A Fast Procedure Solving Gauss' Form of Kepler's Equation

We developed a procedure solving Gauss' form of Kepler's equation, which is suitable for determining position in the nearly parabolic orbits. The procedure is based on the combination of asymptotic solutions, the method of bisection, and the Newton method of succesive correction. It runs 3–4 times faster than the original Gauss' method. This revised version was published online in July 2006 with corrections to the Cover Date.     

Content of plutonium,thorium and protactinium in sea water and recent coral in the North Pacific

The contents of plutonium isotopes (²³⁹Pu and²³⁸Pu), thorium isotopes (²³²Th,²³⁰Th and²²⁸Th) and protactinium-231 in sea water collected in the North Pacific, the East China Sea and the Japan Sea were determined. These nuclides were sequentially analyzed byα-ray spectrometry after separating them mainly with solvent extraction technique. The contents of²³⁹Pu in surface sea water ranged from 0.6 to 1.6 pCi/10001,²³⁸Pu/²³⁹Pu activity ratios being 0.2～0.7. The²²⁸Th/²³²Th activity ratios for the North Pacific waters varied between 7.6 and 30, whereas the sample from the East China Sea showed the very high value, 65. The contents of²³¹Pa are less than 6 percent of that in equilibrium with its parent²³⁵U. Furthermore, the analysis of plutonium isotopes in recent coral from Yoron Island was carried out and it was confirmed that plutonium isotopes have concentrated in recent coral with the concentration factor of about 1～2×10³.     

How does the ocean response to the withdrawal of water from a watergate located at the eastern boundary on a beta-plane?

The formation of the spun up region by the withdrawal of water from a watergate located in the eastern boundary in a homogeneous ocean on a beta-plane at low Rossby number is presented. The spun up region penetrates only westward from the Watergate because of the special character of the generated Rossby waves. The growth rate and the final longitudinal length of the spun up region in the dissipative system is much affected by the watergate scale in the north-south direction.The relation with the experiment ofLong (1952) and the geophysical application are presented.     

Climate variability in the southern Indian Ocean as revealed by self-organizing maps

Using a non-linear statistical analysis called “self-organizing maps”, the interannual sea surface temperature (SST) variations in the southern Indian Ocean are investigated. The SST anomalies during austral summer from 1951 to 2006 are classified into nine types with differences in the position of positive and negative SST anomaly poles. To investigate the evolution of these SST anomaly poles, heat budget analysis of mixed-layer using outputs from an ocean general circulation model is conducted. The warming of the mixed-layer by the climatological shortwave radiation is enhanced (suppressed) as a result of negative (positive) mixed-layer thickness anomaly over the positive (negative) SST anomaly pole. This contribution from shortwave radiation is most dominant in the growth of SST anomalies. In contrast to the results reported so far, the contribution from latent heat flux anomaly is not so important. The discrepancy in the analysis is explained by the modulation in the contribution from the climatological heat flux by the interannual mixed-layer depth anomaly that was neglected in the past studies.     

Temporal variability of winter mixed layer in the mid-to high-latitude North Pacific

Temperature and salinity data from 2001 through 2005 from Argo profiling floats have been analyzed to examine the time evolution of the mixed layer depth (MLD) and density in the late fall to early spring in mid to high latitudes of the North Pacific. To examine MLD variations on various time scales from several days to seasonal, relatively small criteria (0.03 kg m⁻³ in density and 0.2°C in temperature) are used to determine MLD. Our analysis emphasizes that maximum MLD in some regions occurs much earlier than expected. We also observe systematic differences in timing between maximum mixed layer depth and density. Specifically, in the formation regions of the Subtropical and Central Mode Waters and in the Bering Sea, where the winter mixed layer is deep, MLD reaches its maximum in late winter (February and March), as expected. In the eastern subarctic North Pacific, however, the shallow, strong, permanent halocline prevents the mixed layer from deepening after early January, resulting in a range of timings of maximum MLD between January and April. In the southern subtropics from 20° to 30°N, where the winter mixed layer is relatively shallow, MLD reaches a maximum even earlier in December–January. In each region, MLD fluctuates on short time scales as it increases from late fall through early winter. Corresponding to this short-term variation, maximum MLD almost always occurs 0 to 100 days earlier than maximum mixed layer density in all regions.