Modeling population density across major US cities: a polycentric spatial regression approach   总被引：3，自引：0，他引：3  

Daniel A. Griffith  David W. Wong 《Journal of Geographical Systems》2007,9(1):53-75

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Thermochron iButton: Limitation of this Inexpensive and Small-Diameter Temperature Logger   总被引：1，自引：0，他引：1  

Brad D. Wolaver  John M. Sharp Jr. 《Ground Water Monitoring & Remediation》2007,27(3):127-128

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Meridional variations of temperature, C₂H₂ and C₂H₆ abundances in Saturn's stratosphere at southern summer solstice     

Thomas K. Greathouse  John H. Lacy  Bruno Bézard  Caitlin A. Griffith 《Icarus》2005,177(1):18-31

Measurements of the vertical and latitudinal variations of temperature and C₂H₂ and C₂H₆ abundances in the stratosphere of Saturn can be used as stringent constraints on seasonal climate models, photochemical models, and dynamics. The summertime photochemical loss timescale for C₂H₆ in Saturn's middle and lower stratosphere (∼40-10,000 years, depending on altitude and latitude) is much greater than the atmospheric transport timescale; ethane observations may therefore be used to trace stratospheric dynamics. The shorter chemical lifetime for C₂H₂ (∼1-7 years depending on altitude and latitude) makes the acetylene abundance less sensitive to transport effects and more sensitive to insolation and seasonal effects. To obtain information on the temperature and hydrocarbon abundance distributions in Saturn's stratosphere, high-resolution spectral observations were obtained on September 13-14, 2002 UT at NASA's IRTF using the mid-infrared TEXES grating spectrograph. At the time of the observations, Saturn was at a LS≈270°, corresponding to Saturn's southern summer solstice. The observed spectra exhibit a strong increase in the strength of methane emission at 1230 cm⁻¹ with increasing southern latitude. Line-by-line radiative transfer calculations indicate that a temperature increase in the stratosphere of ≈10 K from the equator to the south pole between 10 and 0.01 mbar is implied. Similar observations of acetylene and ethane were also recorded. We find the 1.16 mbar mixing ratio of C₂H₂ at −1° and −83° planetocentric latitude to be and , respectively. The C₂H₂ mixing ratio at 0.12 mbar is found to be at −1° planetocentric latitude and at −83° planetocentric latitude. The 2.3 mbar mixing ratio of C₂H₆ inferred from the data is and at −1° and −83° planetocentric latitude, respectively. Further observations, creating a time baseline, will be required to completely resolve the question of how much the latitudinal variations of C₂H₂ and C₂H₆ are affected by seasonal forcing and/or stratospheric circulation.  相似文献   

Reply to letter to the editor from Wenzens re Kaplan et al. (2005) Quaternary Research, 63, 301-315     

Michael R. Kaplan  Brad S. Singer  Robert P. Ackert 《Quaternary Research》2006,66(2):367-369

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Galactic haloes in MONDian cosmological simulations     

Alexander Knebe  Brad K. Gibson 《Monthly notices of the Royal Astronomical Society》2004,347(4):1055-1064

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A note on a conjecture of Wintner and its disproof by Waldvogel     

Griffith  J. S. 《Celestial Mechanics and Dynamical Astronomy》1973,7(3):315-320

A conjecture of Wintner, partially disproved by Waldvogel, is shown to be completely false. The relationship between work by Kurth and Waldvogel's results is demonstrated.  相似文献   

Verifying Inventory Predictions of Animal Methane Emissions with Meteorological Measurements   总被引：1，自引：0，他引：1  

O. T. Denmead  R. Leuning  D. W. T. Griffith  I. M. Jamie  M. B. Esler  L. A. Harper  J. R. Freney 《Boundary-Layer Meteorology》2000,96(1-2):187-209

The paper examines the strengths and weaknesses of a rangeof meteorological flux measurement techniques that mightbe used to verify predictions of greenhouse gas inventories.Recent research into emissions of methane (CH₄)produced by enteric fermentation in grazing cattle and sheepis used to illustrate various methodologies. Quantifying thisimportant source presents special difficulties because the animalsconstitute moving, heterogeneously distributed, intermittent, pointsources. There are two general approaches: one, from the bottom up,involves direct measurements of emissions from a known number ofanimals, and the other, from the top down, infers areal emissions ofCH₄ from its atmospheric signature. A mass-balance methodproved successful for bottom-up verification. It permits undisturbedgrazing, has a simple theoretical basis and is appropriate for fluxmeasurements on small plots and where there are scattered pointsources. The top-down methodologies include conventional flux-gradientapproaches and convective and nocturnal boundary-layer (CBL and NBL)budgeting schemes. Particular attention is given to CBL budget methods inboth differential and integral form. All top-down methodologies require ideal weather conditions for their application, and they suffer from the scattered nature of the source, varying wind directions and low instrument resolution. As for mass-balance, flux-gradient micrometeorological measurements were in good agreement with inventory predictions of CH₄ production by livestock, but the standard errors associated with both methods were too large to permit detection of changes of a few per cent in emission rate, which might be important for inventory, regulatory or research purposes. Fluxes calculated by CBL and NBL methods were of the same order of magnitude as inventory predictions, but more improvement is needed before their use can be endorsed. Opportunities for improving the precision of both bottom-up and top-down methodologies are discussed.  相似文献   

景观类型分析在土地覆被变化中的作用   总被引：1，自引：1，他引：0  

JerryAGRIFFITH 《地理学报(英文版)》2004,14(1):3-17

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Eigenvector selection with stepwise regression techniques to construct eigenvector spatial filters   总被引：1，自引：0，他引：1  

Yongwan Chun  Daniel A. Griffith  Monghyeon Lee  Parmanand Sinha 《Journal of Geographical Systems》2016,18(1):67-85

Because eigenvector spatial filtering (ESF) provides a relatively simple and successful method to account for spatial autocorrelation in regression, increasingly it has been adopted in various fields. Although ESF can be easily implemented with a stepwise procedure, such as traditional stepwise regression, its computational efficiency can be further improved. Two major computational components in ESF are extracting eigenvectors and identifying a subset of these eigenvectors. This paper focuses on how a subset of eigenvectors can be efficiently and effectively identified. A simulation experiment summarized in this paper shows that, with a well-prepared candidate eigenvector set, ESF can effectively account for spatial autocorrelation and achieve computational efficiency. This paper further proposes a nonlinear equation for constructing an ideal candidate eigenvector set based on the results of the simulation experiment.  相似文献   

Chronology of latest Pleistocene mountain glaciation in the western Wasatch Mountains, Utah, U.S.A.     

Benjamin J.C. Laabs  David W. Marchetti  Jeffrey S. Munroe  Kurt A. Refsnider  John C. Gosse  Elliott W. Lips  Richard A. Becker  David M. Mickelson  Brad S. Singer 《Quaternary Research》2011,76(2):272-284

Understanding the timing of mountain glacier and paleolake expansion and retraction in the Great Basin region of the western United States has important implications for regional-scale climate change during the last Pleistocene glaciation. The relative timing of mountain glacier maxima and the well-studied Lake Bonneville highstand has been unclear, however, owing to poor chronological limits on glacial deposits. Here, this problem is addressed by applying terrestrial cosmogenic ¹⁰Be exposure dating to a classic set of terminal moraines in Little Cottonwood and American Fork Canyons in the western Wasatch Mountains. The exposure ages indicate that the main phase of deglaciation began at 15.7 ± 1.3 ka in both canyons. This update to the glacial chronology of the western Wasatch Mountains can be reconciled with previous stratigraphic observations of glacial and paleolake deposits in this area, and indicates that the start of deglaciation occurred during or at the end of the Lake Bonneville hydrologic maximum. The glacial chronology reported here is consistent with the growing body of data suggesting that mountain glaciers in the western U.S. began retreating as many as 4 ka after the start of northern hemisphere deglaciation (at ca. 19 ka).  相似文献