Planation surfaces: Peneplains,pediplains, and etchplains: George F. Adams (Editor). Benchmark Papers in Geology Vol. 22, Halstead Press, 1975, 476 pp., $28.00     

Arthur D. Howard 《Quaternary Research》1976,6(3):460-461

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Climatological aspects of the tropical convective boundary layer     

E. B. Kraus  Howard P. Hanson 《Boundary-Layer Meteorology》1974,6(1-2):219-233

The characteristics of a boundary layer depend both on conditions at the surface and in the interior of the medium. In the undisturbed tropics, the latter are largely determined by subsidence and by infrared radiational cooling. One-dimensional models are used to establish relationships between the inversion height, subsidence, upper-air humidity and sea-surface temperature. In particular, it is shown that a universally colder tropical ocean would probably be covered by more extensive clouds.Contribution No. 1700 Rosenstiel School of Marine and Atmospheric Science, University of Miami.  相似文献   

Surface history of some Apollo 17 lunar soils     

Robert L. Fleischer  Howard R. Hart 《Geochimica et cosmochimica acta》1974,38(10):1615-1623

Cosmic ray track densities in Apollo 17 soil samples are used to infer surface exposure times of soils from a trench at Van Serg Crater, from on and near a boulder at Camelot Crater, and from the position of the heat flow and neutron flux experiments (the ALSEP site). The topmost 2 cm of soil at Van Serg was exposed for 11 m.y., the top cm at Camelot for 36 m.y. A layering chronology and average deposition rate are proposed for the trench. For all soils the median track densities imply predispositional irradiation in the top 15 cm of the lunar surface for times that were long compared with the actual residence in the stratigraphic positions from which the soils were collected. Van Serg crater is inferred to have been formed approximately 24 m.y. ago.  相似文献   

A MEXICAN CORPORATE CAMPAIGN IN CONSERVATION     

Ernst Griffin  Howard W. Dennis 《The Professional geographer》1969,21(5):358-359

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Role of hypsometry and planform in basin hydrologic response     

Alan D. Howard 《水文研究》1990,4(4):373-385

The effects of variations of drainage basin morphometry and relief characteristics on flood peak magnitude and time-to-peak are investigated using simulated stream networks. The networks are produced by three models: headward growth, systematic capture, and minimum power relaxation. Translational and kinematic wave flood routing were used to generate synthetic hydrographs. Peak discharge and time-to-peak are predictable to a high degree by five different sets of morphometric-relief parameters. In order of decreasing order of importance in predictive ability the parameters characterize basin size, relative relief, basin concavity, and basin shape. Both simulated and natural stream networks exhibit strong dependence of planimetric morphometry upon basin concavity. The effect of this dependency is to increase the effect of basin concavity upon flood hydrographs.  相似文献   

Optical archival spectra of blazar candidates of uncertain type in the 3rd Fermi Large Area Telescope Catalog     

N. Álvarez Crespo  F. Massaro  R. D’Abrusco  M. Landoni  N. Masetti  V. Chavushyan  E. Jiménez-Bailón  F. La Franca  D. Milisavljevic  A. Paggi  V. Patiño-Álvarez  F. Ricci  Howard A. Smith 《Astrophysics and Space Science》2016,361(9):316

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The fallen sky. An intimate history of shooting stars     

Howard Plotkin 《Meteoritics & planetary science》2010,45(2):336-338

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Reconstructing CME Structures from IPS Observations Using a Phenomenological Model     

S. J. Tappin  T. A. Howard 《Solar physics》2010,265(1-2):159-186

We present an extension of the Tappin?–?Howard (TH) phenomenological model (Tappin and Howard, Space Sci. Rev. 147, 55, 2009) for coronal mass ejection reconstruction to use interplanetary scintillation g-map data. The necessary changes to the model are discussed. We then use the modified model to reconstruct two major interplanetary disturbances observed using the Cambridge 3.6 ha Array in September 1980. We find that despite the lower cadence of IPS observations compared with white-light imagers, a consistent reconstruction can be generated which is in agreement with in-situ measurements and solar observations.  相似文献   

Modal mineralogy of CV3 chondrites by X-ray diffraction (PSD-XRD)     

K.T. Howard  G.K. Benedix  P.A. Bland  G. Cressey 《Geochimica et cosmochimica acta》2010,74(17):5084-252

Using position sensitive detector X-ray diffraction (PSD-XRD) we determine a complete modal mineralogy for all phases present in abundances greater than 1 wt% in Vigarano, Efremovka, Mokoia, Grosnaja, Kaba and Allende. Reduced CV3 samples are comprised of (vol%): olivine (83-85%); enstatite (6.5-8.1%); anorthite (1.1-1.2%); magnetite (1.4-1.8%); sulphide (2.4-5.1%); Fe, Ni metal (2-2.2%). The oxidized samples are comprised of: olivine (76.3-83.9%); enstatite (4.8-7.8%); anorthite (1.1-1.7%); magnetite (0.3-6.1%); sulphide (2.9-8.1%); Fe, Ni metal (0.2-1.1%); Fe-oxide (0-2.7%) and phyllosilicate (1.9-4.2%). When our modal data is used to calculate a bulk chemistry that is compared to literature data a near 1:1 correlation is observed. PSD-XRD data indicates that olivine compositions may span almost the entire Fe-Mg solid solution series in all CV samples and that these contain a component (4-13%) of fine-grained olivine that is more Fe-rich (>Fa₆₀) than is typically reported. Modal mineralogy shows that there are mineralogic differences between CV3 samples classified as oxidized and reduced but that these sub-classes are most clearly distinguished by the relative abundance of metal and Ni content of sulphide, rather than abundance of magnetite. The most significant difference in modal mineralogy observed is the relative absence of phyllosilicate in reduced CV that essentially escaped aqueous alteration.Fayalite, ferrous olivine and magnetite are typically considered secondary alteration products. The abundances of these minerals overlap in oxidized and reduced samples and correlate positively supporting common conditions of formation in a relatively oxidizing environment. The abundances of fayalite, ferrous olivine and magnetite show no relationship to petrographic type and if these abundances were used as a proxy for alteration, Allende would be the least altered CV - contrary to all previous data. The implication is that thermal metamorphism on the parent body was de-coupled from formation of Fe-rich secondary minerals. Low temperature fluid-assisted metamorphism can also not easily explain the origin of fayalite, ferrous olivine and magnetite, since the reduced CVs appear to be largely unaffected by this process. Parent body models require an anhydrous low-temperature mechanism of secondary alteration. The alternative is that these phases formed prior to accretion of the final CV parent body.  相似文献   

The Quaternary history of the Wash fluvial network, UK     

Steve Boreham  Tom S. White  Andy J. Howard 《Proceedings of the Geologists' Association. Geologists' Association》2010,121(4):393-449

This paper appraises and compares the Middle-Upper Pleistocene sedimentary sequences preserved in the fluvial systems draining into the Fenland Basin and the Wash estuary. Of the main Fenland rivers the longest records, which extend back to the initial Anglian (glacial) formation of the basin, are found in the Great Ouse and its tributaries, particularly the Cam and the Nar. These sequences preserve sediments representing all four post-Anglian interglacials. The Nene also has an extensive post-Anglian history, with evidence for a Hoxnian estuary that is presumed to have been the precursor of the Wash. North of the Nene, however, the Welland and Witham (proto-Trent) have relatively short sequences, which are thought to commence with a later (post-Anglian-pre-Devensian) glaciation that affected Lincolnshire and fed the previously-recognized Tottenhill outwash delta south of Kings Lynn. Prior to Devensian deglaciation the Witham valley was occupied by the Trent, which was the trunk river of the late Middle Pleistocene Wash system. During periods of low sea level the river would have extended north-eastwards across what is now the floor of the North Sea, possibly via the Inner Silver Pit. Several of the central Fenland sequences show evidence of infrequent terrace formation during the late Quaternary, although this might in part be due to poor vertical separation between terraces, so that differentiating them has been difficult; this has been exacerbated by mixed biostratigraphical signals due to the preservation of sediments representing more than one interglacial beneath a single terrace surface. In several of the systems there is evidence for valley rejuvenation to the lowest terrace or valley-floor level during the MIS 4-3 transition. The observed differences within what, during the predominant periods of lower sea level, would have been a single Wash river system are difficult to explain.  相似文献