风暴潮数值模拟中风应力拖曳系数的伴随法反演研究

借助伴随同化方法,利用实测水位资料,对空间分布的风应力拖曳系数做了反演研究.假定风应力拖曳系数具有空间分布特征,即在模拟海区中均匀选取一些独立点,利用这些独立点的风应力拖曳系数线性插值得到全场的风应力拖曳系数.同化实验结果表明,采用空间分布的风应力拖曳系数得到的模拟结果,明显优于将风应力拖曳系数取为常数和依照经验公式计...     

潮坪风暴沉积特征及其研究意义

风暴沉积是20世纪70年代后期才指提出的一个重要概念，被认为是沉积学理论的一次重大突破。但是以往的研究多集中在对浅海陆棚区风暴沉积的研究，而对近岸地带潮坪风暴沉积的研究则比较薄弱。系统总结了近20年来国内外对现代潮坪风暴沉积研究的成果，同时介绍了在古代地层中首次识别出的潮坪风暴岩沉积特征，最后指出了潮坪风暴沉积的研究意义。     

基于风暴相对螺旋度的降雨预报方法研究

风暴相对螺旋度是一个衡量对流风暴发展强度的物理量,所以对强对流天气的预报具有实际意义。通过提取2008-2010年3年天津地区153个降雨过程的多普勒天气雷达风场数据来计算了风暴相对螺旋度,然后将风暴相对螺旋度与从雷达反射率因子图中提取的风暴信息相融合,得到基于风暴相对螺旋度的降雨预报模型。经过2014年4月到8月天津地区59个降雨过程对本文所提出的降雨预报模型进行验证,结果表明本文提出的降雨预报模型的准确率达到61%,其中提前2小时预测降雨占41%,在2小时间以内预测降雨占59%。上述结果说明,风暴相对螺旋度在结合其他降雨特征后对降雨具有良好的预报效果。     

The effects of Hurricane Irene and Tropical Storm Lee on the bed sediment geochemistry of U.S. Atlantic coastal rivers

Hurricane Irene and Tropical Storm Lee, both of which made landfall in the U.S. between late August and early September 2011, generated record or near record water discharges in 41 coastal rivers between the North Carolina/South Carolina border and the U.S./Canadian border. Despite the discharge of substantial amounts of suspended sediment from many of these rivers, as well as the probable influx of substantial amounts of eroded material from the surrounding basins, the geochemical effects on the <63‐µm fractions of the bed sediments appear relatively limited [<20% of the constituents determined (256 out of 1394)]. Based on surface area measurements, this lack of change occurred despite substantial alterations in both the grain size distribution and the composition of the bed sediments. The sediment‐associated constituents which display both concentration increases and decreases include: total sulfur (TS), Hg, Ag, total organic carbon (TOC), total nitrogen (TN), Zn, Se, Co, Cu, Pb, As, Cr, and total carbon (TC). As a group, these constituents tend to be associated either with urbanization/elevated population densities and/or wastewater/solid sludge. The limited number of significant sediment‐associated chemical changes that were detected probably resulted from two potential processes: (1) the flushing of in‐stream land‐use affected sediments that were replaced by baseline material more representative of local geology and/or soils (declining concentrations), and/or (2) the inclusion of more heavily affected material as a result of urban nonpoint‐source runoff and/or releases from flooded treatment facilities (increasing concentrations). Published 2013. This article is a U.S. Government work and is in the public domain in the USA.     

Reconstruction of Hurricane Katrina's wind fields for storm surge and wave hindcasting

As the most costly US natural disaster in history, Hurricane Katrina fostered the IPET forensic study to better understand the event. All available observations from several hundred space-, land-, sea-, and aircraft-based measurement platforms were gathered and processed to a common framework for height, exposure, and averaging time, to produce a series of wind field snapshots at 3 h intervals to depict the wind structure of Katrina when in the Gulf of Mexico. The stepped-frequency microwave radiometer was calibrated against GPS sondes to establish the upper range of the instrument and then used to determine the wind field in the storm's core region in concert with airborne Doppler radar winds adjusted to the surface from near the top of the PBL (500 m). The SFMR data were used to develop a method to estimate surface winds from 3 km level reconnaissance aircraft observations, taking into consideration the observed azimuthal variation of the reduction factor. The “SFMR method” was used to adjust reconnaissance flight-level measurements to the surface in the core region when SFMR and Doppler winds were not available. A variety of coastal and inland mesonet data were employed, including portable towers deployed by Texas Tech University, University of Louisiana at Monroe, and the Florida Coastal Monitoring Program, as well as fixed mesonet stations from Louisiana State Universities Marine Consortium, University of Southern Mississippi, and Agricultural Networks from Louisiana, Mississippi, and Alabama, and the Coastal Estuarine Network of Alabama and Mississippi. Also included were land- (WSR-88D VAD and GBVTD, ASOS, Metar, LLWAS, HANDAR), space- (QuikScat, GOES cloud drift winds, WindSat), and marine- (GPS sondes, Buoys, C-MAN, ships) platforms. The wind fields serve as an analysis of record and were used to provide forcing for wave and storm surge models to produce hindcasts of water levels in the vicinity of flood control structures.     

Appllication of Excess Rotation Kinetic Energy in Distinguishing the Tornadic and Non-Tornadic Mesocyclones in China

多普勒天气雷达中气旋算法是为探测直径在1.8～9.2km（1～5nmi）的中气旋而设计的。绝大多数强龙卷都属于发生在中气旋内部的超级单体龙卷,但并不是所有的中气旋都能发展成龙卷。文中引入中气旋核的逾量旋转动能（ERKE）概念,结合中气旋算法和速度产品,分析了龙卷和非龙卷中气旋个例维持期间ERKE值的演变特征,并计算了一些超级单体风暴个例的中气旋初始的ERKE及其权重高度值。结果表明,与非龙卷中气旋相比,龙卷中气旋中ERKE的值普遍较大且其权重高度较低;超级单体风暴的初始中气旋ERKE值及其权重高度可以有效地区分中、低对流层中的龙卷和非龙卷中气旋,并可作为龙卷中气旋识别的定量指标。同时在我国平均中气旋气候特征的基础上,还绘制了ERKE图解,可从中气旋旋转速度和旋转半径快速查得对应ERKE值的大小。     

Numerical Simulation of Extreme Sea Levels for the Tamil Nadu (India) and Sri Lankan Coasts

Numerical modeling of extreme sea levels associated with tropical cyclones in the Indian seas has been confined to the northern part of the Bay of Bengal (north of Tamil Nadu). However, limited attempts have been made for modeling of surges along the Tamil Nadu and Sri Lankan coasts. Although, very rarely, cyclones form south of 10°N, there are some instances of severe cyclonic storms hitting these areas and causing widespread destruction to life and property. Keeping this in view, a suitable location-specific, high-resolution, numerical model has been developed for the prediction of storm surges in these regions with a grid resolution of 3 km. Using the model, numerical experiments are performed to simulate the storm surge associated with the 1964 Rameswaram cyclone, the 1978 Batticaloa cyclone, the 1992 Tuticorin cyclone, the 1993 Karaikal cyclone, and the 1994 Madras cyclone. During the years 1964, 1978, and 1992, the cyclones struck both Sri Lanka and Tamil Nadu coasts, while in 1993 and 1994, the cyclones struck only the Tamil Nadu coast. It is found that the computed sea surface elevations are in close agreement with the available observations/estimates.     

梧州“6.9”大暴雨过程诊断分析

利用常规气象观测资料和单站气象要素以及新一代天气雷达产品等资料,对2010年6月9日下午发生在梧州市的短时大暴雨过程进行诊断分析,结果发现,此次大暴雨产生的主要原因是在梧州市上空形成一个小尺度天气系统,地面中尺度辐合线及雷达多个产品对梧州产生的强降水都有较好的表征。