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1.
A multi-proxy reconstruction of spatial and temporal variations in Asian summer temperatures over the last millennium 总被引：1，自引：0，他引：1
Feng?Shi Quansheng?GeEmail author Bao?Yang Jianping?Li Fengmei?Yang Fredrik?Charpentier?Ljungqvist Olga?Solomina Takeshi?Nakatsuka Ninglian?Wang Sen?Zhao Chenxi?Xu Keyan?Fang Masaki?Sano Guoqiang?Chu Zexin?Fan Narayan?P.?Gaire Muhammad?Usama?Zafar 《Climatic change》2015,131(4):663-676
To investigate climate variability in Asia during the last millennium, the spatial and temporal evolution of summer (June–July–August; JJA) temperature in eastern and south-central Asia is reconstructed using multi-proxy records and the regularized expectation maximization (RegEM) algorithm with truncated total least squares (TTLS), under a point-by-point regression (PPR) framework. The temperature index reconstructions show that the late 20th century was the warmest period in Asia over the past millennium. The temperature field reconstructions illustrate that temperatures in central, eastern, and southern China during the 11th and 13th centuries, and in western Asia during the 12th century, were significantly higher than those in other regions, and comparable to levels in the 20th century. Except for the most recent warming, all identified warm events showed distinct regional expressions and none were uniform over the entire reconstruction area. The main finding of the study is that spatial temperature patterns have, on centennial time-scales, varied greatly over the last millennium. Moreover, seven climate model simulations, from the Coupled Model Intercomparison Project Phase 5 (CMIP5), over the same region of Asia, are all consistent with the temperature index reconstruction at the 99 % confidence level. Only spatial temperature patterns extracted as the first empirical orthogonal function (EOF) from the GISS-E2-R and MPI-ESM-P model simulations are significant and consistent with the temperature field reconstruction over the past millennium in Asia at the 90 % confidence level. This indicates that both the reconstruction and the simulations depict the temporal climate variability well over the past millennium. However, the spatial simulation or reconstruction capability of climate variability over the past millennium could be still limited. For reconstruction, some grid points do not pass validation tests and reveal the need for more proxies with high temporal resolution, accurate dating, and sensitive temperature signals, especially in central Asia and before AD 1400. 相似文献
2.
夏季亚洲-太平洋涛动与中国近海热带气旋活动的关系 总被引：3，自引：2，他引：1
采用联合台风警报中心的台风最伟路径资料和NCEP/NCAR再分析资料,分析了夏季亚洲-太平洋涛动(Asian-Pacif-ic Oscillation,简称APO)与东亚近海-西北太平洋大气环流的关系,并进一步探讨了APO与中国近海热带气旋(tropical cy-clone,简称TC)活动的关系.研究表明:(1)夏季APO强弱与同期西北太平洋及中国东部近海TC活动存在密切关系,即在APO强(弱)年,西北太平洋TC活动偏西(东)和偏北(南),中国东部近海TC明显增多(减少);(2)当APO偏强(弱)时,中国东部近海大气环流有(不)利于TC的维持和发展,表现为低层存在异常气旋性(反气旋性)环流,对流层高低层纬向风垂直切变减小(增大),且对流加强(减弱);(3)APO强弱也影响着TC引导气流的方向:在APO强(弱)年,西北太平洋副热带高压(以下简称副高)偏北和偏东(偏南和偏西),副高南侧偏东气流减弱(加强),有利于TC的向西北行或在偏北(南)纬度西行,进入中国东部近海的TC增多(减少);(4)APO强弱也影响着南海-热带西太平洋TC源地上空的大气环流,在APO强(弱)年,南海-热带西太平洋季风槽偏北、偏西(偏南、偏东),热带西太平洋TC活动偏北和偏西(偏南和偏东),有利于进入中国东部近海TC的增多(减少). 相似文献
3.
2016年共有3个台风登陆、4个台风影响福建,呈前少后多分布,登陆台风偏多,灾害影响重。分析表明：（1）2016年以来赤道中东太平洋海温距平的演变及大气环流异常响应是造成影响福建台风呈前少后多分布及登陆台风偏多的主要原因。（2）7月下旬至8月中旬和9月上旬至中旬西太平洋台风群发,“莫兰蒂”和“马勒卡”一周内相继登陆和影响福建,是季风槽增强或持续偏强的结果,且季风槽呈现显著的低频变化特征。（3）2016年西北太平洋生成和影响福建的台风与热带大气季节内振荡关系密切,近7成生成于MJO第5~7位相。（4）基于大气低频变化理论的延伸期预报填补了月—季预测和中短期天气预报之间的空白。 相似文献
4.
M. Rodrigo-Gámiz F. Martínez-Ruiz F.J. Jiménez-Espejo D. Gallego-Torres V. Nieto-Moreno O. Romero D. Ariztegui 《Quaternary Science Reviews》2011,30(15-16):2018-2034
Eolian input fluctuations and paleoceanographic conditions in the western Mediterranean have been reconstructed by using a multi-proxy approach to infer climate variability for the last 20,000 yr. A sediment core from the East Alboran Sea basin provides high-resolution geochemical, mineralogical and grain size distribution records from the Last Glacial Maximum onward. The accurate chronology obtained, closely related with the North Greenland Ice core Project, has provided a detailed paleoclimate reconstruction at the centennial–millennial time scale. Mineral and chemical compositions as well as sediment grain size distribution have been used to establish both fluvial and eolian input variations, deep-water current intensity, and ventilation and productivity conditions at the time of deposition. During the cold period Greenland Stadial-2a, the analyzed proxies evidence significant climate oscillations. Redox proxies, showing marked Mn/Al and Fe/Al peaks, as well as granulometric parameters, support major changes in thermohaline circulation, with active circulation triggered by the Western Mediterranean Deep Water formation. Ba/Al ratios and the presence of authigenic barite point to high productivity during the Last Heinrich event. At this time, Zr/Al, Si/Al and Ti/Al ratios as well as quartz and palygorskite contents also corroborate dryer conditions in the Alboran borderlands, with a major reorganization of atmospheric circulation at the beginning of the deglaciation and during the Last Heinrich event. In contrast, a decreasing trend in the Zr/Al ratio and increasing Mg/Al, K/Al and illite + chlorite/kaolinite ratios would indicate enhanced river runoff and supporting lower eolian dust input and wetter periods during the Bölling–Alleröd. Short-term and abrupt climate oscillations such as the Intra-Alleröd Cold Period are likewise reflected by minor yet conspicuous changes in eolian proxies. During the Younger Dryas, we distinguish an initial cold and dry phase, with major westerlies intensity, thermohaline reactivation, and high productivity levels, and a second wetter phase characterized by sporadic rainfalls over poorly vegetated surrounding continental areas. Then, during the Holocene, alternating phases of major humidity and aridity were recorded by major fluctuations in detrital input. These are also correlated with recurrent forest cover declines reported from pollen records, with a noteworthy early decline in the African Humid Period. During the Holocene, an initial demise of the Last Organic-Rich Layer is also evidenced, tentatively associated with aspiration forces promoted by intense thermohaline circulation through the Gibraltar Strait. 相似文献
5.
华南前汛期福建一次致洪暴雨过程的中尺度结构特征 总被引：3，自引：0，他引：3
利用FY-2E卫星云顶亮温资料、全国加密自动站资料和NCEP再分析资料,对2010年6月19～20日华南前汛期福建一次特大暴雨过程的中尺度对流系统的演变及其结构特征进行了分析和讨论。结果表明,特大暴雨发生在稳定的环流背景下,整个过程有4个主要的中尺度对流系统,沿着低层切变线东移和发生、发展,为强降水的发生提供了有利条件;高层辐散和低层辐合促进了强降水区中的上升运动,低层辐合的水汽在强上升过程中释放凝结潜热,进一步促进了水汽的上升运动和低涡的发展,是强降水发生的动力特征;地面不稳定能量和西南暖湿气流在强上升运动作用下,与中高层沿等θse线向低层侵入的干冷空气在对流层中层相遇并形成锋区,是特大暴雨过程的热力特征;湿位涡的诊断分析表明,对流不稳定和条件性对称不稳定的发展促使强降水区附近的涡旋发展,上升运动的加强,对强降水的发生和持续起了重要作用。 相似文献
6.
城市热岛效应是人类活动对大气系统影响的最主要体现之一。本文利用(Space and Time Multiscale Analysis System, STMAS)时空多尺度分析系统,融合了地面自动站、雷达、卫星等多源高时空分辨率观测资料,建立了城市热岛三维数据集。并在此基础上统计了2021年北京夏季的城市热岛强度变化特征,选取其中一次超强城市热岛个例(2021年6月11—12日)详细分析了其三维精细化结构特征。结果表明：(1)本个例中,夜间郊区近地面迅速降温,形成逆温层;而城市近地面降温缓慢,使得近地面城郊温差不断增大。(2)本次超强城市热岛三维温度场暖心结构在地面和990 hPa以下低空等压面清晰可见,风场距平呈现气旋性环流特征并在低空从郊区向城区辐合,引起可到达中高空的上升运动,说明城市热岛效应有增强垂直环流的作用。 相似文献
7.
Using the Joint Typhoon Warning Center (JTWC) optimal typhoon tracks data and the NCEP/NCAR reanalysis,an investigation is made on the summer Asian-Pacific Oscillation (APO) in relation to synchronous air circulation from the coastal waters of East Asia to western North Pacific (WNP),along with a further exploration on the relationship between the APO and the tropical cyclone (TC) activities over the coastal waters of China.The results show that there exists a strong correlation between the APO intensity an... 相似文献
8.
秋季亚洲-太平洋涛动与中国近海热带气旋活动的关系 总被引：1，自引：0，他引：1
采用联合台风警报中心的台风最佳路径资料和NCEP/NCAR再分析资料,分析了秋季(9—10月)亚洲-太平洋涛动(APO)强度的年际变化与东亚-太平洋大气环流的关系,探讨了APO与西北太平洋和中国近海热带气旋(TC)活动的关系。结果表明:秋季APO年际变化与同期西北太平洋和中国近海TC活动关系紧密,即当APO偏强(弱),西北太平洋TC活跃区明显偏西(东),中国近海TC偏多(少);APO可以通过影响中国近海对流层纬向风垂直切变、低层辐合和对流层中层引导气流等,从而影响西北太平洋和中国近海TC活动;当APO偏强(弱)时,东亚大槽偏弱(强),东亚冬季风偏弱(强),使得侵入中国近海和热带西北太平洋的冷空气活动偏弱(强),有(不)利于这些海域TC的生成和发展;此外,在APO偏强时,西太平洋副热带高压脊偏西,其南侧偏东气流加强,有利于TC在偏强的偏东气流引导下向西移动或者其转向点偏西;而在APO弱年,副热带高压脊偏弱和偏东,偏东引导气流减弱,不利于TC西行或有利于其转向点偏东。 相似文献
9.
华南前汛期雨涝强、弱年的确定及其环流特征对比 总被引：4，自引：1，他引：3
用区域性暴雨过程综合强度评估方法,在对1961—2010年华南前汛期逐场暴雨过程评估的基础上,通过定义华南区域雨涝强度指数(RWI),划分和确定了雨涝强、弱年,并对雨涝强、弱年的环流特征进行合成分析。结果显示:(1) RWI存在显著的年际变化和年代际变化特征。雨涝强度在1990s初以后呈现明显的增加趋势,雨涝强年明显增多。(2)雨涝强(弱)年,南亚高压偏南(北),副高位置偏西(东),欧亚中高纬500 hPa位势高度差值场自西向东呈现+ - +的波列分布,则有利(不利)于华南区域降水的发展和持续;(3)华南前汛期雨涝的强(弱)与大气低层来自华中—华南北部的偏北风输送加强(减弱)、高原东南侧的偏西风和经西太平洋—南海进入华南的西南风及水汽输送异常加强(减弱)有着密切的关系。而与来自孟加拉湾进入华南的偏南风及水汽输送强(弱)呈现反相关。(4)雨涝强(弱)年,冷空气活动频率较高(低),持续时间较长(短),强中心偏南(北)。且暖湿空气较早(晚)到达25 °N地区,并在30 °N以南地区维持时间较长(短),季风推进快(慢)。 相似文献
10.
Many arid basins in western North America are likely to experience future changes in precipitation timing and amount. Where shallow water tables occur, plant acquisition of groundwater and soil water may be influenced by growing season precipitation. We conducted a rainfall manipulation experiment to investigate responses of four common native plant species to ambient, increased, and decreased summer monsoon rainfall. We measured plant xylem pressure potentials (Ψ) and stable oxygen isotope signatures (δ18O) to assess effects of altered precipitation on plant water relations and water acquisition patterns. Reduced rainfall decreased Ψ more in the grasses Sporobolus airoides and Distichlis spicata than the more deeply rooted shrubs Sarcobatus vermiculatus and Ericameria nauseosa. E. nauseosa had little response to natural or experimental differences in available soil water. Plant xylem water δ18O indicated that S. airoides and D. spicata are almost entirely dependent on rain-recharged soil water, while E. nauseosa is almost entirely groundwater-dependent. Sarcobatus vermiculatus used groundwater during dry periods, but utilized precipitation from soil layers after large rainfall events. Persistent changes in precipitation patterns could cause shifts in plant community composition that may alter basin-scale groundwater consumption by native plants, affecting water availability for human and ecosystem uses. 相似文献