Climatic characteristics of convective and stratiform precipitation over the Tropical and Subtropical areas as derived from TRMM PR

Climatic characteristics of convective and stratiform precipitation over the Tropical and Subtropical areas are investigated based on the measurements of Tropical Rainfall Measuring Mission’s(TRMM) Precipitation Radar(PR) from 1998 to 2007.Results indicate that convective precipitation are distributed mainly over the Intertropical Convergence Zone(ITCZ),the South Pacific Convergence Zone(SPCZ),the Asian Monsoon Region,regions between the South America and the Mid-America,and the Tropical Africa where the frequencies lie between 1% and 2%.But in four seasons,total area fractions of convective precipitation frequencies less than 1% all exceed 85%.The frequencies of stratiform precipitation are much higher than those of convective precipitation,and total area fractions of stratiform precipitation frequencies >1% are over 55% during four seasons.However,frequencies of the two rain types show not only remarkable regionality,but also distinct seasonal variations.Conditional rain rates of convective precipitation range from 6 to 14 mm/h whereas those of stratiform precipitation are smaller than 4 mm/h.Meanwhile,rain tops of convective precipitation are higher than those of stratiform precipitation.The mean profiles of the two rain types show significant latitudinal dependency.And the seasonal variations of precipitation profiles are displayed mainly in the variations of rain tops.The frequencies and conditional rain rates of both rain types over ocean are higher than those over land,but rain tops are just the opposite.Moreover,the seasonal variations of both rain types over ocean are weaker than those over land because of the different stable states of underlying surfaces.     

静力平衡近似下大气中非线性对称运动的稳定性、分岔和突变

本文在考虑基本气流具有非线性切变情况下,导出了对称运动所满足的非线性常微分方程,并用非线性系统的稳定、分岔、突变理论,严格地讨论了非线性对称运动的稳定性、分岔和突变问题,获得了一个推广的对称不稳定判据,找到了突变产生的条件。     

GPS/LEO掩星技术中超折射效应的修正

在GPS掩星探测地球大气技术中，Abel积分变换要求大气折射指数n是折射半径a的单值函数，当大气折射率的垂直梯度达到小于一个极限值dN／dr≈-0．16N-unit m^-1上述单值性不成立，称其为超折射，此时Abel积分变换不再适用,如果还是在形式上应用经典的Abel变换，在反演结果中就会产生负大气折射率偏差．描述了低对流层中超折射现象的物理特性和数学表示；在广义Abel积分变换的基础上，讨论了超折射层内和超折射层下的大气剖面反演算法；选择了一个简单的采样间隔内等大气折射率垂直梯度假设，对英国高分辨率无线电探空观测资料进行模拟计算，验证了负超折射与大气折射率偏差的关系，并提出的广义Abel变换的合理性.     

超新星在星际^26Al问题中的作用：星际^26Al的天体源泉问题之三

讨论了迄今超新星爆发现论中各种爆炸性核燃烧核合成＾２６Ａｌ的问题。评述了星际＾２６Ａｌ天体起源的ＳＮＩＩ＋ＳＮＩｂ模型的有利因素和不足之处。最后提出一种产生星＾２６Ａｌ的新途径和有关部分星际＾２６Ａｌ起源于ＳＮＩａ的初步设想。     

Analysis on monthly-averaged distribution of sea surface wind and wave over the seas southeast of Asia using ERS-2 scatterometer data

The wind system over the seas southeast of Asia (SSEA) plays an important role in China's climate variation. In this paper, ERS scatterometer winds covering the period from January 2000 to December 2000 and the area of 2-41 °N, 105- 130°E were analyzed with a distance-weighting interpolation method and the monthly mean distribution of the sea surface wind speed were given. The seasonal characteristics of winds in the SSEA were analyzed. Based on WAVEWATCH Ⅲ model, distribution of significant wave height was calculated.     

GPS无线电掩星数据处理系统

GPS无线电掩星技术能提供高精度、高分辨率、全球覆盖的地球电离层和中性层大气剖面。它具有全天候、低费用、无系统长期漂移等优点。从1995年4月至1997年3月,首次GPS／MET试验的成功显示了GPS掩星技术对监测全球大气能够发挥重要的作用,从而成为当前空间探测技术的研究热点之一。该文主要叙述了无线电掩星技术的数据处理系统的有关情况,并介绍了美国UCAR的掩星数据处理系统CDAAC的概况,可作为我国开展无线电掩星计划有关工作的借鉴。     

Lyman α radiative transfer in a multiphase medium

Hydrogen Lyman α (Lyα) is our primary emission-line window into high-redshift galaxies. Despite an extensive literature, Lyα radiative transfer in the most realistic case of a dusty, multiphase medium has received surprisingly little detailed theoretical attention. We investigate Lyα resonant scattering through an ensemble of dusty, moving, optically thick gas clumps. We treat each clump as a scattering particle and use Monte Carlo simulations of surface scattering to quantify continuum and Lyα surface scattering angles, absorption probabilities, and frequency redistribution, as a function of the gas dust content. This atomistic approach speeds up the simulations by many orders of magnitude, making possible calculations which are otherwise intractable. Our fitting formulae can be readily adapted for fast radiative transfer in numerical simulations. With these surface scattering results, we develop an analytic framework for estimating escape fractions and line widths as a function of gas geometry, motion, and dust content. Our simple analytic model shows good agreement with full Monte Carlo simulations. We show that the key geometric parameter is the average number of surface scatters for escape in the absence of absorption,     , and we provide fitting formulae for several geometries of astrophysical interest. We consider the following two interesting applications. (i) Equivalent widths ( EWs ). Lyα can preferentially escape from a dusty multiphase interstellar medium if most of the dust lies in cold neutral clouds, which Lyα photons cannot penetrate. This might explain the anomalously high EWs sometimes seen in high-redshift/submillimetre sources. (ii) Multiphase galactic outflows . We show the characteristic profile is asymmetric with a broad red tail, and relate the profile features to the outflow speed and gas geometry. Many future applications are envisaged.     

中性大气掩星标准反演技术

结合JPL和GFZ的中性大气标准反演算法，发展了上海天文台中性大气掩星标准反演算法流程．对CHAMP观测资料进行中性大气反演，并将反演结果与ECMWF(the European Center for Medium Range Weather Forecasting)的预报大气数据进行比较．作为讨论，指出将来的发展方向．     

设计模式及其在J2ME中的应用

设计模式被描述为在一定的环境中解决某一类问题的方案.已成为现代软件系统设计的重要研究对象.介绍了J2ME体系结构,并深入探讨了3种典型设计模式在J2ME开发中的应用.     

定点潮汐形变观测与GPS大地测量

论述了我国定点潮汐形变观测与GPS在观测周期，物理量，频域，实测精度，监测优势者方面的异同，认为定点潮汐形变观测是测震学与大地测量（含GPS）的必要补充，介绍了我国定点潮汐形变观测技术的发展与台网观测技术，以及它在我国10多次中强震测报中的应用。