Distribution of airborne pollen and spores and their long distance transport     

P. H. Gregory 《Pure and Applied Geophysics》1978,116(2-3):309-315

The atmosphere near the ground contains a mixed population of pollen and spores in the 1 to 90 m diameter range. Continuous sampling at Rothamsted Experimental Station at 2 m above ground level indicated concentrations averaging 12,000 m^–3 over 5 summer months, but 1 million m^–3 can occur for short periods. Concentrations change rapidly with locality, season, time of day or night and weather. Normally concentration in the troposphere decreases logarithmically with height. The occurrence of long distance transport of pollen and spores by wind is demonstrated by sampling from aircraft, and supported by much circumstantial evidence. Possible effects of this air spora on the atmosphere may be sought in alterations to: opacity, ionization, condensation nuclei, and sinks for minor gases.  相似文献   

Till ridges in Wensleydale,Yorkshire     

R.A. Cullingford  K.J. Gregory 《Proceedings of the Geologists' Association. Geologists' Association》1978,89(1):67-79

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Hillslope hydrology | M.J. Kirkby (editors), 1978. Wiley and Sons,Chichester, 389 pp., £ 18.25, U.S. $ 33.00     

K.J. Gregory 《Earth》1979,14(3):301-302

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Rare earth element distribution in some hydrothermal minerals: evidence for crystallographic control   总被引：1，自引：0，他引：1  

John W. Morgan  Gregory A. Wandless 《Geochimica et cosmochimica acta》1980,44(7):973-980

Rare earth element (REE) abundances were measured by neutron activation analysis in anhydrite (CaSO₄), barite (BaSO₄), siderite (FeCO₃) and galena (PbS). A simple crystal-chemical model qualitatively describes the relative affinities for REE substitution in anhydrite, barite, and siderite. When normalized to ‘crustal’ abundances (as an approximation to the hydrothermal fluid REE pattern), log REE abundance is a surprisingly linear function of (ionic radius of major cation—ionic radius of REE)² for the three hydrothermal minerals, individually and collectively. An important exception, however, is Eu, which is anomalously enriched in barite and depleted in siderite relative to REE of neighboring atomic number and trivalent ionic radius. In principle, REE analyses of suitable pairs of co-existing hydrothermal minerals, combined with appropriate experimental data, could yield both the REE content and the temperature of the parental hydrothermal fluid.The REE have only very weak chalcophilic tendencies, and this is reflected by the very low abundances in galena—La, 0.6 ppb; Sm, 0.06 ppb; the remainder are below detection limits.  相似文献   

东亚地区沙尘气溶胶影响硫酸盐形成的模式评估   总被引：14，自引：0，他引：14  

肖辉  Gregory R. Carmichael  Yang Zhang 《大气科学》1998,22(3):343-353

利用STEM-II三维区域大气化学模式,耦合沙尘气溶胶表面相过程,研究了1994年3月1日至14日间东亚地区沙尘气溶胶对硫酸盐形成的影响。结果表明,SO2气体在沙尘气溶胶表面上进行的非均相氧化过程是硫酸盐形成的一条重要途径,由这条途径提供的硫酸盐占其总浓度的20%～50%。 并发现在模拟时段,沙尘暴过程主要影响沙尘源地下游的中国东部地区硫酸盐的分布,使得那里的硫酸盐浓度增加60%以上。  相似文献   

Assessment of Hydraulic Parameters of the Aquifers Around the Sea of Galilee   总被引：1，自引：0，他引：1  

Gregory Bergelson  Ronit Nativ  Amos Bein 《Ground water》1998,36(3):409-417

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Lichens and the determination of river channel capacity     

Ken J. Gregory 《地球表面变化过程与地形》1976,1(3):273-285

The identification of channel capacity associated with a particular frequency of peak discharges is necessary for discharge estimation for planning purposes at ungauged sites. Although lichen limits have been suggested to be useful for this purpose, previous studies have not elaborated their hydrological significance. Lichen limits are clearly defined on the sides of rock channels in New England. Australia and they are analyzed in relation to discharge at 6 gauging stations with up to 52 years of continuous record. It is demonstrated that the lowest lichen limit is maintained by peak discharges which occur on average at least once or twice each year. Recurrence intervals based on Annual Series and on Annual Exceedance Series are calculated and for the annual series are fairly consistent for the lowest lichen limit and range from 1·14 to 1·37 years. Lichenometry can be applied to the analysis of river channels in relation to the frequency of peak discharges. By reference to growth curves based upon lichens on Armidale tombstones it is shown that lichenometry may be employed to indicate dates for channel modification due to the removal of blocks and to dam construction and also to date the rock surface between lichen limits. Detailed analysis of the record from gauging stations indicates that where several lichen limits occur in a channel cross section each limit is related to periods when peak discharges exceeded the limits on at least 5 occasions. The lichen-free surfaces were then recolonized by Parmelia spp. and the size of the lichen thalli indicates the time elapsing since these frequent high discharges.  相似文献   

Plastic pellets on New Zealand beaches   总被引：1，自引：0，他引：1  

Murray R Gregory 《Marine pollution bulletin》1977,8(4):82-84

Small plastic pellets, of the kinds commonly being recorded as contaminants on beaches, and in coastal as well as oceanic waters adjoining industrialized regions of the Northern Hemisphere are also widely distributed on the beaches of New Zealand.  相似文献   

Special Issue on ‘Nonlinear Modeling,Analysis, and Simulation for Earthquake Engineering’ Earthquake Engineering and Structural Dynamics (EQE)     

Gregory L. Fenves  Anil K. Chopra 《地震工程与结构动力学》2007,36(15):i-ii

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A study of arctic sea ice and sea‐level pressure using POP and neural network methods     

Benyang Tang  Gregory M. Flato  Greg Holloway 《大气与海洋》2013,51(3):507-529

Abstract

We examine Arctic sea‐ice concentration (SIC) and sea‐level pressure (SLP) data using principal oscillation pattern (POP) and neural network methods. The POP method extracts oscillating patterns from multivariate time series, each pattern being characterized by an oscillation period and a decay time. Predictions can be made for patterns whose decay time is comparable with the period. For both the SIC and SLP, however, the decay times are much shorter than the oscillation periods, and therefore the forcast skill is poor. A neural network is a model of the learning behaviour of a living neural system. Presented with training data, a neural network can learn the linear or non‐linear rules embedded in the data. We trained neural networks with sea‐ice and sea‐level pressure data, and estimated the forecast skill using a cross‐validation technique. The neural networks did not exhibit forecast skill significantly better than that of persistence. We contrast the Arctic situation with previous studies in which POP and neural networks were successfully used to forecast El Niño at lead times up to 6 months. Reasons for the lack of skill in both methods are discussed.  相似文献