华南沿海地区太阳直接辐射、能见度及大气气溶胶变化特征分析

分析了中国华南地区福州、广州、海口、南宁等地1961～1990年太阳直接辐射总量、日照时数、总云量、大气能见度和地面水汽压等资料,并利用这些资料反演了该地区大气气溶胶的光学厚度值。结果表明：近30年来,华南地区太阳直接辐射总量和日照时数呈明显下降趋势。与60年代相比,80年代各站太阳直接辐射总量的年平均值均下降20%以上,其中广州下降29.2%;日照时数,广州减少了1.1 h,福州1 h,南宁0.9 h,海口0.5 h。分析发现,造成下降的原因不是由于云量或大气中水汽含量的变化,而是由于地面能见度的明显减小和大气气溶胶的增加。4站中,14时地面能见度均以夏季最好,最高值出现在7月;而地面能见度最差的季节海口、南宁两站在冬季,福州和广州两站在春季3、4月份。相比较而言,海口能见度最好,福州和南宁次之,广州最差。4站大气气溶胶光学厚度值的大小、年及季节变化与地面能见度有密切的关系,但两者不尽一致,因此,在研究气溶胶的辐射和气候效应时必须合理地考虑中高层大气气溶胶的分布。     

Multi-Wavelength Synchrotron Radiation XRF Determination of U and Th in Sedimentary Cores from Lake Baikal

A new technique for the determination of uranium and thorium in lacustrine sediments is based on non-destructive synchrotron radiation X-ray fluorescence analysis (SR-XRF) of sediment samples using monochromatic beams of different energies as excitation sources, with the recording and subsequent iterative processing of the X-ray fluorescence spectra. The technique has a multielement capability and enables fast, simultaneous analysis of a few tens of elements. The proposed SR-XRF technique was tested against INAA and ICP-MS methods and showed a number of advantages with a generally good correlation of results by the three methods. Uranium and Th profiles have been measured at a time resolution of 2 kyr in a drill core (BDP-96) from Lake Baikal bottom sediments deposited between 780 and 40 kyr B P. During this time span, peaks in the U and U/Th concentration marked warm climates. Oscillations of U and U/Th in Baikal bottom sediments during the Brunhes chron reflect climate-induced global change in the volume of polar ice, controlled by long-term cyclicity of the Earths orbital parameters. The response of these warm periods is similar to that observed earlier in shorter cores that span the two last interglacials (220-0 kyr BP).     

沙尘气溶胶对直接太阳辐射的衰减研究

基于在腾格里沙漠东南端进行的太阳辐射与气象要素观测,探讨晴空无云时沙尘气溶胶对直接太阳辐射的衰减;并利用太阳辐射观测资料,给出沙漠边缘垂直上空的大气混浊度的变化。根据4月份至9月份的观测资料,只选取天空无云(可测的太阳辐射)的气象条件,研究沙尘气溶胶造成的直接太阳辐射的衰减。结果表明,在晴好天气约为47.0%~2.6%,平均衰减约为16.9%;在沙尘天气约为90%~10%,平均衰减约为38%;沙尘天气气溶胶对太阳辐射衰减变化较大。大气混浊度(atmospheric turbidity:τ_a)在晴好天气下约为0.048~0.631,平均约为0.260;沙尘天气约为0.177~2.475,平均约为0.741。     

近300a来古里雅与长江下游温度变化所受太阳活动、火山活动的影响分析

分析了近300a来古里雅冰芯δ¹⁸O值和长江下游温度变化与太阳活动、火山活动的关系.结果表明,无论在年际尺度,还是在10a尺度上,西昆仑山的古里雅冰芯和中国东部的长江下游地区的温度与以太阳辐照和太阳黑子周期长度为代用指标的太阳活动有良好的相关关系.火山活动对古里雅、合肥冬温和杭州春温有明显的降温作用.1810’s—1830’s时段不仅合肥冬温和杭州春温发生了剧烈的变化,而且处于高亚洲中西部的古里雅冰芯δ¹⁸O值也急剧下降,同时在北半球温度重建曲线上这一时段也是一个冷谷,表明该时段的气候变化可能具有全球性,而强烈的火山活动和微弱的太阳活动可能对温度的快速降低起触发作用。     

中国地区云对地气系统太阳短波吸收辐射强迫的气候研究

本文利用地球辐射平衡试验（ＥＲＢＥ）和国际卫星云气候计划（ＩＳＣＣＰ）提供的总云量、行星反射率资料,计算并分析了我国年、月平均云对地气系统太阳短波吸收辐射的强迫及其敏感性系数,揭示了它们之间的关系,最后绘制了地气系统短波辐射云强迫的全国分布图。结果表明：我国地气系统短波辐射云强迫及其敏感性系数都与总云量有较好的非线性相关,呈幂指数形式,且季节变化明显。短波辐射云强迫的地理分布与总量配合较好。     

紫外线指数及其预报技术介绍

对南宁市近7a来的紫外线辐射强度与太阳辐射总量、总云量、低云量的关系进行统计分析,建立了紫外线指数与太阳辐射总量之间的气候平均值对应关系,在此基础上,制作南宁市未来24h的紫外线指数预报,并根据预报结果提醒人们采取相应的防护措施,服务于社会公众.     

Evidence for solar forcing of climate variation from δ18O of peat cellulose

There have been a number of investigations for examining the possible link between long-term climate variability and solar activity. A continuous δ¹⁸O record of peat cellulose covering the past 6 000 years and the response of climate variation inferred from the proxy record to solar forcing are reported. Results show that during the past 5 000 years the abrupt climate variations, including 17 warming and 17 cooling, and a serious of periodicities, such as 86, 101, 110, 127, 132, 140, 155, 207, 245, 311, 820 and 1 050 years, are strikingly correlative to the changes of solar irradiation and periodicity. These observations are considered as further evidence for a close relationship between solar activity and climate variations on time scales of decades to centuries.     

岫岩—海城5.6级地震前电磁前兆变化特征

岫岩－海城５．６级地震前半年内,先后出现了义县地电阻率,台安地电阻率异常变化,这些异常信息也是该次地震成功预报和重要前兆判据之一。研究认为,震前的义县、台安地电阻异常属于“场兆”,而临震前的电磁辐射信息是“源兆”。同时,电阻率的异常变化显示出向震中迁移的特点。     

Relativistic anisotropic pair plasmas

The properties of waves able to propagate in a relativistic pair plasma are at the basis of the interpretation of several astrophysical observations. For instance, they are invoked in relation to radio emission processes in pulsar magnetospheres and to radiation mechanisms for relativistic radio jets. In such physical environments, pair plasma particles probably have relativistic, or even ultrarelativistic, temperatures. Besides, the presence of an extremely strong magnetic field in the emission region constrains the particles to one-dimensional motion: all the charged particles strictly move along magnetic field lines.
We take anisotropic effects and relativistic effects into account by choosing one-dimensional relativistic Jűttner–Synge distribution functions to characterize the distribution of electrons and/or positrons in a relativistic, anisotropic pair plasma. The dielectric tensor, from which the dispersion relation associated with plane wave perturbations of such a pair plasma is derived, involves specific coefficients that depend on the distribution function of particles. A precise determination of these coefficients, using the relativistic one-dimensional Jűttner–Synge distribution function, allows us to obtain the appropriate dispersion relation. The properties of waves able to propagate in anisotropic relativistic pair plasmas are deduced from this dispersion relation. The conditions in which a beam and a plasma, both ultrarelativistic, may interact and trigger off a two-stream instability are obtained from this same dispersion relation. Two astrophysical applications are discussed.     

The contribution of unresolved radio-loud AGN to the extragalactic diffuse gamma-ray background

We present a calculation of the blazar contribution to the extragalactic diffuse γ -ray background (EGRB) in the EGRET energy range. Our model is based on inverse-Compton scattering as the dominant γ -ray production process in the jets of flat spectrum radio quasars (FSRQs) and BL Lac objects, and on the unification scheme of radio-loud AGN. According to this picture, blazars represent the beamed fraction of the Fanaroff–Riley radio galaxies (FR galaxies).
The observed log  N –log  S distribution and redshift distribution of both FSRQs and BL Lacs constrain our model. Depending slightly on the evolutionary behaviour of blazars, we find that unresolved AGN underproduce the intensity of the extragalactic background radiation. With our model only 20–40 per cent of the extragalactic background emission can be explained by unresolved blazars if we integrate to a maximum redshift of Z _max=3. For Z _max=5, blazars could account for 40–80 per cent of the EGRB. Roughly 70–90 per cent of the AGN contribution to the EGRB would result from BL Lacs. While the systematic uncertainties in our estimate for the FSRQ contribution appear small, in the case of BL Lacs our model parameters are not consistent with the results from studies in other wavelength regimes, and therefore may have larger systematic uncertainties. Thus we end up with two possibilities, depending on whether we underpredict or overpredict the BL Lac contribution: either unresolved AGN cannot account for the entire EGRB, or unresolved BL Lacs produce the observed background.
We predict a significant flattening of the γ -ray log  N –log  S function in the next two decades of flux below the EGRET threshold.