长江下游酷暑与冷夏的分析

长江下游的酷暑与冷夏是旱涝以外的另一种重要灾害性天气,本文以南京为代表,确定了长江下游酷暑年和冷夏年的三条标准。盛夏(7—8月)温度主要决定于7月平均温度T,并与副热带高压和中高纬度的冷空气活动以及印度季风低压—ITCZ有关。在酷暑年,印度低压更为频繁而强烈,位置略偏南;副热带高压较强,且直接控制江淮流域。100hPa青藏高压明显偏强,位置偏北偏东;青藏高原上常有500hPa暖中心东移。冷夏年三种成因:一是冷空气较强,梅雨明显而持久;二是ITCZ和热带系统强而活跃,盛夏频繁影响长江流域;三是以上两种天气系统的影响,形成混合型冷夏。     

华南暴雨中云物理过程的数值研究

利用“海峡两岸及临近地区暴雨试验”(HU AM EX)取得的观测资料, 使用高分辨非静力平衡中尺度数值模式 M M 5 湿物理显式方案, 模拟研究了 1998 年 5 月 23～ 24 日自粤北移向南海海岸的冷锋及锋前对流云团造成的华南暴雨中的云物理过程。 结果表明, 由于对流形成的具有冰相参加的冷云过程是华南暴雨形成发展的主要云物理过程, 当对流较弱因而只有水相而无冰相的暖云过程只造成范围虽大但强度较弱的降水。     

高原及冷空气对1998和1991年夏季西太副高及雨带的影响

为了寻找西太副高南北急剧摆动的中、短期预报着眼点 ,本文利用 1998和 1991年 6～ 8月的逐日天气图资料、第二次青藏高原气象科学试验的实测资料 ,以及NCEP/NCAR的 2 .5°× 2 .5°经 /纬度格点的日平均u、v及高度再分析资料等 ,分析了高原涡东移、南亚高压南北摆动 ,以及北方冷空气入侵等对西太副高脊线及其相伴雨带摆动的影响。主要结论如下 :1)凡高原东部气柱平均厚度ΔH3 0 050 0 ≥392gpdm时 ,未来高原涡将东移出高原 ,激发西南涡产生东移 ,使西太副高南落 ,长江中、下游流域产生暴雨 ;2 )南亚高压东段脊线和西太副高西段脊线的南北摆动趋势相同 ,但前者更稳定 ,且常提前 3天 ,可据此预报西太副高的摆动及其相伴雨带的位置 ;3)若北方有冷空气持续南下 ,华北与华南、江南分别出现 2m·s-1以上的南风负、正距平 ,将易在该南风正、负距平过渡区且偏于负距平区一侧产生暴雨 ,并使西太副高稳定少动。     

河西走廊地质记录中的新仙女木事件及其前后古地理环境演变

新仙女木事件在河西走廊地区开始于 12 5 8ka·B·P ,结束于 9 4ka·B·P ,极盛期为11 0ka·B·P左右。新仙女木事件使河西走廊地区晚更新世末转温暖湿润的气候在 12 0～ 10 0ka·B·P之间发生间断。降温期间 ,突发性洪水、干旱、风暴、沙暴、尘暴极端事件和突发性火灾频繁发生。降水减少 ,湖泊干涸 ,生态环境恶劣 ,沙漠化日益严重。古地理环境的演变 ,影响和限制了动物群的繁衍和人类文化的发展。     

Chemical, biological and hydrological controls on the C content of cold seep carbonate crusts: numerical modeling and implications for convection at cold seeps

Understanding the hydrology of cold seep environments is crucial to perform accurate estimates of fluid and chemical fluxes at sedimentary wedges. Shallow convection processes may affect fluid flux estimates and could favor the destabilization of gas hydrate accumulations, increasing the sediment-ocean methane flux. Evidence for the occurrence of convection at cold seeps, however, is still limited. We use the concentration of ¹⁴C (D¹⁴C) in carbonate crusts formed at cold seeps of the eastern Mediterranean Sea as a tracer for convective recirculation of seawater-derived fluids. A numerical model is applied to investigate the controls on ¹⁴C incorporation in cold seep carbonates. Our simulations show that increased amounts of CH₄ in the expelled fluids result in elevated crust D¹⁴C, while high Ca²⁺ and HCO₃⁻ concentrations produce the opposite effect. Convection is the only transport process that can significantly increase crust D¹⁴C. Advection, bioirrigation, eddy diffusion and bioturbation instead, have little effect on, or produce a decrease of, crust D¹⁴C. In addition, the presence of old or modern carbon (MC) in host sediments prior to cementation and the ¹⁴C-decay associated to the time needed to form the crust contribute in defining the D¹⁴C of carbonate crusts. We then use the model to reproduce the ¹⁴C content of the eastern Mediterranean Sea crusts to constrain the chemical and hydrological conditions that led to their formation. Some crusts contain relatively low amounts of ¹⁴C (−945.0<D¹⁴C ‰<−930.2) which, assuming no ageing after crust formation, can be reproduced without considering convection. Other crusts from two sites (the Amsterdam and Napoli mud volcanoes), instead, have a very high ¹⁴C-content (−899.0<D¹⁴C ‰<−838.4) which can only be reproduced by the model if convection mixes deep fluids with seawater. Order-of-magnitude calculations using the Rayleigh criterion for convection suggest that the slow seepage (about 10 cm year⁻¹) of low salinity (20‰) fluids at the Amsterdam sites could trigger haline convection there. On the Napoli mud volcano, where high-density brines are expelled, density-driven convection cannot take place and other processes, possibly involving the rapid movement of free gas in the sediment, could be important.     

A GLACIAL STAGE SPANNING THE ANTARCTIC COLD REVERSAL IN TORRES DEL PAINE (51°S), CHILE, BASED ON PRELIMINARY COSMOGENIC EXPOSURE AGES

ABSTRACT. Initial cosmogenic ¹⁰Be results from a former ice limit in Torres del Paine indicate a shortlived stillstand or readvance of Patagonian ice culminating at 12–15 kyr BP with a mean age of 13.2 ± 0.8 kyr BP. The glacier extended some 40 km beyond the present ice margin and was within 15 km of the presumed Last Glacial Maximum limits. The timing of the glacier stage spans the cooling event recorded in Antarctic ice cores, termed the Antarctic Cold Reversal (14.5–12.9 kyr BP). This result implies that glaciers at these latitudes were out of phase with those in the northern hemisphere; instead they mirrored the climate structure of Antarctica during the last glacial to interglacial transition.     

辽宁海城7.3级地震死亡人数-年龄分布的分析

2004年2月，我们在辽宁省海城市档案馆发现了《海城市县委关于全县干部人员受地震伤亡统计表名单》。通过对地震时死亡以及震后冻死、烧死、捂死和病死者年龄段的分析，得出不同的原因致死者所集中的年龄段不同。这个结论对于中国北方冬季的防震减灾有相当的参考价值，对今后的防震减灾工作有一定的指导意义。     

中国东部冷、热夏与近海强热带气旋变化的若干特征

利用１９５１－１９９４年台风鉴和气温资料，在划分冷、热夏标准的基础上，分别统计分析了我国东部近海强热带气旋活动的某些特征。结果发现，我国东部冷夏年近海强热带气旋无论在其频数，路径，强度和移速变化等均与热夏年迥然不同。讨论了这种差异的环流背景特征。     

北半球冬季冷涌及其反馈过程对我国南方降水的影响

分析了北半球冬季中、低纬度天气系统之间的相互作用及其与我国南方降水的关系，指出在降水出现时北半球极锋急流和副热带急流合并增强，而且急流入口区出现超地转风。这些现象有时与北半球冷涌到达中、低纬度后所引起的对流和哈得莱环流的增强及其反馈过程有联系，并且为我国南方降水提供了有利条件。     

稀王水冷浸—活性炭富集测定501铀矿床和土壤样品中的金

本文介绍了用稀王水冷浸、活性炭富集测定铀矿床和土壤样品中金的方法及结果。