aftereffects of the preceding modification, and the schedule of heater operation is considered for both the development stage after pump turn-on and the decay stage after pump turn-off. The temporal evolution of ASI spectral characteristics during the heater period is discussed. An empirical model for the ASI, based on the data available, was elaborated and verified by computer simulation of SEE generation.  相似文献   

Temporal evolution of HF-excited plasma waves, measured at different pump frequencies by stimulated electromagnetic emission (SEE)     

E.N. Sergeev  V.L. Frolov  G.P. Komrakov  B. Thidé  T. Carozzi 《Journal of Atmospheric and Solar》1997,59(18):2383-2400

Experimental results concerning the growth and decay times of different spectral components of stimulated electromagnetic emission (SEE) are presented. A new method of measurement, employing a special pulsed pump scheme for the ionospheric plasma modification, has been elaborated and applied for studying HF-induced processes with high time resolution. The measurements performed show that the development and relaxation of different SEE features have an intricate pattern which depends on the emission frequency shift from the pump frequency, on the proximity of the pump frequency to the gyroharmonic frequencies, on the intensity of artificial ionospheric turbulence, and on the ionospheric conditions. The scope of this method for studies of HF plasma turbulence is discussed.  相似文献   

The northwest european shelf temperature and salinity variability     

Gerd A. Becker  Alexander Frohse  Peter Damm 《Ocean Dynamics》1997,49(2-3):135-151

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Data buoy measurements of phytoplankton dynamics in southampton water, UK, a temperate latitude estuary with high nutrient inputs     

Paul N. Wright  David J. Hydes  Mary Lou Lauria  Jonathan Sharples  Duncan A. Purdie 《Ocean Dynamics》1997,49(2-3):203-211

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Response of the wadden sea to a rising sea level: a Predictive empirical model     

Burghard W. Flemming  Alexander BartholomÄ 《Ocean Dynamics》1997,49(2-3):343-353

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Untersuchung der Sorptionseigenschaften des Kationenaustauschers KB-2M mit Makronetzstruktur zur Abtrennung von Zinkionen aus Ab- und Spülwässern     

O. N. Kononowa  A. G. Cholmogorow  G. L. Paschkow  G. P. Wdowina 《洁净——土壤、空气、水》1997,25(4):208-212

Study of Sorptional Properties of the Cation Exchanger KB-2M with Macroreticular Structure for Recovery of Zinc Ions from Sewage and Rinsing Water Although a number of ion-exchange methods have been employed for the recovery of some transition metals from industrial effluents, knowledge about ion-exchange resins with macroreticular structure is poor. The present paper describes the mechanism of sorption on such exchangers and their application for recovery of zinc from sewage rinsing water. Ion exchanger of macroreticular structure are polymers with long-chained cross-linking agents. We have synthesized carboxylic ion-exchange resins by hydrolysis of copolymerisates of methyl acrylate with different cross-linking agents: divinylbenzene, divinyl sulfide, divinyl ester of ethylene glycol and divinyl ester of di- or triethylene glycol. The sorption process on modifications of the carboxylic resins KB-2 of various structure was studied with different methods: potentiometric titration, infrared spectroscopy, electron microscopy, X-ray structural analysis. The initial zinc concentration in rinsing water was 0.05 mol/L at pH from 3 to 6. For the sorption, 0.2…1.0 g of resin were equilibrated with 100 mL of zinc solution. After equilibrium (12 h), the resin was separated from solution. The zinc ions were determined by atomic absorption spectrometry after stripping with 100 mL of 10% sulfuric acid. The distribution ratio D was calculated (D: mmole of Zn sorbed per gram of resin divided by mmole of Zn per millilitre of solution). By means of infrared spectroscopy, the mechanism of sorption of zinc ions from rinsing water was determined. There may be a possibility of the formation of complexes in the cation-exchange resin phase. It was found out in this paper that the cation-exchanger KB-2M of macroreticular structure is the most effective for the sorption of the Zn²⁺-ions from sewage and rinsing water.  相似文献   

A short note on: Identification of the shape of simple causative sources from gravity data     

B.K. Nandi  R.K. Shaw  B.N.P. Agarwal 《Geophysical Prospecting》1997,45(3):513-520

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Remote sensing detection of atmospheric pollutants by differential absorption LIDAR 510M/SODAR PA2 mobile system     

J. Keder  M. Střižík  P. Berger  A. Černý  P. Engst  I. Němcová 《Meteorology and Atmospheric Physics》2004,85(1-3):155-164

Summary Air pollution problem in the Czech Republic is very complex due to large number of factors as turbulent dispersion and chemical reactions concurring in the status of the PBL. For this 3D distribution of pollutants is a key information that cannot be given by conventional monitoring stations. Combined use of DIAL lidar and sodar can give access to such information. Case studies of air pollutants transport are presented using 3D concentration fields of NO₂ and ozone measured by lidar and meteorological conditions monitored by Doppler Sodar.  相似文献   

Radiative Exchange in an Urban Street Canyon   总被引：1，自引：4，他引：1  

Ian N. Harman  Martin J. Best  Stephen E. Belcher 《Boundary-Layer Meteorology》2004,110(2):301-316

The influence of building geometry on the radiation terms ofthe surface energy balance is a principal reason for surfacetemperature differences between rural and urban areas.Methods exist to calculate the radiation balance in an urban area,but their validity across the range of urban geometries andmaterials has not been carefully considered.Here the exchange of diffuse radiation in an urban street canyon isinvestigated using a method incorporating all reflections of radiation.This exact solution is compared to two commonly used approximationsthat retain either no reflections, or just one reflection of radiation.The area-averaged net radiative flux density from the facets of the canyondecreases in magnitude monotonically as the canyon aspect ratio increases.The two approximate solutions possess unphysical differences from thismonotonic decrease for high canyon aspect ratios or low materialemissivities/high material albedos.The errors of the two approximate solutions are small for near blackbodymaterials and small canyon aspect ratios but can be an order ofmagnitude for intermediate material properties and deep street canyons.Urban street canyon models need to consider at least one reflectionof radiation and multiple reflections are desirable for full applicability.  相似文献   

A systematic algorithm for obtaining SODAR wind profiles     

S. G. Bradley  S. v. Hünerbein 《Meteorology and Atmospheric Physics》2004,85(1-3):77-84

Summary Current methods of obtaining wind profiles from SODARs generally employ ad hoc strategies for Doppler spectrum peak selection, profile smoothing, and consistency checks. This paper addresses the problem of systematically obtaining vertical profiles of wind vectors from a SODAR. A new approach is to regard every spectrum frequency as a possible estimator of the radial wind component, but to weight these Doppler estimates according to the spectral power at each frequency. This allows the peak detection, smoothing, and assimilation of a priori information to be combined into a constrained linear inversion methodology. The inversion process also allows an estimation of signal-to-noise ratio, degrees of freedom, and information content versus height. Examples are given of profiles obtained using this new inverse method. The relationship to the physical limitations of the SODAR instrument and the atmosphere is discussed.  相似文献