A note on the top-down and bottom-up gradient functions over a forested site     

Weiguo Wang  Kenneth J. Davis  Chuixiang Yi  Edward G. Patton  Martha P. Butler  Daniel M. Ricciuto  Peter S. Bakwin 《Boundary-Layer Meteorology》2007,124(2):305-314

The dimensionless bottom-up and top-down gradient functions in the convective boundary layer (CBL) are evaluated utilizing long-term well-calibrated carbon dioxide mixing ratio and flux measurements from multiple levels of a 447-m tall tower over a forested area in northern Wisconsin, USA. The estimated bottom-up and top-down functions are qualitatively consistent with those from large-eddy simulation (LES) results and theoretical expectations. Newly fitted gradient functions are proposed based on observations for this forested site. The integrated bottom-up function over the lowest 4% of the CBL depth estimated from the tower data is about five times larger than that from LES results for a ‘with-canopy’ case, and is smaller than that from LES results for a ‘no-canopy’ case by a factor of 0.7. We discuss the uncertainty in the evaluated gradient functions due to stability, wind direction, and uncertainty in the entrainment flux and show that while all of these have a significant impact on the gradient functions, none can explain the differences between the modelled and observed functions. The effects of canopy features and atmospheric stability may need to be considered in the gradient function relations.  相似文献   

Unwinding the discovery of spiral nebulae     

M E Bailey  C J Butler  J McFarland 《Astronomy& Geophysics》2005,46(2):2.26-2.28

M E Bailey, C J Butler and J McFarland take a close look at the earliest observations of spiral nebulae, made with the Leviathan of Parsonstown in the 1840s.  相似文献   

Hydraulic Tests with Direct-Push Equipment   总被引：8，自引：0，他引：8  

James J. Butler Jr.    John M. Healey  G. Wesley McCall  Elizabeth J. Garnett  Steven P. Loheide II 《Ground water》2002,40(1):25-36

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Effects of spatial variations in source areas upon dust concentration profiles during three wind erosion events in Australia     

H. J. Butler  W. L. Hogarth  G. H. McTainsh 《地球表面变化过程与地形》2001,26(10):1039-1048

Dust storms are a major contributor to soil erosion in inland Australia, and the Simpson Desert–Channel Country region is one of the most active wind erosion regions. While information is available on wind erosion rates at the land‐type level, little is known about the influence that spatial variations in the erodibility within a land type have on the resulting dust concentration profile. A Gaussian plume model, DSIS, is presented along with tower‐based dust data, to describe the influence of different spatial combinations of dust source areas, during three dust events on the Diamantina River floodplain in Western Queensland, Australia. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

Lithologic, structural, and geomorphic controls on ribbon forest patterns in a glaciated mountain environment   总被引：2，自引：0，他引：2  

David R. Butler  George P. Malanson  Matthew F. Bekker  Lynn M. Resler 《Geomorphology》2003,55(1-4):203

So-called “ribbon forests” have been attributed to snowdrift patterns and fire history without reference to geomorphology [Vegetatio 19 (1969) 192.]. This paper illustrates how site conditions of geomorphology and geology explain the origin of ribbon forests. In Glacier National Park, MT (USA), regional tectonic uplift associated with the Laramide Orogeny produced structural features that amplify lithologic differences. Pleistocene glaciation scoured deeply along the strike of bedding planes, highlighting this pattern and in some cases producing fine-scale parallel finger lakes between forested ribbon strips.Twelve ribbon forest sites on both sides of the Continental Divide were closely studied on stereoscopic aerial photographs, and several of these sites were examined in the field or from helicopter overflights. In all cases, geologic and geomorphic conditions explain the location and distribution of the ribbon forests. Change-detection of the distribution of trees versus nontree-covered surfaces in an area of ribbon forest on Flattop Mountain, a complex uplifted synclinal structure, was undertaken using panchromatic, low-altitude aerial photographs from 1966 to 1991. Areas changed from forest to meadow and from meadow to forest in roughly equal amounts in a generally random spatial pattern. No evidence was seen to suggest that the creation of one ribbon eventually created another downwind, as suggested by Billings. Aerial photograph interpretation, field examination and soils analyses of forest ribbons and adjacent unforested meadows clearly illustrated that trees occupy higher, parallel to subparallel, well-drained sites where the spatial pattern is in turn a distinct reflection of the spatial pattern of structure and stratigraphy. Meadows occupy topographically lower positions between ridges where erosion along bedding plane strike was concentrated. Topography sets conditions that allow tree growth in certain locations while precluding it in immediately adjacent areas. Ribbon forests there are thus a spatial manifestation of the interaction between structure, lithology, and topography.  相似文献   

Sensitivity Models and Design Protocol for Partitioning Tracer Tests in Alluvial Aquifers   总被引：1，自引：0，他引：1  

M. Jin  G. W. Butler  R. E. Jackson  P. E. Mariner  J. F. Pickens  G. A. Pope  C. L. Brown  D. C. McKinney 《Ground water》1997,35(6):964-972

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Oxygen vacancy ordering and the incommensurate structure of mullite     

B. D. Butler  T. R. Welberry  R. L. Withers 《Physics and Chemistry of Minerals》1993,20(5):323-332

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Authors' Reply     

James J. Butler II  John M. Healey 《Ground water》1998,36(6):867-868

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A statistical study of the relationship between the solar cycle length and tree-ring index values     

Keqian Zhou  Rp  C.J. Butler 《Journal of Atmospheric and Solar》1998,60(18):1711-1718

We have determined the correlation coefficient between tree-ring index values and the sunspot cycle length for 69 tree-ring data sets from around the world of greater than 594 years duration. A matrix of correlation coefficients is formed with varying delay and smoothing parameters. Similar matrices, formed from the same data, but randomly scrambled, provide a control against which we can draw conclusions about the influence of the solar cycle length on climate with a reasonable degree of confidence. We find that the data confirm an association between the sunspot cycle length and climate with a negative maximum correlation coefficient for 80% of the data sets considered. This implies that wider tree-rings (i.e. more optimum growth conditions) are associated with shorter sunspot cycles. Secondly, we find that the climatic effect of the solar cycle length is smoothed by several decades and the degree of smoothing is dependent on the elevation and the geographical location of the trees employed. Thirdly, we find evidence for a cyclic variation of ∼200 years period in either solar cycle length or tree ring index. © 1999 Elsevier Science Ltd. All rights reserved.  相似文献   

A backbarrier overwash record of intense storms from Brigantine, New Jersey     

Jeffrey P. Donnelly  Jessica Butler  Stuart Roll  Micah Wengren  Thompson Webb  III 《Marine Geology》2004,210(1-4):107-121

Analysis of aerial photographs and historic charts indicates that the barrier beach at Brigantine, NJ has migrated landward 300 to 400 m since 1869, primarily as a result of overwash during hurricanes and winter storms. A series of vibracores from the backbarrier salt marsh reveals a millennial-scale stratigraphic record of overwash deposition. Carbon-14 (C-14) and Cesium-137 (Cs-137) radioisotopic methods were used to date overwash deposits (washovers). The ages of recent washovers are consistent with deposition during intense storms in 1938, 1944, 1950, and 1962. An additional overwash deposit recovered in five of the sediment cores was likely deposited by an intense hurricane strike in 1821 or possibly in 1788. Two prehistoric overwash fans were likely deposited by intense storms striking the New Jersey Coast in the 7th to 14th centuries and 6th to 7th centuries A.D. The landward barrier migration indicates that the older overwash sediments were likely transported a considerably greater distance than the more recent overwash fans. The greater distance of transport may indicate that the prehistoric storms that deposited overwash fans across the study site were more intense than the most intense storm to strike this coast in the historic period, the hurricane of 1821. The spatially variable occurrence of overwash deposition at this site points to a need for multisite stratigraphic surveys of extensive stretches of the coast in order to develop reliable records of past intense storm frequency from backbarrier environments.  相似文献