Nonlinear models of pulsation and mass loss

We briefly discuss the current status of our radiation-hydrodynamical models of pulsation in various stellar objects and of dust-driven mass loss in LPVs. We emphasize the importance of a future combined modelling of pulsation and mass loss in AGB stars which has to be based on reliable physical and numerical methods.     

Determination of origin of NASA stratospheric particles

Paper presents a reanalysis of four stratospheric particles registered in the Cosmic Dust Catalogs (CDC). Two particles have been classifed in the NASA Johnson Space Centre (JSC) in Houston as natural, terrestrial contaminants and the origin of the other two particles was found questionable, probably cosmic. Present study has confirmed these conclusions; however some new additional features in the chemical analysis have been found which can finally determine the classification of the particles with unclear origin.     

LAMOST望远镜的大气色散校正

大气折射与大气色散会影响大视场多目标光纤光谱观测的质量和效率.一个焦距为20m,焦比为F5、位于北纬40.4°的LAMOST望远镜在中天和中天前后0.75小时产生的色散值,用模拟计算得到结果,并用数值计算得到验证.对校正色散可能用的几种色散棱镜进行了计算分析比较,确定了色散棱镜的型式,并分析了色散棱镜的二级光谱以及色散棱镜在望远镜跟踪过程中的残留色散,及色散棱镜的安装误差.     

Improvements for group delay fringe tracking

Group delay fringe tracking using spectrally dispersed fringes is suitable for stabilizing the optical path difference in ground-based astronomical optical interferometers in low light level situations. We discuss the performance of group delay tracking algorithms when the effects of atmospheric dispersion, high-frequency atmospheric temporal phase variations, non-ideal path modulation, non-ideal spectral sampling, and the detection artifacts introduced by electron-multiplying CCDs are taken into account, and we present ways in which the tracking capability can be optimized in the presence of these effects.     

Magnetic measurements of recent sediments from Big Moose Lake,Adirondack Mountains,N.Y., USA

Measurements of anhysteretic (ARM) and isothermal (IRM) remanences in cores 6 and 8 from Big Moose Lake reveal evidence for changes in magnetic mineralogy and grain size within and between the two cores. It is proposed that changes in the strength and demagnetization characterizations of the IRM reflect the accumulation of atmospherically deposited magnetic minerals resulting from industrial processes. The record of magnetite deposition especially in Core 6 parallels that for coal soot at the site. In both cores, the record of haematite deposition parallels that for several anthropogenic indicators.This is the fourth of a series of papers to be published by this journal which is a contribution of the Paleoecological Investigation of Recent Lake Acidification (PIRLA) project. Drs. D. F. Charles and D. R. Whitehead are guest editors for this series.     

2017年12月大气环流和天气分析

2017年12月大气环流的主要特征如下：北半球极涡呈偶极型分布,欧亚中高纬环流呈两槽一脊型;南支槽位于70°E 附近,较常年同期偏西,副热带高压位置偏西,不利于水汽向我国中东部地区输送。12月,全国平均降水量为5.9 mm,比常年同期（10.8 mm）偏少44.8%,我国北方大部分地区降水量较常年同期偏少4~8成。全国平均气温-2.2℃,较常年同期（-3.2℃）偏高1℃;受偏强东北低涡影响,东北地区和内蒙古中东部气温较常年同期偏低1~3℃。月内,冷空气活动频繁,但强度较弱,出现5次一般强度冷空气过程。受频繁冷空气影响,雾 霾天气较常年同期偏少,仅28—30日出现一次大范围持续性雾 霾天气。     

塔克拉玛干沙漠腹地气溶胶不同波段散射系数比较

利用2010年塔克拉玛干沙漠腹地塔克拉玛干沙漠大气环境观测试验站(下文简称"塔中")多波段(450、525、635 nm)积分浊度计和PM_(10)自动监测仪观测资料,并结合塔中地面气象观测资料,分析了沙漠腹地不同波段气溶胶散射系数的变化特征。分析结果显示:(1)塔中气溶胶对635 nm太阳辐射的散射作用最大,其次是525 nm,最小为450 nm。三波段(450、525、635 nm)散射系数平均值分别为:288.0、318.4、443.8 Mm~(-1)。(2)三波段散射系数日变化与PM_(10)质量浓度一致,都呈单峰变化:夜间高、白天低。在日变化中,散射系数始终保持635 nm最大,525 nm次之,450 nm最小。(3)三波段散射系数年变化基本一致,都与PM_(10)变化接近。1—5月中,除3月散射系数是450 nm最大外,另外4个月均是635 nm最大,450 nm次之,525 nm最小。6—12月散射系数都是635 nm最大,525 nm次之,450 nm最小。(4)三波段散射系数均是沙尘暴下最大,扬沙次之,浮尘最小。不同沙尘天气下,塔中气溶胶对635 nm散射作用都是最明显的,对450 nm和525nm散射作用不同:沙尘暴时,对525 nm的散射强于450 nm,在扬沙和浮尘时,对450 nm的散射强于525 nm,尤其在浮尘时。(5)三波段散射系数与PM_(10)质量浓度都呈显著正相关,PM_(10)质量浓度与525 nm散射系数相关程度最大,450 nm次之,635 nm最小。但是季节内相关程度略有差异:春、冬季PM_(10)浓度与450 nm散射系数相关程度最大,525 nm次之,635 nm最小。夏、秋季则是525nm最大。     

非洲地区大气气溶胶光学厚度时空变化及亚速尔高压对沙尘越大西洋传输的影响

研究了非洲地区大气气溶胶光学厚度（AOD）的时空变化及沙尘气溶胶越大西洋海区的传输。结果表明：1）源于撒哈拉沙漠的沙尘及其随赤道东风向西输送使得沙尘气溶胶成为非洲沙漠地区和紧邻的大西洋海区的主要气溶胶组分;AOD高值区和沙尘气溶胶光学厚度高值区在1—7月随赤道辐合带北移同步向北移动,而在8—12月则向南回撤。2）刚果盆地大气气溶胶主要为热带雨林和稀树草原排放的有机碳（OC）和黑碳（BC）气溶胶;其中与生物质燃烧源排放有关的OC、BC高值主要集中在干季（6—9月）的后半段（8—9月）;而生物源OC排放全年连续,其排放峰值出现于雨季开始时;生物质燃烧排放高值期与生物源排放高值期前后相继,形成干季（尤其是后半段）时期的OC、BC光学厚度高值。3）亚马逊河入海口地区主要气溶胶组分为海盐气溶胶,9—11月该区风力输送增强,风向由东南风转变为东风,海盐进入亚马逊河入海口处,形成AOD和海盐气溶胶光学厚度高值区。4）撒哈拉沙漠沙尘气溶胶向大西洋传输的偏北月份为7—9月、偏南月份为1—3月;2000—2016年海区沙尘气溶胶的传输路径存在向南移动的变化趋势,与同期亚速尔高压的增强和沙尘传输路径以北北风分量的增强以及赤道辐合带的移动一致。上述研究结果揭示了利用大气气溶胶时空变化特征反映区域大气环流和气候变化的可能性。