热带风暴形成过程中的涡旋自组织及其复杂性：一个典型个例的红外云图分析

应用高分辨率的红外卫星云图资料,对台风8807从热带低压发展成热带风暴的过程进行了分析,给出了热带风暴形成过程伴随着复杂涡旋自组织现象的观测证据。结果发现,涡旋自组织可在从数十到十万km2的各种尺度扰动云团之间发生,发生合并的云团除了理想数值试验中的两类前景之外,还存在第三类前景,即较大尺度的云团会发生分裂,部分与其他云团合并。合并形成的新云团可能发展也有可能减弱,这应取决于新云团所处的环境以及是否有其他云团补充并入。用二维Fourier分析可以清楚地看到8807发展成热带风暴的过程可分为两个阶段,一是多涡共存,不同方向、不同尺度系统能量转换频繁阶段,另一是单涡发展阶段,谱密度等值线形态稳定少变。分维计算结果表明,热带风暴形成过程中的相关云团较已有研究分析的云团略显规则,分维略小于已有结果。此外,临界温度取值不同,分维是有差异的,边界温度越低,分维越小。     

“07．7”鄂东南强对流天气的多普勒雷达资料分析

利用武汉多普勒天气雷达资料,对2007年7月27日发生在武汉及其周边部分地区的一次强对流天气过程,特别是引起武汉、洪湖的冰雹和地面大风灾害的2个强风暴（A、B）进行了详细分析,得到如下结论：（1）这次强对流天气的主要天气背景是,副热带高压西侧强烈的西南气流诱发了中小尺度扰动,强的低层垂直风切变,大的垂直不稳定,低层较干和中高层更干的水汽条件。（2）产生灾害性天气的对流系统最初是一条近乎南北向的断续型对流带,强风暴A和B在其成熟阶段都有低层弱回波和中高层悬垂回波结构,最大回波强度均大于60dBz;风暴A在其崩溃阶段,近地面径向速度迅速增大,随其北移．造成武汉市黄陂区大风灾害;风暴B在平均径向速度图上存在明显的中层气流辐合（MARC）,是即将出现地面强辐散风的标识。（3）强回波中心高度迅速降低是地面灾害性天气发生的标识,VIL密度比VIL本身更能反映风暴的强度,特别是当因雷达扫描策略的影响导致探测不到风暴顶或风暴底时。（4）在用冰雹探测算法（HDA）探测冰雹时,要注意修改可调参数．特别是0℃和-20℃环境温度的高度．这样才能大大降低冰雹误报率。     

利用大地电磁站间阻抗估算磁暴引起的大地电场

由磁暴引起的地下感应电场(geomagnetic induction electric field,GIE)会影响电网的安全稳定运行,GIE的大小取决于磁暴时磁场的变化率和周围地下介质的电性结构.本文利用在地表观测的磁场与电场数据,首先求得频率域实际地下三维大地电磁站间阻抗,再结合磁暴时段的磁场数据,计算GIE的频谱,最后通过傅里叶反变换,得到GIE时间序列.本文以日本地区三个长期观测的电磁电台站为例,讨论了站间阻抗的长期稳定性,并选取一次典型的磁暴事件,对本文方法进行了验证.结果表明,合成的GIE与实测数据基本一致,说明利用大地电磁站间阻抗,结合地磁台站数据,可以高精度合成GIE.本文方法有助于定量评价磁暴发生时产生的GIE对电网可能造成的破坏作用.     

QuikSCAT风场在台风风暴潮计算中的应用

业务化风暴潮计算中多采用模型风场的算法来给出风暴潮强迫场。最大风速半径是模型风场最难确定的参数之一。利用QuikSCAT卫星风场数据拟合台风最大风速半径是确定该参数的有效方法。将拟合得到的最大风速半径代入模型风场计算风暴潮的驱动场,模拟的沿岸风暴增水与实况更为接近。     

The morphological response of foredunes at a breached barrier system to winter 2013/2014 storms on the southwest coast of Ireland

The level of storminess in Ireland during the winter of 2013/2014 was exceptional, the effects of which cost the Irish state in excess of €260 million in infrastructure repair and insurance claims. In Ireland, a lack of coastal process data from monitoring programmes means that the response of protective barrier coasts to such events remains largely un‐investigated. This study addresses this issue through an examination of the geomorphic impacts of recent storms, including those that occurred during the winter 2013/2014, on a breached barrier on the southwest coast of Ireland. Data from a two‐year terrestrial laser scanning (TLS) monitoring campaign shows that the winter 2013/2014 events caused a major (>50 m) dune recession at Rossbehy, County Kerry. Results from a simple linear regression analysis indicate storm duration plays an important role in the removal of foredunes at the study site. Given the fact that the frequency of intense storms in the vicinity of Ireland is forecast to increase within the next century, a scientific understanding of barrier response to such events is critical to inform sound management practices. Copyright © 2016 John Wiley & Sons, Ltd.     

2004年11月7-8日巨磁暴期间场向电流的分布特征

利用CHAMP卫星磁场数据分析研究了2004年11月7日至8日巨磁暴(DstH和AE指数对比分析得出,早上扇区的大尺度电流片的分布特征更多地受到亚暴活动的影响,而下午扇区的电流片分布则明显反映出磁暴环电流活动的特征.     

Distribution of boulders at Miyara Bay of Ishigaki Island,Japan: A flow characteristic indicator of tsunami and storm waves

This study investigates the distribution of boulders at Miyara Bay of Ishigaki Island, Japan. These boulders were deposited on a reef flat extending approximately 400–1300 m in width. Most boulders were rectangular to ellipsoidal, without sharp broken edges. They are reef and coral rock fragments estimated as <335 m³ (<633 t). Locally in the bay, the relationship between the boulder weight and position shows that boulders of a given weight have a clear limit on seaward distribution on the reef flat. For example, more than 1, 10, and 100 tons of boulders were deposited, respectively, more than 500, 300, and 100 m from the reef edge. The line is consistent with the possible landward transport limit by maximum storm waves at the Ryukyu Islands, suggesting that the line was formed by the reworking of some boulders by maximally strong storm waves, although we can not exclude the possibility that the line was formed by tsunamis. Furthermore, 68% of boulders at the bay are deposited beyond this line. Therefore, the presence of these boulders at their present positions is difficult to explain solely by storm waves, implying the possible tsunami origin of these boulders. The boulders are characteristically concentrated along the high‐tide line, suggesting the drastic reduction of the tsunami hydraulic force along the line. Previous studies using radiocarbon age dating, as well as our study, imply that at least 69 boulders at Miyara Bay were probably deposited at their present positions by the 1771 Meiwa tsunami, although some of these boulders might have been emplaced and displaced on the reef flat by prior tsunami or storm surges.     

一次特大沙尘暴成因的卫星云图分析

运用1小时间隔的GMS-4数字展宽红外资料和部分常规气象资料,分析了1993年5月5日下午至夜间发生在甘肃和宁夏等省(区)部分地区罕见的特大沙尘暴的形成原因。结果指出,这场特大沙尘暴主要由强冷锋前部的中尺度对流系统(MCS)及其伴随的飑线造成的。它们的移动大体与地面强冷锋及700～500hPa间的平均气流方向一致。最后对此MCS及其伴随的飑线的可预报性问题作了简要讨论。     

一次中气旋冰雹天气过程的诊断分析

对2002年9月27日发生在山东省境内的一次冰雹天气过程进行了中小尺度和雷达资料分析。结果表明:华北冷性低槽的东移南压,并配合低空切变线和地面冷锋的共同影响是这次过程的直接大尺度影响系统;高空冷平流、地面暖平流,在对流层中低层形成了大范围上冷下暖的不稳定层结;低层中尺度低压环流的扰动,并与高空急流南侧的辐散区耦合,产生强烈的上升运动;雷达回波分析也发现,这次过程具有典型的小型超级单体风暴特征,存在并维持尺度较小的中气旋结构。     

Flow direction and magnetic mineralogy of lava flows from the central parts of the Peninsula of Baja California,Mexico

Magnetic properties of two apparently unrelated lava suites (one tholeiitic and the other alkalic) coexisting in the central parts of the Peninsula of Baja California, Mexico, were measured in this study. Macroscopic indicators and measurements of anisotropy of magnetic susceptibility (AMS) were combined to infer the flow direction on those lavas. These measurements were used to investigate the likelihood of the existence of an abnormally long tholeiitic lava flow in this part of the Peninsula. The obtained results indicate that the tholeiitic flows in the region constitute regular length flows, and are likely to have been issued through vents located within the area of study. Additionally, comparison of the magnetic signature of tholeiitic and alkalic lavas reveals a systematic difference in some of the magnetic parameters (bulk susceptibility and Curie temperatures). In particular, it is proposed that the narrow range of Curie temperatures characteristic of each lava type can be used as a reliable proxy for the identification of each lava type in the region. All of these findings show that the alkalic and tholeiitic lavas of the region are more closely related to each other than previously suspected.Editorial responsibility: R. Cioni