Evaluating practical macrophyte control tools on small agricultural waterways in Canterbury,New Zealand

Excessive macrophytes can cause significant problems in agricultural waterways requiring active management. Conventional control techniques can have a range of adverse effects. We investigated several control tools in two experiments: firstly, we tested eight treatments at a small-scale (2?m?×?2?m). We found intensive hand weeding, weed mat and herbicide spraying to be effective treatments, reducing macrophyte cover to <5%. Hand weeding and weed mat immediately reduced cover, while dieback from herbicide took two months. Weed mat was a novel and effective control mechanism along stream banks. Secondly, we tested the impact of shading on macrophyte growth. Macrophyte growth was enhanced under partially shaded conditions, but with 80% effective shading over the entire channel, cover was reduced to 17%. Once treatments ceased, macrophytes grew back within 3–5 months. Long-term, control methods will require combinations of tools but will need to include optimal shading for the target species.     

第24太阳活动周武汉电离层VTEC变化特性分析

利用2008-2015年(第24太阳活动周)中国地壳运动监测网络(CMONOC)武汉站(30.5°N,114.4°E)GPS双频接收机监测的垂直总电子含量(VTEC)数据,分析电离层VTEC变化特性,并讨论VTEC与太阳活动的相关性.结果表明,VTEC估值周日变化在14:00-16:00LT左右达到最大值;同时,电离层VTEC也表现出明显的逐日变化特性,特别是在VTEC峰值处呈现较大差异.在太阳活动高年(2011-2015),VTEC变化呈现明显的双峰结构,即所谓的"半年异常"现象,春季峰值大于秋季峰值,"冬季异常"也更为明显.在各个季节(除春季外),VTEC与F_10.7p的相关性最好,与F_10.7的相关性次之,与太阳黑子数(SSN)的相关性稍弱;秋季VTEC与太阳活动的相关性最好(Max_F10.7p=0.92232,Max_SSN=0.85575),冬季VTEC与太阳活动的相关性最差(Min_F10.7p=0.79028,Min_SSN=0.72703).     

Revisiting the response of western North Pacific tropical cyclone intensity change to vertical wind shear in different directions

不同方向垂直风切变对热带气旋强度变化的影响存在明显差异,但对热带气旋无维强度变化的影响却差异较小.研究发现不同方向垂直风切变对无维强度变化的影响的细微差异与热带气旋周围的高层西风槽,倒槽,低层季风槽等天气系统配置有关.这一结果表明,在研究不同方向切变对热带气旋强度变化的影响时,除了下垫面热力作用外,还应考虑与切变相关的...     

Comparison of overflow simulations on different vertical grids using the Finite Element Ocean circulation Model

The Finite Element Ocean circulation Model (FEOM) is applied to study the sensitivity of density driven overflows to the vertical discretization and bottom topography representation using the dynamics of overflow mixing and entrainment (DOME) setup. FEOM allows for hybrid grids combining σ, z + σ, full cell, partly shaved cell and fully shaved cell grids within the same numerical kernel thus isolating as far as possible effects of mesh geometry from those of model numerics. The sensitivity of diapycnal mixing, entrainment, plume thickness and plume meridional distribution to vertical discretization and partly to the subgrid process parameterization is explored. It is shown that simulations on pure σ grids or the combination of z + σ resolve the overflow processes best in terms of downslope plume propagation, plume thickness and dilution, and also have the least resolution dependence. Grids using z-levels generate excessive spurious mixing when resolution is insufficient. Applying partial cells improves the plume representation, but still requires higher horizontal and vertical resolution to converge to the σ grid results. It is demonstrated that increasing lateral viscosity causes the plume thickness to reduce whereas increasing lateral diffusivity has opposite effect. When keeping the Prandtl number constant, the increase in diffusivity and viscosity leads to an increase in mixing and plume thickness on z-level grids and also on σ-grids when lateral dissipation is oriented along geopotential surfaces. Using the along σ- diffusion helped to obtain correct plume thickness and entrainment on σ grids. Increasing the vertical mixing coefficients leads to an increase in diapycnal mixing and in downslope penetration as well.     

陕西中部地区跨断层垂直形变与水平应变相关性分析

利用陕西中部地区近年来跨断层垂直形变资料和由GPS结果给出的水平最大剪应变场资料, 对2005年度会商中提出的8处跨断层形变异常点位置, 插值拟合出其水平应变值, 并与垂直形变数据进行相关性分析发现, 临潼-长安断裂垂直形变和水平应变正相关显著; 口镇-关山断裂与华山山前断裂呈现负相关; 岐山-马召断裂北段正相关显著, 而中段与南段相关性差。 这可能是由于这些断裂以及各段受力情况不同造成的, 其中口镇-关山断裂东段和岐山-马召断裂北段近年来垂直运动幅度大活动强烈, 应加以特别关注。     

河西走廊东部西北气流型沙尘暴的大气物理特征分析

利用2006—2022年河西走廊东部常规高空地面观测资料、民勤探空站08时和20时间隔50 m高空加密观测资料,分析冬季和春季西北气流型沙尘暴气象要素时间、垂直结构变化及大气层结特征。结果表明:（1）研究区西北气流型沙尘暴出现在地气温度和温差最大、相对湿度最小、地面气压和风速陡增时,特别春季沙尘暴发生时风速大、地表干且近地层热力对流最强。（2）垂直结构特征是早干晚湿、风速随高度递增,风向先顺转后逆转,低层暖高层冷,而春季低层气温较高,垂直温度梯度增幅大,温度露点差大,冷暖空气强度强且交汇高度较低（1 km附近）,层结更不稳定,易发生沙尘暴。（3）位温随不稳定层结高度变化梯度较大时间春季为08时和冬季为20时,即沙尘暴春季出现早于冬季。春季20时和冬季08时不稳定高度厚而低,因而春季下午到夜间、冬季中午沙尘暴较强。（4）500 hPa冷平流中心强度(≥-34℃) 和西北急流(≥26m/s) 越强,对应700 hPa河西风速大于20 m/s及低层暖区范围越大,沙尘暴强度越强,持续时间越长。     

南极菲尔德斯半岛潮间带南极帽贝的种群生态学研究──夏季种群数量变化和垂直分布

于1994年12月—1995年3月（南极夏季）期间,对南极菲尔德斯半岛卵石滩、岩石滩潮间带南极帽贝的种群数量、垂直分布进行了定点、定时、定量的调查和观察。结果表明,南极帽贝的种群数量有明显下降,分别仅为起始数量的35％和52％。卵石滩潮间带的帽贝分布于中潮区及低潮区,尤其是低潮区,且有随季节（冬季来临）向潮下带移动的趋势。岩石滩潮间带的帽贝具有类似的垂直分布特征,但其在分布带上的发生频次有很大差异,呈波动状态。在垂直岩面上,帽贝数量在低潮区的底部更为集中。讨论了导致数量变化、垂直分布的可能原因。今后有必要深入研究种群数量的时空动态及其调控机理。     

山西活动断陷带主要断层垂直形变分段特征

断层运动方式与滑动速率是断层活动性研究和地震危险性判定的重要参数。本文基于山西断陷带多年积累的跨断层水准观测资料,在处理与重构的基础上采用断层活动性分析方法,基于构造分区给出各构造区主要断层现今运动特征。结果表明,山西断陷带主要断层在观测期内以继承性正断运动为主,各盆地断层运动特征具有显著差异,表现为南、北两段的垂直活动量明显大于中段,其中,忻定盆地累积变化量值最小。从断层垂直活动速率来看,五台山断裂、系舟山山前断裂、唐河断裂和霍山山前断裂跨断层测段活动速率明显低于全区水平;受长期构造应力加载及区域中强地震影响,各时段断层运动也存在差异变化,下达枝、亭旨头、太原、广胜寺等部分跨断层测段表现出明显的断层逆继承运动、断层相对闭锁等特征。     

2019年太原青运会期间空气质量评估

为评估太原青运会期间大气污染控制措施对空气质量的改善效果,对青运会会前、会期和会后三个阶段太原市6种污染物浓度的演变及气溶胶在垂直方向上的变化进行了分析。结果表明：青运会期间太原市PM₁₀、PM_2.5、CO、NO₂、O₃较青运会前分别下降30.5%、37.3%、20.2%、18.0%和18.6%,SO₂削减程度不明显。垂直方向上,青运会期间气溶胶消光系数峰值降低24.6%,其中低湿天气下气溶胶消光系数峰值下降46%,高湿天气下峰值下降21.6%,青运会期间大气中PM_2.5在PM₁₀中的占比降低,垂直大气中气溶胶的吸湿增长能力增强。与2017和2018年同期相比,青运会期间PM₁₀、PM_2.5、CO、NO₂浓度均有大幅下降,O₃浓度较近两年同期无显著变化。因此,青运会期间的各项控制措施有效降低了本地颗粒物浓度。     

Petrogenesis of A-type granites and origin of vertical zoning in the Katharina pluton, Gebel Mussa (Mt. Moses) area, Sinai, Egypt

The central pluton within the Neoproterozoic Katharina Ring Complex (area of Gebel Mussa, traditionally believed to be the biblical Mt. Sinai) shows a vertical compositional zoning: syenogranite makes up the bulk of the pluton and grades upwards to alkali-feldspar granites. The latters form two horizontal subzones, an albite–alkali feldspar (Ab–Afs) granite and an uppermost perthite granite. These two varieties are chemically indistinguishable. Syenogranite, as compared with alkali-feldspar granites, is richer in Ca, Sr, K, Ba and contains less SiO₂, Rb, Y, Nb and U; Eu/Eu* values are 0.22–0.33 for syenogranite and 0.08–0.02 for alkali-feldspar granites. The δ¹⁸O (Qtz) is rather homogeneous throughout the pluton, 8.03–8.55‰. The δ¹⁸O (Afs) values in the syenogranite are appreciably lower relative to those in the alkali–feldspar granites: 7.59–8.75‰ vs. 8.31–9.12‰. A Rb–Sr isochron (n = 9) yields an age of 593 ± 16 Ma for the Katharina Ring Complex (granite pluton and ring dikes).

The alkali–feldspar granites were generated mainly by fractional crystallization of syenogranite magma. The model for residual melt extraction and accumulation is based on the estimated extent of crystallization ( 50 wt.%), which approximates the rigid percolation threshold for silicic melts. The fluid-rich residual melt could be separated efficiently by its upward flow through the rigid clusters of crystal phase. Crystallization of the evolved melt started with formation of hypersolvus granite immediately under the roof. Fluid influx from the inner part of the pluton to its apical zone persisted and caused increase of P_H2O in the magma below the perthite granite zone. Owing to the presence of F and Ca in the melt, P_H2O of only slightly more than 1 kbar allows crystallization of subsolvus Ab–Afs granite. Abundance of turbid alkali feldspars and their ¹⁸O/¹⁶O enrichment suggest that crystallization of alkali-feldspar granites was followed by subsolvus fluid–rock interaction; the δ¹⁸O (Fsp) values point to magmatic origin of fluids.

The stable and radiogenic isotope data [δ¹⁸O (Zrn) = 5.82 ± 0.06‰, I_Sr = 0.7022 ± 0.0064, ε_Nd (T) values are + 3.6 and + 3.9] indicate that the granite magma was generated from a ‘juvenile’ source, which is typical of the rocks making up most of the Arabian–Nubian shield.