四川美姑发现侏罗纪恐龙足迹化石

2016年8月,在位于西昌盆地边缘的四川美姑县中侏罗统沙溪庙组底部薄层粉砂岩之上,发现有恐龙足迹化石。恐龙足迹共3个,均与跷脚龙足迹相似。该发现对于古气候、古地理和地层对比都具有重要的意义,足迹详细分类有待进一步研究。     

Age of the pterosaur and web-footed bird tracks associated with dinosaur footprints from South Korea

Abstract   An absolute age has been determined for the Cretaceous Uhangri Formation in which web-footed bird tracks, pterosaur tracks and dinosaur tracks have been discovered recently. This combined track discovery is a first from Asia. There is one other similar find in the world, however, the Uhangri site is greater in abundance and frequency. Moreover, the size of the pterosaur tracks indicates that the track maker had a wingspan of 10 m or more. Well-preserved tuffaceous rocks in the formation made it possible to measure geological age by Rb–Sr and K–Ar methods. Rb–Sr whole rock ages for the volcanic rocks are: 96.0 ± 2.5 Ma (MSWD = 0.354) for lapilli andesitic tuff, 81.0 ± 2.0 Ma (MSWD = 0.296) for felsic tuff and 77.9 ± 4.1 Ma (MSWD = 4.41) for Hwangsan welded tuff. K–Ar ages are younger, 83.2–68.8 Ma. The layer containing fossil tracks of pterosaurs and web-footed birds are preserved in black shale sandwiched by the lapilli andesitic tuff and felsic tuff, and are thus 96–81 Ma in age. Dinosaur footprints are dated at 96–78 Ma. Thus the pterosaurs, web-footed birds and dinosaurs coexisted in the same environment from Cenomanian to Campanian time.     

人造台风模型及资料同化对T213L31模式台风路径预报能力的影响

利用2003年台风季节T213L31的12时10天预报分析了国家气象中心全球中期数值预报模式系统T213L31对台风路径的预报能力,并就如何改进其对台风路径的预报能力进行了探讨。结果表明,在台风季节,T213L31模式在近57%的预报中对台风路径有预报,但初始位置误差较大。没有预报的区域主要集中在13～20°N,120°E以东的台风生成较为集中的地方,而此区域恰好不存在常规观测资料。对于目前仍采用OI分析的T213L31中期预报系统,常规观测资料在此区域的匮乏是其在此台风集中生成区预报能力较弱的主要原因。为了改进T213L31对台风路径的预报能力,本文就增加常规观测、加入人造台风模型进行了数值试验。试验结果显示,有限的常规观测对T213L31对台风的预报能力有明显提高。人造台风的加入无疑会改善T213L31在无常规资料区的预报,也会改善T213L31在资料较丰富地区的短期台风路径预报能力(36小时以内预报),而对较长时效预报的影响则有好有坏。     

Two modes and their seasonal and interannual variation of the baroclinic waves/storm tracks over the wintertime North Pacific

In this study, a newly developed method, termed moving empirical orthogonal function analysis (MEOF), is applied to the study of midlatitude baroclinic waves over the wintertime North Pacific from 1979 to 2009. It is shown that when the daily, high-pass filtered (2-10 days) meridional wind at 250 hPa is chosen as the variable of the MEOF analysis, typical features of baroclinic waves/storm tracks over the wintertime North Pacific can be well described by this method. It is found that the first two leading modes of the MEOF analysis, MEOF1 and MEOF2, assume quite different patterns. MEOF1 takes the form of a single wave train running in the east-west direction along 40°N, while MEOF2 is a double wave train pattern running in the east-west direction along 50°N and 30°N, respectively. The shift composites of various anomalous fields based on MEOF1 and MEOF2 assume typical baroclinic wave features. MEOF1 represents a primary storm track pulsing with an intrinsic time scale of two days. It shows significant "midwinter suppression" and apparent interannual variability. It is stronger after the mid-1990s than before the mid-1990s. MEOF2 represents a double-branch storm track, also with an intrinsic time scale of approximately two days, running along 50°N and 30°N, respectively. It shows no apparent seasonal variation, but its interannual and decadal variation is quite clear. It oscillates with larger amplitude and longer periods after the mid-1990s than before the mid-1990s, and is heavily modulated by El Niño-Southern Oscillation (ENSO).     

中国贵州中生代四足类足迹化石的回顾与新发现*

贵州省拥有丰富的中生代脊椎动物化石记录,多为三叠纪海生爬行类化石,侏罗纪和白垩纪的脊椎动物化石较少。目前,贵州省已发现中生代爬行类足迹点9处,分别为贞丰牛场、贞丰龙场、安顺幺铺、赫章辅处、毕节响水(2处)、仁怀茅台、赤水宝源和习水同民足迹点。文中除描述了贞丰龙场新增的一批足迹化石外,整理并总结了所有足迹点的发现史、研究现状、足迹类型与特征以及所反映的古生态信息。已发现的遗迹记录由69条行迹和420个孤立足迹组成,足迹总数达991个。所有的遗迹化石指示了至少477个造迹者,包括海生爬行类、手兽足迹类、非鸟兽脚类、鸟类、蜥脚类和鸟臀类等,其中三叠纪以海生爬行类主导,侏罗纪和白垩纪以蜥臀类主导。这个数据集为贵州中生代古生物类群的多样性提供了重要的信息,是晚中生代稀缺骨骼化石记录的良好补充,为研究贵州省中生代脊椎动物群的古生态与古环境提供了更多的证据。     

西北太平洋热带气旋路径异常偏折的分类特征

基于中国台风网CMA-STI热带气旋（TC）最佳路径资料,对1949—2016年西北太平洋TC路径发生异常偏折的地理位置进行K-means聚类分析,并将其分为五个区域。对各区TC路径异常偏折的频数、方向变化、周期及时间变率等特征进行分析。结果表明:(1)不同分区TC异常偏折高频月份不同,纬度较高区域主要发生在夏季,纬度较低区域则主要发生在秋季。(2)异常右折TC在发生偏折前移向主要为西北向,偏折后为北向;异常左折TC偏折前主要为北向,偏折后主要转为西北向。(3)西北太平洋TC异常偏折总频数存在准2~4年、准3~6年的年际变化周期,其长期变化趋势表现为20世纪80年代中期之前呈增加趋势,其后呈减少趋势, 低纬区域年变化与之最为相似,中高纬区域变化趋势不明显。（4）将研究区域按5 °×5 °进一步栅格化统计TC异常偏折频数的时间变率,发现其地理分布表现为中国沿海为正、台湾岛以东海域为负的变化特征。其中沿海的增加趋势主要由异常右折增加引起,台湾岛以东洋面的减弱趋势主要由异常左折的减少引起。(5)异常右折TC强度增强的高频中心主要位于菲律宾半岛以东洋面,次中心位于中国南海中部,而强度减弱位于台湾岛西南区域;异常左折TC强度增强的高频中心位于南海中部,强度减弱中心位于我国东南沿海。      

贵州贞丰中三叠统关岭组中Chirotherium--原始爬行类足迹研究

在贵州省贞丰县龙场镇和牛场镇两地中三叠统关岭组下段的泥质白云岩中保存有古老的爬行类--"手兽"的足迹化石--Chirotherium.该足迹为四足动物留下的行走轨迹,后足保存较完整,前足可见零星和不完整的趾痕.单个足迹由五个脚趾和后掌组成,由于其中的四个脚趾伸向前方而第五趾由后掌外侧横向伸出且向后弯曲,整个足迹看上去犹如人的手掌印痕.由前足脚印保存不完全可以判断,该造迹动物既可以四足行走又可以仅靠后足奔跑.龙场足迹点保存完整的后足脚印最大为长16cm,宽14cm,平均单步长70.2em,复步长为140cm;而牛场足迹点所见最大后足脚印长达25cm,宽17cm,平均单步长为52cm,复步长为98.5cm.笔者等参照国际上流行的计算方法,根据脚印长度和步长大小计算了两地造迹动物的臀高和行走速度:臀高大约0.64～1.0 m,估计身长可达2～3m,行走速度4～10km/h.考虑到造迹动物当时仅仅处于漫步和小跑状态,推测其奔跑速度可以达到20km/h以上.于欧洲、美洲等地发现的Chirotherium多数保存于三叠纪的红色砂泥岩层表面,其中多数岩层发育泥裂构造;还有些则保存于薄层碳酸盐岩层的表面,也多数发育泥裂构造.贞丰的两处足迹都保存于中三叠统关岭组下段发育泥裂构造的泥质白云岩表面,同样反映了当时炎热干旱的气候特点.在欧洲、南美洲、北美洲和亚洲的中国都发现了仅存于三叠纪的Chirotherium,说明这些地点在当时曾经属于同一个大陆,而且都处于干旱、炎热的低纬地区.由于该足迹点当时处于扬子古大陆南缘的台地上,而其东南侧则是著名的三叠纪南盘江复理石盆地,对该足迹的进一步研究有利于探讨台地和盆地的相变关系和生态差异,进而揭示盆地演化过程中与扬子板块的相互作用.     

Estimating the Predictability Limit of Tropical Cyclone Tracks over the Western North Pacific Using Observational Data

In this study, the nonlinear local Lyapunov exponent (NLLE) approach was used to quantitatively determine the predictability limit of tropical cyclone (TC) tracks based on observed TC track data obtained from the Joint Typhoon Warning Center. The results show that the predictability limit of all TC tracks over the whole western North Pacific (WNP) basin is about 102 h, and the average lifetime of all TC tracks is about 174 h. The predictability limits of the TC tracks for short-, medium-, and long-lived TCs are approximately 72 h, 120 h, and 132 h, respectively. The predictability limit of the TC tracks depends on the TC genesis location, lifetime, and intensity, and further analysis indicated that these three metrics are closely related. The more intense and longer-lived TCs tend to be generated on the eastern side of the WNP (EWNP), whereas the weaker and shorter-lived TCs tend to form in the west of the WNP (WWNP) and the South China Sea (SCS). The relatively stronger and longer-lived TCs, which are generated mainly in the EWNP, have a longer travel time before they curve northeastwards and hence tend to be more predictable than the relatively weaker and shorter-lived TCs that form in the WWNP region and SCS. Furthermore, the results show that the predictability limit of the TC tracks obtained from the best-track data may be underestimated due to the relatively short observational records currently available. Further work is needed, employing a numerical model to assess the predictability of TC tracks.     

重庆綦江白垩系夹关组恐龙足迹群沉积环境

重庆綦江莲花保寨保存有大量以莲花卡利尔足迹为主的恐龙足迹,研究其沉积环境对恢复当时恐龙动物群的生活环境有着十分重要的意义。运用岩石学、沉积学和古生物学方法,通过岩石学特征、沉积构造特征、粒度分布特征等分析重庆綦江莲花保寨恐龙足迹群的沉积环境,认为当时的沉积环境为曲流河沉积,恐龙足迹的赋存层位为曲流河边滩和河漫滩环境。     

几个典型台风路径的同化试验

从上海台风所的台风路径统计动力预报模型SD-90出发,利用变分同化方法结合反问题正则化思想和最优控制技巧(而非统计方法),反演出台风所受到的除科氏力以外所有力的合力及台风的初始速度,用实际台风定位资料分析不同的正则化参数及最优控制参数的组合对同化结果的影响,分析不同路径特征台风路径的拟合效果。该方法具有模式简单、应用资料少、拟合精度高等优点,为台风路径的预报提供了新的思路。