A weighing lysimeter in a regenerating eucalypt forest: Design,construction, and performance

A 36 tonne monolithic weighing lysimeter (3.7 m diameter and 1.5 m deep) was installed in Kioloa State Forest near Batemans Bay, New South Wales, Australia, to provide a continuous record of water use from a regenerating natural eucaplyt community, five years old at installation. The resolution is equivalent to 0.05 mm of evaporation and provides hourly information for diurnal variation of forest evaporation. The sensitivity of 14 ppm compares favourably with those reported for other lysimeters, similar in magnitude, in the U.S.A. Design criteria for selecting, isolating and suspending a sample community ‘in situ’ with an electro-mechanical balance are outlined. Procedures adopted during installation are described with emphasis placed on precautions taken to minimize disturbance and to avert possible changes in character of the isolated natural community. Lysimeter performance was assessed both in terms of its accuracy and its operation as a remote facility with infrequent attention.     

Magnetic energy buildup in a quadrupole field by photospheric shear motion

Using a two-dimensional, dissipative magnetohydrodynamic model, this paper presents a numerical simulation of the magnetic energy buildup in a quadrupolar field by photospheric shear motion. When electric current density is larger than a certain critical value, an anomalous resistivity is introduced in order to account for the dissipation caused by instabilities in high current regions. It is shown that like a bipolar field, a quadrupolar field can efficiently store magnetic free energy through photospheric shear motion. Electric current formed by shear concentrates on the separatrix and magnetic loops rooted in areas where the shear velocity gradient is large. The atmosphere is heated by anomalous resistive dissipation during the shear. Both magnetic and thermal energy increases nonlinearly with shearing displacement. When the anomalous resistivity increases or the critical current density decreases, the growth rate reduces for magnetic energy but goes up for thermal energy.     

A correlation between large-scale asymmetry of the Moon and the foci of moonquakes

Some evidence is produced to show that the Moon is asymmetric on the large scale as regards its figure, structure, composition, the distribution of tidal force, natural remnant magnetism and magnetic anomaly. This asymmetry produces the state of stress in the Moon, causing most foci of moonquakes to be located in the nearside of the Moon.     

Kernel regression for determining photometric redshifts from Sloan broad-band photometry

We present a new approach, namely kernel regression, to determine photometric redshifts for 399 929 galaxies in the Fifth Data Release of the Sloan Digital Sky Survey (SDSS). Kernel regression is a weighted average of spectral redshifts of the neighbours for a query point, and higher weights are associated with points that are closer to the query point. One important design decision when using kernel regression is the choice of bandwidth. We apply 10-fold cross-validation to choose the optimal bandwidth, which is obtained as the cross-validation error approaches its minimum. The results show that the optimal bandwidth is different for different input patterns: the lowest rms error of photometric redshift estimation arrives at 0.019 using colour+eClass as the inputs, the lowest rms errors comes to 0.020 using ugriz +eClass as the inputs. Where eClass is a galaxy spectral type, and 0.021 using colour+ r as the inputs. Thus, in addition to parameters such as magnitude and colour, eClass is a valid parameter with which to predict photometric redshifts. Moreover, the results suggest that the accuracy of estimating photometric redshifts is improved when the sample is divided into early-type and late-type galaxies; in particular, for early-type galaxies, the rms scatter is 0.016 with colour+eClass as the inputs. In addition, kernel regression achieves high accuracy when predicting the photometric eClass  (σ_rms= 0.034)  using colour+ r as the input pattern. For kernel regression, the accuracy of the photometric redshifts does not always increase with the number of parameters considered, but is satisfactory only when appropriate parameters are chosen. Kernel regression is a comprehensible and accurate regression method. Experiments reveal the superiority of kernel regression over other empirical training approaches.     

On the Relations between Infrared Colors and Mass Loss Rates for S Stars

A relation between the infrared color K-[12] and the mass loss rate, dM/dt,is found for the intrinsic S stars. This relation is qualitatively similarto the ones for carbon stars and oxygen-rich Mira stars, but quantitativelydifferent. It could be useful in the context of the near infrared surveys,DENIS and 2MASS, which are in progress. Correlations between J-K and[12]–[25] indices and dM/dt are found to be loose for S stars.     

Numerical representation of planetary ephemerides

The Jet Propulsion Laboratory provides high-precision numerically integrated planetary and lunar ephemerides in support of spacecraft navigation and other activities relating to solar system bodies. Hundreds of users around the world have requested copies of the ephemerides. In the interests of compactness and utility, techniques have been developed for (1) the generation of the coefficients of an interpolating polyncmial based on output from the integrator, and (2) transformation of the contents of an ephemeris file to a standard form usable on virtually any computer.     

Evaluation of the ventilated chamber for measuring evaporation from a forest

Evaporation from a regenerating forest was determined concurrently by atmospheric measurements of the Bowen ratio, soil water depletion, and by weighing lysimeter. The methods agreed closely over 18 days in spring and 11 days in summer. Accordingly, the Bowen ratio technique was then used as the control against which any effect on evaporation by enclosure of the lysimeter with a chamber of varied ventilation rate could be quantified hourly and daily. Accuracy of gas analysis was checked against lysimeter values. Daily evaporation by the lysimeter was generally unaffected by enclosure—on a few afternoons there was a statistically significant enhancement of hourly values by the chamber. This was accounted for by difference in turbulence between chamber and forest. The general agreement in daytime hourly values is attributed to the frequent occurrence of equilibrium evaporation (rate at which evaporation is independent of ventilation). At night, evaporation was higher during enclosure. Comparisons were not possible with rain or dew. Determination of evaporation by gas analysis agreed within about 5 per cent of lysimeter values during a dry period. We conclude that the ventilated chamber as used provides realistic estimates of evaporation by forests. We show how periods of bias can be anticipated and corrected by theory.