Mean, interannual variability and trends in a regional climate change experiment over Europe. II: climate change scenarios (2071–2100)

We present an analysis of climate change over Europe as simulated by a regional climate model (RCM) nested within time-slice atmospheric general circulation model (AGCM) experiments. Changes in mean and interannual variability are discussed for the 30-year period of 2071–2100 with respect to the present day period of 1961–1990 under forcing from the A2 and B2 IPCC emission scenarios. In both scenarios, the European region undergoes substantial warming in all seasons, in the range of 1–5.5°C, with the warming being 1–2°C lower in the B2 than in the A2 scenario. The spatial patterns of warming are similar in the two scenarios, with a maximum over eastern Europe in winter and over western and southern Europe in summer. The precipitation changes in the two scenarios also show similar spatial patterns. In winter, precipitation increases over most of Europe (except for the southern Mediterranean regions) due to increased storm activity and higher atmospheric water vapor loadings. In summer, a decrease in precipitation is found over most of western and southern Europe in response to a blocking-like anticyclonic circulation over the northeastern Atlantic which deflects summer storms northward. The precipitation changes in the intermediate seasons (spring and fall) are less pronounced than in winter and summer. Overall, the intensity of daily precipitation events predominantly increases, often also in regions where the mean precipitation decreases. Conversely the number of wet days decreases (leading to longer dry periods) except in the winter over western and central Europe. Cloudiness, snow cover and soil water content show predominant decreases, in many cases also in regions where precipitation increases. Interannual variability of both temperature and precipitation increases substantially in the summer and shows only small changes in the other seasons. A number of statistically significant regional trends are found throughout the scenario simulations, especially for temperature and for the A2 scenario. The results from the forcing AGCM simulations and the nested RCM simulations are generally consistent with each other at the broad scale. However, significant differences in the simulated surface climate changes are found between the two models in the summer, when local physics processes are more important. In addition, substantial fine scale detail in the RCM-produced change signal is found in response to local topographical and coastline features.     

北太平洋700毫巴月平均环流形势与海温的相互关系

北太平洋700 mb环流形势具有相当鲜明的季节性与地域性特征.北太平洋的海、气相互作用是这些特征以及东亚季风形成的一个原因.从海、气相互作用的角度出发,对比分析北太平洋700 mb环流形势和海表温度距平的分布,可以看出:有些情况下,大气对海洋的影响比较明显;在另一些情况下,海洋对700 mb环流形势的影响较为明显.它们之间的矛盾与矛盾的主要方面是不断地、经常地在转化以及相互影响着.它们的转化、演变对我国副热带高压及旱涝天气的变化有一定的关系。     

Dependence of the agcm climatology on the method of prescribing surface boundary conditions and its climatological implication

By using IAP 9L AGCM, two sets of long-term climatological integration have been per-formed with the two different interpolation procedures for generating the daily surface boundary conditions. One interpolation procedure is the so-called “traditional” scheme, for which the daily surface boundary conditions are obtained by linearly interpolating between the observed monthly mean values, however the observed monthly means cannot be preserved after interpolation. The other one is the “new” scheme, for which the daily surface boundary conditions are obtained by linearly interpolating between the "artificial" monthly mean values which are based on, but are dif-ferent from the observed ones, after interpolating with this new scheme, not only the observed monthly mean values are preserved, the time series of the new generated daily values is also more consistent with the observation. Comparison of the model results shows that the differences of the globally or zonally averaged fields between these two integrations are quite small, and this is due to the compensating effect between the different regions. However, the differences of the two patterns (the global or regional geographical distributions), are quite significant, for example, the magni-tude of the difference in the JJA mean rainfall between these two integrations can exceed 2 mm/day over Asian monsoon regions, and the difference in DJF mean surface air temperature can also exceed 2oC over this region. The fact that the model climatology depends quite strongly on the method of prescribing the daily surface boundary conditions suggests that in order to validate the climate model or to predict the short-term climate anomalies, either the " new* interpolation scheme or the high frequency surface boundary conditions (e.g., daily or weekly data instead of the monthly data) should be introduced. Meanwhile, as for the coupled model, the daily coupling scheme between the different component cli?mate models (e.g., atmospheric and oceanic general circulation models) is preferred in order to partly eliminate the “climate drift” problem which may appear during the course of direct coupling.     

一件张家湾巢湖龙（双孔下纲：鱼龙型超目）标本的新认识

早三叠世是鱼龙起源和早期演化的关键阶段，Chaohusaurus则是该时期化石材料最丰富、研究程度最高的鱼龙类群之一，但其标本几乎全部产自华南下扬子区的安徽巢湖，此外仅在中扬子区北部的湖北远安曾有少量发现和报道。本次对一件曾初步研究的远安Chaohusaurus zhangjiawanensis标本开展进一步修复和观察，对该属种形态信息缺失较多的头骨进行描述并重点与Ch zhangjiawanensis最早报道的两件标本及安徽研究程度较高的其他Chaohusaurus进行对比分析，以期补充完善对Ch zhangjiawanensis比较解剖和形态功能特征的认识并加强对Chaohusaurus内群演化、生活环境和活动范围等方面的了解。发现Ch zhangjiawanensis与Ch chaoxianensis、Ch brevifemoralis等安徽分子的骨骼整体比例和头骨各孔构成等特征相似，但较Ch chaoxianensis和Ch brevifemoralis上颌骨更长、附着牙齿更多且更密集强壮，外鼻孔的后置不明显，骨架更粗壮，躯干更僵硬。研究认为Ch zhangjiawanensis与安徽Chaohusaurus的骨骼形态差异可能是不同环境导致，推测其多而强壮的后部上颌牙和僵硬的躯干可能是因其以高度骨化的湖北鳄等脊椎动物为食和生活在局限、高盐度的浅海环境而发生的适应性演化，但也不能排除是继承自更古老的类群，或是其活动范围更大、食物来源更广等原因。据此分析，由于早三叠世恶劣的海洋生态环境，碎片化分布的小生态地理区可能广泛存在，使典型的游泳型生物鱼龙在起源和辐射后又在这些缺乏交流的“避难所”中分别演化并形成不同的形态属，但这也导致从特殊骨骼形态探讨早期鱼龙各类之间的演化关联及追索其共同祖先变得困难，因此尚需继续加强对已知早三叠世鱼龙化石层下部层位及相应化石产区附近同时期不同环境海相化石的追寻和分析。     

Distribution and transport of suspended sediments off the Yellow River (Huanghe) mouth and the nearby Bohai Sea

Hydrological and sedimentological investigations were carried out off the Yellow River (Huanghe) mouth and the nearby Bohai Sea during August–September 2007 to examine the distribution and transport of suspended sediments. Our data witnessed that suspended sediments from the Yellow River mouth primarily extend southerly and southeasterly during the flood season. High suspended sediment concentration (SSC) occurs as turbid plume on both sides of the river mouth, where it can reach >20 mg l^?1 in the surface water and >40 mg l^?1 in the bottom water. Accordingly, salinity varies from 25 to 29 psu, mean grain size (Dmz) is >200 μm, and volume concentration (VC) is >100 μl l^?1. High SSC was concentrated in the river mouth area as two muddy patches, i.e. the North Mud and South Mud, consisting mostly of fine-grained silt and clayey silt sediments. Our results have verified the larger extent of the South Mud than that of the North one, implicating south- and southeastward sediment dispersal paths that prevail near the river mouth area. The existing anti-clockwise and clockwise flows in the river mouth area were synthesized as the major hydrodynamics responsible for forming the two muddy patches. Tidal and residual currents are considered as the key hydrodynamic factors controlling the sediment distribution and transport in the region.     

Observation and Research on the Twisting Characteristics of Flare Loop System

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基于EEMD的明代北京地区干旱灾害特征分析

集合经验模态分解（EEMD）是一种适用于非线性、非平稳序列的信号分析方法,将EEMD应用于气候要素时间序列,可提取真实可靠的气候变化信号。根据北京地区历史时期干旱灾害资料,采用EEMD分解方法对明代（1368—1644年）北京地区干旱灾害等级序列进行多时间尺度的分析,获得简洁且平稳性较好的固有模态函数分量,并与所统计的明代北京地区干旱灾害频次多项式拟合曲线进行对比。结果表明：将EEMD应用于干旱灾害等级序列,可以提取干旱灾害中各个尺度的变化,对明代北京地区干旱灾害进行多尺度分析。明代北京地区干旱灾害存在着2.8年、6.3年的年际周期,11.5年、26.6年、53.6年的年代际周期和118.7年、299.5年的世纪周期。北京地区干旱灾害在明代整个时间跨度上呈现着先增加后微减的变化趋势,总体而言明代中期以后旱灾明显增多。     

Asteroseismic Analysis of a Cen B: Preliminary Tests of Effects of Rotation and Interior Magnetic Field in the Solar-like Star

Taking into consideration the effects of rotation and interior magnetic field during the lifetime of the star, we reconstruct the model of a Cen B to satisfy the latest nonasteroseismic and asteroseismic observational constraints. We find that the effects can induce a change of about 0.3 μHz in the large frequency spacings and can speed up the star's evolution. The model of a Cen B has thereby been improved.     

Ground-roll separation of seismic data based on morphological component analysis in two-dimensional domain

Ground roll is an interference wave that severely degrades the signal-to-noise ratio of seismic data and affects its subsequent processing and interpretation. In this study, according to differences in morphological characteristics between ground roll and reflected waves, we use morphological component analysis based on two-dimensional dictionaries to separate ground roll and reflected waves. Because ground roll is characterized by low-frequency, low-velocity, and dispersion, we select two-dimensional undecimated discrete wavelet transform as a sparse representation dictionary of ground roll. Because of a strong local correlation of the reflected wave, we select two-dimensional local discrete cosine transform as the sparse representation dictionary of reflected waves. A sparse representation model of seismic data is constructed based on a two-dimensional joint dictionary then a block coordinate relaxation algorithm is used to solve the model and decompose seismic record into reflected wave part and ground roll part.The good effects for the synthetic seismic data and application of real seismic data indicate that when using the model, strong-energy ground roll is considerably suppressed and the waveform of the reflected wave is effectively protected.