Meso-scale available gravitational potential in the world oceans

The pitfalls of applying the commonly used definition of available gravitational potential energy （AGPE） to the world oceans are re-examined. It is proposed that such definition should apply to the meso-scale problems in the oceans, not the global scale. Based on WOA98 climatological data, the meso-scale AGPE in the world oceans is estimated. Unlike previous results by Oort et al. , the meso-scale AGPE is large wherever there is a strong horizontal density gradient. The distribution of meso-scale AGPE reveals the close connection between the baroclinic instability and the release of gravitational potential energy stored within the scale of Rossby deformation radius.     

条件性对称不稳定与昆明准静止锋风雹

用对称不稳定理论，对１９９７年春季滇南一次连续性静止锋风雹过程进行分析，结果表明：条件性对称不稳定、锋生强迫、锋面次级环流是形成云南低纬高原上风雹天气的重要因子。     

Digital photogrammetry as a tool in analogue modelling: applications to volcano instability

Three techniques of digital photogrammetry have been applied successfully to laboratory analogue models to study surface displacements caused by various volcano deformation types. Firstly, side-perspective videos are used to differentiate profile displacements between cryptodome intrusion models and models deforming by ductile inner-core viscous flow. Both models show similar morphologic features including a bulged flank and an asymmetric upper graben. However, differences in displacement trajectories of the bulge crest reflect upward intrusion push contrasting with essentially downward displacement vectors of weak core models. The other two techniques use vertical views correlated automatically either as time-sequence monoscopic views or as coeval stereoscopic pairs. This exploits to a maximum the method’s potential by imaging surface displacements over the whole model. Successive monoscopic photograms, because they suffer only moderate numerical processing for topographic effect removal, can detect very small displacements occurring early in deformation processes. As illustrated by analysis of intrusion models, the monoscopic method allows prediction of fault locations and main displacement locations. It can also anticipate the principal strain directions, and separate different deformation stages. On the other hand, the stereo-photogrammetry technique, although more complicated, provides topography and volume changes, as well as pictures of surface displacements in three dimensions. Results are presented for the spreading of volcano models on a ductile substratum and viscous cored cones. We have found digital photogrammetry to be a useful tool for analogue modelling, because it provides quantitative data on surface displacements, including movement invisible to the eye, as well as topographic changes. It is a good method for investigating and comparing different deformation mechanisms. It is especially useful for interpretation of displacement patterns obtained from monitoring of natural active volcanoes. In fact, results of the methods used in the laboratory can be directly compared with field data from geodetic or photogrammetric surveys, as at Mount St. Helens in 1980.     

肩关节后方不稳定的CT和MR特点?

目的：总结分析肩关节后方不稳定的CT、MRI表现特点。方法：16例经关节镜手术检查证实病例,对肩关节后方不稳定患者的关节盂、肱骨头和后盂唇关节囊复合体异常在 CT、MRI上表现特点进行总结分析。结果：肩关节后方不稳定影像征象包括关节盂发育不良（后部关节盂缘缺如）、反Bankart骨折、反Hill-sachs骨折、Bennett病变、后盂唇关节囊复合体病变、肱骨头后方半脱位或完全脱位。结论：对于肩关节后方不稳定的患者,行患侧肩关节 CT、MRI能够清晰显示关节盂、肱骨头和后盂唇关节囊复合体异常,是肩关节后方不稳定的一种有效准确的检查方法。     

Climatic variations in the past 140 ka recorded in core RM, east Qinghai-Xizang Plateau

The sequences of climatic evolution are reconstructed by the analyses of δ¹³C and δ¹⁸O of carbonate from core RM in the Zoige Basin since 140 kaB. P. During the Last Glaciation there existed at least seven warm climatic fluctuations and five cold events correlated with the records of ice core and deep sea, and during the preceding last interglacial period there were two cold climatic variations coinciding with the record of ice core GRIP. These results de-pict climatic instability in east Qinghai-Xizang Plateau over the last interglacial period. In addition, the environmental proxies of the carbonate content and pigments indicate the similar results to the stable isotope record from core RM. Project supported by the Chinese Climbing Project (85-029-02-01).     

日照沿海海陆风的气候特点及其对天气的影响

使用近海海温资料和莒县站、日照站气象资料,用对比分析的方法分析了日照地区沿海海陆风的气候特征及对当地天气的影响。发现海陆风明显的季节变化和日变化对当地气温、降水、湿度及天空状况等气象要素的空间和时间分布影响显著。海风强盛季节的午后和陆风强盛季节的早上,沿海的温度梯度常具有海风锋和海岸锋的特征,使沿海地区低云和雷暴天气明显增多,降水分布具有明显的海陆风和地形影响特征。     

华东雾和霾日数的变化特征及成因分析

基于华东449个气象站点1961-2007年的雾、霾、气温和露点温度数据、1980和2005年土地利用数据及2000-2007年MODIS气溶胶光学厚度数据,利用气候统计诊断、遥感和地理信息系统技术分析了华东雾、霾日数的气候变化特征及成因,结果表明:1961-2007年期间,华东雾日数在全年及四季都呈现出先增多后减少的年际变化特征,霾日数在全年及四季则呈现出逐渐增多的年际变化特征。在1961-1980年和1981-2007年期间,华东多数地区的雾日数分别呈现出增多和减少的变化趋势,霾日数则在两个时期都表现为增多趋势。华东雾日数和霾日数的变化特征与我国已有的研究结果一致,气象条件的变化、区域城市化和土地利用变化以及大气污染物排放量增加所导致的气温升高和城市热岛效应增强、空气湿度和风速降低、气溶胶光学厚度增加等是华东雾和霾出现频率变化的主要原因。     

中国近30年气候要素时空变化特征

利用1971~2000年中国603个气象站点逐日平均温度和降水量数据,借助ArcGIS空间分析工具,采用自组织特征映射模型(SOFM),对中国气候变化的时空特征进行分析。研究结果表明:近30年中国气候变化的总体特征以增温为主,增温增湿的地区面积最为广大;季节变化构型也以增温增湿为主,秋季略有异常;从年代际变化来看,1971~1980年间,中国的气候以降温为主,而从1981年开始的20年间,全国的气候变化转为增温占主导。SOFM网络分类结果可以描述为缓增温少降水、剧增温平降水、缓增温缓降水和剧增温剧降水等四种类型。     

Climatic fluctuation and disasters during recent 100 years in China’s tropics

The temperature appeared rising trend during the 20th century in China’s tropics. Two cooling stages and two warming stages in the process of climatic fluctuation can be recognized. After the 1980s the climate is the warmest which corresponds to the global change, but the warmest period is the 1940s in Kunming. The climate pattern mostly appears contemporaneity of warming and humidity, which is different from the situation of whole China. The natural disasters tend to be aggravated. The number of typhoons increased. Flood damages occurred frequently in the years of more typhoons. The number of droughts and cold damages increased. It was snowed in Guangzhou. There was frost in Haikou and Yaxian. Four years of heavy snow have been recorded in Kunming.     

西安地区全新世古土壤下部木本植物根孔的发现与研究

在西安南郊和东郊全新世古土壤下部发现了许多木本根孔及充填物,根孔直径多为1~2cm,大者为5cm,分布深度达4m多。密集的木本根孔和其中乔木根孔的存在指示当时植被为繁茂的森林。根孔充填物的颜色、粒度和矿物组成均与全新世古土壤粘化层相同,表明充填物来自全新世古土壤。根孔以机械充填为主,后期有胶体化学充填。根孔的充填发生在全新世古土壤发育的中、后期,推测当时出现了气候突然变干的事件。根孔中分布深达2m左右的光性粘士胶膜指示全新世古土壤具森林土壤特征,当时年均降水量可达80.0mm左右。