Characteristics of water mass under the surface mixed layer in Tsushima Straits and the southwestern Japan Sea in autumn

Two different cold waters were found under the surface mixed layer in Tsushima Straits and the southwestern Japan Sea in autumn 2004. One is cold saline water with a low concentration of dissolved oxygen, and the other is cold less saline water with a high concentration of dissolved oxygen. The older saline water originates from the bottom of the East China Sea, strongly influenced by the Kuroshio water with high salinity. The bottom density in the eastern channel of the Tsushima Straits is coincident with that of the East China Sea in autumn, corresponding to the season when the cold saline water was frequently found in the Tsushima Straits. The newer less saline water originates from the front of Tsushima Warm Current between the Tsushima Warm Current water and the surface cold water in the Japan Sea. This water is formed by subduction above the isopycnal surface from the front of the Tsushima Warm Current.     

Simulating the carbon balance of a temperate larch forest under various meteorological conditions

Background  

Changes in the timing of phenological events may cause the annual carbon budget of deciduous forests to change. Therefore, one should take such events into account when evaluating the effects of global warming on deciduous forests. In this article, we report on the results of numerical experiments done with a model that includes a phenological module simulating the timing of bud burst and other phenological events and estimating maximum leaf area index.     

Parameters of the Magnetic Flux inside Coronal Holes

The parameters of the magnetic flux distribution inside low-latitude coronal holes (CHs) were analyzed. A statistical study of 44 CHs based on Solar and Heliospheric Observatory (SOHO)/MDI full disk magnetograms and SOHO/EIT 284?Å images showed that the density of the net magnetic flux, B _net, does not correlate with the associated solar wind speeds, V _x . Both the area and net flux of CHs correlate with the solar wind speed and the corresponding spatial Pearson correlation coefficients are 0.75 and 0.71, respectively. A possible explanation for the low correlation between B _net and V _x is proposed. The observed non-correlation might be rooted in the structural complexity of the magnetic field. As a measure of the complexity of the magnetic field, the filling factor, f(r), was calculated as a function of spatial scales. In CHs, f(r) was found to be nearly constant at scales above 2 Mm, which indicates a monofractal structural organization and smooth temporal evolution. The magnitude of the filling factor is 0.04 from the Hinode SOT/SP data and 0.07 from the MDI/HR data. The Hinode data show that at scales smaller than 2 Mm, the filling factor decreases rapidly, which means a multifractal structure and highly intermittent, burst-like energy release regime. The absence of the necessary complexity in CH magnetic fields at scales above 2 Mm seems to be the most plausible reason why the net magnetic flux density does not seem to be related to the solar wind speed: the energy release dynamics, needed for solar wind acceleration, appears to occur at small scales below 1 Mm.     

Numerical investigation on the orbital evolution of 1:2 resonant asteroids between Jupiter and Saturn

According to some investigations (Lecar and Franklin, 1973; Franklin et al., 1989; Soper et al., 1990) asteroids cannot remain for along time between Jupiter and Saturn. But as it is well known there is a near 5:2 commensurability between Jupiter and Saturn. So there might be a possibility that asteroids between Jupiter and Saturn could be trapped in a resonant relation.In order to investigate this possibility, the changes of orbital elements of an asteroid whose initial value of semi-major axis corresponds to that of a 1:2 resonant orbit were investigated by means of a double precision Cowell method. The integration routine was kindly supplied by Dr Yoshikawa.We considered first a planar restricted problem of three bodies, Sun-Jupiter-Asteroid, then a four body problem, Sun-Jupiter-Asteroid-Saturn. When integrating the equations of motion, short periodic terms were not eliminated and in the second test the interactions between Jupiter and Saturn were retained. Whether a close approach occured or not was not investigated. In every case a _j = 5.20, a _s = 9.54 and a = 8.26 were adopted as initial values of the semi-major axis of Jupiter, Saturn and Asteroid respectively.     

Statistical studies on the wave-form and maximum height of large Tsunamis

The tide-gauge records of large tsunamis are classified into three types, A, B and C. The “A” type record is made up of one or a few large waves near the wave front. The “B” type record consists of one or a few wave groups. The “C” type is the combination of the “A” and “B” types. The data used are; the Kamchatka Tsunami of Nov. 4, 1952, the Aleutian Tsunami of March 9, 1957, the Chilean Tsunami of May 22, 1960 and the Alaska Tsunami of March 28, 1964. The A type occurs mostly at isolated islands in the Pacific Ocean and occasionally at continental coasts. The B type is mostly distributed on the continental coast and along the island-arc. The distribution of the C type differs from tsunami to tsunami. The relation between the delay time of the maximum wave and the the travel time of the wave front is as follows:

1. For the wave of the A type and the head wave of C type, the delay time (t _D ) is constant for all travel times.
2. For the first wave group of B and C types, the delay time (T ₁) is constant or slow decreases with travel time. For the second and third wave groups of B and C types, the definite decrease of delay times (T ₂ andT ₃) with travel time is observed.

The height (h) of the maximum wave of A and C types decreases generally with travel time. The maximum wave height along the path between Kamchatka and Chile, however, shows the increase. For all wave groups the wave heights (H ₁,H ₂ andH ₃) of B and C types increases with travel time. Some speculations on the causes of these features are also presented.