On the 3/1 planar and circular resonant problem

The simplest model of a resonant problem of second order is the planar and circular case. Simplification like this is very old and for 3/1 resonance, several authors have studied this problem with different purposes. In this work, we test this model for the available asteroids, by applying Hori's perturbation method. Explicit solutions of the intermediate orbit are obtained. In the plane of two constants of the problem, all types of motion are described. By testing the model, it is shown that, in general, one can confirm results of numerical integrations indicating libration for a few number of asteroids and circulation for most of them. However, agreement in numerical values for amplitude and period of librations seems to be not possible mainly if Jupiter's eccentricity is neglected. On the other hand, even though there might be some physical reasons determining that only asteroids with high eccentricity may librate, it is shown that, from mathematical point of view, libration may occur even in the case of small eccentricities provided that some relations are satisfied.     

Characterization of slip zone associated with the 1999 Taiwan Chi-Chi earthquake: X-ray CT image analyses and microstructural observations of the Taiwan Chelungpu fault

To characterize the fault-related rocks within the Chelungpu fault, we performed X-ray computed tomography (CT) image analyses and microstructural observations of Hole B core samples from the Taiwan Chelungpu-fault Drilling Project. We identified the slip zone associated with the 1999 Chi-Chi earthquake, within the black gouge zone in the shallowest major fault zone, by comparison with previous reports. The slip zone was characterized by low CT number, cataclastic (or ultracataclastic) texture, and high possibility to have experienced a mechanically fluidized state. Taking these characteristics and previous reports of frictional heating in the slip zone into consideration, we suggested that thermal pressurization was the most likely dynamic weakening mechanism during the earthquake.     

Is the single scattering model invalid for the coda excitation at long lapse time?

Supposing that the distribution of scatterers in a three-dimensional medium is not uniform but fractally homogeneous with fractal dimensionD, we have made the dimensional analysis for the temporal decay of the multiple scattering energy density at the hypocenter.The number of scatters in a sphere of radiusR is assumed to be proportional toR ^D . Then, the energy density of thekth order scattering decays according to the [(D–2)k–3]th power of lapse time. A fractal dimension ofD=3 corresponds to the uniform distribution. If 2<D3, multiple scattering terms of orderk2 dominate over the single scattering term (k=1) at long lapse time. IfD=2, energy density of every order decays according to the — 3rd power of lapse time. The single scattering model survives on conditionD<2; the single scattering term dominates over the higher order multiple scattering terms even at long lapse time, since the negative power of lapse time fork=1 is the smallest of all.     

Comparison of four ensemble methods combining regional climate simulations over Asia

A number of uncertainties exist in climate simulation because the results of climate models are influenced by factors such as their dynamic framework, physical processes, initial and driving fields, and horizontal and vertical resolution. The uncertainties of the model results may be reduced, and the credibility can be improved by employing multi-model ensembles. In this paper, multi-model ensemble results using 10-year simulations of five regional climate models (RCMs) from December 1988 to November 1998 over Asia are presented and compared. The simulation results are derived from phase II of the Regional Climate Model Inter-comparison Project (RMIP) for Asia. Using the methods of the arithmetic mean, the weighted mean, multivariate linear regression, and singular value decomposition, the ensembles for temperature, precipitation, and sea level pressure are carried out. The results show that the multi-RCM ensembles outperform the single RCMs in many aspects. Among the four ensemble methods used, the multivariate linear regression, based on the minimization of the root mean square errors, significantly improved the ensemble results. With regard to the spatial distribution of the mean climate, the ensemble result for temperature was better than that for precipitation. With an increasing number of models used in the ensembles, the ensemble results were more accurate. Therefore, a multi-model ensemble is an efficient approach to improve the results of regional climate simulations.     

Characteristics of alkenone distributions in suspended and sinking particles in the northwestern North Pacific

We investigated alkenones recorded in suspended particles and a settling particle time series collected at three stations, 40N (40°N, 165°E), KNOT (44°N, 155°E), and 50N (50°N, 165°E), in the northwestern North Pacific from December 1997 to May 1999. Emiliania huxleyi, the most abundant alkenone producer in this area, is present in surface to subsurface (to ∼50 m depth) waters. The alkenone concentrations recorded in the suspended particles indicated that the seasonal alkenone particle distribution differed significantly interannually. Alkenone export fluxes at the three sediment-trap stations ranged from 0.16 to 49.3 μg m⁻² day⁻¹, and the maximum export flux, which occurred in summer to fall (July-November), was associated with a high organic carbon export flux. The amount of alkenone produced during the maximum export season accounted for 60-80% of the total annual amount of alkenone, and the alkenones accumulated in the sediment below the traps had characteristics corresponding to subsurface waters during the summer-autumn season. Alkenone-derived temperatures recorded in suspended particles corresponded to the in situ temperature within ∼2 °C. Although alkenone-derived temperatures corresponded approximately to the temperatures observed in the stratified subsurface waters at the three trap stations during the high-export season, large differences were observed during the low-export (winter-spring) period. For example, the alkenone-derived temperatures observed at stations KNOT and 50N were much higher than the in situ subsurface temperatures reported in the World Ocean Atlas 2001. Relatively large differences between alkenone-derived temperatures and in situ temperatures in the subarctic might be due to (1) a low-light limitation or (2) contributions of allochthonous alkenones in particulate material transported from subtropical areas within a warm-core ring.     

Climate simulations for 1880–2003 with GISS modelE

We carry out climate simulations for 1880–2003 with GISS modelE driven by ten measured or estimated climate forcings. An ensemble of climate model runs is carried out for each forcing acting individually and for all forcing mechanisms acting together. We compare side-by-side simulated climate change for each forcing, all forcings, observations, unforced variability among model ensemble members, and, if available, observed variability. Discrepancies between observations and simulations with all forcings are due to model deficiencies, inaccurate or incomplete forcings, and imperfect observations. Although there are notable discrepancies between model and observations, the fidelity is sufficient to encourage use of the model for simulations of future climate change. By using a fixed well-documented model and accurately defining the 1880–2003 forcings, we aim to provide a benchmark against which the effect of improvements in the model, climate forcings, and observations can be tested. Principal model deficiencies include unrealistically weak tropical El Nino-like variability and a poor distribution of sea ice, with too much sea ice in the Northern Hemisphere and too little in the Southern Hemisphere. Greatest uncertainties in the forcings are the temporal and spatial variations of anthropogenic aerosols and their indirect effects on clouds. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

The examination of fracturing process subjected to triaxial compression test in Inada granite

The behavior of a granite subject to a triaxial compression test ranging from the prefailure stage to the postfailure stage was studied using a fluorescent technique from the geological point of view. Microscopic observations of the specimens at different stages showed changes in the failure process. The start of formation of new microcracks paralleled the compression direction through their propagation until the onset of faulting and ended with the failure of shear zones after the strength failure point. Pores chiefly identified in the feldspar increased in length and width in the early stages, but not in number. It seems that the effect of pore spaces did not have any effect of failure. The microcracks generated on angular edges of quartz or feldspar grains and around biotite grains with increasing compression force. The phenomenon appearing on the crystal boundaries among biotite and quartz or feldspar agrees with the result calculated based on the theory on stress fields with ellipsoidal inhomogeneity suggested by Eshelby.