不同季节北大西洋上爆发性气旋云微物理特性的分析与比较

本文利用CloudSat卫星产品、MODIS(Moderate Resolution Imaging Spectroradiometer)可见光云图和欧洲中期天气预报中心提供的ERA5再分析资料,对不同季节北大西洋上四个爆发性气旋个例的云微物理特性的垂直结构进行了分析,结果表明,爆发性气旋所伴随的云系以雨层云、深对流云和高层云为主,云系最大高度可达12km以上;深对流云和雨层云中常出现雷达反射率大值区,存在较强的对流运动;云中冰粒子沿0℃等温线开始出现,冰粒子尺度随高度的增加而减小,秋季个例和冬季个例的冰粒子有效半径最大值大于春季个例和夏季个例;在深对流云和雨层云内部,冰粒子数浓度随高度的增加而增大,大尺度冰粒子更为集中,出现冰水含量大值区,冰粒子数浓度最大值和冰水含量最大值以秋季个例的数值最大,冬季和春季个例次之,夏季个例最小。     

中南半岛及南海海域烟雾混合层积云的微观特性研究

中南半岛地区生物物质燃烧活动使其成为东南亚烟雾气溶胶的高值区,排放的烟雾可以传播到南海海域,影响当地层积云的微观特性和降水活动,进而对气候产生影响。本文利用2007—2019年CALIPSO和CloudSat卫星数据筛选了190个烟雾气溶胶与层积云混合的个例,其中中南半岛等陆地上空(代表陆地)的烟雾混合层积云为88个,南海海域(代表海洋)的烟雾混合层积云为102个。基于个例的研究发现：相对于海洋上的烟雾混合层积云,陆地上的烟雾混合层积云中云的液态粒子数浓度(Number concentration of liquid water drops, LNC)、液态粒子有效半径(Geometric mean radius of liquid water drops, LER)和液态水含量(Liquid water content, LWC)的值都更高。与清洁层积云相比,烟雾气溶胶主要通过半直接效应影响海洋上的层积云,而主要作为云凝结核(Cloud condensation nuclei, CCN)通过间接效应影响陆地上的层积云。当气溶胶光学厚度(Aerosol optical depth, A...     

热带气旋“桑美(2006)”冰云微物理属性垂直分布规律

利用2006年8月3日—11日CloudSat卫星的云反演资料,探讨了热带气旋"桑美(2006)"在形成期、发展成熟期和减弱期不同部位云中冰粒子的垂直分布规律。结果表明:星载雷达扫过热带气旋"桑美(2006)"不同部位时,云中冰粒子主要分布在5~16.5km高度;冰粒子等效半径随高度递增而递减,大值区主要分布在冰云下部;冰粒子数浓度随高度递增而递增,大值区主要分布在冰云上部;冰水含量的垂直分布呈单峰或双峰特征;星载雷达监测到的该热带气旋不同部位的冰粒子等效半径、冰粒子数浓度、冰水含量的最大值分布范围分别为107.9~177.7mm、123.8~827.9粒×L~(-1)、211~2858mg·m~(-3),最大值出现高度存在差异。     

基于CloudSat卫星资料的青岛地区云特征研究

利用2007——2010年CloudSat卫星资料,对青岛地区(35. 583°～37. 150°N,119. 050°～121. 000°E)云特征参量进行了统计分析。结果表明:单层云出现频率为39%左右,多层云主要以2层云为主,出现频率均为18%左右;月平均云量在64. 1%～77. 6%之间,从1月至12月呈递减趋势;卷云、高层云、高积云和层积云平均频率之和为86. 5%,其他类型的云出现的频率均不高;云水路径在4、5月和8、9月较大,分别达到了200 g·m~(-2)以上和350 g·m~(-2)以上;云液态有效粒子半径在6～16μm之间,春、夏、秋季高值区位于云体中部至上部;云冰晶有效粒子半径在20～120μm之间,高值区位于云体中部至底部;青岛南部,即近海区域云有效粒子半径和云水含量大于北部。     

2006年6月北大西洋上热带风暴Alberto变性后爆发性发展机理分析

本文利用欧洲中期天气预报中心(European Centre for Medium-Range Weather Forecasts,ECMWF)的ERA5客观再分析资料、气象卫星合作研究所(Cooperative Institute for Meteorological Satellite Studies,CIMSS)提供的红外卫星云图资料,对2006年6月14~20日发生在北大西洋上的一个爆发性气旋进行分析。该气旋由热带风暴阿尔贝托(Tropical Storm Alberto)变性后发展而来,是2000—2016年的17个夏季(6、7和8月)发生在北大西洋上的中心气压加深率最大的爆发性气旋个例。该气旋的演变过程可划分为初始、发展、成熟和衰亡四个阶段。本文旨在分析气旋演变过程中的云系特点、气旋爆发前后的高低空环流形势和高低空相互作用。分析显示,低层强烈的温度平流导致的大气斜压性是利于气旋发展的重要环境条件;500 hPa槽前的正涡度平流可为气旋发展提供动力强迫;高层异常PV的下传对气旋发展有促进作用;潜热释放(Q2/CP)主要位于对流层的中低层,这有利于气旋发展。利用Zwack-Okossi方程进行诊断分析发现,在该气旋发展过程中绝对涡度平流项和非绝热项的贡献为正,且非绝热加热对气旋快速发展的贡献最大,而温度平流项和绝热项对气旋发展起阻碍作用。     

北太平洋爆发性气旋的统计特征

利用FNL(Final Analyses)全球格点资料,对2000—2015年冷季(10月至来年4月)发生于北太平洋(20°N~65°N,110°E~100°W)的爆发性气旋进行了分析研究。依据爆发性气旋的空间分布特征和高时间分辨率的资料,将爆发性气旋定义修订为海表面中心气压(地转调整到45o N)12h平均加深率达到1hPa/h以上的气旋。根据爆发性气旋最大加深率的大小,在强度上将其划分为4类:弱、中、强和超强。日本海、西北太平洋、中西太平洋、中东太平洋和东北太平洋为北太平洋爆发性气旋的5个多发区域,发生于各区域的爆发性气旋依次称之为:JOS(Japan-Okhotsk Sea)、NWP(Northwestern Pacific)、WCP(West-Central Pacific)、ECP(East-Central Pacific)和NEP(Northeastern Pacific)爆发性气旋。北太平洋爆发性气旋发生频数自西向东逐渐减少,呈现出"西多东少"的分布特征。爆发性气旋的统计特征因发生区域不同而呈现出较大差异,NWP爆发性气旋多发生于冬季和早春,而NEP爆发性气旋多发生于秋季和早春;相对于NEP爆发性气旋,NWP爆发性气旋发展较为剧烈,中心最低气压较低,爆发史长和发展史长较长。NWP爆发性气旋的移动路径多为西南-东北向,随着爆发强度的增强,其移动路径更趋于集中。NEP爆发性气旋的移动路径因生成位置的不同而呈现出较大差异,在中西太平洋和中太平洋海域生成的NEP爆发性气旋,其移动路径前期多为偏东向,后期折向西北;而在中东太平洋海域生成的NEP爆发性气旋,其移动路径多为西南-东北向。海洋暖流为NWP和NEP爆发性气旋的急剧发展提供了有利的海洋物理环境场。     

西北太平洋一个超强爆发性气旋的分析

利用NCEP(National Centers for Environmental Prediction)提供的CFSv2(Climate Forecast System Version 2)资料和日本高知大学提供的MTSAT-1R(Multi-functional Transport Satellites-1R)卫星红外波段反照率资料,对2013年1月发生在西北太平洋上的一个超强爆发性气旋进行了研究,利用天气分析和诊断分析等方法,详细分析了该爆发性气旋的结构特征。发现该气旋在爆发性发展的后期位于高空急流的北侧,高空的强辐散有利于气旋的发展。气旋上空500hPa的低压槽在14日12UTC显著加深,槽前的正涡度平流有利于海平面气压降低。与气旋伴随的冷锋存在鼻状结构,在800hPa以下,假相当位温随高度降低,低层大气呈对流性不稳定状态。利用涡度方程对气旋进行诊断分析,发现平流项和拉伸项为气旋涡度变化的主要贡献项。设计了围绕气旋中心15(°)×15(°)的区域,发现不同时刻的沿区域四边积分的环流、区域内面积平均的非绝热加热、水汽通量散度和垂直速度4个物理量存在正反馈过程,即气旋爆发性发展的前期存在类似CISK的正反馈机制。     

南大洋夏季气旋的统计特征

为增加对南半球气旋及爆发性气旋的理解,利用美国国家环境预报中心NCEP(National Centers for Environmental Prediction)提供的1(°)×1(°)FNL格点资料对南大洋2004~2007年3个夏季(12,1,2月)热带地区以外的气旋及爆发性气旋的位置及路径等特征进行统计分析,发现1月份为南大洋夏季气旋与爆发性气旋发生发展的高峰月,55°S~70°S为气旋分布最大值区,较多的气旋生成于南美洲东部、南极半岛附近,而爆发性气旋则大多生成于澳大利亚大陆西南50°S~60°S内,南极半岛东北部以及20°E,60°E附近,并且随着夏季向秋季过渡,南大洋气旋位置分布逐渐向高纬度集中。南大洋夏季气旋及爆发性气旋路径走向大多为东-东南走向,个别为东北走向。南大洋夏季气旋生命周期平均为2~6 d,水平尺度平均约为1000 km,爆发性气旋一般维持在1周左右,水平尺度平均约为3000 km。特殊的地理环境使得南大洋气旋具有发生频率高、中心气压值低、水平尺度大等特点。     

西北太平洋上三个爆发性气旋的对比分析和数值模拟研究

利用FNL(Final Analysis)再分析资料对西北太平洋上三个爆发性气旋,即2007年11月18—21日的OJ(Okhotsk-Japan Sea Type)型,2012年1月10—13日的PO-O(Pacific Ocean-ocean Type)型,以及2014年3月28—31日的PO-L(Pacific Ocean-land Type)型,进行了分析,结果表明:不同类型气旋由于其发生、发展位置不同使得气旋的水平结构和垂直结构存在差异。利用WRF(Weather Research and Forecasting)模式的非绝热加热试验表明,潜热释放和表面热通量对不同类型爆发性气旋个例的贡献不同,对PO-O型和PO-L型气旋个例潜热释放的贡献更大,而对OJ型气旋个例表面热通量的贡献更大。海温敏感性试验表明,海温升高或降低对气旋移动路径影响较小,海温升高使气旋进一步加深,而海温降低使气旋相对减弱。     

自动计算热带气旋位置和范围的方法研究

本文以卫星云图的热带气旋云系为研究对象,基于Canny边缘检测、contour轮廓提取等方法,研究了通过图像的形状特征和范围大小对热带气旋云系进行自动识别,得到了较好的效果。这种方法有助于提高热带气旋云系识别的自动化程度,实现热带气旋的自动跟踪,从而为热带气旋的预报提供了便利。     

Microbial Biomass and Organic Nutrients in the Deep-Sea Sediments of the Central Indian Ocean Basin

In order to assess the impact of deep-sea mining on the in situ benthic life, we measured the microbial standing stock and concentration of organic nutrients in the deep-sea sediments of the Central Indian Ocean Basin in the Indian pioneer area. Sediments were collected using box core and grab samples during September 1996. The total bacterial numbers ranged from 10 10 -10 11 cells per g -1 dry weight sediment. There was a marginal decrease in the number of bacteria from surface to 30 cm depth, though the subsurface section registered a higher number than did the surface. The highest numbers were encountered at depths of 4-8 cm. The retrievable number of bacteria were two orders less in comparison with the direct total counts of bacteria. An almost homogeneous distribution of bacteria, total organic carbon, living biomass, and lipids throughout the depth of cores indicates active microbial and benthic processes in the deep sea sediments. On the other hand, a uniform distribution of total counts of bacteria, carbohydrates, and total organic carbon in all the cores indicates their stable nature and suggests that they can serve as useful parameters for long-term monitoring of the area after the benthic disturbance. Further studies on temporal variability in this region would not only verify the observed norms of distribution of these variables but would also help to understand restabilization processes after the simulated benthic disturbance.     

Assessing the Validity of Seismo-Acoustic Predictor Equations for Obtaining Seabed and Sub-Surface Sediment Physical Properties

The interdependence between the seismo-acoustic properties of a marine sediment and its geotechnical/physical parameters has been known for many years, and it has been postulated that this should allow the extraction of geotechnical information from seismic data. Though in the literature many correlations have been published for the surficial layer, there is a lack of information for greater sediment depths. In this article, a desktop study on a synthetic seafloor model illustrates how the application of published near-surface prediction equations to subsurface sediments (up to several tens of meters burial depth) can lead to spurious predictions. To test this further, acoustic and geotechnical properties were measured on a number of sediment core samples, some of which were subjected to loading in acoustically-equipped consolidation cells (oedometers) to simulate greater burial depth conditions. For low effective pressures (representing small burial depths extending to around 10 meters subsurface), the general applicability of established relationships was confirmed: the prediction of porosity, bulk density, and mean grain size from acoustic velocity and impedance appears generally possible for the investigated sedimentary environments. As effective pressure increases through, the observed relationships deviate more and more from the established ones for the near-surface area. For the samples tested in this study, in some instances increasing pressure even resulted in decreasing velocities. There are several possible explanations for this abnormal behavior, including the presence of gas, overconsolidation, or bimodal grain size distribution. The results indicate that an appropriate depth correction must be introduced into the published prediction equations in order to obtain reliable estimates of physical sediment properties for greater subsurface depths.     

海上大直径钢管桩打桩过程中桩周土强度弱化研究

海上大直径钢管桩打桩过程中,桩周土体受到强烈扰动而发生强度弱化,掌握桩周土体强度弱化规律对于准确预测打桩过程、保证工程安全具有重要意义。为研究土体强度弱化规律,开展了环剪试验模拟打桩对桩周土体的扰动,测试土体强度随剪切速率的变化规律,建立了描述土体强度弱化规律的拟合公式,引入到打桩分析软件中。研究结果表明：土体的强度折减程度不仅与土体本身的性质有关还受到土体的埋深和剪切速率的影响,埋深越深土体强度折减程度越低,剪切速率越高土体强度折减越高,在打桩分析中可采用这里推荐的线性折减方法来模拟不同深度处土体强度的折减规律。     

Geoacoustic Inversion via Genetic Algorithm and Its Application to Manganese Sediment Identification

An acoustic inversion method using a wide-band signal and two near field receivers is proposed and applied to multiple layered seabed models including a manganese sediment. The inversion problem can be formulated into a probabilistic model comprised of signals, a forward model, and additive noise. The forward model simulates wide-band signals, such as chirp signals, and is chosen to be the source-waveletconvolution plane wave modeling method. The wavelet matching technique, using weighted least-squares fitting, estimates the sediment sound-speed and thickness on which determination of the possible numerical ranges for a priori uniform distribution is based. The genetic algorithm is applied to a global optimization problem to find a maximum a posteriori solution for determined a priori search space. Here the object function is defined by an L 2 norm of the difference between measured and modeled signals. Not only the marginal pdf but also its statistics are calculated by numerical evaluation of integrals using the samples selected during importance sampling process of the genetic algorithm.     

Interannual Sea Level Variations and Annual Tides in the Northwestern Pacific

Specific properties of the interannual sea level variations and annual tides in the Northwestern Pacific were studied. Several tide stations were monitored. The monthly mean sea level for the year of 1995 was analyzed at each tide station. A seismic event in 1995, some tectonic activity around the subject area, and the Kuroshio (the oceanic western boundary current) may possibly contaminate results which would have occurred from the astronomical annual tide alone.     

Deep-Sea Sediment Compression Curves: Some Controlling Factors, Spurious Overconsolidation, Predictions, and Geophysical Reproduction

Oedometer tests have been carried out on 70 undisturbed surficial clays (at approximately 250 mm below the mudline), mostly collected by free-fall corers from sites widely scattered throughout the deep-sea North Atlantic. Acoustic measurements were also made, initially on contiguous samples and ultimately on the same sample using a geophysically instrumented oedometer which also collected electrical resistivity data. Apart from those quiescent areas below the carbonate compensation depth, such as north of the West Indies where very fine clays exist, most of the samples are silty clays whose geotechnical-geophysical properties are dependent on the type of clay minerals present (and their ability to take in moisture), the sand-size fraction, and the quantity of carbonate present. Thus the pure clays have high compressibilities which decrease on the addition of coarse particles, while the converse is true for the acoustic parameters, these increasing with the sand fraction. Using the notion of the intrinsic compression line for all samples, and comparison to it of the measured compression curves, it is clear that, contrary to some previously held ideas, most deep-sea clays are normally consolidated; the addition of carbonate has the effect of creating an open, stronger sediment skeleton. Interestingly, where information is available, the variation with depth of a sample's acoustic velocity follows the void ratio pressure relationship of the compression curve. This allows the construction of an in-situ sediment compression curve using the in-situ geophysical observations.     

Phylogenetic diversity and phenotypic characterization of cultivable bacterioplankton isolated from polar oceans

A set of 27 marine planktonic bacteria isolated from the polar regions was characterized by 16S rDNA sequencing and physiological and biochemical testing. More than half of these bacteria were positive for caseinase, gelatinase and 13-glucosidase, and could utilize glucose, maltose or malic acid as carbon source for cell growth. Twelve isolates expressed nitrate reduction activities. Except for one antarctic isolate BSwlO175 belonging to Actinobacteria phylum, these isolates were classified as γ-Proteobacteria, suggesting that γ-Proteobacteria dominated in cultivable marine bacterioplankton at both poles. Genus Pseudoalteromonas was the predominant group in the Chukchi Sea and the Bering Sea, and genus ShewaneUa dominated in cultivable bacterioplankton in the Prydz Bay. With sequence similarities above 97%, genus Psychrobacter was found at both poles. These 27 isolates were psychrotolerant, and significant 16S rDNA sequence similarities were found not only between arctic and antarctic marine bacteria （ 〉 99% ）, but also between polar marine bacteria and bacteria from other aquatic environments （ ≥ 98.8% ）, including temperate ocean, deep sea, pond and lake, suggesting that in the polar oceans less temperature-sensitive bacteria may be cosmopolitan and have a bipolar, even global, distribution at the species level.     

Flow Cytometric Analysis of Coastal Lagoon Bacterioplankton and Picophytoplankton: Fixation and Storage Effects

The effect of different fixation and storage protocols on the flow cytometric (FCM) simultaneous analysis of bacterioplankton and phytoplankton in coastal seawater samples (Mediterranean coastal lagoons) was investigated. FCM measurements (cell number, fluorescence and scatter characteristics) were obtained through DAPI staining. Three fixatives [glutaraldehyde (GA), formaldehyde (FA) and paraformaldehyde (PFA)] and two storage (3 months duration) methods (5 °C and −196 °C) were tested. Two dominant populations were detected in studied samples: bacteria and eukaryotic picophytoplankton. Adding fixatives (2% final concentration) appears necessary to obtain FCM exhaustive counts of all the bacteria and phytoplanktonic cells. This was related to the permeation effect of fixatives which allowed a better DAPI staining of the cells. Maximum fluorescence, i.e. optimal staining of the cells was obtained with FA or PFA, and significant lower fluorescences with GA. Fixed samples stored at 5 °C induced rapid cell loss. Only storage in liquid nitrogen of samples fixed with FA or PFA, allows mid-term (≥4 months) preservation of bacteria or picophytoplankton cell numbers, and limited evolution of DAPI-induced fluorescence and scatter characteristics.