盐尘暴及其生态效应

总结了盐尘暴的概念及其一般特征,系统分析了盐尘暴的发生条件、分布、扩散沉积和生态效应。盐尘暴是由干旱、半干旱地区干涸湖底蒸发盐风蚀所致的一种化学尘暴;大面积松散富盐沉积物和频繁的大风天气是其发生的基本条件;盐尘暴扩散过程中沉积通量和化学组分随迁移距离表现出明显的分异规律;盐尘暴扩散导致干旱区“盐随风来”,致使土壤盐渍化,加剧冰雪消融,抑制植物叶片对营养元素的正常吸收。系统认识盐尘暴对干旱区灾害防治和生态建设具有重要指导意义。     

Influence of vegetation cover on sand transport by wind: field studies at Owens Lake,California

Field studies conducted at Owens Lake, California, provide direct measurements of sand flux on sand sheets with zero to 20 per cent cover of salt grass. Results from 12 different sand transport events show that aerodynamic roughness length and threshold wind shear velocity increase with vegetation cover as measured by vertically projected cover and roughness density (λ). This results in a negative exponential decrease in sediment flux with increasing vegetation cover such that sand transport is effectively eliminated when the vertically projected cover of salt grass is greater than 15 per cent. A general empirical model for the relation between sand flux and vegetation cover has been derived and can be used to predict the amount of vegetation required to stabilize sand dune areas. © 1998 John Wiley & Sons, Ltd.     

Study of the Wind Conditions in the South China Sea and Its Adjacent Sea Area

An increasing number of marine structures have been built for coastal protection and marine development in recent years,and wind,which is crucial to marine structures,should be analyzed.Therefore,typhoon frequency,wind climate,wind energy assess-ment,and extreme wind speed in the South China Sea(SCS)are investigated in detail in this study.The data are obtained from the China Meteorological Administration,the European Centre for Medium-range Weather Forecasts,and the National Centers for Envi-ronmental Prediction.The offshore wind energy potential is analyzed at five sites near the coast.The spatial and monthly frequencies of tropical cyclones for different intensity categories are analyzed.The extreme wind speed is fitted by five distribution models,and the generalized extreme value(GEV)distribution is selected as the most suitable function according to the goodness of fit.The spa-tial distributions of extreme wind speeds in the SCS are plotted on the basis of the GEV distribution and ERA5 data sets.The influ-ences of the distribution models and data sets on the calculated results are discussed.Moreover,the monthly extreme wind speed and comparison with the results of previous studies are analyzed.This study provides a reference for the design of wind turbines.     

基于2010—2020年东海风浪统计数据的海上风电吸力桶基础动荷载承载特性

为了得到桶基础承受风、浪动荷载的承载性能,结合我国东海地质条件,统计中国东海2010—2020年浅、深海风速和最大海浪数据,通过计算得到风浪荷载并制成ABAQUS软件幅值曲线施加到海上风电吸力桶基础上,分析了吸力桶基础在动荷载作用下的承载特性。结果表明：吸力桶基础受风、浪荷载影响明显,桶基础迎力面受到风浪动荷载产生拉拔现象。在浅海区,桶基础在风浪荷载作用下桶身自上而下变形不协调,风浪荷载最大的10月份桶基础迎力面最大位移超出了规范0.02D的限制,基础失稳;桶基础背力面受压变形较小。在深海区,桶基础在风浪荷载作用下桶身自上而下变形相对协调,施加风浪荷载后桶体迎力面最大位移为14.9 mm,整体上迎力面位移比背力面位移大4 mm,桶体处于稳定状态。相较浅海区的吸力桶单桶结构,深海区吸力桶结构由于尺寸增加,桶体的稳定性得到提高,说明吸力桶结构的尺寸对稳定性起决定性作用。     

Wind energy input in coastal seas east of China

This study investigates the wind energy input, an important source of mechanical energy, in the coastal seas east of China. Using the wind field from the high-resolution sea surface meteorology dataset in the Bohai Sea, Yellow Sea, and East China Sea, we studied the wind energy input through surface ageostrophic currents and surface waves. Using a simple analytical formula for the Ekman Spiral with timedependent wind, the wind energy input through ageostrophic currents was estimated at ～22 GW averaged from 1960 to 2007, and through use of an empirical formula, the wind energy input through surface waves was estimated at ～169 GW. We also examined the seasonal variation and long-term tendency of mechanical energy from wind stress, and found that the wind energy input to the East China Sea decreased before the 1980s, and then subsequently increased, which is contrary to what has been found for the Bohai Sea and Yellow Sea. More complicated physical processes and varying diffusivity need to be taken into account in future studies.     

渤海海面风场的一种动力诊断方法

给出一种动力诊断获取渤海海面风场的简便方法.首先建立一个简单的水平二维地面风场诊断模式,根据由微机支持的数字化仪输入的地面格点气压场,诊断出地面风场;然后利用渤海沿岸和岛屿海洋观测站(含石油平台站)实测风资料,运用简单的资料同化方法(张驰逼近方法)对诊断风场进行调整,从而得到渤海海面风场.结果表明,此方法简便有效.     

Microscale Response of Sediment Variables to Benthic Disturbance in the Central Indian Ocean Basin

The response of sediment bacteria and biochemical variables to benthic disturbance was investigated in the Central Indian Ocean Basin from cores at nine stations. Generally, bacterial density and biochemical variables declined vertically with depth in the upper layers of the cores. Mechanical disturbance caused by a hydraulic disturber brought about a substantial decrease in total bacterial numbers. However, the numbers of retrievable bacteria increased by two orders of magnitude. The biochemical parameters decreased in quantity with a shift in the linear relationship. The data suggest that abiotic artifacts will directly affect the biomass and biochemistry of the sediment.     

U-Net深度卷积神经网络在沙脊线提取中的应用

沙丘形态演变过程记录着近地表风况与环境演化的历史,然而对其特征研究一直受限于大范围沙脊线提取效率低和成本高等问题.本文基于深度卷积神经网络搭建U-Net模型,实现批量、高精度沙脊线的提取.将数据增强技术、随机失活神经元、批标准化以及迁移学习技术应用于模型训练和参数更新,使得模型的精度更高.结果 表明:U-Net模型以及...     

Analysis of the heliospheric current sheet fine structure: Single or multiple current sheets

When studying the heliospheric current sheet (HCS) local structure, it is not unusual to find wide HCS crossings. In this paper, we present one crossing that appears to have a complex internal structure composed of three parallel sheets and several possible HCS crossings that are consecutive and are on the order of minutes. Depending on their origin, different scenarios can explain multiple current sheets such as complex structures of helmet streamer at the Corona flowing into the solar wind, local waviness in the HCS structure, local oscillations of the HCS, and inverted magnetic fields or planar magnetic structures (PMS) close to the HCS. Distinguishing among these scenarios using just one observational point is very difficult because all of them are 3D structures. Nevertheless, we think that nearly parallel sheets are more likely in the first and in the last scenarios, i.e. multiple helmet streamer structure and PMS. In order to make the distinction between them, we have studied the possible reversal in the Q_e·B sign for every event. Our results suggest that the existence of not-wide HCS composed of multiple parallel sheets cannot be rejected.