夏季青藏高原及周边上对流层水汽质量及其向平流层传输年际异常. II：向平流层的绝热和非绝热传输

夏季7～8月青藏高原及周边地区上对流层水汽质量的年际异常分布为整体异常型和东西偶极异常型所主导。本文基于ERA-Interim再分析资料并利用HYSPLIT（Hybrid Single Particle Lagrangian Integrated Trajectory）轨迹模式,分析了两个主导分布型对应的水汽质量向平流层绝热和非绝热传输的异常特征,结果表明:青藏高原上空水汽质量整体偏多（少）时,对应南亚高压和青藏高原地区垂直向上的水汽质量非绝热输送偏强（弱）,青藏高原及周边水汽质量向平流层的绝热和非绝热传输均偏强（弱）。水汽质量整体偏多与偏少年,水汽质量向平流层绝热和非绝热传输的主要区域和层次相近,只是水汽质量整体偏多年,水汽质量向平流层非绝热传输的层次略高。当青藏高原上空水汽质量呈西多/东少分布时,对应南亚高压偏西,青藏高原西北、东北侧水汽质量向中纬度平流层的绝热传输偏强,青藏高原南侧高层水汽质量向热带平流层的经向绝热传输也偏强,而青藏高原北侧水汽质量向中纬度平流层的经向绝热传输明显减弱。同时青藏高原主体上空水汽质量向平流层的非绝热传输偏强,而青藏高原南侧高层和北侧低层水汽质量向平流层的非绝热传输偏弱。水汽质量呈西少/东多分布时有相反的结果。轨迹模式模拟的结果证实了水汽质量整体偏多年,青藏高原及周边地区绝热进入平流层的轨迹频次偏多;也证实了水汽质量呈西多/东少分布时,青藏高原西北、东北和南侧绝热进入平流层的轨迹频次偏多,而青藏高原北侧绝热进入平流层的轨迹频次偏少。     

冰云光学特性与等效球Mie理论的误差分析

用改进的射线光学理论和等效球Ｍｉｅ理论，计算了若干冰晶和冰晶尺度分布在太阳光谱区中一系列波长上的光学特性和散射特性，详细分析了Ｍｉｅ散射计算的误差，并假定冰云光学特性有１０％误差的情况下，用Ｄｅｌｔａ－Ｅｄｄｉｎｇｔｏｎ近似对所引起的冰云辐射特性的误差进行了数值试验。结果表明，沿用已久的等效球Ｍｉｅ理论因计算冰云光学特性在波长小于２．６μｍ波段误差过大，将引起冰云辐射特性有显著误差，最后提出了计算冰云光学特性的新方案。     

Heavy Element Enrichment in the Intergalactic Medium for Large Red Shifts

A simple model for heavy element enrichment in the intergalactic medium is examined. The dependence of the heavy element abundance in the intergalactic medium on star formation processes in primary galaxies is studied. The results are in agreement with observational data on the abundance of heavy elements in L _a-clouds.     

The Rôle Of Astrochemistry In Low Mass Star Formation

Molecular processes play both active and passive/diagnostic rôles in the process of star formation. Various molecular behaviours can be identified in star-forming regions with the result that different molecular species can be used to constain different aspects of the infall process, such as the density structures, the kinematics and the evolutionary history of star-forming cores. The main limitations in the chemical analysis of infall sources arise from poorly constrained boundary conditions; in particular the chemical and physical initial conditions are usually very uncertain. The most promising application of astrochemical modelling is probably in the analysis of the infall dynamics through combined chemical/radiative transfer modelling of molecular emission line profiles.     

Observations of the infrared source in s 140 and the heating of the associated gas

Near infrared observation of the infrared source in S140 was made using the 1.26 m infrared telescope of Beijing Observatory, yielding fluxes in the J, H and K bands. Combining with data from satellite and ground-based IR and submillimetre observations, we found the spectral gradient, IR luminosity and the shell structure of the IR source.

We also combined observations of CO and NH₃ in an analysis of the heating of the gas associated with the source. Besides through dust, the central source may also input energy into the gas through shock waves. External sources of heat and heating by photoelectric process and cosmic rays are also discussed.     

Instabilities in two-fluid magnetized media with inter-component drift

We analyse the stability of a magnetized medium consisting of a neutral fluid and a fluid of charged particles, coupled to each other through a drag force and exposed to differential body forces (for example, as the result of radiation forces on one phase). We consider a uniform equilibrium and simple model input physics, but do not arbitrarily restrict the relative orientations of the magnetic field, slip velocity and wavevector of the disturbance. We find several instabilities and classify these in terms of wave resonances. We briefly apply our results to the structure of SiO maser regions appearing in the winds from late-type stars.