南海上层水温分布的季节特征

为对南海上层水温分布特征有一总体认识,利用气候平均的1°×1°网格的Levitus资料,分析了南海0－200m层共10个等深面上的季平均温度分布状况。结果表明,南海上层水温分布的季节变化明显,季风和太阳辐射对水温分布有显著影响,四季平均水温分布与平均环流状况对应较好。冬、春两季在吕宋岛西北海域有一冷涡（即吕宋冷涡）,夏、秋季在越南沿岸出现另一冷涡（即越南冷涡）。这两个冷涡均对应着本海区尺度较小的气旋式环流和正的风应力旋度。吕宋冷涡还与黑潮在吕宋海峡的形变有关,越南冷涡则与局地强上升流有联系。     

2009年大连春季强对流雨雪天气过程分析

2009年4月15日大连出现了春季最晚的降雪天气。利用常规资料、自动气象站和雷达等多种资料及中尺度模式MM5对这次强对流雨雪天气过程进行了分析和模拟,结果表明,200hPa急流、500hPa贝加尔湖冷槽南压形成的冷涡、中低层南支槽前水汽输送以及地面冷锋是产生大连春季强对流雨雪天气的环流背景;中层干冷空气叠加在低层暖湿层...     

Precise radiocarbon dating of Late-Glacial cooling in mid-latitude South America

Variability of atmospheric ¹⁴C content often complicates radiocarbon-based chronologies; however, specific features such as periods of constant ¹⁴C age or steep changes in radiocarbon ages can be useful stratigraphic markers. The Younger Dryas event in the Northern Hemisphere is one of those periods, showing conspicuous ¹⁴C wiggles. Although the origin of those variations is not fully understood, we can make practical use of them and determine: (i) whether the Younger Dryas was global in extent; if so, (ii) were the initial cooling and the final warming synchronous worldwide; and (iii) what are the implications of these similarities/differences? Here we report high-resolution AMS ¹⁴C chronologies from the mid-latitudes of South America that pinpoint a cool episode between 11,400 and 10,200¹⁴C yr B.P. The onset of the final cool episode of the Late Glacial in the southern mid-latitudes, i.e., the Huelmo/Mascardi Cold Reversal, preceded the onset of the Younger Dryas cold event by ∼550 calendar years. Both events ended during a radiocarbon-age plateau at ∼10,200¹⁴C yr B.P. Thus, the Huelmo/Mascardi Cold Reversal encompasses the Younger Dryas, as well as a couple of short-term cool/warm oscillations that immediately preceded its onset in the North Atlantic region.     

不同定义指标下的乌鲁木齐寒潮过程气候特征对比分析

利用乌鲁木齐市1951—2015年逐日最低气温(TD)、日平均气温(TT)资料,依据《寒潮等级》国家标准,以TD、TT为定义指标来普查寒潮降温过程,采用数理统计方法对2种指标统计的寒潮降温气候变化特征进行对比分析。结果表明:2种指标方法统计的降温频数存在显著性差异,在年际、季节时间尺度上均呈不显著减少趋势,TT法统计的年降温频数减少趋势显著强于TD法;90%的降温过程持续时间在1~3 d,TD、TT法统计的最长降温持续日数均出现在11月,且不同降温幅度的频数最大值亦在秋季;以TD、TT法统计的全年95.5%和94.6%的降温过程达不到寒潮的标准,2种方法统计的寒潮等级频数均表现为一般寒潮强寒潮特强寒潮;2种方法统计的寒潮频数在年际、季节尺度上均呈现减少趋势,峰值期分别为4月和10月,20世纪50年代为多发期,2001—2015年为相对少发期;TT法统计寒潮频数未来持续性强度弱于TD法;相关性分析发现,寒潮频数与年均TD、TT呈极显著的负相关关系,且年均TD的相关性强于年均TT,表明TD是影响寒潮频数变化的一个重要指标参数。     

Research Advance of Shrub Dendrochronology in the Cold and Arid Regions of China

Along with the booming of dendrochronology in China, the woody species for the tree-ring study have expanded gradually from tree species to the shrub and dwarf shrub species in the last decades. The zonal woody species in the vast alpine mountains, arid desert areas and arid regions in China are mostly shrubs and semi-shrubs, which is very important to understand the process of regional evolution, environmental protection and ecological recovery. In this paper, the shrub species which have been studied on tree rings in cold and arid areas of China were collected and sorted, and the fundamental research advances were presented, which include the shrub tree ring identification, radial growth characteristics, and chronology construction by different parameters. The applications of shrub dendrochronology to the subjects in eco-response, paleoclimate reconstruction, hydrological process, ecological study of artificial forest and ecological restoration were also presented. The prospect of shrub dendrochronology in the future was also discussed.     

Spatial scale and habitat-dependent diversity patterns in nematode communities in three seepage related sites along the Norwegian Sea margin

Assessing the relative contribution of local diversity to regional biodiversity may be the key to understanding large-scale and even global patterns in species diversity. Here, the contribution of habitat heterogeneity of cold seeps at three spatial scales [micro-scale (ms), macro-scale (10 to 100s of ms), and mega-scale (10 to 100s of km)] to the total nematode biodiversity (genus level) along the Norwegian continental margin is evaluated. Due to the development of higher resolution bathymetry and increased bottom sampling in recent years, continental margins, once regarded as monotonous landscapes, are now acknowledged to have a high degree of habitat complexity and diversity. By calculating the additive partitioning of gamma diversity in alpha and beta fractions, we examined to what extent habitat diversity of seep sites significantly increases the nematode genus composition and diversity at different spatial scales. Siboglinidae patches and control sediments yielded comparably high levels of nematode genus richness. They exhibited low turnover rates within and across the different seep sites. In contrast, the bacterial mats at Håkon Mosby Mud Volcano (HMMV) and the reduced sediments at the Nyegga pockmarks harboured genus-poor nematode communities with an equally high dominance of one or two species, which were different for each seep. Different habitats, in particular at the HMMV, contributed significantly to the seep nematode richness. This study demonstrates that the presence of distinct habitat types within multiple seep sites contributes to the high diversity of nematode communities inhabiting the seeps in the Norwegian deep sea.     

Spectral Characteristics and Multi-Scale Structure of the Boundary-Layer Wind Field During Cold Front Passages Over East China

In this paper, data obtained from a 164 m and a195 m meteorological tower in the northern suburb ofNanjing have been used to estimate and analyzetime-space distributions for velocity spectra andscales of multi-scaling turbulence during thepassages of two cold fronts. Results show that anon-precipitating weak cold front and aprecipitating cold front were clearly revealed bytheir wind field structures. The frontal passageinfluenced all meteorological variables over aperiod of 18–24 hours for the former, and a longerperiod of 44–56 hours for the latter. During these periods there occurred gust surges and eddymotions of various meso- and micro-scales with periodsof 3–4 hours and 1–20 minutes respectively. In the inertialsubrange Kolmogorov's -2/3 power law for thevelocity spectrum is partly distorted and theturbulence in the atmospheric boundary layer is not isotropic.     

2004/2005年冬季强寒潮事件的等熵位涡分析

利用2004年12月1日—2005年2月28日的NCAR/NCEP逐日再分析资料,对2004年12月22日—2005年1月1日的强寒潮事件进行等熵位涡分析。结果表明:这次强寒潮事件的强冷空气来自欧亚北部和北极地区的高纬平流层下部与对流层上部。在寒潮爆发前期,高位涡强冷空气传播到贝加尔湖南侧,并被来自低纬度的低位涡空气所切断,在欧亚地区形成北部低位涡(阻塞高压)南部高位涡(低涡)的偶极型环流。随着低位涡的减弱消亡,高位涡强冷空气沿高原北侧向东南方向移动,当高位涡中心移到中国东部地区,高位涡空气柱在垂直方向上强烈向下伸展,使得气柱的气旋性涡度加强,东亚大槽迅速加深,引起寒潮的爆发。进一步分析表明,高位涡中心向南、向下传播过程中,等熵面上高位涡中心附近气流在其西侧和北侧地区沿等熵面下沉,引起上述地区低层西伯利亚高压迅速发展,导致强寒潮爆发。     

昆仑山垭口小南川末次冰期早期成层坡积的沉积特征和气候意义

成层坡积结构构造特征、粒度、化学、电镜扫发描分析和测年资料揭示其形在于末次冰期间冰段（６００００ａＢＰ～４４０００ａＢＰ）。存在由湿冷向干冷的气候变化。成层坡积上覆的坡积黄土则代表末次冰期全盛及全新世环境以显著干冷为特征。此剖面突出表明昆仑山垭口地区末次冰期早期不是干冷，而是湿冷，与季风模式不吻合。故只能认为当时该区受西风带影响。     

冷涡背景下不同类型强对流天气的成因对比分析

为提高对东北地区雷暴大风的分析和预报能力,基于2017—2021年东北地区自动气象站、闪电定位仪、葵花8号卫星综合判识雷暴大风天气,利用ERA5再分析资料计算强对流物理量和东北冷涡中心及半径等特征参量,研究东北地区雷暴大风的观测特征及其与东北冷涡（简称“冷涡”）的关系。结果表明：（1）东北地区雷暴大风（简称“总体”）集中出现在蒙古高原至大兴安岭以西、东北平原和辽宁沿海。冷涡导致的雷暴大风占总体雷暴大风的50.6%,辽河平原是冷涡雷暴大风最高发区域。东北地区总体和冷涡雷暴大风均具有单峰分布的日变化特征,在午后发生频率最高,但是深夜和上午时段雷暴大风多与冷涡有关,占比达75%。（2）雷暴大风逐小时出现的站数（简称“站数”）大多小于10次,站数大于10次的雷暴大风个例中,冷涡个例占56.5%,高于非冷涡。相比于非冷涡,冷涡雷暴大风发生在更干冷、850与500 hPa强温度直减率以及强的风垂直切变和风暴承载层环境中。（3）冷涡系统的不同象限出现的雷暴大风占冷涡雷暴大风的百分比从大到小依次为东南象限（73.5%）、西南象限（17.5%）、东北象限（7.5%）和西北象限（1.5%）。冷涡外围的雷暴大风次数多于冷涡本体,集中出现在冷涡东南象限距离冷涡中心0.5—2个冷涡半径的范围内,该区域大气中层存在干层、低层存在大的温度垂直递减率、中等以上的风垂直切变和更大的风暴承载层风速,并且更容易受低空切变线的影响,这也是冷涡雷暴大风集中出现在该区域的原因。（4）导致雷暴大风的冷涡中心集中于（45°—55°N,111°—128°E）,其中导致区域性雷暴大风的冷涡中心的频次分布为南北向,集中在116°E和122°E处。造成区域性雷暴大风的冷涡中心和最外围环流的位势高度均低于造成局地雷暴大风的冷涡,春、秋季差异更明显;冷涡半径在8月略大于导致局地雷暴大风冷涡,其他月份则反之。以上研究证明东北冷涡是导致东北地区雷暴大风最主要的天气系统,总结的冷涡不同象限处雷暴大风的空间分布和产生区域性雷暴大风的冷涡的特征,可供东北冷涡雷暴大风预报、预警时参考。