A physically‐based algorithm for estimating the relationship between aerosol mass and cloud droplet number     

PAUL GLANTZ  KEVIN J. NOONE 《Tellus. Series B, Chemical and physical meteorology》2000,52(5):1216-1231

In this study, we present a relationship between total accumulation mode aerosol mass concentrations and cloud droplet number concentrations ( N _d). The fundamental aim with the present method is to arrive at a physically‐based conversion algorithm in which each step in the conversion is based on real physical processes that occur and can be observed in the atmosphere, and in which all of the fields involved can be observed or modeled. In the last conversion (the critical part in the algorithm), we use measurements of the size distributions of cloud droplet residual particles for different pollution conditions. This conversion assumes that the size of the residual particles can be described with a lognormal distribution function and uses the Hatch–Choate relationship to convert between residual volume and number. The relatively sparse data set with which we have developed the present algorithm results in a course classification of the aerosol mass field. Consequently, uncertainties need to be recognized when using the algorithm in its present form in model calculations. The algorithm has been used on data from 15 days and the agreement between calculated and observed N _d values is, with one exception, within a factor of 2 and for many of these cases also much better than a factor of 2. In addition to the results of the algorithm itself, we also present a least‐squares fit to the predicted N _d values. To improve the algorithm in the longer‐term requires more data of scavenging fractions, particle chemical composition and density, and residual particle size distributions as a function of aerosol mass loading and cloud type.  相似文献   

Southern Ocean transformation in a coupled model with and without eddy mass fluxes     

KEVIN SPEER  ERIC GUILYARDI  GURVAN MADEC 《地球，A辑:动力气象学与海洋学》2000,52(5):554-565

A coupled air–sea general circulation model is used to simulate the global circulation. Different parameterizations of lateral mixing in the ocean by eddies, horizontal, isopycnal, and isopycnal plus eddy advective flux, are compared from the perspective of water mass transformation in the Southern Ocean. The different mixing physics imply different buoyancy equilibria in the surface mixed layer, different transformations, and therefore a variety of meridional overturning streamfunctions. The coupled‐model approach avoids strong artificial water mass transformation associated with relaxation to prescribed mixed layer conditions. Instead, transformation results from the more physical non‐local, nonlinear interdependence of sea‐surface temperature, air–sea fluxes, and circulation in the model's atmosphere and ocean. The development of a stronger mid‐depth circulation cell and associated upwelling when eddy fluxes are present, is examined. The strength of overturning is diagnosed in density coordinates using the transformation framework.  相似文献   

Meditating on petroleum geology at the Barbican     

J. H. McD. WHITAKER  KEVIN T. PICKERING 《Geology Today》1987,3(2):52-53

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Early Gardening on Mana Island, Cook Strait, New Zealand     

KEVIN L. JONES 《New Zealand geographer》1987,43(1):18-22

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TransCom 3 CO₂ inversion intercomparison: 2. Sensitivity of annual mean results to data choices     

RACHEL M. LAW  YU-HAN CHEN  KEVIN R. GURNEY  TRANSCOM MODELLERS 《Tellus. Series B, Chemical and physical meteorology》2003,55(2):580-595

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Alkaline Lavas in the Volcanic Front of the Western Mexican Volcanic Belt: Geology and Petrology of the Ayutla and Tapalpa Volcanic Fields   总被引：6，自引：1，他引：6  

RIGHTER  KEVIN; ROSAS-ELGUERA  JOSE 《Journal of Petrology》2001,42(12):2333-2361

The Plio-Quaternary Ayutla and Tapalpa volcanic fields in thevolcanic front of the western Mexican Volcanic Belt (WMVB) containa wide variety of alkaline volcanic rocks, rather than onlycalc-alkaline rocks as found in many continental arcs. Thereare three principal rock series in this region: an intraplatealkaline series (alkali basalts and hawaiites), a potassic series(lamprophyres and trachylavas), and a calc-alkaline series.Phlogopite-clinopyroxenite and hornblende-gabbro cumulate xenolithsfrom an augite minette lava flow have orthocumulate textures.The phlogopite-clinopyroxenite xenoliths also contain apatiteand titanomagnetite and probably formed by accumulation of mineralsfractionated from an augite minette more primitive than thehost. The intraplate alkaline series is probably generated bydecompression melting of asthenospheric mantle as a result ofcorner flow in the mantle wedge beneath the arc. Alkaline magmasmay be common in the WMVB as a result of prior metasomatism(during Tertiary Sierra Madre Occidental magmatism) of the Mexicansub-arc mantle. Generation of the more evolved andesites anddacites of the calc-alkaline series is due to either combinedassimilation and fractional crystallization (AFC) or magma mixing.The preponderance of alkaline and hydrous lavas in this regiondemonstrates that these lava types are the norm, rather thanthe exception in western Mexico, and occur in regions that arenot necessarily associated with active rifting. KEY WORDS: arc basalt; subduction; alkali basalt; minette; hawaiite; metasomatism  相似文献   

COLORADO FOURTEENERS AND THE NATURE OF PLACE IDENTITY*     

KEVIN S. BLAKE 《Geographical review》2002,92(2):155-179

ABSTRACT. The fifty‐four Colorado Fourteeners–mountains more than 14,000 feet in elevation–were early symbols of westward expansion, mineral wealth, and wondrous scenery, and they are increasingly popular as environmental icons in place attachment at national, regional, state, and local scales. The symbolism of this contrived yet iconic collection of peaks is examined through the evolution of the Fourteener concept, the popularity of peakbagging, and the role of the Sawatch Range Fourteeners in creating a larger community identity. Elevation is the gatekeeper into the Fourteener club, in which a distinctive landscape iconography of shape, accessibility, and aesthetics reflects the role of idealized nature and mountains in place identity.  相似文献   

Trace fossils as diagnostic indicators of deep-marine environments, Middle Eocene Ainsa-Jaca basin, Spanish Pyrenees   总被引：1，自引：0，他引：1  

THOMAS G. HEARD†  KEVIN T. PICKERING 《Sedimentology》2008,55(4):809-844

A quantitative study of trace fossil abundance in the Middle Eocene deep-marine clastic systems, Ainsa-Jaca basin, Spanish Pyrenees, shows that they are powerful discriminators of submarine fan and related environments. Sixteen fan and related environments are recognized from upper-slope gully to the distal basin-floor. For each environment, the degree of bioturbation (density), trace-fossil diversity, number of pre-depositional and post-depositional trace fossils, as well as the number of graphoglyptid ichnospecies were quantified. In the more laterally confined and channel-dominated Ainsa basin, there is a trend of increasing bioturbation intensity and trace-fossil diversity away from channel-axis to off-axis environments. In the more unconfined and distal Jaca basin, there is a trend of increasing trace-fossil diversity and number of pre-depositional trace fossils including graphoglyptids from the channel-lobe transition to the fan-fringe. The trace-fossil assemblages of the Ainsa-Jaca basin are characteristic of a number of sub-ichnofacies of the Nereites ichnofacies. In the distal Jaca basin, the Paleodictyon sub-ichnofacies occurs in the lobe-fringe and fan-fringe, whereas the distal basin-floor has a trace-fossil assemblage typical of the Paleodictyon sub-ichnofacies, but with a high proportion of post-depositional fodinichnia . Trace-fossil assemblages of proximal basin, axial, environments are characteristic of the Ophiomorpha rudis sub-ichnofacies, whilst proximal off-axis environments, have a mixed Paleodictyon-Ophiomorpha rudis sub-ichnofacies trace-fossil assemblage.  相似文献   

Physical initialization for numerical weather prediction over the tropics   总被引：5，自引：0，他引：5  

T. N. KRISHNAMURTI  JISHAN XUE  H. S. BEDI  KEVIN INGLES  D. OOSTERHOF 《Tellus. Series B, Chemical and physical meteorology》1991,43(4):53-81

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Inhibition of dissolution within shallow water carbonate sediments: impacts of terrigenous sediment input on syn-depositional carbonate diagenesis   总被引：2，自引：0，他引：2  

CHRISTOPHER T. PERRY  KEVIN G. TAYLOR 《Sedimentology》2006,53(3):495-513

The early diagenetic chemical dissolution of skeletal carbonates has previously been documented as taking place within bioturbated, shallow water, tropical carbonate sediments. The diagenetic reactions operating within carbonate sediments that fall under the influence of iron‐rich (terrigenous) sediment input are less clearly understood. Such inputs should modify carbonate diagenetic reactions both by minimizing bacterial sulphate reduction in favour of bacterial iron reduction, and by the reaction of any pore‐water sulphide with iron oxides, thereby minimizing sulphide oxidation and associated acidity. To test this hypothesis sediment cores were taken from sites within Discovery Bay (north Jamaica), which exhibit varying levels of Fe‐rich bauxite sediment contamination. At non‐impacted sites sediments are dominated by CaCO₃ (up to 99% by weight). Pore waters from the upper few centimetres of cores show evidence for active sulphate reduction (reduced SO₄/Cl^? ratios) and minor CaCO₃ dissolution (increased Ca²⁺/Cl^? ratios). Petrographic observations of carbonate grains (specifically Halimeda and Amphiroa) show clear morphological evidence for dissolution throughout the sediment column. In contrast, at bauxite‐impacted sites, the sediment is composed of up to 15% non‐carbonate and contains up to 6000 μg g^?1 Fe. Pore waters show no evidence for sulphate reduction, but marked levels of Fe(II), suggesting that bacterial Fe(III) reduction is active. Carbonate grains show little evidence for dissolution, often exhibiting pristine surface morphologies. Samples from the deeper sections of these cores, which pre‐date bauxite influence, commonly exhibit morphological evidence for dissolution implying that this was a significant process prior to bauxite input. Previous studies have suggested that dissolution, driven by sulphate reduction and sulphide oxidation, can account for the loss of as much as 50% of primary carbonate production in localized platform environments. The finding that chemical dissolution is minor in a terrigenous‐impacted carbonate environment, therefore, has significant implications for carbonate budgets and cycling, and the preservation of carbonate grains in such sediment systems.  相似文献