贝壳中维界面的亲疏水特征

【目的】从亲疏水特征的角度对贝壳各层次结构中的界面进行分析探讨。【方法】采用接触角测量仪对贝壳的中维界面、无机文石及无机方解石进行水接触角测量。【结果】贝壳内表面的水接触角普遍大于90°,其中最大值为113°,最小值为91°;贝壳表壳层内表面边缘位置的水接触角平均值为67°,内部位置的水接触角平均值为112°;无机文石及无机方解石平整表面的水接触角均小于90°,其平均值分别为50°、49°。【结论】贝壳内表面具有疏水性,即有机质层具有疏水性;由于具有亲水特征的文石及方解石为贝壳矿物的主要成分,说明贝壳矿物结构具有亲水性;贝壳表壳层内表面边缘呈现亲水特征,内部呈现疏水特征。     

Mesoscale and Microphysical Characteristics of a Double Rain Belt Event in SouthChina on May 10–13, 2022

A second rain belt sometimes occurs ahead of a frontal rain belt in the warm sector over coastal South China,leading to heavy precipitation. We examined the differences in the mesoscale characteristics and microphysics of thefrontal and warm sector rain belts that occurred in South China on May 10–13, 2022. The southern rain belt occurred in anenvironment with favorable mesoscale conditions but weak large-scale forcing. In contrast, the northern rain belt wasrelated to low-level horizontal shear and the surface-level front. The interaction between the enhanced southeasterly windsand the rainfall-induced cold pool promoted the persistent growth of convection along the southern rain belt. The con vective cell propagated east over the coastal area, where there was a large temperature gradient. The bow-shaped echo inthis region may be closely related to the rear-inflow jet. By contrast, the initial convection of the northern rain belt wastriggered along the front and the region of low-level horizontal shear, with mesoscale interactions between the enhancedwarm-moist southeasterly airflow and the cold dome associated with the earlier rain. The terrain blocked the movement ofthe cold pool, resulting in the stagnation of the frontal convective cell at an early stage. Subsequently, a meso-γ-scalevortex formed during the rapid movement of the convective cell, corresponding to an enhancement of precipitation. Therepresentative raindrop spectra for the southern rain belt were characterized by a greater number and higher density ofraindrops than the northern rain belt, even though both resulted in comparable hourly rainfalls. These results help us betterunderstand the characteristics of double rain belts over South China.     

AN ANALYSIS OF DISTRIBUTION AND MESOSCALE STRUCTURE OF PRECIPITATION ABOUT LANDFALL TROPICAL CYCLONE KOPPU (0915)

Observation from automatic weather stations, radars and TRMM satellites are employed to investigate the precipitation distribution of tropical cyclone (TC) Koppu (0915) that made landfall on Guangdong province in 2009. The results show that the precipitation of landfall TC Koppu is featured by significant asymmetry and mesoscale structure, and occurs mainly to the left of its moving path. By examining the sea surface temperature (SST), water vapor flux, Q vector, vertical wind shear of environment etc., it is found out that the distribution of SST, water vapor convergence, low-level convective ascending and vertical wind shear facilitates the TC precipitation to take place to the left of the TC moving path. The mesoscale structure separated by Barnes band-pass filter presents that the precipitation of landfall KOPPU has some organized mesoscale spiral structures, which is around the TC center and composed of the form of belts or blocks. The heavy local rainfall of landfall TC Koppu is primarily associated with the rainfall due to mesoscale spiral structure.     

粗糙地形对内波生成影响的实验研究

为了研究粗糙地形对内波共振生成的影响,本文在实验中采用粒子图像测速法(PIV)对内波速度场进行测量。实验中设置了两种不同尺度的粗糙地形,其中一种地形的粗糙尺度大于黏性边界层厚度(δ),另一种地形的粗糙尺度小于δ。结果表明两种粗糙地形都使共振内波的能量减弱,粗糙地形一侧生成的内波强度约为光滑地形一侧生成内波强度的40%。当粗糙地形的尺度大于δ时,在粗糙地形一侧除了共振内波以外还有明显的内波射线生成,粗糙地形上的每一个凸形间断点都成为了一个新的内波源点,每条内波射线的强度约为共振内波强度的1/10,由新源点生成的内波射线相位基本一致,落后于正压潮3π/5个相位。当粗糙地形的尺度小于δ时,粗糙地形一侧仅有共振内波生成,共振内波的相位与正压潮相位十分接近。     

Spatio‐temporal changes in bog pool bottom topography – temperature effect and its influence on pool development: an example from a raised bog in Estonia

Increases in pool water and peat temperature in summer accelerate peat decomposition and production of biogenic gases, which can be trapped in peat pores and cause oscillation of peatland surfaces and the rise of peat from the bottom of bog pools. Associated changes in peat water conductivity, holding capacity and transpiration also affect bog hydrology. Our multi‐year study is the first to show in detail the extent and dynamics of changes in bog pool depth and bottom topography associated with changes in temperature, peat type and other factors. The true seasonal rise of peat from the pool bottom begins once the water temperature at the pool bottom exceeds 13–14 °C, although the speed and extent of the rise depends on peat properties, making the rise more erratic than its subsequent descent. The more rapid descent occurs after the first large drop in the temperature of the pool's surface water at the end of summer, resulting from the combination of reduced methane production and increased gas solubility with less influence by peat properties. Much higher dissolved organic carbon concentrations (216 ± 26 mg l^?1) in the pore water of peat risen from the bottom to the pool surface compared with that in the same type of peat at the pool bottom (62 ± 20 mg l^?1) indicate an acceleration of peat decomposition at the warmer pool surface. We show the extent and character of changes in pool depth and bottom topography and how annual differences relate to temperature. Only a few degrees' increase in pool water temperature could induce the pool bottom to rise faster and more extensively for a longer period and enhance decomposition in the peat at the pool surface. This should be evaluated in greater detail to assess the effects of temperature increase on the carbon budget and hydrology of peatlands. Copyright © 2012 John Wiley & Sons, Ltd.     

A mesoscopic model for the behaviour of concrete under high confinement

When impact loaded, concrete is submitted to high triaxial stresses. The experimental response of concrete under quasi‐static triaxial compression is studied using a triaxial press capable of applying a mean pressure greater than 1 GPa on cylindrical samples measuring 7 cm in diameter and 14 cm high. A numerical analysis of these previous experiments is performed herein at a mesoscopic scale. Concrete is modelled as a biphasic material consisting of a mortar (cement paste and fine aggregates) and roughly spherical aggregates (with a diameter exceeding 2 mm) whose characteristics are applied on a regular cubic finite element mesh. A damage‐plasticity model is then used to model the behaviour of mortar. An identification of model parameters on mortar samples and the subsequent comparison between numerical and experimental tests will be presented for hydrostatic and triaxial compression. Copyright © 2009 John Wiley & Sons, Ltd.     

GPS-RTK无验潮快速水下地形勘测肢术在码头建设中的应用

简要介绍GPS-RTK无验潮快速水下地形勘测技术和施工要求,GPS-RTK与相应测深仪器配合能自动采集实时三维座标、时间等数据,提高了作业效率和测量点位精度,达到预期成果质量精度。     

STRUCTURE OF MESO-β AND -γ-SCALE ON SOUTH CHINA HEAVY RAINFALL ON 12～13 JUNE 2005 USING DUAL-DOPPLER RADAR

The three-dimensional wind fields of the heavy rain on 12-13 June 2005 in Guangdong province are retrieved and studied with the volume scan data of the dual-Doppler radar located in the cities of Meizhou and Shantou. It is shown that the meso-β-scale and meso-γ-scale convergence lines located in the convective system at the low and middle layer play an important role in the heavy rainfall. The convergence line is the initiating and maintaining mechanism of the rain. A three dimensional kinematic structure model is also given.     

香港地区海陆风的显式模拟研究

利用MM5模式对香港地区的海陆风进行了显式数值研究,模拟的风向、风速和温度与站点的观测值比较一致,较详细地分析了海陆风的日变化规律和三维结构特征,结果显示香港地区海风分布复杂,主要受偏西、偏南和偏东海风气流的影响,形成多个辐合带,海风锋最远可以深入内陆约90 km;陆风较简单,主要是偏北气流,陆风的风速和强度都比海风要弱,与山谷风、城市热岛环流等形成弱的辐合。香港是一个海岸曲折、多丘陵的地区,其中75%的面积是山区,为了研究这些丘陵地形对香港地区海陆风的影响,设计了保留海陆分布,去掉丘陵地形的敏感性试验,结果表明,由于丘陵地形的存在,在白天地形的热力作用是主要的,增强了海风的强度;而晚上动力阻挡作用比较明显,减弱了陆风的强度。     

辽宁长历时暴雨中尺度对流系统特征分析

选取发生在辽宁的3次典型长历时暴雨过程,利用NCEP/NCAR 1°×1°再分析、FY-2E黑体亮温TBB、多普勒天气雷达和自动气象站等资料,分析了降水实况、天气形势背景、卫星红外云图、雷达回波的结构和强度变化的代表性特征。结果表明:辽宁长历时暴雨是在有利于产生暴雨的大尺度环流背景下,异常稳定的形势场导致冷暖空气在某一地区长时间相互对峙而形成的。该型暴雨的降水实况具有雨强变化小、强降水无明显阶段性特征和雨强变化大、强降水具有明显阶段性两种特征。一般性对流云团、暖云和深对流云团均可造成该型暴雨,其中一般性对流云团的云顶亮温变化幅度小,在-47～-36℃,暖云的云顶亮温在-8～3℃,深对流云团的云顶亮温-68～-50℃且强降水发生在云顶亮温低值中心偏向温度梯度大值区一侧。该型暴雨的雷达反射率因子强回波质心较低,表现为上游回波同一方向连续移入形成的"列车效应"、本地生成回波并不断加强以及不同方向的强回波先后移入影响三种类型,小时平均回波强度及其变化对降水强度和趋势有较好的指示意义。需要特别关注副热带高压西侧低层高能高湿、凝结高度低、整层近乎饱和且又具有局地地形抬升触发条件地区的暖云强降水的分析和监测。