台风期间南海北部岛礁及下坡海底对水下噪声的影响研究

The correlation of ambient noise with wind speed, and the depth dependence of ambient noise are both investigated, where the ocean noise data were recorded by a vertical line array in the northern South China Sea. It is shown that the correlation coefficients increase with increasing hydrophone depth during typhoon periods when the frequency ≥ 250 Hz, which opposes the generally accepted knowledge that the correlation coefficients of noise level and wind speed decrease with increasing depth during non-typhoon periods. Particularly at frequencies of 250 Hz, 315 Hz and 400 Hz, the correlation coefficients increase by more than 0.05 at depths ranging from 155 m to 875 m. At the three frequencies, the average noise levels also increase with increasing depth during typhoon periods. It is suggested that these differences are attributed to the wind-generated noise in shallow waters and the effect of "downslope enhancement" to sound propagation. During typhoon periods, the surf breaking and surf beat upon the shores and reefs are strengthened, and the source levels are increased. The wind-generated noise in shallow waters interacts with the downslope sea floor, with the noise-depth distribution changed by a "downslope enhancement" effect promoting noise propagation.     

Drop shape and erosivity part I: Experimental set up,theory, and measurements of drop shape

Simulated raindrops falling in still air have a shape that is mainly determined by surface tension and hydrostatic pressure. Drops released from capillary tips show an initial shape variation ranging from prolate to oblate but eventually this oscillation is damped. At terminal velocity drops have attained equilibrium and have an oblate shape. Measurements of the shape of simulated rain drops produced by capillary tubes were made using a simple, newly-developed photographic set up. The measurements showed that models describing the oscillation frequency and amplitude of drops falling at terminal velocity can also be applied to the simulated drops. A comparison is made between the shape of raindrops in natural storms and simulated drops. Recommendations are given regarding fall heights in simulation in relation to the drop shape in nature.     

Monte Carlo simulation of small air-mass showers

The present model permits simulation of any geographic region and the symmetrical or random positioning of any number of rain gauges. The operator has the option of entering precipitation parameters: rain cell diameter, duration, rain swath length, vector angle, and precipitation amount for any number of discrete showers. In a series of computations the model generates (1) a random first echo location and resulting rain swath, which is superimposed on a specific grid of rain gauges; (2) the number of rain gauge receiving a hit; and (3) the number of undetected rain events within an area.By use of a portion of the Iowa climatological rain gauge network and parameters derived from radar and rain gauge observations the model shows that only 7% of single cell showers are detected by the existing sampling grid.Journal Paper No. J-10378 of the Iowa Agriculture and Home Economics Experiment Station, Ames, IA 50011. Project 2449.A portion of this paper was presented at the 93rd Annual Meeting of the Iowa Academy of Science, April 1981.     

Image Filtering by Factorial Kriging—Sensitivity analysis and application to Gloria side-scan sonar images

Factorial Kriging (FK) is a data- dependent spatial filtering method that can be used to remove both independent and correlated noise on geological images as well as to enhance lineaments for subsequent geological interpretation. The spatial variability of signal, noise, and lineaments, characterized by a variogram model, have been used explicitly in calculating FK filter coefficients that are equivalent to the kriging weighting coefficients. This is in contrast to the conventional spatial filtering method by predefined, data-independent filters, such as Gaussian and Sobel filters. The geostatistically optimal FK filter coefficients, however, do not guarantee an optimal filtering effect, if filter geometry (size and shape) are not properly selected. The selection of filter geometry has been investigated by examining the sensitivity of the FK filter coefficients to changes in filter size as well as variogram characteristics, such as nugget effect, type, range of influence, and anisotropy. The efficiency of data-dependent FK filtering relative to data-independent spatial filters has been evaluated through simulated stochastic images by two examples. In the first example, both FK and data-independent filters are used to remove white noise in simulated images. FK filtering results in a less blurring effect than the data-independent fillers, even for a filter size as large as 9 × 9. In the second example, FK and data-independent filters are compared relative to the extraction of lineaments and components showing anisotropic variability. It was determined that square windows of the filter mask are effective only for removing Isotropie components or white noise. A nonsquare windows must be used if anisotropic components are to be filtered out. FK filtering for lineament enhancement is shown to be resistant to image noise, whereas data-independent filters are sensitive to the presence of noise. We also have applied the FK filtering to the GLORIA side-scan sonar image from the Gulf of Mexico, illustrating that FK is superior to the data-independent filters in removing noise and enhancing lineaments. The case study also demonstrate that variogram analysis and FK filtering can be used for large images if a spectral analysis and optimal filter design in the frequency domain is prohibitive because of a large memory requirement.     

ON DIAGNOSTIC ANALYSIS OF ENERGY FIELDS OF EXPLOSIVE ENHANCEMENT OF TYPHOON OFFSHORE

The energetics process of offehore typhoon in three kinds of explosive enhancement (T_EE) are ana lyzed using ECMWF data. The results are as follows: (a) During the explosive development process,the enhancement of the rotational kinetic enersy (K_W) is mainly in the lower troposphere while that ofthe potential energy (PE) is in the upper troposphere. The magnitude of rotational kinetic energy islargely bigger than that of divergent enersy (K_Χ). (b) The environmental energy advected into the typhoon was about 30% of the internal increment of typhoon energy. The magnitude of energy was an order larger than increment of typhoon energy. (c) Among those three kinds of explosively developed typhoon, the enersy transformation mechanisms are different. (d) The influence of environment fields onabrupt intensification of typhoons couldn't be overestimated.     

商丘地区高炮增雨效果分析

用不同统计单元统计分析了河南省民权县１９９１－１９９２年高炮作业的增雨效果，以日雨量为统计单元，３３个作业日中７６％（２５天）显著地增加了雨量，２年共增雨３２９．１ｍｍ。以月，季为统计单元，作业期间增雨显著的４８％以上，而增雨效果不显著或雨量减少的２１％以下，但总的看，以年雨量统计单元，民权县的人工增雨作业年均增雨１４％两年共增雨的１７２．２ｍｍ。     

近海突然加强台风能量场的诊断分析

用欧洲中心格点资料计算分析了近海三类突然加强台风加强过程中的能量学过程。结果表明：（１）台风突然加强过程中，旋转风动能的增加主要在低层，位能增加主要在高层。台风突然加强主要是低层的旋转风动能增加所引起的，它远大于辐散风动能的增加。（２）环境场通过边界平流输入台风内部的能量只是其增量的３０％左右，内部的转换量比增量大一个量级。（３）三类台风内部能量的转换机理不同。（４）环境场对近海台风突然加强的作用     

中等植被覆盖区金矿蚀变TM及JERS－1OPS遥感信息增强技术

本文分析了与金矿化相伴的蚀变矿物(铁氧化物、粘土矿物、碳酸盐矿物)的反射光谱吸收特征及金矿区上覆植被反射光谱对金矿化蚀变信息的干扰,同时介绍了利用植被指数法、比值-主成份变换法和植被掩模法对陆地卫星TM、JERS-1OPS等遥感图像进行处理,压抑植被反射光谱干扰信息和增强金矿化蚀变反射光谱信息的方法和效果。     

多因素严重干扰区成矿围岩蚀变信息的计算机图像处理──以加拿大西北某地找金实践为例

本文从分析ＴＭ各波段图像信息特征入手，在冰雪和植被等环境因素干扰严重的地区，试验应用了图像掩膜、波段比值、主成分分析等技术，成功地从ＴＭ图像中提取了与金成矿有关的蚀变围岩信息。在此基础上，进一步研究了蚀变与断裂构造和围岩类型的关系，确定了金矿找矿远景区。     

浙江沿岸水对“魔蝎”台风的响应

台风"魔蝎"于2018年8月12日夜子时登陆浙江温岭，台风登陆前后造成了浙江近海海水物理特性的诸多变化。台风登陆时的最大风速约为27.5 m/s，登陆时正值天文大潮期间，引起了超过0.30 m的沿岸增水，增水持续了3~4 d。在台风登陆前的7 h内，锚系点水域的海水温度降幅超过1℃。分析表明，海气热交换引起的海水热量损失是锚系点水域温度降低的主要因素，而海水垂向混合带来的海水降温幅度有限。降温在水平区域分布上具有不对称性，台风路径两侧的降温中心呈现明显的不对称性，台风路径右侧的表层海水温度降幅明显强于路径左侧。长江口外至苏南外海水温降幅最为明显，最大降温接近3℃，舟山东南方向海域和温岭东南方向海域最大降温分别超过1.6℃和1.2℃，而在台风路径左侧海域，表层海水温度降幅普遍小于1℃。在台风登陆前的7 h内，海水盐度降低了1.2，研究表明台风带来的强降雨是海水盐度降低的主要因素。本研究，得到了台风"魔蝎"登陆前、登陆时和登陆后，锚系点及周边海域海流、水位、温度、盐度等的变化特征，初步获悉台风期间海水物理特性变化的动力因素，可以为台风影响研究、预防和降低台风带来的风险和损失等提供动力学方面的依据。