Northern Hemisphere forcing of climatic cycles in Antarctica over the past 360,000 years

The Milankovitch theory of climate change proposes that glacial-interglacial cycles are driven by changes in summer insolation at high northern latitudes. The timing of climate change in the Southern Hemisphere at glacial-interglacial transitions (which are known as terminations) relative to variations in summer insolation in the Northern Hemisphere is an important test of this hypothesis. So far, it has only been possible to apply this test to the most recent termination, because the dating uncertainty associated with older terminations is too large to allow phase relationships to be determined. Here we present a new chronology of Antarctic climate change over the past 360,000 years that is based on the ratio of oxygen to nitrogen molecules in air trapped in the Dome Fuji and Vostok ice cores. This ratio is a proxy for local summer insolation, and thus allows the chronology to be constructed by orbital tuning without the need to assume a lag between a climate record and an orbital parameter. The accuracy of the chronology allows us to examine the phase relationships between climate records from the ice cores and changes in insolation. Our results indicate that orbital-scale Antarctic climate change lags Northern Hemisphere insolation by a few millennia, and that the increases in Antarctic temperature and atmospheric carbon dioxide concentration during the last four terminations occurred within the rising phase of Northern Hemisphere summer insolation. These results support the Milankovitch theory that Northern Hemisphere summer insolation triggered the last four deglaciations.     

Regional insolation forcing of late Quaternary climate change in the Southern Hemisphere

In agreement with the Milankovitch orbital forcing hypothesis it is often assumed that glacial-interglacial climate transitions occurred synchronously in the Northern and Southern hemispheres of the Earth. It is difficult to test this assumption, because of the paucity of long, continuous climate records from the Southern Hemisphere that have not been dated by tuning them to the presumed Northern Hemisphere signals. Here we present an independently dated terrestrial pollen record from a peat bog on South Island, New Zealand, to investigate global and local factors in Southern Hemisphere climate changes during the last two glacial-interglacial cycles. Our record largely corroborates the Milankovitch model of orbital forcing but also exhibits some differences: in particular, an earlier onset and longer duration of the Last Glacial Maximum. Our results suggest that Southern Hemisphere insolation may have been responsible for these differences in timing. Our findings question the validity of applying orbital tuning to Southern Hemisphere records and suggest an alternative mechanism to the bipolar seesaw for generating interhemispheric asynchrony in climate change.     

Highly variable Northern Hemisphere temperatures reconstructed from low- and high-resolution proxy data

A number of reconstructions of millennial-scale climate variability have been carried out in order to understand patterns of natural climate variability, on decade to century timescales, and the role of anthropogenic forcing. These reconstructions have mainly used tree-ring data and other data sets of annual to decadal resolution. Lake and ocean sediments have a lower time resolution, but provide climate information at multicentennial timescales that may not be captured by tree-ring data. Here we reconstruct Northern Hemisphere temperatures for the past 2,000 years by combining low-resolution proxies with tree-ring data, using a wavelet transform technique to achieve timescale-dependent processing of the data. Our reconstruction shows larger multicentennial variability than most previous multi-proxy reconstructions, but agrees well with temperatures reconstructed from borehole measurements and with temperatures obtained with a general circulation model. According to our reconstruction, high temperatures--similar to those observed in the twentieth century before 1990--occurred around ad 1000 to 1100, and minimum temperatures that are about 0.7 K below the average of 1961-90 occurred around ad 1600. This large natural variability in the past suggests an important role of natural multicentennial variability that is likely to continue.     

自由落体东偏南偏的讨论

本文在计算和讨论自由落体的东偏和南偏时,考虑了惯性离心力和科里奥利力．结果表明：由惯性离心力引起的南偏要比科里奥利力引起的南偏大的多．而落体的东偏则主要是由科里奥利力引起的．     

Reconstruction of the Northern Hemisphere temperature from 1500 to 1949 by optimal regional averaging method

The rareness and inhomogeneity of the data points cause difficulties in the reconstruction of past average temperature. Optimal regional averaging is a method that can overcome these difficulties and obtain the average temperature of target area by means of optimal weights using limited temperature data. In this paper, the average temperature in the Northern Hemisphere is calculated by the optimal regional averaging method using two types of data： temperature data from Climatic Research Unit from 1901 to 2000 and maximum latewood density dataset of tree from 1500 to 1949. Five, ten, fifteen data points from CRU and forty data points from MXD are used in our research. The results show that even with the relatively less data used in this reconstruction, the method allows the reconstruction of the average temperature of the Northern Hemisphere more accurately, which provides the temperature information for palaeoclimate reconstruction.     

北半球斜上抛体的运动方程

给出了同时考虑地球自转和空气阻力两种影响并当空气阻力与抛体速度的一次方成正比时北半球斜上抛体运动方程的精确解。     

High-resolution record of Northern Hemisphere climate extending into the last interglacial period

Two deep ice cores from central Greenland, drilled in the 1990s, have played a key role in climate reconstructions of the Northern Hemisphere, but the oldest sections of the cores were disturbed in chronology owing to ice folding near the bedrock. Here we present an undisturbed climate record from a North Greenland ice core, which extends back to 123,000 years before the present, within the last interglacial period. The oxygen isotopes in the ice imply that climate was stable during the last interglacial period, with temperatures 5 degrees C warmer than today. We find unexpectedly large temperature differences between our new record from northern Greenland and the undisturbed sections of the cores from central Greenland, suggesting that the extent of ice in the Northern Hemisphere modulated the latitudinal temperature gradients in Greenland. This record shows a slow decline in temperatures that marked the initiation of the last glacial period. Our record reveals a hitherto unrecognized warm period initiated by an abrupt climate warming about 115,000 years ago, before glacial conditions were fully developed. This event does not appear to have an immediate Antarctic counterpart, suggesting that the climate see-saw between the hemispheres (which dominated the last glacial period) was not operating at this time.     

1998年夏季北半球斜压波活动与长江流域洪涝灾害分析

对流层上层的斜压波、高空槽对天气的变化有重要的影响。1998年夏季我国出现了大范围的天气异常，在长江流域发生了20世纪第二大的全流域性洪水，分析了1998年夏季北半球的西风急流、风暴轴、以及对流层上的斜压波活动与气候平均情况的异同，并揭示了1998年夏季北半球斜压波活动传播的主要区域、斜压波活动的持续性、斜压波向传播的速度以及斜压波传播时所具有的明显的下游效应。1998年夏季北半球的波包 次数共有11次，与夏季气候状况相比属于正常偏多，其中5月和8月的波包活动次数稍多。但更为明显的一个特点就是在7月中旬到8月上旬大西洋－欧洲的斜压波包活动比往年集中频繁，而且持续时间偏长， 为造成我国异常梅雨天气和长江流域洪涝灾害的乌拉尔阻塞高压的发展和维持提供了能量支持，同时为长江流域以及同期我国东北的大范围降雨提供了有利的水汽输送条件。最后分析了地面气旋生成与斜压波、高空槽之间的联系，指出在大多数向东部发展的高空槽的槽前，地面上有对应气旋地生成。     

2010年夏季北半球气温异常偏高现象及其成因

利用常规气象观测资料、NCEP/NCAR再分析资料,对2010年夏季6-8月北半球异常高温现象进行了分析.结果表明,夏季北半球大部分地方地面气温偏高,局部地区气温异常偏高,地而气温距平值达+6℃;北半球对流层平均气温正距平值达近30年以来最大值,并且各月平均气温异常偏高的区域,在对流层各层次都表现为一致的偏高;北半球对...     

Role of Ferrel cell in daily variability of Northern Hemisphere Annular Mode

The Northern Hemisphere Annular Mode(NAM) represents the zonally symmetric planetary-scale atmospheric mass fluctuations between middle and high latitudes, whose variations have shown a large impact on other components of the climate system. Previous studies have indicated that the NAM is correlated with the Ferrel cell in their monthly or longer timescale variability.However, there have been few studies investigating their connections at daily timescale, though daily variability of NAM has been suggested to be an important component and has significant implication for weather forecast. The results from this study demonstrate that variability of the Ferrel cell leads that of the NAM by about 1–2 days. This statistically identified temporal phase difference between NAM and Ferrel cell variability can be elucidated by meridional mass redistribution. Intensified(weakened)Ferrel cell causes anomalously smaller(larger) poleward mass transport from the middle to the high latitudes,resulting in an increase(a decrease) in mass in the middle latitudes and a decrease(an increase) in the high latitudes.As a consequence, anomalously higher(lower) poleward pressure gradient forms and the NAM subsequently shifts to a positive(negative) phase at a time lag of 1–2 days. The findings here would augment the existing knowledge for better understanding the connection between the Ferrel Cell and the NAM, and may provide skillful information for improving NAM as well as daily scale weather prediction.     

北半球不同强度、生命期阻塞高压的变化特征及其对温度的影响

分析了1968-2010年北半球阻塞高压频发区不同强度、生命期阻高的变化特征,从阻高强度和阻高生命期两方面分析阻高多发年、少发年与北半球地表温度的关系,结果显示:北半球的3个阻高频发区中,大西洋地区阻高出现总次数最多,太平洋地区次之,欧亚区最少;从阻高强度来看,3个阻高频发区强阻高次数均有减少趋势,以大西洋区最为显著,弱强度阻高变化趋势不明显;对于阻高生命期,长生命期阻高发生次数在21世纪以前变化不大,但近10年增加明显,短生命期阻高发生次数只有大西洋区在减少.大西洋区强阻高中长生命期阻高占25%,而太平洋区仅为14%,阻高强度越强时,出现长生命期阻高的概率也就越大.不同强度、生命期阻高对温度的影响差异显著.3个阻高频发区的长生命期阻高多发年与少发年温度差值的负异常区主要分布在中低纬度地区,而正异常区主要在高纬度地区;大西洋区、太平洋区长生命期阻高在多发年引起中低纬度地区的降温及高纬度地区的增温比强阻高产生的影响显著.     

Carbon dioxide release from the North Pacific abyss during the last deglaciation

Atmospheric carbon dioxide concentrations were significantly lower during glacial periods than during intervening interglacial periods, but the mechanisms responsible for this difference remain uncertain. Many recent explanations call on greater carbon storage in a poorly ventilated deep ocean during glacial periods, but direct evidence regarding the ventilation and respired carbon content of the glacial deep ocean is sparse and often equivocal. Here we present sedimentary geochemical records from sites spanning the deep subarctic Pacific that--together with previously published results--show that a poorly ventilated water mass containing a high concentration of respired carbon dioxide occupied the North Pacific abyss during the Last Glacial Maximum. Despite an inferred increase in deep Southern Ocean ventilation during the first step of the deglaciation (18,000-15,000 years ago), we find no evidence for improved ventilation in the abyssal subarctic Pacific until a rapid transition approximately 14,600 years ago: this change was accompanied by an acceleration of export production from the surface waters above but only a small increase in atmospheric carbon dioxide concentration. We speculate that these changes were mechanistically linked to a roughly coeval increase in deep water formation in the North Atlantic, which flushed respired carbon dioxide from northern abyssal waters, but also increased the supply of nutrients to the upper ocean, leading to greater carbon dioxide sequestration at mid-depths and stalling the rise of atmospheric carbon dioxide concentrations. Our findings are qualitatively consistent with hypotheses invoking a deglacial flushing of respired carbon dioxide from an isolated, deep ocean reservoir, but suggest that the reservoir may have been released in stages, as vigorous deep water ventilation switched between North Atlantic and Southern Ocean source regions.     

北半球中低纬大气太阴潮汐对Es层的影响

本文采用中低纬度数个台站的数字测高仪观测数据分析了Es层参数的大气太阴半日变化,结果表明:Es的临界频率(foEs)、遮蔽频率(fbEs)及虚高(h-Es)中均存在太阴半日周期的振荡.foEs和fbEs的太阴半日潮日变化及季节变化趋势非常相似,只是foEs太阴半日潮的幅度大干fbEs太阴半日潮的幅度,两者的相位几乎无差值.中低纬5个台站Es层参数的太阴半日潮幅度和相位的日变化值、季节变化值均不同,随纬度变化.foEs和h'Es的太阴半日潮存在年变化,在不同年份的相同月份,Es太阴半日潮的幅度和相位均有不同.值得提出的是我们还发现武汉foEs和h'Es的太阴半日潮最大值和武汉中层和低热层大气太阴半日潮汐风最大值出现的月份相同.     

SHRIMP U-Pb zircon dating for Qiashikansayi granodiorite, the Northern Altyn Tagh Mountains and its geological implications

The Qiashikansayi granodiorite is foliated resulting in a granodioritic gneiss. Its geochemical features, such as alumina saturation index(A/CNK) of 0.81-0.99, Na2O/K2O values>1, TiO2 contents <1.0%, LREE enrichment with high fractionation factors, weakly negative or no Eu anomalies, and significant Ba and Ti negative anomalies, suggest that it is similar to a typical island arc pluton. The trace elements of the Qiashikansayi granodiorite are plotted in the island arc field in the tectonic setting discrimination diagrams as well. Cathodoluminescence images demonstrated that the zircons have clear rhythmic crystallized zoning, without any remnant core and new crystallized rim, suggesting the zircons be magmatic ones. Their U and Th contents vary in the range of 574-870 μg/g, and 279-556μg/g respectively, with the Th/U ratio in the range of 0.52-0.68. SHRIMP zircon U-Pb dating yielded the 481.5±5.3 Ma age for the intrusion of the granodiorite, which is coeval with the island arc volcanic rocks in the no     

对北半球自由落体东偏南偏的计算

本文在地心参照系下求出了北半球自由落体东偏和南偏的大小，结果表明：南偏值主要与ω的二次方有关，而东偏值主要与ω的一次方有关．     

浙江梅雨分型与梅汛期前期北半球大气环流演变关系研究

对1971-1999年浙江省梅雨的空间分布进行客观分型,研究各种雨型前期500hPa高度场的相应变化特征,初步提示历年梅雨雨型与其前期高空环流中预兆因子的关系。结果表明,前期冬季春季环流变化特征的异同是导致梅雨型各自特点的重要原因。通过对3种梅雨型一些重要环流前兆因子的分析研究,发现前冬500hPa高度场上低纬度为正异常或负异常是导致次年浙江省梅雨期北部少梅或多梅的最显著的前兆,而春季南亚到西太平洋的负距平区发展强弱情况则是预报该年浙江省西南部是否出现少梅的重要判据之一。     

Global estimate of aerosol direct radiative forcing from satellite measurements

Atmospheric aerosols cause scattering and absorption of incoming solar radiation. Additional anthropogenic aerosols released into the atmosphere thus exert a direct radiative forcing on the climate system. The degree of present-day aerosol forcing is estimated from global models that incorporate a representation of the aerosol cycles. Although the models are compared and validated against observations, these estimates remain uncertain. Previous satellite measurements of the direct effect of aerosols contained limited information about aerosol type, and were confined to oceans only. Here we use state-of-the-art satellite-based measurements of aerosols and surface wind speed to estimate the clear-sky direct radiative forcing for 2002, incorporating measurements over land and ocean. We use a Monte Carlo approach to account for uncertainties in aerosol measurements and in the algorithm used. Probability density functions obtained for the direct radiative forcing at the top of the atmosphere give a clear-sky, global, annual average of -1.9 W m(-2) with standard deviation, +/- 0.3 W m(-2). These results suggest that present-day direct radiative forcing is stronger than present model estimates, implying future atmospheric warming greater than is presently predicted, as aerosol emissions continue to decline.     

北半球大气中CCl3F和CCl2FCClF2随纬度变化的特征和趋势研究

从1999年7月到9月作者与中国极地考察队合作,从北半球中纬度到极极圈地区进行了大规模的气体样品采样,运用气相色谱电子捕获检测器得到了随纬度变化的CFCs的特征浓度,并从地理位置和气象条件对所有样品的趋势进行了分析,研究结果有助于更好的理解北半球发达国家与发展中国家逐步取消卤化碳类化合物的现状和趋势。     

Thermoluminescence dating of the late Neanderthal remains from Saint-Césaire

Anatomically modern humans have long been thought to have been responsible for the Aurignacian and Chatelperronian industries of the early Upper Palaeolithic of Western Europe, whereas the Middle Palaeolithic Mousterian industry has been attributed to Neanderthals. The presence of both Middle and Upper Palaeolithic strata at Saint-Césaire in France offers an excellent opportunity for studying the cultural transition between the two. Saint-Césaire is the only Chatelperronian site that has yielded really diagnostic hominid fossils, and the discovery there of Neanderthal remains alongside Chatelperronian tools cast doubt on the exclusive association between industries and taxon. We report thermoluminescence dates for 20 burnt flints from the site. Those found near the Neanderthal remains were dated at 36,300 +/- 2,700 years BP (before present), making this specimen the youngest Neanderthal dated so far. This date places the stratum close in age to several French but much younger than some Spanish Aurignacian sites believed to have been occupied by modern humans. The possibility of contact between the West European Neanderthals and the intrusive modern humans who replaced them cannot therefore be excluded.