The wind fields in Typhoon 0418 (Songda; 7 to 8 September 2004) and Typhoon 9119 (Mireille; 27 to 28 September 1991), which hit western Japan on nearly the same track and caused extensive wind damage, were analyzed using routine data of the Japan Meteorological Agency. In T0418, the strongest wind was on the right (southeastern) side of the center, while the wind on the left (northwestern) side was relatively weak. This wind distribution is roughly explained by the sum of an axially symmetric vortex and the storm motion. The strong wind of T9119 was both on the right (southeastern) side and in the left-rear (western) quadrant, coinciding with a region of low temperature and a rain-band. It is likely that the dry-air intrusion into the rain-band caused evaporative cooling and generated a surge of cold air. Such a feature was lacking in T0418, for which convective clouds in the western quadrant had almost disappeared after landfall.
A new storm surge model that includes the effect of wave set-up has been developed. This model is based on the Princeton Ocean Model (POM) and the third generation wave model MRI-III originally developed at MRI. The wave set-up effect is included in the storm surge calculation via parameterized radiation stress from the calculated wave spectra in the wave model. Additional complex mechanisms are not considered in this model in order to facilitate operational use. This model yields satisfactory accuracy for storm surges occurring on ocean coasts. A large storm surge of almost 2.5m caused by Typhoon (TY) Kirogi (0003) was observed at Yaene tide station on Hachijo Island, located in the western Pacific Ocean. The conventional storm surge model can simulate a far lower value (a maximum storm surge of 0.51m); the new model simulates a more realistic value (2.22m), which is 1.71m higher, by considering the wave set-up effect. However, our result still underestimated the measured surge.
The Mogi model is a fundamental crustal deformation model in volcanology. Although Sasai(1991) derived an analytic solution for the Piezomagnetic field due to the Mogi model, it is necessary to evaluate topographical effects since volcanic topographies surround volcanic areas. The topographical effects have not been well studied, probably because a procedure of the 3-D numerical computing is somewhat complicated. In this study, we evaluate the topographical effects of a conical volcano, which is a typical volcanic topography, on the piezomagnetic field. A finite-element method is applied to compute a stress field in the crust. Next, the stress field is converted to piezo-magnetization applying the linear piezomagnetic law. To obtain the piezomagnetic effects at the surface, numerical volume integration is then performed over the whole crust. As a result, we found that the ratio of topographical effects on the piezomagnetic field at the volcano surface reaches almost 50%. We also found a piezomagnetic anomaly field at the foot area of the volcano caused by stress concentration.
Partial pressures of CO2 in surface seawater (pCO2sea) and the overlying air (pCO2air) were measured in the North Pacific (mainly 30-40°N) from January 1999 to October 2000 (9 cruises) onboard the voluntary observation ship MS Alligator Liberty. Distributions of pCO2air and pCO2sea showed that the western North Pacific (west of 180°) acted as a sink for atmospheric CO2 throughout the year except for August, whereas the eastern North Pacific (east of 160°W) acted as a sink for only half the year (November to May). Total dissolved inorganic carbon (TCO2) estimated from pCO2sea and total alkalinity showed a larger seasonal decrease (April to June) in the western North Pacific than in the eastern North Pacific, in accordance with the seasonal decrease in nitrate + nitrite (NOx = NO3- + NO2-). The 9.5 C/N ratio calculated from the relationship between decreased TCO2 and [NOx] implied a larger influence of biological activity in the western North Pacific. Using pCO2sea estimated from the relationship between pCO2sea and sea surface temperature, we assessed the monthly CO2 fluxes in the western North Pacific for the year 2000. The fluxes ranged from ca. 0 Gt-C yr-1 in the summer to ca. -0.4 Gt-C yr-1 in the winter, with an annual average of -0.2 Gt-C yr-1, which corresponds to about 10% of the annual oceanic CO2 uptake over the 1990s.
Marine aerosol particles were collected in February and March 1993 using an impactor at a remote Pacific island, Minamitorishima (Marcus Island) (24.3°N, 154.0°E). The composition of individual aerosol particles with radii of 0.4 to 2.0 μm was examined with an energy-dispersive X-ray (EDX) analyzer equipped with a transmission electron microscope (TEM). The dominant aerosol type was found to be sea-salt comprising 89 to 98% of the total particles in this radius range in each sample. Sulfur-rich particles and mineral particles were collected with small number fractions (both 3%) of the total particles. About 5% of the sea-salt particles exhibited weight ratios of Cl/Na less than 1, indicating chlorine deficiencies. However, the modified sea-salt particles were found in a relatively large percentage (about 25%) of sea-salt particles in the sample collected from the air transported from the marine atmosphere close to the Asian continent. These modified sea-salt particles were produced through heterogeneous reactions during long-range transportation under the influence of continental anthropogenic polluted air.