Wind and wind forces in a plantation spruce forest   总被引：2，自引：0，他引：2  

B. A. Gardiner 《Boundary-Layer Meteorology》1994,67(1-2):161-186

Observations have been made of the tubulent structure within and above a dense (LAI=10.2) plantation spruce forest along with measurements of the movement of individual trees. The mean statistics of the turbulence and the turbulence spectra are compared with observations in other crops and complementary wind-tunnel studies using 175 scale plastic trees. The measurements show that momentum transport and the subsequent motion of the trees is dominated by intermittent sweep/ejection events associated with honami waves moving across the forest. The trees themselves act as forced damped harmonic oscillators and appear to short circuit the normal turbulent energy dissipation process by efficiently absorbing energy at their resonant frequencies. It is argued that understanding the nature and formation of honami waves over forests and crops is a crucial problem in agricultural and forest meteorology because of their important role both in turbulent transport and in causing wind damage.  相似文献   

Temporal and spatial cyclicity of accretion at slow-spreading ridges—evidence from the Reykjanes Ridge     

Christine Peirce  Alex Gardiner  Martin Sinha 《Geophysical Journal International》2005,163(1):56-78

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Modelling Canopy Flows over Complex Terrain     

Eleanor R. Grant  Andrew N. Ross  Barry A. Gardiner 《Boundary-Layer Meteorology》2016,161(3):417-437

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Measurements of stratospheric chlorine monoxide (ClO) from groudbased FTIR observations     

W. Bell  C. Paton-Walsh  T. D. Gardiner  P. T. Woods  N. R. Swann  N. A. Martin  L. Donohoe  M. P. Chipperfield 《Journal of Atmospheric Chemistry》1996,24(3):285-297

Infrared absorption features due to ClO in the lower stratosphere have been identified from groundbased solar absorption spectra taken from Aberdeen, U.K. (57° N, 2° W) on 20 January 1995. A vertical column abundance of 3.42 (±0.47)×10¹⁵ molec cm^-2 has been derived from 13 independent absorption features in the P and R branches of the (0–1) vibration-rotation band of ³⁵ClO, spanning the spectral region 817–855 cm^-1. The observed absorption features are consistent with very high levels of ClO (approximately 2.6 parts per billion by volume (ppbv)) in the altitude range 16–22 km. A comparison of this profile with a 3D chemical transport model profile indicates the observation was made inside the polar vortex and shows good qualitative agreement but the model underestimates the concentrations of ClO. Simultaneous measurements of other species were made including HCl, HF and ClONO₂. These columns yield a value for HCl+ClONO₂+ClO of 7.02±0.65×10¹⁵ molec cm^-2. This is lower than the total inorganic chlorine (ClO _y ) column of 10.7±1.6×10¹⁵ molec cm^-2 estimated from mean measured (HCl+ClONO₂)/HF ratios together with in-vortex HF measurements. The discrepancy is probably due to significant amounts of the ClO dimer (Cl₂O₂) in the lower part of the stratosphere. The measurements of highly elevated levels of ClO are used to estimate O₃ loss rates at the 400, 475 and 550 K levels making assumptions about the probable distribution of ClO and Cl₂O₂. These are compared with loss rates derived from ozone sonde data.  相似文献   

Ground-based FTIR Measurements with High Temporal Resolution     

W. Bell  C. Paton Walsh  P.T. Woods  T.D. Gardiner  M.P. Chipperfield  A.M. Lee 《Journal of Atmospheric Chemistry》1998,30(1):131-140

We outline how ground-based Fourier transform infrared (FTIR) measurements of stratospheric trace species, obtained with high temporal resolution, could be used to detect filaments of polar vortex air at mid-latitudes and therefore test high spatial resolution chemical transport models (CTMs). Vertical column abundances of HCl, ClONO2, HNO3, N2O and HF have been obtained from FTIR solar absorption measurements made throughout the day from Aberdeen, UK (57°N, 2°W) on several days during winter/spring 1993/94 and 1994/95. The short-timescale ( 2 hours) variability observed in the columns is attributed to real atmospheric variations and is often associated with the passage of high latitude air over Aberdeen. This is confirmed by 3D modelling studies which qualitatively reproduce and rationalise the observed changes in the column data on January 19 1994, January 20 1995 and February 26 1995. We describe the viewing geometry of ground-based FTIR measurements and we suggest a measurement strategy which should maximise the information retrieved on horizontal gradients in stratospheric trace species columns from FTIR measurements.  相似文献   

Topics: Virtual geological outcrops – fieldwork and analysis made less exhaustive?     

Jamie Pringle  y Gardiner  & Robin Westerman 《Geology Today》2004,20(2):67-71

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A simple unsplit Godunov method for multidimensional MHD     

James M. Stone  Thomas Gardiner 《New Astronomy》2009,14(2):139-148

We describe a numerical algorithm based on Godunov methods for integrating the equations of compressible magnetohydrodynamics (MHD) in multidimensions. It combines a simple, dimensionally-unsplit integration method with the constrained transport (CT) discretization of the induction equation to enforce the divergence-free constraint. We present the results of a series of fully three-dimensional tests which indicate the method is second-order accurate for smooth solutions in all MHD wave families, and captures shocks, contact and rotational discontinuities well. However, it is also more diffusive than other more complex unsplit integrators combined with CT. Thus, the primary advantage of the method is its simplicity. It does not require a characteristic tracing step to construct interface values for the Riemann solver, it is straightforward to extend with additional physics, and it is suitable for use with nested and adaptive meshes. The method is implemented as one of two dimensionally unsplit MHD integrators in the Athena code, which is freely available for download from the web.  相似文献   

The geology of the Gloucester district     

C.I. Gardiner  S.H. Reynolds  Stanley Smith  A.E. Trueman  J.W. Tutcher 《Proceedings of the Geologists' Association. Geologists' Association》1934,45(2):109-IN2

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Planar charged-particle trajectories in multipole magnetic fields     

D. M. Willis  A. R. Gardiner  V. N. Davda  V. J. Bone 《Annales Geophysicae》1997,15(2):197-210

This paper provides a complete generalization of the classic result that the radius of curvature () of a charged-particle trajectory confined to the equatorial plane of a magnetic dipole is directly proportional to the cube of the particles equatorial distance () from the dipole (i.e. ³). Comparable results are derived for the radii of curvature of all possible planar chargedparticle trajectories in an individual static magnetic multipole of arbitrary order m and degree n. Such trajectories arise wherever there exists a plane (or planes) such that the multipole magnetic field is locally perpendicular to this plane (or planes), everywhere apart from possibly at a set of magnetic neutral lines. Therefore planar trajectories exist in the equatorial plane of an axisymmetric (m = 0), or zonal, magnetic multipole, provided n is odd: the radius of curvature varies directly as ⁿ⁼². This result reduces to the classic one in the case of a zonal magnetic dipole (n = 1). Planar trajectories exist in 2m meridional planes in the case of the general tesseral (0 < m < n) magnetic multipole. These meridional planes are defined by the 2m roots of the equation cos[m()–_n^m)] = 0, where _n^m = (1/m) arctan (h_n^m/g_n^m); g_n^m and h_n^m denote the spherical harmonic coefficients. Equatorial planar trajectories also exist if (n – m) is odd. The polar axis ( = O,) of a tesseral magnetic multipole is a magnetic neutral line if m > I. A further 2_m(n – m) neutral lines exist at the intersections of the 2_m meridional planes with the (n – m) cones defined by the (n – m) roots of the equation P_n^m(cos ) = 0 in the range 0 < 9 < , where P_n^m(cos ) denotes the associated Legendre function. If (n – m) is odd, one of these cones coincides with the equator and the magnetic field is then perpendicular to the equator everywhere apart from the 2m equatorial neutral lines. The radius of curvature of an equatorial trajectory is directly proportional to ⁿ⁼² and inversely proportional to cos[m(–)]. Since this last expression vanishes at the 2m equatorial neutral ines, the radius of curvature becomes infinitely large as the particle approaches any one of these neutral lines. The radius of curvature of a meridional trajectory is directly proportional to rⁿ⁺², where r denotes radial distance from the multiple, and inversely proportional to P_n^m(cos )/sin . Hence the radius of curvature becomes infinitely large if the particle approaches the polar magnetic neutral ine (m > 1) or any one of the 2m(n – m) neutral ines located at the intersections of the 2m meridional planes with the (n – m) cones. Illustrative particle trajectories, derived by stepwise numerical integration of the exact equations of particle motion, are pressented for low-degree (n 3) magnetic multipoles. These computed particle trajectories clearly demonstrate the non-adiabatic scattering of charged particles at magnetic neutral lines. Brief comments are made on the different regions of phase space defined by regular and irregular trajectories.Also Visiting Reader in Physics, University of Sussex, Falmer, Brighton, BN1 9QH, UK  相似文献   

Influence of elemental sulfur, micronutrients, phosphorus, calcium, magnesium and potassium on growth of Prosopis alba on high pH soils in Argentina     

M. Velarde  P. Felker  D. Gardiner 《Journal of Arid Environments》2005,62(4):525-539

A field trial on 3-year-old Prosopis alba growing on pH 8.5 soils in Argentina was conducted to identify mineral nutrients that were most limiting growth and to determine correlations among these nutrients. As applications of nutrients such as Zn, Cu and P would be soon rendered unavailable due to the high pH, combinations of elemental S to decrease the pH were examined along with macro and micronutrient soil additions. Thirty trees were selected with stem diameters ranging from 2.8 to 4.5 cm and divided into five treatments in a completely randomized design with 1 tree per replicate. The treatments were: (1) control, (2) addition of elemental S to lower the pH, (3) addition of S and triple superphosphate (P), (4) addition of S, P and a complete blend of micronutrients and (5) addition of S, P, micronutrients and K and Mg. Biomass increases were estimated using regression equations on stem diameter increases. A small non-significant decrease in pH of about 0.3 pH was obtained in the treatments with S, except for treatment which contained micronutrients in the form of strong base oxides. There was a significant increase in electrical conductivity due to the oxidation of the S. The best treatment containing S, P and micronutrients had a 42% increase significant biomass increase over the control. Growth was positively correlated with leaf levels (decreasing order of significance) of K, S, P, and Zn and negatively correlated with leaf Na and Ca. The leaf K, which had the highest positive correlation with growth, was highly significantly positively correlated with leaf S, P, N, and Zn and highly significantly but negatively correlated with leaf Ca, Mg and Mn. Leaf N was very highly correlated with leaf Zn, S and P concentrations. Indian workers have found that 20 years after establishment Prosopis juliflora changed the soil pH from 10.4 to 8.0. Since trees on 10 m×10 m spacings are suggested to be ultimate climax density for these ecosystems, apparently it will only necessary to add inexpensive small quantities of elemental S, Zn and K directly around 100 small trees ha⁻¹ to effect a major soil reclamation over the entire ha.  相似文献