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731.
水体辐射传输方程是复杂的微积分方程,只能利用数值方法求解,如Monte Carlo光线追踪法、不变嵌入法、离散坐标法等,其中,Monte Carlo方法是目前解决水体水下光场三维问题的唯一有效方法.根据辐射传输理论,开发了水下光场的Monte Carlo模拟模型,主要包含大气、水-气界面、层化水体和水底边界4个模块.实现了模拟任意太阳角度、不同水体固有光学属性和任意深度条件下,考虑大气、粗糙水面和水底边界的水下光场,能够获取辐亮度、辐照度等辐射量的空间分布.该模型暂不考虑Raman散射、偏振、内部光源的影响.实现了GPU加速水下光场Monte Carlo模拟,并用Mobley等提出的海洋光学标准问题中的问题1~6进行验证.在两种计算环境下,通过对不同边界条件下的CPU、GPU运行时间及加速比的对比,发现GPU计算可以达到几百至上千倍的加速比. 相似文献
732.
通用型海洋水色遥感精确瑞利散射查找表 总被引:2,自引:1,他引:2
当前对海洋水色遥感精确瑞利散射的计算均采用查找表方式进行,但由于这些查找表是针对特定遥感器生成的,无法直接应用于新的水色遥感器,给实际应用带来一定程度的麻烦,为此提出了一种通用的海洋水色遥感精确瑞利散射查找表.首先,详细地推导了加倍法解大气矢量辐射传输方程的基本关系式和实际的计算原理.通过与MODIS精确瑞利散射查找表计算结果比较,证明利用加倍法计算瑞利散射的精度优于0.25%,完全能够满足当前海洋水色遥感大气校正对瑞利散射计算精度的要求,并可以用来生成精确瑞利散射查找表.其次,利用加倍法解大气矢量辐射传输方程,生成了一个通用的海洋水色遥感精确瑞利散射查找表,验证结果表明该查找表可用于所有水色遥感器的精确瑞利散射计算,且计算精度优于0.5%. 相似文献
733.
This paper proposes a rain considered geophysical model function (GMF), to be noted as GMF plus Rain. GMF plus Rain is based on the basic raidative transfer model with attenuation and scattering effects of rain on radar signal considered. Combined with the NSCAT2 GMF and the rain correction model, the GMF plus Rain model is used to retrieve the ocean wind vectors from the collocated QuikSCAT and SSM/I rain rate data for typhoon Melor. The resulting wind speed estimates of typhoon Melor show improved agreement with the wind fields derived from the best track analysis of Japan Meteorological Agency (JMA). The results imply that compared with the GMF model, the GMF plus Rain model can improve the precision of wind retrieval under the rain condition. Then, a new general algorithm of locating the eye of typhoon through the normalized radar cross section (NRCS) is proposed. The implementation of this algorithm in the ten QuikSCAT observations of typhoon Melor suggests that this algorithm is effective. 相似文献
734.
735.
Valery Suleimanov Juri Poutanen 《Monthly notices of the Royal Astronomical Society》2006,369(4):2036-2048
Spectra of the spreading layers on the neutron star surface are calculated on the basis of the Inogamov–Sunyaev model taking into account general relativity correction to the surface gravity and considering various chemical composition of the accreting matter. Local (at a given latitude) spectra are similar to the X-ray burst spectra and are described by a diluted blackbody. Total spreading layer spectra are integrated accounting for the light bending, gravitational redshift and the relativistic Doppler effect and aberration. They depend slightly on the inclination angle and on the luminosity. These spectra also can be fitted by a diluted blackbody with the colour temperature depending mainly on a neutron star compactness. Owing to the fact that the flux from the spreading layer is close to the critical Eddington, we can put constraints on a neutron star radius without the need to know precisely the emitting region area or the distance to the source. The boundary layer spectra observed in the luminous low-mass X-ray binaries, and described by a blackbody of colour temperature T c = 2.4 ± 0.1 keV , restrict the neutron star radii to R = 14.8 ± 1.5 km (for a 1.4-M⊙ star and solar composition of the accreting matter), which corresponds to the hard equation of state. 相似文献
736.
F. Zagury 《Astronomische Nachrichten》2013,334(10):1107-1114
The 2200 Å bump is a major figure of interstellar extinction. However, extinction curves with no bump exist and are, with no exception, linear from the near‐infrared down to 2500 Å at least, often over all the visible‐UV spectrum. The duality linear versus bump‐like extinction curves can be used to re‐investigate the relationship between the bump and the continuum of interstellar extinction, and answer questions as why do we observe two different kinds of extinction (linear or with a bump) in interstellar clouds? How are they related? How does the existence of two different extinction laws fits with the requirement that extinction curves depend exclusively on the reddening E (B – V) and on a single additional parameter? What is this free parameter? It will be found that (1) interstellar dust models, which suppose the existence of three different types of particles, each contributing to the extinction in a specific wavelength range, fail to account for the observations; (2) the 2200 Å bump is very unlikely to be absorption by some yet unidentified molecule; (3) the true law of interstellar extinction must be linear from the visible to the far‐UV, and is the same for all directions including other galaxies (as the Magellanic Clouds). In extinction curves with a bump the excess of starlight (or the lack of extinction) observed at wavelengths less than λ = 4000 Å arises from a large contribution of light scattered by hydrogen on the line of sight. Although counter‐intuitive this contribution is predicted by theory. The free parameter of interstellar extinction is related to distances between the observer, the cloud on the line of sight, and the star behind it (the parameter is likely to be the ratio of the distances from the cloud to the star and to the observer). The continuum of the extinction curve and the bump contain no information on the chemical composition of interstellar clouds. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献