Sensitivity of WRF simulated typhoon track and intensity over the South China Sea to horizontal and vertical resolutions

To determine the grid resolutions of the WRF model in the typhoon simulation,some sensitivity analysis of horizontal and vertical resolutions in different conditions has been carried out.Different horizontal resolutions(5,10,20,30 km),nesting grids(15 and 5 km),different vertical resolutions(35-layers,28-layers,20-layers)and different top maximum pressures(1 000,2 000,3 500,5 000 Pa)had been used in the mesoscale numerical model WRF to simulate the Typhoon Kai-tak.The simulation results of typhoon track,wind speed and sea level pressure at different horizontal and vertical resolutions have been compared and analyzed.The horizontal and vertical resolutions of the model have limited effect on the simulation effect of the typhoon track.Different horizontal and vertical resolutions have obvious effects on typhoon strength(defined by wind speed)and intensity(defined by sea level pressure,SLP),especially for sea level pressure.The typhoon intensity simulated by the high-resolution model is closer to the real situation and the nesting grids can improve computational accuracy and efficiency.The simulation results affected by vertical resolution using 35-layers is better than the simulation results using 20-layers and 28-layers simulations.Through comparison and analysis,the horizontal and vertical resolutions of WRF model are finally determined as follows:the two-way nesting grid of 15 and 5 km is comprehensively determined,and the vertical layers is 35-layers,the top maximum pressure is 2 000 Pa.

Coastal Reservoirs Strategy for Water Resource Development—A Review of Future Trend

Water use and access become a more and more important determinant of environmental equity and human development according to the view held by the UN [1]. Water scarcity is one of the major crises which has overarching implications for other world problems especially poverty, hunger, ecosystem degradation, desertification, climate change, threatening world peace and security [2]. In the decades to come, freshwater consumed by human will get to a tipping point. Many projects and concepts have been proposed and implemented for several years to improve the effectiveness of using water. These research activities can be grouped as: desalination plants;water detention (like rainwater tanks for collection and reuse);wastewater reuse;dams and reservoirs. This paper summarized the characters of these water solutions. But these methods can’t provide enough fresh water due to limitations imposed by these methods as well as following industry and population’s development. To overcome these shortcomings, coastal reservoir strategy is proposed in the paper. This new strategy is technically feasible, environmentally sustainable and cost effective by demonstration and comparison.

基于Sentinel-1A SAR的洞庭湖汛期水体面积动态变化监测研究

洞庭湖水体面积动态变化监测对防洪、维系生态系统的稳定及生物多样性具有重要意义。以经典Unet网络模型和创新性HRNet网络模型为代表的深度学习技术已成为遥感图像信息获取的高效途径,实验以Sentinel-1A SAR影像为主要数据源,定性、定量地分析了Sentinel-1双极化水体指数法(Sentinel-1 Dual-Polarized Water Index,SDWI)、面向对象分类法、UNet网络模型和HRNet网络模型4种方法的水体提取效果,并基于最佳水体提取方法对洞庭湖2016~2021年汛期(4~10月)水体面积进行时空变化特征分析。结果表明:①HRNet和Unet网络模型较传统方法具有更优的水体提取效果,其中,HRNet网络模型在抑噪、抗阴影等方面表现更佳,F1分数、误判率和平均交并比分别为0.9616、0.0078和0.9586;②汛期洞庭湖水体面积在月际变化上呈现出“涨—丰—退”的变化特征,湖面从4~5月份开始扩张,6~8月份水域面积维持在较高水平,此后由于来水减少,9~10月的水体面积逐步减小。研究期间所监测到的最大水体面积为2020年7月30日的2263.90 km2;③洞庭湖汛期的水体淹没频率从湖体中心和干流向外逐渐降低,不同湖区的淹没频率分布格局不同,东洞庭湖“湖心高四周低”,南洞庭湖和西洞庭湖“南高北低”。综上所述,Sentinel-1A SAR影像与深度学习技术的结合应用可以实现洞庭湖水体信息高效获取与水面面积高频监测,为高动态湖泊水域监测提供了一种新思路。

Experimental investigation about the incipient velocity of spherical particles on a hemispherical bed surface

The sediment particles play a huge role in shaping the bed load transport.In this research,240 water-tunnel experiments are carried out to investigate the incipient velocity of the observation particles in two particle arrangements.To accurately predict the incipient velocity of the observation particles,the equation is conceived by the rolling instability mechanism.The incipient velocity equations and experimental data are used to analyze the trend of dispersive pressure and the effect of arrangement position on velocity.We find that it is appropriate to choose the coefficient of drag as 0.261 and the coefficient of lift as 0.198 for the incipient velocity equation of spherical particles on the hemispherical bed surface.Furthermore,the dispersive pressure is closely related to the flow state,particle size,and particle arrangement,which leads to the incipient velocity of the observation particle being at a minimum when the interference particle angle is 45°.Finally,the particle spacing and the projected area changed with the arrangements,directly affecting the incipient velocity of the observed particle.The analysis of four aspects for the coefficients,dispersive pressure,different particle spacing,and projected area will facilitate the prediction of particle incipient velocity,especially on hemispherical beds.

基于海气耦合模式的南中国海北部风暴潮模拟

伴随台风产生的大风、暴雨、巨浪、风暴潮形成的台风灾害链对沿岸地区产生巨大影响,研究台风的形成和运动机理,减小风暴潮灾害,具有重要的科学价值和社会意义.台风影响期间,大气与海洋之间存在强烈的质量、能量交换,风场、流场、波浪场等物理场相互作用、相互影响.基于中尺度大气模式WRF和区域海洋模式ROMS,构建南中国海地区海气耦合模式,针对2012年台风"启德"进行数值模拟.通过观测数据对台风路径和强度进行验证,结果表明,建立的WRF-ROMS耦合模式在对台风"启德"影响下的南中国海风暴潮模拟中展现出较高的模拟精度.通过数值模式计算结果揭示了台风、风暴增水和风生流场的时空分布特征.台风运动过程中台风动力场、风暴增水及流场在空间上均具有"右偏性"的不对称分布特征,近岸风暴增水对台风的响应在时间上存在滞后性,风生流场具有较明显的滞后性特征.

通航隧道内船行波传播特性及对船舶连续通航安全影响

为填补通航隧道船舶通航安全关键技术研究的空白,基于完全非线性Boussinesq方程的开源程序包FUNWAVETVD建立了直线运河中通航隧道内船行波运动的数值模型,重点分析了船舶在通航隧道中诱导生成的船首孤立波波高以及波速的时空分布规律,并讨论了船行波对船舶连续通航的安全影响.研究得到了最大船首孤立波波高ηmax与船舶吃水P、Fr、通航隧道的水深、宽度以及船型的多元非线性回归方程;基于孤立波波面方程的理论假设,对通航隧道内船首孤立波的波速进行分析,发现船首孤立波的前波面与孤立波波面方程吻合较好,以孤立波的理论波速作为船首孤立波的传播速度,给出了通航隧道内船舶连续通航时安全航距应满足的关系式.结果表明,该模型能较好地捕捉船行波在通航隧道中的传播演变过程.研究结果可为单线直线运河中通航隧道的设计提供参考和依据,并可为通航隧道船舶通航安全关键技术标准或规范的制定奠定理论基础.

破碎区水体掺气特征及空隙率分布规律

为了解破碎区水体掺气过程中空隙率的分布及其与波浪要素之间的关系,基于波浪水槽实验,通过高速摄像机和气泡测量系统分别记录了卷破波作用下破碎区内水体掺气过程和空隙率时空分布,着重分析了影响空隙率分布的主要因素.实验结果表明:空隙率的分布与水深、波浪特征指标以及与破碎点的距离有关;讨论了空隙率的时均分布特征,引入C_0和k_1两个经验参数建立了其函数关系表达式,并通过实验数据进行拟合反推得到参数k_1与波高成反比、C_0是波陡、相对水深、无量纲水平位置的函数.基于拟合公式分析了各要素与空隙率之间的关系,得到本实验条件下水面处最大的空隙率接近20%,气泡最大穿透深度接近静水面下5cm;破碎区域内空隙率随水深的增加呈e指数的函数关系衰减.研究结果能较好地用于预测破碎区空隙率的分布,为深入研究波浪破碎作用下气泡输运机制提供参考.