This letter investigates the edge effects on the tree height retrieval over coniferous plantations using X-band interferometry. A coherent version of the water cloud model is used to evaluate the influence of observation conditions such as incidence angle, tree height, and slope, each of which affects the extent of areas affected by edge effects. Results from the model simulation are discussed in the context of actual X-band data over pine plantations. A generic expression to indicate the extent of edge effects is described. 相似文献
The Arrhenius expressions and the data plotted in Figure 2 of Rodriguez et al. 2008 give rate coefficients of approximately 2?×?10-8 cm3 molecule-1 s-1 at 255 K. Such values are approximately two orders of magnitude larger than expected from simple collision theory (Finlayson-Pitts and Pitts 1986). The rate coefficients reported at sub-ambient temperatures are substantially greater than the gas kinetic limit and are not physically plausible. The rate coefficients reported by Rodriguez et al. imply a long range attraction between the reactants which is not reasonable for reaction of neutral species such as chlorine atoms and unsaturated alcohols. We also note that the pre-exponential A factors (10-23-10-20) and activation energies (?15 kcal mol-1) are not physically plausible. We conclude that there are large systematic errors in the study by Rodriguez et al. (Atmos Chem 59:187–197, 2008). 相似文献
The relative rate technique has been used to measure rate constants for the reaction of chlorine atoms with peroxyacetylnitrate (PAN), peroxypropionylnitrate (PPN), methylhydroperoxide, formic acid, acetone and butanone. Decay rates of these organic species were measured relative to one or more of the following reference compounds; ethene, ethane, chloroethane, chloromethane, and methane. Using rate constants of 9.29×10–11, 5.7×10–11, 8.04×10–12, 4.9×10–13, and 1.0×10–13 cm3 molecule–1 sec–1 for the reaction of Cl atoms with ethene, ethane, chloroethane, chloromethane, and methane respectively, the following rate constants were derived, in units of cm3 molecule–1 s–1: PAN, <7×10–15; PPN, (1.14±0.12)×10–12; HCOOH, (2.00±0.25)×10–13; CH3OOH, (5.70±0.23)×10–11; CH3COCH3, (2.37±0.12)×10–12; and CH3COC2H5, (4.13±0.57)×10–11. Quoted errors represent 2 and do not include possible systematic errors due to errors in the reference rate constants. Experiments were performed at 295±2 K and 700 torr total pressure of nitrogen or synthetic air. The results are discussed with respect to the previous literature data and to the modelling of nonmethane hydrocarbon oxidation in the atmosphere.In recent discussions with Dr. R. A. Cox of Harwell Laboratory, UKAEA, we learnt of a preliminary value for the rate constant of the reaction of Cl with acetone of (2.5±1.0)×10–12 cm3 molecule–1 sec–1 measured by R. A. Cox, M. E. Jenkin, and G. D. Hayman using molecular modulation techniques. This value is in good agreement with our results. 相似文献
The behaviour of energetic electrons in the distant magnetosphere near the midnight meridian during polar substorms has been studied for the period March 5th–April 4th, 1965, using data from two end window Geiger counters flown on the IMP 2 satellite (apogee 15.8 Earth radii) and magnetic records from a chain of auroral zone stations around the world at magnetic latitudes equivalent to L = 7.4 ± 2.0.
When the satellite was in the distant radiation zone or in the plasma sheet which extends down the Earth's magnetic tail, sudden decreases in the horizontal magnetic field component at ground stations near the midnight meridian (negative magnetic bays) were followed by sudden increases in 40 keV electron fluxes (electron islands) at the satellite. When the satellite was at high latitudes in the magnetic tail ‘bays’ often were not followed by ‘islands.’ When the satellite was near the centre of the plasma sheet, energetic electron fluxes were observed even during magnetically quiet periods. The time delay between the sharp onset of magnetic bays in the auroral zone and the corresponding rapid increase in energetic electron intensity at the satellite, typically some tens of minutes, was least when the satellite was close to the Earth and increased with its increasing radial distance from the Earth. The delay was also a function of distance of the satellite from the centre of the plasma sheet, and of the magnitude of the intensity increase (smaller delays for larger intensity increases). We deduce that the disturbance producing the magnetic bays and associated particle acceleration originates fairly deep in the magnetosphere and propagates outward to higher L values, and down the plasma sheet in the Earth's magnetic tail on the dark side of the Earth. It is unlikely that the accelerated electrons are themselves drifting away from the Earth, because the apparent velocity with which the islands move away from the Earth decreases with increasing distance from the Earth.
It is suggested that the polar substorm and the associated particle acceleration are part of an impulsive ejection mechanism of magnetospheric energy into the ionosphere, rather than an impulsive injection mechanism of solar wind energy into the magnetosphere. 相似文献
Tesbihdere is one of a number of spatially close epithermal Cu-Pb-Zn-Ag-Au deposits hosted by andesites and rhyolites, typical of deposits in the Biga peninsula. Microthermometry of fluid inclusions shows a wide range of temperatures, ～360–170°C, and salinities, ～10-0.5 wt.% NaCl, in the different deposits studied. Dilution of a moderately saline magmatic? fluid with meteoric water occurred at constant temperature indicating, the temperature of both fluids was controlled by the geological environment. Boiling was not a major factor, but did occur in very minor amounts. The large range of temperatures within individual samples can only reasonably be explained by variations from near lithostatic to hydrostatic pressure during vein and fracture opening. That this pressure decrease did not produce extensive boiling suggests that vein opening was gradual rather than aggressive, allowing the pressure and temperature decrease to follow a path close to the L-V boiling curve. P-T reconstruction places emplacement of these ore veins at between 300–500 m beneath the surface. Similarities of LA-ICPMS of fluid inclusions from Tesbihdere, Azitepe and Basmakci, supports the conclusion that they were part of the same contemporaneous mineralizing system. The fluids are dominated by Na, with the concentrations of K>Ca>Mg combined equivalent to the concentration of Na. The range of K/Na ratios is not consistent with the fluid inclusion temperatures as the calculated temperatures are significantly higher indicating the fluids were not close to equilibrium with the enclosing rocks. Elevated K concentrations are consistent with acid-sulphate waters in shallow epithermal systems. Ore metals Cu, Zn and Pb are present in significant concentrations ～500, 300 and 200 ppm respectively and the low Fe/Mn ratios are indicative of a relatively oxidising fluid. The negative δ34S values of sulphides are consistent with boiling and oxidising redox conditions. 相似文献
The kinetics of the reaction of nitrous acid (HONO) with nitric acid (HNO3), nitrate radicals (NO3) and dinitrogen pentoxide (N2O5) have been studied using Fourier transform infrared spectroscopy. Experiments were performed at 700 torr total pressure using synthetic air or argon as diluents. From the observed decay of HONO in the presence of HNO3 a rate constant of k<7×10-19 cm3 molecule-1 s-1 was derived for the reaction of HONO with HNO3. From the observed decay of HONO in the presence of mixtures of N2O5 and NO2 we have also derived upper limits for the rate constants of the reactions of HONO with NO3 and N2O5 of 2×10-15 and 7×10-19 cm3 molecule-1 s-1, respectively. These results are discussed with respect to previous studies and to the atmospheric chemistry of HONO. 相似文献
