基于EOF和小波分析的福建近40年旱涝时空变化特征研究

采用经验正交函数分解（EOF）、快速富里叶变换（FFT）、连续（CWT）和正交小波变换（OWT），对近41a来福建省25个代表站不同雨季旱涝指数（Z指数）序列进行了分析。结果表明：（1）福建旱涝在1965—1975年及1990年代具有显著的2-3a周期；（2）在1980年代中期以后南北反向变化具有显著的1a和3-4a周期；（3）中西部与其它区域的反向变化，在1985—1998年间有显著的1-2a周期，在1980年代以后9-13a周期较强；（4）近40年来有干旱趋势，南部（东部）比北部（西部）明显，其中1990年代这种趋势显著。（5）1960年代和1980年代相对湿润，而1970年代和1990年代则相对干旱。     

边界层辐合线对强对流系统形成和发展的作用

应用天津CINRAD/SA雷达探测到的边界层辐合线信息,对2008—2009年6—9月发生在天津地区的边界层辐合线进行了统计分析,与2002—2007年海风锋触发形成的局地强对流天气分析相结合,研究结果表明:天津地区边界层辐合线的雷达低仰角基本反射率因子产品的回波特征一般表现为弱的窄带回波,回波强度仅为15~25 dBZ,宽度一般为3~10 km。在合适的层结状态和水汽条件下,这些边界层辐合线的演变和碰撞与强对流天气的发生、发展密切相关。单一边界层辐合线一般不能形成大范围的雷暴天气;两条以上边界层辐合线之间碰撞,一般在碰撞交叉处能够形成强对流天气。若已存在强对流天气,则强对流天气将加强。     

广西夏季降水的多时间尺度特征及影响因子

利用1951—2011年广西夏季降水站点资料和NCEP/NACR等多种再分析资料,通过相关分析、经验模态分解、统计检验分析了广西夏季降水的多时间尺度特征及其影响因子,利用多元线性回归方法对夏季降水进行拟合和预测试验。结果显示:广西夏季降水具有多时间尺度特征,不同时间尺度对应着环流因子不同时间尺度的分量;在准2年尺度上,主要影响因子为季风槽、低空急流、高空急流、贝加尔湖高度场、南印度洋东部海温。利用对广西夏季降水影响显著的环流因子本征模态函数分量和多元线性回归方法拟合夏季降水,相关系数为0.73,表明广西夏季降水是环流因子多时间尺度共同作用的结果。利用前期冬季南印度洋东部海温异常本征模态函数作为前兆因子预报广西夏季降水,6个独立样本检验显示预测与实况趋势一致,该工作可供利用多时间尺度信息进行区域气候预测参考。     

Spatial and temporal characterization of nutrient net uptake in a vegetated urban stream: Stream bank features leading to net uptake hotspots

Urban stream features can be used to promote nutrient retention; however, their interactions with different hydrological regimes impact nutrient cycling, decrease their retention capacity, and inhibit stream ecosystem functioning. This study analysed the temporal and spatial dynamics of the uptake of three nutrients (nitrate, ammonium, and phosphorus) in an urban drainage stream during high flows. In particular, we studied variations in net uptake along the right margin (with native vegetation and a roots mat) comparatively to the left margin (a non‐rooted grassy bank). Applying the spiralling approach within each subreach on either side, we determined nutrient subreach (sr) retention metrics: uptake rate coefficients , mass transfer rates , and areal uptake rates . Our results showed nitrate (NO₃) and ammonium (NH₄) net uptakes on the right side were higher and more frequent along subreaches where the root mat was more abundant ( [μg m^?2 s^?1] = 22.80 ± 1.13 for NO₃ and 10.50 ± 0.81 for NH₄), whereas on the left side both nutrients showed patchy and inconsistent net uptake patterns despite the homogeneous grass distribution. Net uptake for filtered reactive phosphorus (FRP) was not observed on either side at any flow rate. The impact of hydrological factors such as discharge, travel time, water depth, and concentration, on uptake metrics was studied. Despite increases in travel time as the flow decreased, there was a reduction in net uptake rates, and , on either side. This was attributed to a reduction in water level with declining flows, which decreased hydrologic connectivity with the stream banks, combined with a decrease in water velocity and a reduction in nutrient concentrations. We concluded the rooted bank acted as an effective retention area by systematically promoting net uptake resulting in a twofold increased dissolved inorganic nitrogen (DIN) retention relative to the non‐rooted side where net uptake was spatially localized and highly dynamic. Overall, this work emphasized the importance of strategically sampling close to biologically active surfaces to more accurately determine areas where gross uptake surpasses release process.     

安徽省地震成组活动特征及其危险性分析

利用强震组增益P、强震组效能R和强震组分布变异值S等3种指标，对安徽省1300年以来地震成组活动的客观性进行了检验，结果显示，该区不同时段、不同震级的地震活动呈现不同的特征和分布类型；同时，用b值方法分析了目前地震活动状态；在此基础上，应用泊松模型对未来地震趋势进行了概率预测。     

Characteristics of the May 12,2008 Wenchuan M_S8.0 Earthquake Sequence and Discussion on Relevant Problems

The aftershock activity of the May 12, 2008 Wenchuan Ms8.0 Earthquake Sequence shows an obvious segmented feature. Most of the large aftershocks were distributed in the north and south parts of the aftershock zone. Thrusting was dominant with a small amount of strike-slip component in the south part. The aftershock activity decayed gradually, presenting the sequence features of a mainshock-aftershock pattern. The north part was the ending area of the maiushock fracture where strike-slipping was dominant, showing an obvious swarm feature. Therefore it became the major area for large aftershocks. The modulation of the earth tide on aftershock activity is remarkable; most large aftershocks occur during the period of flood and neap tide. The time period around 16:00 was the dominant occurring time for large aftershocks. The p-value, a parameter of modified Omori formula, increases gradually with time, and reaches about 1 at the end. Based on previous study, the sequence patterns, magnitude of maximum aftershock, as well as the duration of aftershock activity has been discussed. The primary results also show that the magnitude difference between the maiushockand the maximum aftershock is proportional to the rupture size of the maiushock for huge earthquakes of about Ms8.0. This means that when the magnitudes of the earthquakes are nearly the same, large rupture size corresponds to sufficient energy release.     

西藏当惹雍错和扎日南木错现代湖泊基本特征

湖泊现代特征的调查和对比研究是湖泊学和古湖泊学研究工作的基础,青藏高原大部分湖泊目前仍缺少详细的基本特征考察资料.基于2009年9月实地考察,本文报道藏北高原腹地的两个内陆封闭大湖——扎日南木错和当惹雍错的水深分布和现代湖水基本特征.测深结果显示扎日南木错大部分湖区水下地形较为平坦,最大水深为71.55m;当惹雍错实测最大水深为214.48m,是青藏高原上已知最深的湖泊,也是我国已知的第二深水湖.湖水理化性质显示在垂直方向上两湖都呈现明显的分层结构,温跃层的温度梯度分别为1.1℃/m和0.57℃/m,当惹雍错底层水温最低仅为1.6℃;两湖表水层的电导率分别高达18500μS/cm和12900μS/cm;两湖表水层pH都超过10,而底层水的pH都降低到5左右,上下层湖水显示了不同的酸碱性质.湖水电导率和溶解氧在温跃层都具有同步跃变特征,反映了温度对湖水性质的影响.     

泸沽湖近代沉积环境时空变化特征及原因分析

通过对泸沽湖沉积岩芯粒度、磁化率(χ_(lf))、化学蚀变指数(CIA)等沉积指标的分析,结合~(210)Pb和~(137)Cs定年结果以及区域降水和人类活动等资料,研究了近150年来泸沽湖沉积环境的时空变化特征与主要影响因素.泸沽湖沉积物粒度组成以黏土与细粉砂为主(80%),细颗粒组分(如黏土)含量与χ_(lf)、CIA之间具有显著相关性.各岩芯沉积指标垂向变化规律相似,1920s之前,沉积指标较为稳定,为人类活动影响较弱的准自然沉积阶段;1920s以来,χ_(lf)、CIA值与黏土含量逐渐升高,反映了风化与成壤作用较强的细颗粒表土物质侵蚀开始加强,可能与流域农业发展及森林砍伐等人类活动影响有关;约1970年以来,χ_(lf)、CIA值与黏土含量进一步升高,指示了流域内表土侵蚀与上述人类活动影响的进一步增强,与文献记录的1970s—1980s两次大规模的森林砍伐吻合;约2002年以来,χ_(lf)、CIA值与黏土含量降低,反映了表土侵蚀减弱,与近年来流域植被逐渐恢复及降水减少有关.与器测资料对比研究表明,降水等气候因素对近代泸沽湖沉积环境演变的影响相对较弱.空间上,各沉积指标表现出一定的异质性.黏土含量在南部和北部湖区两侧靠近洪积扇及冲积平原的湖区沉积物中较高;近50年以来,各沉积岩芯所反映的平均沉积通量为0.020~0.043 g/(cm~2·a),南部湖区高于北部湖区,主要受入湖水系分布及流域南部地区高强度人类活动导致的土壤侵蚀的影响.     

Magma Chamber Process of Post-collisional Magmatism: Insight from Textural and Elemental Characteristics of Plagioclase from the Tatun Volcanic Group, Northern Taiwan Volcanic Zone

The Taiwan mountain belt, one of the youngest orogenies in the world, is caused by the collision of the Luzon arc with the Eurasian margin, which leads to post-collisional extension and magmatism in the Northern Taiwan Volcanic Zone (NTVZ). The magma chamber process in this region has not previously been elucidated in detail. In this paper, the textural and compositional features of plagioclase phenocrysts in basalt from the Tatun Volcanic Group (TTVG) were studied to restrict the dynamics of magma system. Results show that the magma melts in TTVG are mainly sourced from the underlying MORB-like mantle wedge but influenced by incorporation of subduction components, causing the elevated Sr/Y and Ba/Y ratios in magma melts. The subduction components are mainly transported in the form of sediment melt. The plagioclase phenocrysts in the TTVG volcanic rocks are generally coarsely core-sieved with a clear rim. The An contents in the rims of plagioclase are much lower than those of cores, and elevated FeO concentrations are detected in the plagioclase rims. We propose there exists a double-layer magma chamber in this region. The core of the plagioclase was crystalized in the deeper quiescent magma chamber (~21 km), which was subsequently partially dissolved during the ascent of magma melt under H2O-undersaturated condition, forming the typical coarsely sieved texture and synneusis. When this crystal-rich melt migrates into the shallower chamber, water saturation is reached and more sodic plagioclase formed as the rim of phenocryst. Due to the considerably higher fO2 in the shallow chamber than in the deeper one, and the distribution of Fe between plagioclase and melt positively correlates with fO2, the FeO content in the plagioclase rim elevates in conjunction with increasing fO2.     

钦杭成矿带南段粤西大金山地区的区域地球化学特征与成矿规律探讨

粤西大金山地区位于大金山旋转构造带中,是粤西S、Ag、Pb、W、Sn、Au重要的成矿远景区,该地区矿产地多,矿化类型多,成矿带分布广。其1∶5万水系沉积物综合异常为一个环长35km、宽2~5km,面积约220km2的环带状异常,主要由W、Sn、Bi、Mo、Pb、Zn、Ag、Au等元素组成,具有元素组合复杂,规模大,强度高的特点;环绕着大金山旋转构造带分布有大金山大型钨锡矿、大降坪特大型硫铁矿、高枨大型银铅锌矿、九曲岭中型锡矿、石门头中型铅锌矿等矿床。本文基于化探综合异常,解析各典型矿床特征认为:1大金山地区以"穹隆"为中心,成矿元素自内向外依次形成有规律的水平分带:W、Sn、Bi→Sn→Sn、Pb、Zn、Ag→Ag、Pb、Zn(Au)→Au;2钨锡矿床和铅锌矿床具有清晰的垂直分带规律;3钨锡铅锌银矿床均形成于燕山晚期。在此基础上,建立了大金山地区成矿模式:震旦纪海底火山喷流(气)活动形成的浅变质岩系,为锡铅锌银矿床的形成提供了物质来源;燕山运动早期,在两个区域性北东向断裂带的左旋扭动下,形成大金山旋转构造带;燕山晚期岩浆活动使大金山旋转构造带扩容,且携带部分成矿物质(如钨等)的深源热液溶解了大绀山组地层中的锡、铅、锌、银、金等元素,在各裂隙系统中成矿。