Links between global CO<Subscript>2</Subscript> variability and climate anomalies of biomes

The global rate of fossil fuel combustion continues to rise, but the amount of CO₂ accumulating in the atmosphere has not increased accordingly. The causes for this discrepancy are widely debated. Particularly, the location and drivers for the interannual variability of atmospheric CO₂ are highly uncertain. Here we examine links between global atmospheric CO₂ growth rate (CGR) and the climate anomalies of biomes based on (1986–1995) global climate data of ten years and accompanying satellite data sets. Our results show that four biomes, the tropical rainforest, tropical savanna, C₄ grassland and boreal forest, and their responses to climate anomalies, are the major climate-sensitive CO₂ sinks/sources that control the CGR. The nature and magnitude by which these biomes respond to climate anomalies are generally not the same. However, one common influence did emerge from our analysis; the extremely high CGR observed for the one extreme El Niño year was caused by the response of the tropical biomes (rainforest, savanna and C₄ grassland) to temperature.     

Quantitative study on pollen-based reconstructions of vegetation history from central Canada

Based on high-resolution pollen records from lake cores in central Canada, the present study instructed pollen taxa assignations in ecosystem groups and modern analogue technique, reported major results of quantitative reconstructions of vegetation history during the last 1000 years, and discussed the validation of simulated vegetation. The results showed that in central America (115°-95°W, 40°-60°N), best analogue of the modern vegetation is 81% for boreal forest, 72% for parkland, and 94% for grassland-parkland, which are consistent with vegetation distributions of the North American Ecosystem II. Simulations of the past vegetation from the sedimentary pollen showed climate changes during the past 1000 years: it was warm and dry in the Medieval Warm period, cold and wet in the earlier period and cold and dry in the later period of the Little Ice Age. It became obviously increasing warm and drought in the 20th century. The present studies would provide us scientific basis to understand vegetation and climate changes during the last 1000 years in a characteristic region and in 10-100 year time scales.     

宁夏春季降水及其典型年份水汽通量特征分析

选用1961—2006年宁夏19个主要站降水量分析宁夏春季降水的气候特征,得出其存在16 a左右的长周期和8 a左右的短周期,但年际、年代际变化特征不明显。宁夏春季降水量与春季首场透雨出现日期存在显著的负相关关系,春季如果出现首场透雨,其降水量对整个春季降水量贡献很大。研究春季降水典型旱涝年850—700 hPa水汽通量场的分布,发现影响宁夏春季降水的水汽有两支,一支是来自于孟加拉湾洋面上向东北方向输送的水汽,一支是从里海沿我国新疆地区向东输送的水汽,典型涝年这两支水汽带汇合区域明显向北抬,且汇合区域大,中心值大;典型旱年这两支水汽带汇合区偏西、偏小,中心值也较平均年减小。典型旱涝年水汽通量在u方向差别不大,但在v方向上呈反位向分布,典型涝年宁夏为正距平控制,典型旱年为负距平控制。     

A new genus of silken-fungus beetle (Coleoptera: Cryptophagidae) from the Spanish Cretaceous amber

The Cretaceous new species and genus Albocryptophagus cantabricus gen. et sp. n. is described based on a fossil specimen from the El Soplao amber deposit (Spain). The new genus is similar to the extant genera Cryptophagus and Micrambe, but differs from them in the transverse pedicel, anterior angles of pronotum, pronotal margin unmodified, pronotal pits absent. Albocryptophagus gen. n. is undoubtedly the most ancient representative for the subfamily Cryptophaginae described up today. Because the saproxylic habits in recent species of the family, a similar behavior is inferred for this new fossil. It is a new example that agrees with the idea that fossil beetles from Mesozoic ambers are characterized by a saproxylic lifestyle.     

过去2000年冷暖变化的基本特征与主要暖期

根据近年国内外相关研究结果,分析了北半球与中国过去2000 年冷暖变化的阶段性,辨识了百年尺度暖期的起讫年代及其与20 世纪温暖程度的差别。结果表明:(1) 最近新建的多数北半球温度变化序列显示公元1-270 年温暖;271-840 年冷暖相间,但总体偏冷;841-1290年温暖;1291-1910 年寒冷;1911 年以后再次转为温暖;这些冷暖阶段虽分别与Lamb 指出的罗马暖期(约公元前1 世纪-4 世纪中期)、黑暗时代冷期(约4 世纪末-10 世纪前期)、中世纪暖期(约10 世纪中期-13 世纪末)、小冰期(约15-19 世纪) 以及20 世纪增暖大致对应,但各阶段的起讫时间与Lamb确定的时段存在一定差别。(2) 尽管过去2000 年冷暖变化过程及其变幅大小在中国境内各个区域间并不完全一致,但从全国平均看,中国与北半球百年尺度的冷暖波动阶段基本一致,仅起讫年代存在一定差异;其中公元1-200 年、551-760 年、941-1300 年及20世纪气候相对温暖,其他时段则相对寒冷。(3) 多数序列显示中世纪期间北半球的温暖程度至少与20 世纪相当。中国941-1300 年间的最暖百年和最暖30 年(暖峰) 的温度也略高于20 世纪,551-760 年间的最暖百年与20 世纪基本相当,但1-200 年间最暖百年的温暖程度则较20 世纪略低。     

Investigation of El Niño and La Niña effects and the impact of Atlantic sea surface temperatures (SSTs), on precipitation in Nigeria from 1950 to 1992

Monthly precipitation data from meteorological stations in Nigeria are analysed from 1950 to 1992, in relation to sea surface temperatures (SSTs) in the tropical Pacific and Atlantic Oceans. The analyses have shed some light on understanding the variability of rainfall anomalies observed in Nigeria for this period. The correlation values between rainfall anomaly indices (RAI) and different meteorological indices are not all significant. Thus, the analyses show some indication that rainfall in Nigeria is associated with El Niño-related circulation and rainfall anomalies. The low correlations between RAI and SST in the Pacific confirm low correlations between rainfall and southern oscillation indices (SOI). SST correlations in the tropical Atlantic suggest that warm surface water in this part of the Atlantic moves the Inter Tropical Convergence Zone (ITCZ) southward and away from the SouthEast of Nigeria, indicating less rainfall, while, in SouthWest of Nigeria, the warm surface waters in this part of the Atlantic are likely to be responsible for a more northern position of the ITCZ, which produces more rainfall. The lower correlation in Northern Nigeria may be attributed to its continentality, away from the influence of the sea surface conditions in the Gulf of Guinea and the tropical Atlantic. The drought, or rainfall, cycles in Northern Nigeria are more closely connected to the land surface conditions in the nearby Sahel region.     

大气季节内振荡研究进展

在简单回顾大气季节内振荡(MJO)的特征,热带和中高纬MJO的联系及其在半球间相互作用的基础上,较系统地总结了近年来关于MJO的研究进展,涉及MJO和El Nino的关系,MJO的动力学机制及其季节变化和年际异常,并简单讨论了MJO研究中存在的问题及未来的研究前景.     

过去2000年亚洲气候变化(PAGES-Asia2k)集成研究进展及展望

介绍了国际过去全球变化研究计划(PAGES)过去2000年气候变化研究网络的设立背景、研究目的及亚洲在其中的独特性;总结了过去2000年亚洲气候变化(PAGES-Asia2k)集成研究的主要进展及中国的贡献,分析了当前在亚洲区域开展该项研究的主要问题及难点,并对未来研究进行了展望。亚洲历史悠久,高分辨率的代用资料丰富,是开展过去2000年气候变化研究的理想区域,但目前尚处于起步阶段。已有进展表明:在过去1200年中,亚洲830-1220年相对温暖,1340-1880年明显寒冷,20世纪则快速增暖;但亚洲气候类型多、变化过程复杂、区域差异大。因此,发展气候序列重建的新技术方法,提高重建序列的时、空分辨率、空间覆盖度和重建结果的精度,建立亚洲过去2000年气候代用资料数据库,集成重建过去2000年区域温度变化序列及干湿变化空间型,进而开展区域气候变化驱动机制与气候变化影响及适应研究,是该计划下一步的研究重点。     

Nino3区海温的变化对黄河流域夏季降水的影响

利用1961—2011年NCEP/NCAR再分析资料和黄河流域45站降水资料,定义了4月和上年10月的Nino3区海温差（ΔISST3）指数,分析ΔISST3指数与夏季海温的关系以及大气环流和夏季黄河流域降水与ΔISST3指数的相关情况,得到如下结果：(1)ΔISST3升高（降低）时,夏季赤道中东太平洋海温易偏暖（冷）,而我国南海到菲律宾半岛海区易偏冷（暖）。（2）500 hPa高度场上,ΔISST3与100°E~80°W范围的热带和副热带地区高度呈显著的负相关关系;ΔISST3正负异常差值场显示,ΔISST3升高（降低）时,夏季热带和太平洋副热带地区的500 hPa高度偏低（高）,赤道北侧850 hPa西风（东风）距平异常,西太平洋副热带高压明显偏弱（强）,我国东部沿海大陆盛行偏北（南）气流,暖湿气流不活跃（活跃）,季风偏弱（强）,而中高纬度上,蒙古北部气旋（反气旋）发展,致使河套地区处在反气旋性（气旋性）环流中。（3）ΔISST3指数与黄河流域夏季降水呈显著的负相关关系,相关系数为-0.51,当ΔISST3正异常时,黄河流域夏季降水易偏少;ΔISST3负异常时,黄河流域夏季降水易偏多,且负异常对黄河流域夏季降水的影响更显著。     

INFLUENCE OF TIBETAN PLATEAU ON AIR-SEA INTERACTION OVER TROPICAL PACIFIC IN OCEAN-ATMOSPHERIC COUPLED SYSTEM*

A hybrid coupled ocean-atmosphere model is designed,which consists of a global atmospheric general circulation model(L9R15 AGCM)and a simple ocean model(ZC ocean model over tropical Pacific).Using the model,experimental predictions are performed for the 1986/87 El Nino event and the 1988/89 La Nina event with and without the Tibetan Plateau respectively(called TP FORC and NTP FORC hereinafter).It is found as follows:(1)The coupled system can successfully predict the El Nino or La Nina event even if the Tibetan Plateau orography is not included in the model.The patterns of SSTA and wind anomalies in the model without the Tibetan Plateau are similar to those with the Tibetan Plateau,which further verifies the fact that ENSO process is mainly caused by the air-sea interaction in tropical Pacific.(2)However.the existence of the Tibetan Plateau exerts its influences on the intensity and duration of El Nino(or La Nina).It is unfavorable to the development and maintenance of westerly anomalies,so to some extent,restrains the development of El Nino,but favors the development of La Nina.(3)Effects of the Tibetan Plateau orography on the wind anomalies in the coupled system are different from those inuncoupled AGCM simulation.