Snowmelt‐driven macropore flow and soil saturation in a semiarid forest     

Brent D. Newman  Bradford P. Wilcox  Robert C. Graham 《水文研究》2004,18(5):1035-1042

Lateral subsurface flow is generally assumed to occur as a result of the development of a saturated zone above a low‐permeability interface such as at the soil–bedrock contact, and it is often augmented by macropore flow. Our objective was to evaluate the development of lateral subsurface flow and soil saturation at a semiarid ponderosa pine forest in New Mexico with respect to the conceptual model of saturation building above the soil–bedrock contact. At this site, we have long‐term observations of the water budget components, including lateral flow. A 1·5 m deep by 7 m long trench was constructed to observe lateral subsurface flow and development of saturation directly. Our observations are based on flow resulting from a melting snowdrift. The edge of the drift was about 7 m upslope from the trench. Lateral subsurface flow only occurred from root macropores in the Bt soil horizon. Saturation developed and grew outward from flowing root macropores, rather than growing upward from the soil–bedrock interface. This macropore‐centred saturation resulted in a highly heterogeneous distribution of water content until enough macropores began flowing and individual macropore saturated zones grew large enough to coalesce and saturate large volumes of the soil. Our observations are based on one snowmelt event and a relatively short hillslope flow path, and thus do not represent a full range of hydrologic conditions. Nevertheless, the observed behaviour did not conform to the traditional model of soil–bedrock control of saturation and lateral flow. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

Savage Jaguars,King Cats,and Ghostly Tigres: Affective Logics and Predatory Natures in Twentieth-Century American Nature Writing     

Sharon Wilcox 《The Professional geographer》2017,69(4):531-538

The emerging subfield of historical animal geography provides an opportunity to trace the origins and evolutions of how affective logics framing the conservation of an animal species are co-constituted through embodied interaction between humans and nonhumans, revealing the dynamic ways in which charismatic species are imagined into and out of positions of priority within conservation agendas. This article takes an interest in the shifting perception of predatory species in the environmental conservation movement in the United States, looking to the appearance of jaguars (Panthera onca) in the work of prominent U.S. nature writers Theodore Roosevelt, Ernest Thompson Seton, and Aldo Leopold in the early- to mid-twentieth century. These human–jaguar entanglements reveal a period marked by dynamic changes in the ways in which interspecies encounters were constituted in place; a layering on of affective logics that reveal the complicated origins, practices, and potentialities at the outset of the modern conservation movement. The resulting narratives and images of predatory nature were taken up into dynamic assemblages of jaguar-ness, influencing the formation of new logics that framed public perceptions of predatory natures and provoking a reconsideration of long-held attitudes and policies toward these species.  相似文献   

Preferred response of the East Asian summer monsoon to local and non-local anthropogenic sulphur dioxide emissions     

Buwen Dong  Rowan T. Sutton  Eleanor J. Highwood  Laura J. Wilcox 《Climate Dynamics》2016,46(5-6):1733-1751

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A new method of magnetograph observation of the photospheric brightness,velocity, and magnetic fields     

Robert Howard  Andrew S. Tanenbaum  John M. Wilcox 《Solar physics》1968,4(3):286-299

Several improvements have been made to the Mount Wilson Observatory solar magnetograph, including changes to the guider, the Doppler compensator, and the data-handling system. The improved magnetograph has been used for a new type of solar observation consisting of several hundred scans back and forth along a straight line of length 3/4 R ₀ perpendicular to central meridian. The data reduction, which is done entirely with a computer, eliminates those effects which have their origin in the earth-sun geometry. The spatial and temporal properties of the 5-min oscillations are discussed.  相似文献   

The quasi-stationary coronal magnetic field and electron density as determined from a Faraday rotation experiment     

C. T. Stelzried  G. S. Levy  T. Sato  W. V. T. Rusch  J. E. Ohlson  K. H. Schatten  J. M. Wilcox 《Solar physics》1970,14(2):440-456

Pioneer VI was launched into a circumsolar orbit on December 16, 1965, and was occulted by the sun in the latter half of November, 1968. During the occultation period, the 2292-MHz S-band telemetry carrier underwent Faraday rotation due to the interaction of this signal with the plasma and magnetic field in the solar corona. The NASA/JPL 210-ft diameter antenna of the Deep Space Network near Barstow, California, was used for the measurement. The antenna feed was modified for automatic polarization tracking for this experiment. The measurement results are interpreted with a theoretical model of the solar corona. This model consists of a modified Allen-Baumbach electron density and a coronal magnetic field calculated both from Mount Wilson magnetograph observations using a source surface model and field extrapolations from the Explorer 33 satellite magnetometer. The observations and the calculated rotation show general agreement with respect to magnitude, sense, and timing, suggesting the source-surface model and field extrapolations from 1 AU are a valid technique to obtain the magnetic field in the corona from 4 to 12 solar radii. Variations present can easily be ascribed to density enhancements known to be present in the corona. Longitudinal variations of the density in the corona cannot be obtained from coronagraph observations, and thus a purely radial variation was assumed. An improved fit to the Faraday rotation data is obtained with an equatorial electron density $$N = 10^8 \left( {\frac{{6000}}{{R^{10} }} + \frac{{0.002}}{{R^2 }}} \right)...{\text{ cm}}^{{\text{ - 3}}} {\text{ (4 < }}R < 12){\text{ }}...$$ where R is in solar radii. The work of W. V. T. Rusch and J. E. Ohlson was supported in part by research sponsored by the Joint Services Electronics Program through the Air Force Office of Scientific Research under Grant AF-AFOSR 69-1622A at the University of Southern California. The work done by K. H. Schatten was in part supported by the National Academy of Science on a National Research Council postdoctoral fellowship. The work of J. M. Wilcox was supported in part by the Office of Naval Research under Contract Nonr 3656(26), by the National Aeronautics and Space Administration under Grant NGR 05-003-230, and by the National Science Foundation under Grant GA-1319 at the University of California at Berkeley.  相似文献   

Photospheric magnetic field rotation: Rigid and differential     

John M. Wilcox  Kenneth H. Schatten  Andrew S. Tanenbaum  Robert Howard 《Solar physics》1970,14(2):255-262

An autocorrelation of the direction of the large-scale photospheric magnetic field observed during 1959–1967 has yielded evidence that the field structure at some heliographic latitudes can display both differential rotation and rigid rotation properties.  相似文献   

Average photospheric poloidal and toroidal magnetic field components near solar minimum     

Thomas L. Duvall Jr.  Philip H. Scherrer  Leif Svalgaard  John M. Wilcox 《Solar physics》1979,61(2):233-245

Average (over longitude and time) photospheric magnetic field components are derived from 3 Stanford magnetograms made near the solar minimum of cycle 21. The average magnetograph signal is found to behave as the projection of a vector for measurements made across the disk. The poloidal field exhibits the familiar dipolar structure near the poles, with a measured signal in the line Fe i 5250 Å of 1 G. At low latitudes the poloidal field has the polarity of the poles, but is of reduced magnitude ( 0.1 G). A net photospheric toroidal field with a broad latitudinal extent is found. The polarity of the toroidal field is opposite in the nothern and southern hemispheres and has the same sense as subsurface flux tubes giving rise to active regions of solar cycle 21.These observations are used to discusse large-scale electric currents crossing the photosphere and angular momentum loss to the solar wind.Now at Kitt Peak National Observatory, Tucson, Ariz. 85726, U.S.A.  相似文献   

Field measurements of three-dimensional hydraulics in a step-pool channel   总被引：4，自引：0，他引：4  

Andrew C. Wilcox  Ellen E. Wohl 《Geomorphology》2007,83(3-4):215-231

We investigated the effects of morphologic position and discharge on flow structure in a steep (0.10 m/m) mountain channel by collecting three-dimensional measurements of time-averaged and turbulent velocity components with a SonTek FlowTracker Handheld ADV (acoustic Doppler velocimeter) on a 30-m reach of a step-pool channel in the Colorado Rockies. Velocity profiles were measured at morphologic positions characteristic of steep channels (above steps, step lips, base of steps, pools, cascades, runs), and at five different discharges. A marked three-dimensionality of flow structure was documented in East St. Louis Creek. Velocities in the streamwise component were the largest contributors to overall velocity vector magnitudes; cross-stream and vertical components contributed averages of 20% and 15%, respectively, to overall vector magnitudes. Turbulence intensities were especially multi-dimensional, however, with large contributions to turbulent kinetic energy from the vertical component of velocity. Analysis of variance indicated that discharge and morphologic position significantly affected mean streamwise velocities, with substantially higher velocities upstream from steps than in pools. Discharge and morphology effects on cross-stream and vertical velocity components, however, were not significant. Discharge and morphologic position also significantly affected turbulence intensities for all flow components, with the greatest turbulence intensities occurring in pools and at high discharges. These results illustrate the strong discharge-dependence of hydraulics in step-pool channels, where relative submergence of bedforms changes rapidly with discharge, and the substantial spatial variation in hydraulics created by step-pool sequences.  相似文献   

The observed ozone flux by transient eddies, 0–30 km     

R. W. Wilcox 《Pure and Applied Geophysics》1980,118(1):401-415

Ozonesonde data are matched with concomitant rawinsonde data to provide a direct determination of horizontal, meridional, flux of ozone by the transient eddies. Data are from 27 stations in 4 regions: Eastern and western North America, western Europe, and Japan. Results confirm the existence of significant northward flux near 40°N, 10–18 km, in winter and spring, as shown by previous investigators. However, areas of significant equatorward flux are found at high mid-latitudes, 10–16 km, over North America in winter and spring, and at all 3 Japanese stations, 10–18 km, in spring. Transient eddy fluxes are typically small in summer, and are also small throughout the troposphere and most of the middle stratosphere.  相似文献   

The mean magnetic field of the Sun: Observations at Stanford     

Philip H. Scherrer  John M. Wilcox  Leif Svalgaard  Thomas L. Duvall Jr.  Phil H. Dittmer  Eric K. Gustafson 《Solar physics》1977,54(2):353-361

A solar telescope has been built at Stanford University to study the organization and evolution of large-scale solar magnetic fields and velocities. The observations are made using a Babcock-type magnetograph which is connected to a 22.9 m vertical Littrow spectrograph. Sun-as-a-star integrated light measurements of the mean solar magnetic field have been made daily since May 1975. The typical mean field magnitude has been about 0.15 G with typical measurement error less than 0.05 G. The mean field polarity pattern is essentially identical to the interplanetary magnetic field sector structure (see near the Earth with a 4 day lag). The differences in the observed structures can be understood in terms of a warped current sheet model.  相似文献