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121.
The temperature minimum layer, called “dichothermal water”, is a characteristic feature of the North Pacific subarctic gyre.
In particular, dichothermal water having a density of approximately 26.6 sigma-theta (σθ), which corresponds to the densest water outcropping in winter in the North Pacific, is seen in the Bering Sea. In order
to clarify the water properties, and the area in which and the process by which the dichothermal water is formed, a new seasonal
mean gridded climatological dataset with a fine resolution for the Bering Sea and adjacent seas has been prepared using historically
accumulated hydrographic data. Although the waters of the Alaskan Stream have temperature minimum layers, their temperature
inversions are very weak in climatologies and the core densities of the temperature minimum layers are much lighter than 26.6σθ. On the other hand, in the Bering Sea one can see the robust structure of temperature minimum layers, the core density of
the dichothermal water being around 26.6σθ. In addition, it has been found that the properties of the dichothermal water observed in the warming season are almost the
same as those in the winter mixed layer. That is, the dichothermal waters are formed in the winter mixed layer in the Bering
Sea. Since these waters are found in the Kamchatka Strait, i.e., the main exit of the Bering Sea waters, it can be supposed
that the dichothermal waters are exported from the Bering Sea to the Pacific Ocean by the Kamchatka Current.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
122.
Toshio Fukushima 《Celestial Mechanics and Dynamical Astronomy》1997,68(2):121-137
We developed a method to solve Keplers equation for the hyperboliccase. The solution interval is separated into three regions; F 1, F 1, F 1. For the region F is large, we transformed the variablefrom F to exp F and applied the Newton method to the transformed equation.For the region F is small, we expanded the equation with respect to F andapplied the Newton method to the approximated equations. For the middleregion, we adopted a discretization of the Newton method and used the Taylorseries expansion for the evaluation of transcendental functions (Fukushima,1997). Numerical measurements showed that, in the case of Intel Pentiumprocessor, the new method is more than 3.7 times as fast as the combinationof a fourth order correction formula (Fukushima, 1997) and Roysstarting procedure (Roy, 1988) and others. 相似文献
123.
New expansions of elliptic motion based on considering the eccentricitye as the modulusk of elliptic functions and introducing the new anomalyw (a sort of elliptic anomaly) defined byw=u/2K–/2,g=amu–/2 (g being the eccentric anomaly) are compared with the classic (e, M), (e, v) and (e, g) expansions in multiples of mean, true and eccentric anomalies, respectively. These (q,w) expansions turn out to be in general more compact than the classical ones. The coefficients of the (e,v) and (e,g) expansions are expressed as the hypergeometric series, which may be reduced to the hypergeometric polynomials. The coefficients of the (q,w) expansions may be presented in closed (rational function) form with respect toq, k, k=(1–k
2)1/2,K andE, q being the Jacobi nome relatedk whileK andE are the complete elliptic integrals of the first and second kind respectively. Recurrence relations to compute these coefficients have been derived.on leave from Institute of Applied Astronomy, St.-Petersburg 197042, Russia 相似文献
124.
125.
126.
Toshio Fukushima 《Celestial Mechanics and Dynamical Astronomy》1999,75(3):201-226
We developed a procedure to solve a modification of the standard form of the universal Kepler’s equation, which is expressed
as a nondimensional equation with respect to a nondimensional variable. After reducing the domain of the variable and the
argument by using the symmetry and the periodicity of the equation, the method first separates the case where the solution
is so small that it is given an inverted series. Second, it separates the cases where the elliptic, parabolic, or hyperbolic
standard forms of Kepler’s equation are suitable. Here the separation is done by judging whether detouring these nonuniversal
equations will cause a 1-bit loss of information to their nonuniversal solutions or not. Then the nonuniversal equations are
solved by the author’s procedures to solve the elliptic Kepler’s equation (Fukushima, 1997a), Barker’s equation (Fukushima,
1998), and the hyperbolic Kepler’s equation (Fukushima, 1997b), respectively. And their nonuniversal solutions are transformed
back to the solution of the universal equation. For the rest of the case, we obtain an approximate solution by solving roughly
the approximated cubic equation as we did in solving Barker’s equation. Then the correction to the approximate solution is
obtained by Halley’s method precisely. There the special function appeared in the universal equation is rewritten into a combination
of similar special functions of small arguments, so that they are efficiently evaluated by their Taylor series. Numerical
measurements showed that, in the case of Intel Pentium II processor, the new method is 10–25 times as fast as Shepperd’s method
(Shepperd, 1985) and 7–13 times as fast as the standard Newton method.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
127.
Precise computation of acceleration due to uniform ring or disk 总被引:1,自引:0,他引:1
Toshio Fukushima 《Celestial Mechanics and Dynamical Astronomy》2010,108(4):339-356
We describe a precise numerical method to evaluate the acceleration vector of an inverse-square force law caused by a uniform
ring or disk. The method consists of two parts. One is rewriting of the analytic expressions of the vector to reduce the loss
of information in its computation. The other is a procedure to compute a special linear combination of the complete elliptic
integrals of the first and the second kind appeared in the rewritten expressions. 相似文献
128.
There is a large thermal contrast between the Arabian Peninsula and India (Δθ AI) at the mature stage of the Indian summer monsoon (ISM). The forming process of Δθ AI is investigated analyzing various datasets. It forms earlier in the lower troposphere than in the middle and upper layers. The potential temperature in the lower troposphere over the west coast of India (θ IW) abruptly decreases in advance of the rapid enhancement of the westerly wind over the Arabian Sea corresponding to the ISM onset. Such a process was observed for all the target years and the rapid decrease in θ IW could trigger the ISM onset. The decrease in θ IW had two patterns. In one case, cooler air is brought by the strong winds around a cyclone over the Arabian Sea. In another case, θ IW decreases gradually by a synergy of a southwesterly wind over the Arabian Sea and the enlargement of Δθ AI. 相似文献
129.
Anomalous winter climate conditions in the Pacific rim during recent El Niño Modoki and El Niño events 总被引:2,自引:1,他引:1
Present work compares impacts of El Niño Modoki and El Niño on anomalous climate in the Pacific rim during boreal winters of 1979–2005. El Niño Modoki (El Niño) is associated with tripole (dipole) patterns in anomalies of sea-surface temperature, precipitation, and upper-level divergent wind in the tropical Pacific, which are related to multiple “boomerangs” of ocean-atmosphere conditions in the Pacific. Zonal and meridional extents of those “boomerangs” reflect their independent influences, which are seen from lower latitudes in the west to higher latitudes in the east. In the central Pacific, more moisture is transported from the tropics to higher latitudes during El Niño Modoki owing to displacement of the wet “boomerang” arms more poleward toward east. Discontinuities at outer “boomerang” arms manifest intense interactions between tropical and subtropical/extratropical systems. The Pacific/North American pattern and related climate anomalies in North America found in earlier studies are modified in very different ways by the two phenomena. The seesaw with the dry north and the wet south in the western USA is more likely to occur during El Niño Modoki, while much of the western USA is wet during El Niño. The moisture to the southwestern USA is transported from the northward shifted ITCZ during El Niño Modoki, while it is carried by the storms traveling along the southerly shifted polar front jet during El Niño. The East Asian winter monsoon related anticyclone is over the South China Sea during El Niño Modoki as compared to its position over the Philippine Sea during El Niño, causing opposite precipitation anomalies in the southern East Asia between the two phenomena. 相似文献
130.
The mechanism of the Q-burst is investigated in the time and frequency domains. Electric fields in the ELF (extremely low frequency) to VLF (very low frequency) range have been observed with a ball antenna since 2003 in Kochi City, Japan (latitude 33.3°north, longitude 133.4°east). Source-to-observer distances (SODs) of Q-bursts are estimated by analyzing the waveforms. It is found as a result that the Q-burst is produced by combination of direct and antipodal pulses from a source lightning stroke occurring all over the world. 相似文献