天山南坡暖季暴雨过程的水汽来源及输送特征

利用1981—2020年5—9月天山南坡16个气象站逐日降水资料和NCEP/NCAR GDAS再分析资料,分析天山南坡暖季暴雨过程的环流形势,并采用HYSPLIT模式,模拟追踪水汽源地及输送特征。结果表明:天山南坡暖季暴雨主要发生在南亚高压双体型、500 hPa以上西南急流(气流)、700 hPa切变辐合以及天山地形辐合抬升的重叠区域。水汽主要源自中亚、大西洋及其沿岸、地中海和黑海及其附近,经TKAP(塔吉克斯坦、吉尔吉斯坦、阿富汗东北部、巴基斯坦北部和印度西北部)、南疆、北疆关键区,分别从偏西、偏南、偏北通道输入暴雨区,700 hPa以上偏西通道、以下偏北通道占主导地位,且贡献最大的是南疆关键区。源自中亚的水汽主要输送至暴雨区700 hPa及以下,对暴雨的贡献较大,且沿途损失较大;源自大西洋及其沿岸、地中海和黑海及其附近的水汽主要输送至暴雨区700 hPa以上,对暴雨的贡献较小。另外,中低层还存在源自北疆、南疆、北美洲东部、蒙古的水汽。基于上述特征,建立了天山南坡暖季暴雨过程水汽三维精细化结构模型。     

西太平洋雅浦海沟区海底热流原位测量

为了解西太平洋雅浦海沟区俯冲带及岛弧两侧的海底热流分布情况,2015年1-3月期间的西太平洋海山航次中,"科学"号利用最新一代Lister型热流探针对该区域开展了海底热流原位测量工作。沿着横跨俯冲带的站位测线,本次进行了10个热流站位测量,共获得8个站位的有效数据。测量结果表明,该地区地温梯度的变化范围为0.011~0.137 Km-1,平均0.089 Km-1,热导率的变化范围为0.58~1.32 Wm-1K-1,热流值则在14.4~118.85 mWm-2之间,平均为68.02 mWm-2。热流值分布显示,雅浦岛弧附近具有较高的热流值,自雅浦岛弧向两侧热流值逐渐降低,低热流区主要分布在帕里西维拉海盆。由于该地区热流测量数据依然稀缺,深入的讨论有待进一步研究。     

Preliminary optical classification of lakes and coastal waters in Estonia and south Finland

A preliminary optical classification of lakes in Estonia and south Finland which can also be used for small bays of the Baltic Sea is elaborated. The classification is based on the optical properties of water (diffuse attenuation coefficient, diffuse reflectance) and parameters that are routinely monitored in water bodies (Secchi depth, concentration of chlorophyll-a, total suspended matter and yellow substance). The data complex used for our classification covers different types of water ecosystems (ranging from oligotrophic to hypertrophic) and the variability of water constituent concentrations in the ice-free period in Estonia and south Finland. Using cluster analysis, we found 5 optical classes of waters: clear (C), moderate (M), turbid (T), very turbid (V) and brown (B). There is satisfactory correspondence between class of water, shape of diffuse attenuation coefficient and diffuse reflectance spectra and trophic state of the lakes.     

专业认证背景下的测绘工程专业课程体系优化

为了满足工程教育认证制度对高校测绘工程专业人才的培养要求,从测绘工程专业实际出发,对2014级培养方案中的课程体系进行了优化。在介绍课程体系构建背景的基础上,对照工程教育认证标准(2012版)的要求,简要说明了测绘工程专业培养目标、毕业生获取知识和能力、学位授予标准。详细阐述了课程体系优化的背景、课程体系构成与课程体系结构。经过对课程体系的优化能够满足工程教育认证标准中对课程体系的要求,为培养符合工程教育认证标准的毕业生打下扎实的基础。     

一种改进的周跳多项式拟合方法

多项式拟合探测周跳受相位观测值所含误差的影响,随着采样数的增加,其探测周跳的能力随之降低,通常将观测数据分成若干段来进行处理。这样不可避免的增加工作强度,降低工作效率。本文根据多项式拟合探测周跳的基本原理,对多项式进行改进。经实验证明,利用改进后的多项式进行拟合能够有效地弥补传统方法的不足,使周跳的探测与修复更加稳定可靠。     

Differential subduction and exhumation of crustal slices in the Sulu HP-UHP metamorphic terrane: insights from mineral inclusions, trace elements, U-Pb and Lu-Hf isotope analyses of zircon in orthogneiss

Based on new evidence the Sulu orogen is divided from south‐east to north‐west into high‐pressure (HP) crustal slice I and ultrahigh‐pressure (UHP) crustal slices II and III. A combined set of mineral inclusions, cathodoluminescence images, U‐Pb SHRIMP dating and in situ trace element and Lu‐Hf isotope analyses was obtained on zircon from orthogneisses of the different slices. Zircon grains typically have three distinct domains that formed during crystallization of the magmatic protolith, HP or UHP metamorphism and late‐amphibolite facies retrogression, respectively: (i) oscillatory zoned cores, with low‐pressure (LP) mineral inclusions and Th/U > 0.38; (ii) high‐luminescent mantles (Th/U < 0.10), with HP mineral inclusions of Qtz + Grt + Arg + Phe + Ap for slice I zircon and Coe + Grt + Phe + Kfs + Ap for both slices II and III zircon; (iii) low‐luminescent rims, with LP mineral inclusions and Th/U < 0.08. Zircon U‐Pb SHRIMP analyses of inherited cores point to protolith ages of 785–770 Ma in all seven orthogneisses. The ages recorded for UHP metamorphism and subsequent retrogression in slice II zircon (c. 228 and c. 215 Ma, respectively) are significantly older than those of slice III zircon (c. 218 and c. 202 Ma, respectively), while slice I zircon recorded even older ages for HP metamorphism and subsequent retrogression (c. 245 and c. 231 Ma, respectively). Moreover, Ar‐Ar biotite ages from six paragneisses, interpreted as dating amphibolite facies retrogression, gradually decrease from HP slice I (c. 232 Ma) to UHP slice II (c. 215 Ma) and UHP slice III (c. 203 Ma). The combined data set suggests decreasing ages for HP or UHP metamorphism and late retrogression in the Sulu orogen from south‐east to north‐west. Thus, the HP‐UHP units are interpreted to represent three crustal slices, which underwent different subduction and exhumation histories. Slice I was detached from the continental lithosphere at ～55–65 km depth and subsequently exhumed while subduction of the underlying slice II continued to ～100–120 km depth (UHP) before detachment and exhumation. Slice III experienced a similar geodynamic evolution as slice II, however, both UHP metamorphism and subsequent exhumation took place c. 10 Myr later. Magmatic zircon cores from two types of orthogneiss in UHP slices II and III show similar mid‐Neoproterozoic crystallization ages, but have contrasting Hf isotope compositions (εHf_(～785) = ?2.7 to +2.2 and ?17.3 to ?11.1, respectively), suggesting their formation from distinct crustal units (Mesoproterozoic and Paleoproterozoic to Archean, respectively) during the breakup of Rodinia. The UHP and the retrograde zircon domains are characterized by lower Th/U and ¹⁷⁶Lu/¹⁷⁷Hf but higher ¹⁷⁶Hf/¹⁷⁷Hf(t) than the Neoproterozoic igneous cores. The similarity between UHP and retrograde domains indicates that late retrogression did not significantly modify chemical and isotopic composition of the UHP metamorphic system.     

基于马尔科夫链转移概率极限分布的降水过程持续性研究

各地不同气候条件所具有的天气状态转移概率的极限分布实际上代表了各地天气气候的持续性和转折性特征,同时也表明了它的可预报期限。从马尔科夫链理论出发,初步研究了中国160个代表测站逐日天气状态演变过程的极限分布。结果表明,转移概率的极限分布不但其空间分布有明显差异,而且不同季节的极限分布也有明显差异。例如,有的地区仅有2 d持续期,有的可达4—6 d或更长,充分反映出不同地区因其影响的天气系统差异所造成的逐日天气气候的持续性和转折性特征的差异。其研究意义在于,由此可作为天气气候分型区划的一种理论依据。统计分析结果表明,就全中国平均而言,夏季持续期最短,持续期由北向南、由西向东呈增加趋势,且春季平均降水持续期为5.1 d,夏季平均为5.0 d,秋季平均为6.5d,冬季平均为6.2 d。可见夏半年比冬半年的降水持续期短,这可能是因为春夏季的天气系统比较复杂且中小尺度天气系统较多的缘故。这从另一侧面再次证明,各地逐日降水天气状态演变过程具有一定的天气气候状态自然转折的持续性即自然天气周期的气候状况,从而为短期天气预报提供了气候背景。     

简单的热带海气耦合波——Rossby和Kelvin波的相互作用

本文分析了当大气和海洋中未经耦合前的自由波分别为Kelvin波和Rossby波,经相互作用后所产生的耦合波的性质。结果表明,不管大气的自由波为Kelvin波或Rossby波,而海洋的自由波为Rossby波或Kelvin波,经相互作用后的耦合波可以分成两类。一类耦合波的色散关系接近自由的Kelvin波;另一类则由不同经圈模的Rossby波经相互作用后的耦合波。这两类波都具有不稳定性。文中讨论了耦合波的传播和不稳定的物理机制,并指出这类不稳定的热带耦合波,对研究ENSO事件中的某些现象有一定的参考意义。     

黄河流域气候水分盈亏时空格局分析

以中国气象局整编的1961~2001 年的气象资料为数据基础,采用联合国粮食及农业组织(FAO)1998 年推荐使用的Penmanmonteith模型,并以GIS技术为手段进行黄河流域气候水分盈亏的时空分布格局分析。结果表明：黄河流域干旱缺水是一种普遍现象,气候水分盈亏量在空间上总的变化规律表现为自南向北、自东向西气候水分亏缺量呈逐渐增大趋势,大部分地区全年气候水分亏缺量介于200~600 mm之间;就季节分布而言,水分亏缺的主要时期在春季和初夏,亏缺量一般在180~300 mm之间;就典型站点气候水分盈亏量逐月变化而言,存在着区域差异。研究结果和结论对区域充分发挥水分利用效率、发展高效节水农业具有重要意义。     

2021年10月山西一次罕见持续性强降水过程物理机制分析

利用气象观测资料、NCEP/NCAR 1°×1°再分析资料以及GDAS资料,对2021年10月2-7日山西持续性强降水天气过程进行分析。结果表明：稳定的乌拉尔山低槽后部冷空气扩散,中纬度短波槽东移,与副热带高压外围西南暖湿气流持续交汇,同时高低空急流耦合形成强烈上升运动,低层切变线和地面辐合线稳定维持,及低层水汽不断输送并形成辐合,为持续性强降水的发生发展提供有利动力和水汽条件。此次强降水过程分为对流性降水和稳定性降水2个阶段,2阶段水汽输送通道的源地、路径、高度均有明显差异,但水汽输送贡献率均以对流层中低层山西南侧的水汽输送占主导地位。降水开始前,对流层中上层存在对称不稳定,大气可降水量明显跃增;对流性降水阶段,干空气不断入侵,对流不稳定快速建立与释放,对流层中低层水汽辐合区与强上升气流配合,导致山西出现强对流天气。地形的阻挡、抬升及地形收缩作用,对局地极端强降水具有增幅作用。