Quasi-periodicity of temperature changes on the millennial scale

Quasi-periodicity of temperature changes on the millennial scale is found according to the proxy data both from historical documents and natural evidence in China. The auto-correlation of the temperature changes series for the last 2000 years is most significant on the 1350 a time lag. The period of 1350 a includes 4 warm/cold stages: 200～250 a warm stage, 150～200 a cold stage, 300～350 a warm stage, and 550～600 a cold stage. In contrast to the 550～600 a cold stage, the other three stages can be united in one warm dominant stage. Inferred from the 1350 a period, the 20th century warm stage belongs to the 200～250 a warm stage, which is similar to the warm stage occurring during the 570's～770's. The process of temperature change in the 20th century warm stage is similar to that of the 570's～770's. But the warming rate in the 20th century is more rapid. The temperature anomaly in the 1980's～1990's shows a greater departure from the regression equation of that between 1500's～1900's and 150's～650's. Whether it can be regarded as the forcing of human activities is worth studying further.     

Synchronicity of Antarctic temperatures and local solar insolation on orbital timescales

The Milankovitch theory states that global climate variability on orbital timescales from tens to hundreds of thousands of years is dominated by the summer insolation at high northern latitudes. The supporting evidence includes reconstructed air temperatures in Antarctica that are nearly in phase with boreal summer insolation and out of phase with local summer insolation. Antarctic climate is therefore thought to be driven by northern summer insolation. A clear mechanism that links the two hemispheres on orbital timescales is, however, missing. We propose that key Antarctic temperature records derived from ice cores are biased towards austral winter because of a seasonal cycle in snow accumulation. Using present-day estimates of this bias in the 'recorder' system, here we show that the local insolation can explain the orbital component of the temperature record without having to invoke a link to the Northern Hemisphere. Therefore, the Antarctic ice-core-derived temperature record, one of the best-dated records of the late Pleistocene temperature evolution, cannot be used to support or contradict the Milankovitch hypothesis that global climate changes are driven by Northern Hemisphere summer insolation variations.     

夏季北太平洋副热带高压年际变化的特征时间尺度及其时空演变

 应用三维数据的时间小波变换方法分析研究了夏季北太平洋副热带高压年际变化的特征时间尺度及其时空演变.结论为:夏季北太平洋副热带高压年际变化的特征时间尺度分别约为2,5 a和更大的时间尺度;2 a和5 a特征时间尺度的最大振幅能量活动中心分别位于北太平洋西部的(27.5°N,135°E)附近和北部的(35°N,167.5°E)附近;其相应的最大振幅能量活动中心在纬向上表现出了明显的东西向波动的时间演变特征;在经向上则表现出了明显的阶段性和较小振幅的南北向波动的时间演变特征;从较长时间的长期演变来看,5a特征时间尺度的最大振幅能量活动中心的位置有一种向南移动的趋势.     

Constraints on future changes in climate and the hydrologic cycle

What can we say about changes in the hydrologic cycle on 50-year timescales when we cannot predict rainfall next week? Eventually, perhaps, a great deal: the overall climate response to increasing atmospheric concentrations of greenhouse gases may prove much simpler and more predictable than the chaos of short-term weather. Quantifying the diversity of possible responses is essential for any objective, probability-based climate forecast, and this task will require a new generation of climate modelling experiments, systematically exploring the range of model behaviour that is consistent with observations. It will be substantially harder to quantify the range of possible changes in the hydrologic cycle than in global-mean temperature, both because the observations are less complete and because the physical constraints are weaker.     

Effects of historical land cover changes on climate

In order to explore the influence of anthropogenic land use on the climate system during the last mil- lennium, a set of experiments is performed with an Earth system model of intermediate complexity—— the McGill Paleoclimate Model (MPM-2). The present paper mainly focuses on biogeophysical effects of historical land cover changes. A dynamic scenario of deforestation is described based on changes in cropland fraction (RF99). The model simulates a decrease in global mean annual temperature in the range of 0.09-0.16℃, especially 0.14-0.22℃ in Northern Hemisphere during the last 300 years. The responses of climate system to GHGs concentration changes are also calculated for comparisons. Now, afforestation is becoming an important choice for the enhancement of terrestrial carbon sequestration and adjustment of regional climate. The results indicate that biogeophysical effects of land cover changes cannot be neglected in the assessments of climate change.     

35 ka BP climate simulations in East Asia and probing the mechanisms of climate changes

Interglacial or postglacial climates are all of charac-teristic of warmer conditions. However, if condition asso-ciated with the warm feature is wetter or drier than today,it would produce different impacts on natural environ-ments and human society. Quaternary studies found thatclimate with warm-dry or warm-wet conditions had oc-curred in China during the last 40—30 ka BP[1]. For ex-ample, it was warmer than the present during themid-Holocene (3—8 ka BP) and the late phases of MarineIsot…     

气候变化对挠力河径流量的影响

利用Mann Kendall突变检验法分别分析了1956—2005年50年来的宝清站和菜嘴子站年平均径流量演变的阶段性特征,并建立了径流 降雨的经验模型,利用该模型分析了气候变化和人类活动对径流的影响.研究结果表明：50年来宝清站和菜嘴子站的年平均径流量演变可分为两个阶段:1956—1967年的基准期和1968—2005年的变化期.变化期内径流量的年际和年内都发生了较大变化,体现在年平均径流量减少显著,两个站的年平均径流量减少量都在50%左右.径流变差系数有不同程度的增长,其中菜嘴子站增长了近30%.年内分配变化主要体现在径流峰值上,菜嘴子站的夏季径流峰值和最低值的出现时间都较第一阶段提前了一个月.变化期内年均径流量的变化主要是由人类活动引起的,气候变化引起的径流量变化占年均径流量总变化量的40%左右.     

Decadal to monthly timescales of magma transfer and reservoir growth at a caldera volcano

Caldera-forming volcanic eruptions are low-frequency, high-impact events capable of discharging tens to thousands of cubic kilometres of magma explosively on timescales of hours to days, with devastating effects on local and global scales. Because no such eruption has been monitored during its long build-up phase, the precursor phenomena are not well understood. Geophysical signals obtained during recent episodes of unrest at calderas such as Yellowstone, USA, and Campi Flegrei, Italy, are difficult to interpret, and the conditions necessary for large eruptions are poorly constrained. Here we present a study of pre-eruptive magmatic processes and their timescales using chemically zoned crystals from the 'Minoan' caldera-forming eruption of Santorini volcano, Greece, which occurred in the late 1600s BC. The results provide insights into how rapidly large silicic systems may pass from a quiescent state to one on the edge of eruption. Despite the large volume of erupted magma (40-60 cubic kilometres), and the 18,000-year gestation period between the Minoan eruption and the previous major eruption, most crystals in the Minoan magma record processes that occurred less than about 100 years before the eruption. Recharge of the magma reservoir by large volumes of silicic magma (and some mafic magma) occurred during the century before eruption, and mixing between different silicic magma batches was still taking place during the final months. Final assembly of large silicic magma reservoirs may occur on timescales that are geologically very short by comparison with the preceding repose period, with major growth phases immediately before eruption. These observations have implications for the monitoring of long-dormant, but potentially active, caldera systems.     

Global warming and climate forcing by recent albedo changes on Mars

For hundreds of years, scientists have tracked the changing appearance of Mars, first by hand drawings and later by photographs. Because of this historical record, many classical albedo patterns have long been known to shift in appearance over time. Decadal variations of the martian surface albedo are generally attributed to removal and deposition of small amounts of relatively bright dust on the surface. Large swaths of the surface (up to 56 million km2) have been observed to darken or brighten by 10 per cent or more. It is unknown, however, how these albedo changes affect wind circulation, dust transport and the feedback between these processes and the martian climate. Here we present predictions from a Mars general circulation model, indicating that the observed interannual albedo alterations strongly influence the martian environment. Results indicate enhanced wind stress in recently darkened areas and decreased wind stress in brightened areas, producing a positive feedback system in which the albedo changes strengthen the winds that generate the changes. The simulations also predict a net annual global warming of surface air temperatures by approximately 0.65 K, enhancing dust lifting by increasing the likelihood of dust devil generation. The increase in global dust lifting by both wind stress and dust devils may affect the mechanisms that trigger large dust storm initiation, a poorly understood phenomenon, unique to Mars. In addition, predicted increases in summertime air temperatures at high southern latitudes would contribute to the rapid and steady scarp retreat that has been observed in the south polar residual ice for the past four Mars years. Our results suggest that documented albedo changes affect recent climate change and large-scale weather patterns on Mars, and thus albedo variations are a necessary component of future atmospheric and climate studies.     

旋转对超新星塌缩时标的影响

基于超新星前身型模型WS15M⊙,详细计算了在一维球对称未旋转条件和旋转条件下的流体动力学时标和电子俘获时标,进行了比较,发现在形成激波前很短时间内电子俘获时标将小于流体动力学时标,这种差异在旋转的星体下更为明显.计算结果支持了新近提出一种超新星爆发图像,可能对超新星的爆发机制研究有新的影响.       

Decadal changes of the wintertime tropical tropospheric temperature and their influences on the extratropical climate

Science Bulletin - A decadal change of the tropical tropospheric temperature (TT) was identified to occur in the winter of 1997. Compared with that in the former period (1979–1996), the...     

荒漠化扩展对我国区域气候变化影响的数值模拟

使用区域气候模式RegCM3研究了西北沙漠面积变化对我国区域气候变化的影响．共设计了3组试验：控制试验A、沙漠面积扩展试验B、在试验B基础上增大粗糙高度的试验C．分析表明：中国西北沙漠区扩展后对中国夏季降雨量和中国夏季风有明显影响．结果表明：植被退化、荒漠化加剧会导致季风减弱,降水量减少,增大地面粗糙高度后的影响更为显著．     

对黄土高原生态恢复和重建的相关问题探讨

介绍了黄土高原生态的现状,论述了黄土高原生态恢复和重建的理论及实践问题,提出黄土高原生态恢复和重建应采取的措施。     

气候变迁与中国战争史之间的关系综述

气候是政治命运的影响因素之一,在中国近5000a的历史中,气候共经历了4次寒冷期和数次暖期中的短暂冷期．气候的突变,特别是气候变冷给农业社会带来巨大的打击,从而成为战争爆发的导火索．通过对气候变迁以及中国战争史的叠加研究,发现战争的发生和气候变迁存在着很大的关联．     

伽玛暴微光变特征时标研究

伽玛暴光变曲线一般由若干个脉冲组成的“大轮廓”叠加着一些微光变组成的,大部分伽玛暴光变曲线没有呈现周期性,而这些微光变成分可能携带重要的辐射区性质.采用平滑滤波器把伽玛暴光变曲线中的“大轮廓”成分和微光变成分分离,然后采用“最大熵”功率谱密度估算法计算微光变信号的功率谱密度,并分析其周期特征时标.文中分析了Swift/...     

全球气候变化对中国北方地区沙漠化的影响

阐述了沙漠化有关概念,在全球气侯变化下沙漠化正逆演替进程与全球气候系统之间存在着双向耦合关系,二者相互制约.但这种关系具有不确定性,有待进一步研究.     

河西走廊历史时期气候干湿状况变迁考略

检索整理了河西走廊史载以来的气候旱涝资料，采用湿润指数公式进行处理分析；探讨了该地区历史上气候干湿状况变迁的概貌     

气候变化的趋势、原因、影响及对策

百余年来，世界气候已发生了明显的变化，气候异常和气象灾害接连出现，人类的生存环境正面临着巨大的挑战。本文尽可能多地采用最新的资料和研究成果，深刻剖析全球气候变化的基本原因和严重后果。文末关于气候变化问题的对策，可做为政府部门制定规划与对策的依据。