平流层爆发性增温的时空分布特征

利用1950～2003年逐日平均NCEP资料,对平流层爆发性增温（SSW）的特征进行了统计分析,得到如下结果：北半球SSW具有多发性,在这53年里共发现了69次增温事件,平均每年一次以上,有些年份甚至出现2～3次;SSW中心位置随高度变化,在较低层（16 km附近）中心位置大部分偏于西半球的北美北部到北极地区,高层（30 km附近）附近其中心多偏于东半球欧亚大陆的北边到北极地区;北半球SSW最先发生在30 km附近的欧亚大陆以北地区,然后由上向下延伸和传递,同时中心位置也逐渐转到西半球的北美大陆北端;在北半球发生SSW期间,平流层温度场和环流场的变化也会影响到对流层,引起对流层温度场和环流场的变化.对2002年9月发生在南半球平流层的一次强爆发性增温进行分析表明,南半球的这次SSW发生时表现出的特征与北半球稍有不同,在较低层（16 km附近）SSW中心出现在东半球的南端,在较高层（25～30 km）SSW中心位于西半球的南端.     

River discharge changes in the Qinghai-Tibet Plateau

THE QINGHAI-TIBET PLATEAU IS SENSITIVE TO GLOBAL CLI- MATE CHANGES, AND ITS MEAN WARMING AMPLITUDE DURING THE PAST 50 YEARS IS GREATER THAN THAT OF THE NORTHERNHEMISPHERE AND OTHER REGIONS IN THE SAME LATITUDE[1,2]. DUE TO ITS SPECIFIC GEOMORPHIC CONDITIO…     

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.     

Response of global lightning activity to air temperature variation

It is an issue of great attention but yet not very clear whether lightning activities increase or decrease on a warmer world. Reeve et al. presented that lightning activities in global land and the Northern Hemisphere land have positive response to the increase of wet bulb temperature at 1000hPa. Is this positive response restricted only to wet bulb temperature or in land？ What is the response of global lightning activities （in both land and ocean） to the global surface air temperature variation like？ This paper, based on the 5-year or 8-year OTD/LIS satellite-based lightning detecting data and the NCEP reanalysis data, makes a reanalysis of the response of the global and regional lightning activities to temperature variations. The results show that on the interannual time scale the global total flash rate has positive response to the variation in global surface air temperature, with the sensitivity of 17±7% K^-l. Also, the seasonal mean flash rate of continents all over the world and that of continents in the Northern Hemisphere have sensitive positive response to increase of global surface air temperature and wet bulb temperature, with the sensitivity of about 13±5% K^-1, a bit lower than estimation of 40% K^-1 in Reeve et al. However, the Southern Hemisphere and other areas like the tropics show no significant correlation.     

基于GOSAT L4B数据的全球和中国区域近地面CO_2含量变化分析

CO2 作为最重要的温室气体,是造成全球温室效应的主要原因之一。利用GOSAT L4B全球分布数据,分析全球及中国地区近地面CO2 含量的时空分布特征。研究发现,北半球近地面CO2 含量明显高于南半球,CO2 年增长率约2 ppm。全球高值区主要出现在东亚、俄罗斯、欧洲和美国等人口众多、经济发达地区。北半球近地面CO2 含量季节分布显示,冬季的CO2 含量最高,夏季最低。中国区域近地面CO2 含量在空间分布上较为集中,东西差异显著,总体呈东高西低的特征,高值区主要集中于中国华北和长三角地区。中国范围内近地面CO2 含量具有明显的季节变化特征,月平均含量4月(春季)升至最高值,为396.5ppm;7月(夏季)降至最低值,为382.8 ppm。     

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.     

Surface ozone observations during voyages to the Arctic and Antarctic regions

Surface ozone concentration and UV-B data between 75° N and 70° S were obtained aboard the Chinese polar scientific vessel “Xue -long” (Snow-Dragon) during the first voyage to the Arctic and the 16th to the Antarctic in 1999–2000. Analysis of these data presents that variations of the surface ozone concentration have small amplitude during voyages except the mid-latitude in the Northern Hemisphere. As a whole, average surface ozone concentration in the Northern Hemisphere is higher than that in the Southern, and high value occurred when the ship sailed close to the continents. The average diurnal variations of the surface ozone in the Northern Hemisphere are also higher compared to the southern counterparts, and high diurnal variations were found at low latitudes, and relative low level in the polar region.     

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.     

基于十字形扫描雷达的3D料面建模方法

为了解决现有径向雷达难以获得完整的高炉实际料面信息的问题,提出了基于离散雷达检测点二维插值的高炉料面重构方法,实现了料面信息的准确检测。首先根据生产要求建立了雷达检测点提取原则,获得了雷达十字形检测点,并将获取的检测点进行特征料线拟合得到4条不同料线方程。然后利用区域平均计算方法和料线方程式获取插值数据点。最后采用二维插值法进行料面重构。实验部分,通过现场提取的某高炉实测数据利用本文计算方法进行了数值仿真。结果表明,该方法能够实现离散数据点在高炉特殊环境下的可视化料面建模,并且提高了十字形雷达数据点2D料线的重构精度。     

Millennial temperature reconstruction based on tree-ring widths of Qilian juniper from Wulan, Qinghai Province, China

The climate of the past 1000 years is an important context for evaluating the recent climate warming. However, there are few 1000-year-long climate reconstructions with annual resolution in the Qinghal-Tibet Plateau. In this paper, a dendroclimatic analysis was conducted for the radial growth of Qilian juniper from the upper forest limit in Wulan, Qinghai Province. The results of correlation analysis between the tree-ring widths and the climate variables indicate that the growth of junipers at the upper forest limit is mainly limited by low temperatures of September, November and February of the pregrowth season, and July of the current growth season. There is no significant correlation between the tree-ring widths and precipitation. A mean temperature from the previous year＇s September to the current year＇s April was reconstructed for the Wulan area since A.D. 1000. The reconstruction can explain 40.8% of the instrumental variance in the calibration period （1856-2002）. The reconstruction shows that the 20th century is the warmest 100 years, and the 1990s is the warmest decade during the past 1000 years, while the coldest 100 years and decade occur at 1600-1699 and 1642-1651, respectively. The variations are verified well by the temperature reconstruction of the middle Qilian Mountain （QL） and the total organic carbon （TOC） in the Qinghai Lake sediments. The comparison of our reconstruction with the annual temperature reconstruction of extra-tropical Northern Hemisphere suggests that the climate of Wulan during the Medieval Warm Period is of obvious regional specialty, but there was a good response to the climate of hemispheric scales during the recent 400 years.     

主分量逐步回归在气温预测中的应用

以广东省冬季气温场为预报场,前一年的北太平洋海温场和北半球500 hPa高度场为因子场,分别对它们作标准化处理,然后进行主分量分析,得到主分量矩阵。通过相关分析和逐步回归,求得预报场的主分量与因子场的主分量之间的关系,对预报场的标准化主分量进行反算,得到原始场的拟合和预报。结果显示,广东省冬季气温场前4个主分量(对总方差的累积贡献达到97.5%)的预报方程都通过显著性检验,其方程复相关系数基本在0.9以上。对广东省48个代表站2001-2003年冬季气温进行预测检验,大部分预测结果的残余标准差比同期的样本标准差低,同时回归方程的预报误差略低于实际业务预报误差,因而回归方程对实际天气预报业务工作有一定的参考意义。     

North Pacific seasonality and the glaciation of North America 2.7 million years ago

In the context of gradual Cenozoic cooling, the timing of the onset of significant Northern Hemisphere glaciation 2.7 million years ago is consistent with Milankovitch's orbital theory, which posited that ice sheets grow when polar summertime insolation and temperature are low. However, the role of moisture supply in the initiation of large Northern Hemisphere ice sheets has remained unclear. The subarctic Pacific Ocean represents a significant source of water vapour to boreal North America, but it has been largely overlooked in efforts to explain Northern Hemisphere glaciation. Here we present alkenone unsaturation ratios and diatom oxygen isotope ratios from a sediment core in the western subarctic Pacific Ocean, indicating that 2.7 million years ago late-summer sea surface temperatures in this ocean region rose in response to an increase in stratification. At the same time, winter sea surface temperatures cooled, winter floating ice became more abundant and global climate descended into glacial conditions. We suggest that the observed summer warming extended into the autumn, providing water vapour to northern North America, where it precipitated and accumulated as snow, and thus allowed the initiation of Northern Hemisphere glaciation.     

Temporal and spatial distribution of tropospheric CO<Subscript>2</Subscript> over China based on satellite observations

Mid-troposphere CO₂ data retrieved by the AIRS (atmospheric infrared sounder) were validated with five ground-based stations and aircraft measurements in the Northern Hemisphere. AIRS CO₂ products show good agreement with ground and aircraft observations. The data had a monthly average accuracy better than 3 ppmv. In this study, the spatial and temporal distribution of mid-troposphere CO₂ from January 2003 to December 2008 was analyzed based on this satellite product. The average concentration of atmospheric CO₂ was higher in the Northern Hemisphere than in the Southern Hemisphere. The yearly average results show a gradual increase from 2003 to 2008. In China, the annual growth rate was about 2 ppmv/a, similar to the United States, Europe, Australia and India, but was slightly lower than Canada and Russia. Mid-troposphere CO₂ concentrations were higher over northern China than over southern areas, due to differences in natural conditions and industrial layout. There were four centers of high CO₂ concentration between 35° and 45°N over China, with low concentrations over Yunnan Province. There was a significant seasonal CO₂ variation with peak concentration in spring and the lowest concentration in autumn.     

重叠平均法性能分析及帧头辅助

对重叠平均法性能进行定量分析,建立了检测概率和算法参数的数学关系,通过推导可知,当利用重叠平均法加快搜索速度时,不可避免灵敏度损失的问题,即重叠平均点数扩大一倍则检测性能恶化约3dB.为了适应低信噪比环境和高数据率系统,提出了帧头辅助的方法,该方法延长相关积累时间增加积累增益以补偿重叠平均法的灵敏度损失,且实现较为简单.通过仿真对建立的检测概率和算法参数的数学关系进行了验证,显示了帧头辅助的重叠平均快速捕获算法的优点,即利用4ms八点重叠平均几乎达到了2ms直接二点平均的检测性能,但数据处理量减小1/2.     

Detection of human influence on twentieth-century precipitation trends

Human influence on climate has been detected in surface air temperature, sea level pressure, free atmospheric temperature, tropopause height and ocean heat content. Human-induced changes have not, however, previously been detected in precipitation at the global scale, partly because changes in precipitation in different regions cancel each other out and thereby reduce the strength of the global average signal. Models suggest that anthropogenic forcing should have caused a small increase in global mean precipitation and a latitudinal redistribution of precipitation, increasing precipitation at high latitudes, decreasing precipitation at sub-tropical latitudes, and possibly changing the distribution of precipitation within the tropics by shifting the position of the Intertropical Convergence Zone. Here we compare observed changes in land precipitation during the twentieth century averaged over latitudinal bands with changes simulated by fourteen climate models. We show that anthropogenic forcing has had a detectable influence on observed changes in average precipitation within latitudinal bands, and that these changes cannot be explained by internal climate variability or natural forcing. We estimate that anthropogenic forcing contributed significantly to observed increases in precipitation in the Northern Hemisphere mid-latitudes, drying in the Northern Hemisphere subtropics and tropics, and moistening in the Southern Hemisphere subtropics and deep tropics. The observed changes, which are larger than estimated from model simulations, may have already had significant effects on ecosystems, agriculture and human health in regions that are sensitive to changes in precipitation, such as the Sahel.     

热辐射检测系统测量热喷涂粒子参数时的数据处理

建立了适用于单窗调制型热喷涂粒子参数热辐射检测系统的数据处理方法，并应用模拟和实测数据进行了效果评估．结果表明：预处理宜采用低通滤波基础上的算术补偿去除零漂、再应用多邻点平均降噪的复合方法；利用噪声重构法建立的幅值判据可准确确定单个有效脉冲位置并实现相关数据截取．截得的Ⅰ型曲边梯形脉冲可近似为5参量等腰梯形函数，并可运用线性展开与梯度寻优相结合的最小二乘法拟合获得其特征参量，根据所得拟合结果可统计换算出速度、表面温度、直径及景深偏移等关键粒子状态参数。     

Detection of unsymmetrical global tectonic change by using space geodetic data

The global tectonic change deduced from geophysical research was first identified by space geodetic data from VLBI, GPS and SLR measurements. Whether using geodesic rates or using vertical velocities of stations, three kinds of data and their integration give consistent results: within the mid-latitude belt on the Northern Hemisphere there may be about 8–10 mm/a contracting change; within the mid-latitude belt on the Southern Hemisphere there may be about 12–14 mm/a expanding change. This result not only validates the reverse global tectonic change in the Southern and Northern Hemispheres of the Earth, but also gives relatively precise quantative estimations.     

A comparison of the Medieval Warm Period, Little Ice Age and 20th century warming simulated by the FGOALS climate system model

To compare differences among the Medieval Warm Period (MWP), Little Ice Age (LIA), and 20th century global warming (20CW), six sets of transient and equilibrium simulations were generated using the climate system model FGOALS_gl. This model was developed by the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics, Chinese Academy of Sciences. The results indicate that MWP warming is evident on a global scale, except for at mid-latitudes of the North Pacific. However, the magnitude of the warming is weaker than that in the 20th century. The warming in the high latitudes of the Northern Hemisphere is stronger than that in the Southern Hemisphere. The LIA cooling is also evident on a global scale, with a strong cooling over the high Eurasian continent, while the cooling center is over the Arctic domain. Both the MWP and the 20CW experiments exhibit the strongest warming anomalies in the middle troposphere around 200?C300 hPa, but the cooling center of the LIA experiment is seen in the polar surface of the Northern Hemisphere. A comparison of model simulation against the reconstruction indicates that model??s performance in simulating the surface air temperature changes during the warm periods is better than that during the cold periods. The consistencies between model and reconstruction in lower latitudes are better than those in high latitudes. Comparison of the inter-annual variability mode of East Asian summer monsoon (EASM) rainfall during the MWP, LIA and 20CW reveals a similar rainfall anomalies pattern. However, the time spectra of the principal component during the three typical periods of the last millennium are different, and the quasi-biannual oscillation is more evident during the two warm periods. At a centennial time scale, the external mode of the EASM variability driven by the changes of effective solar radiation is determined by the changes of large scale land-sea thermal contrast. The rainfall anomalies over the east of 110°E exhibit a meridional homogeneous change pattern, which is different from the meridional out-of-phase change of rainfall anomalies associated with the internal mode.     

基于史料记载的1470～1949年广东沿海地区台风活动历史重建与分析

根据史料文献记载,并结合现代台风活动特征,对历史时期（公元14701949年）广东沿海地区的台风活动进行了重建,采用相关性分析和交叉小波分析方法探讨了历史时期的台风活动、北半球平均气温以及太平洋年代际震荡（Pacific Decadal Oscillation, PDO）相互之间的关系. 研究结果显示: (1)重建的历史时期台风活动年均频次与现代台风活动统计结果比较接近,二者在登陆区域上的分布比例也基本一致; (2)近500年来北半球平均气温与影响广东沿海地区的台风活动频次之间存在较为显著的正相关性,特别是在PDO暖位相时期二者之间的正相关性显著提高,这在一定程度上意味着在当前全球变暖背景下影响广东沿海地区的台风活动频次有可能增多.     

亚澳季风区大气视热源的季节演变特征

对1950-2000年平均的亚澳季风区大气热源的季节演变和突变特征进行分析.结果发现,亚澳季风区热带低纬的大气热源区随季节由冬到夏而自南半球向北半球移动,在盛夏达到最北,强度也最强,并在春末与北半球中纬度的热源区汇合,到秋季开始南撤;东亚季风区和印度季风区大气热源的冬夏型间转换的过度季节都较短,冬夏型间转换具有明显的突变性,而印度季风区大气热源的冬季型维持时间明显比夏季型要长;亚澳季风区内大气热源的年较差以亚洲季风区的热源年较差最显著,澳大利亚北部次之.