Record Arctic Ozone Loss in Spring 2020 is Likely Caused by North Pacific Warm Sea Surface Temperature Anomalies     

Yan XIA  Yongyun HU  Jiankai ZHANG  Fei XIE  Wenshou TIAN 《大气科学进展》2021,38(10):1723-1736

Record ozone loss was observed in the Arctic stratosphere in spring 2020. This study aims to determine what caused the extreme Arctic ozone loss. Observations and simulation results are examined in order to show that the extreme Arctic ozone loss was likely caused by record-high sea surface temperatures(SSTs) in the North Pacific. It is found that the record Arctic ozone loss was associated with the extremely cold and persistent stratospheric polar vortex over February–April, and the extremely cold vortex was a result of anomalously weak planetary wave activity. Further analysis reveals that the weak wave activity can be traced to anomalously warm SSTs in the North Pacific. Both observations and simulations show that warm SST anomalies in the North Pacific could have caused the weakening of wavenumber-1 wave activity, colder Arctic vortex, and lower Arctic ozone. These results suggest that for the present-day level of ozone-depleting substances, severe Arctic ozone loss could form again, as long as certain dynamic conditions are satisfied.  相似文献   

Role of external forcing on the seasonal and interannual variability of mixed layer depth over the Bay of Bengal using reanalysis datasets during 1980–2015     

《Dynamics of Atmospheres and Oceans》2021

The monsoon reversal winds in different seasons and high influx of freshwater from various rivers make the Bay of Bengal (BoB) a unique region. Thus, the knowledge of the dynamics of the mixed layer over this region is very important to assess the climatic variation of the Indian subcontinent. A comprehensive study of the role of external forcing on the seasonal and interannual mixed layer depth (MLD) variability over the BoB is carried out for 36 years (1980–2015) using reanalysis products. A weak and strong seasonality of MLD is observed over the northern and the southern BoB (NBoB and SBoB) respectively. The partial correlation suggests that the net heat flux (Qnet) is the major contributor to the deepening of MLD over the NBoB, whereas the wind stress controls the deepening over the SBoB. The seasonal variability reveals the deepening of MLD during summer and winter monsoon and the shallowing during pre- and post-monsoon over the BoB. The relation of the interannual MLD variability and the different phases of the Indian Ocean Dipole (IOD) reveals that the negative phase of IOD is associated with deeper MLD over BoB while the positive phase of IOD depicts shallower MLD. In addition, the opposing characteristic of MLD is highly prominent during October-December. This is majorly contributed by variations related to the second downwelling Kelvin and associated Rossby waves over BoB for the opposing phases of the IOD years.  相似文献   

2020年秋季海洋天气评述          下载免费PDF全文

孙舒悦  尹尽勇  张增海  柳龙生 《山东气象》2021,41(1):19-29

2020年秋季(9—11月)大气环流特征表现为,北半球极涡呈单极型分布,中高纬环流呈4波型。9—11月,欧亚大陆中高纬环流经向度不断加大,冷空气势力增强。西太平洋副热带高压较历史平均偏强,热带气旋活动频繁。我国近海出现了19次8级以上大风过程,其中冷空气大风过程6次,台风大风过程4次,入海气旋大风过程1次,冷空气与热带气旋共同影响的大风过程7次,冷空气和温带气旋共同影响的大风过程1次。西北太平洋和南海共生成13个热带气旋,其中10月共有7个热带气旋生成,追平10月热带气旋生成数的历史最高纪录;全球其他海域共生成热带气旋26个。我国近海未出现2 m以上大浪过程的天数仅有12 d,约占秋季总日数的13％。秋季,我国近海海域呈明显降温过程,北部海域的降温幅度明显大于南部海域,受连续北上影响我国北部海域的热带气旋活动影响,9月黄海东部及东海东部的海面温度较气候态明显偏低。  相似文献   

新疆及邻区体波震级初步分析研究          下载免费PDF全文

冉慧敏  李文倩  上官文明 《中国地震》2022,38(1):91-101

依据《地震震级的规定（GB 17740—2017）》,分析了2009—2017年新疆地震台网所记录的新疆及邻区476次中深源地震事件,测定了13601个m_b（短周期体波震级）和12035个m_B（BB）（宽频带体波震级）的数据样本,回归分析m_b和m_B（BB）得到回归方程及量规函数,结果显示m_b和m_B（BB）相关系数为0.966,表明两者显著相关。因此,建议对于中强型中深源地震可以直接从原始速度型宽频带数字地震记录上测定长周期体波震级m_B（BB）,提高地震速报测定的速度和精度。通过震级偏差统计和台站场地响应计算,分析新疆地震台网中的XKR、HTA、ATS和KSZ等地震台站震级偏差较大的原因为砂岩、灰岩、砂土层等类型的台基放大了场地响应,说明台基类型对体波震级偏差的影响较大。与NEIC测定的体波震级对比时,发现新疆地震台网测定体波震级平均偏大0.42级,且偏差随着震源深度的增加有增大的趋势。  相似文献   

2022年1月8日门源6.9级地震山东地震台网测定面波震级对比分析     

石玉燕  张春鹏  颜启  苗庆杰 《地震地磁观测与研究》2022,43(4):1-7

通过对山东地震台网记录的2022年1月8日门源M_S 6.9地震原始波形进行分析,测算出88个测震台站的M_S、M_S7、M_S(BB)等3种面波震级,并与中国地震台网速报和青海区域地震台网编目测定结果进行对比分析。结果表明：①山东地震台网测定门源M_S6.9地震的面波震级M_S、M_S7、M_S(BB)分别为7.20、7.16、6.96;②M_S(BB)震级的测定方法简单,不同台站之间的偏差较小,一致性较好,适合在地震台网的地震速报中使用。这与震级国家标准GB 17740—2017的规定相一致。  相似文献   

典型斜坡地形地震动特征分析     

丁佳龙  郝冰  李远东  周港圣  周正华 《震灾防御技术》2022,17(3):473-480

以云南鲁甸6.5级地震中房屋建筑破坏严重的龙头山集镇斜坡地形为例,通过地脉动测试分析得出斜坡及坡顶测点相对于坡脚参考点谱比峰值均＞1,顺坡向谱比峰值大于垂直坡向谱比峰值,且谱比峰值从斜坡坡脚到坡顶逐渐增大,坡顶处约为3;顺坡向谱比峰值对应的频率为4.57～5.39 Hz,垂直坡向谱比峰值对应的频率稍高,为5.42～5.96 Hz。通过结合黏弹性边界的时域动力有限元方法分析斜坡地形在垂直入射地震动作用下的响应,数值模拟结果表明,斜坡坡顶处的位移放大作用显著,坡脚处放大作用较小;介质剪切波速对斜坡地震动的影响较明显,尤其是坡顶点处不同介质剪切波速模型位移峰值差异较大。由于斜坡地形复杂的散射效应,在斜坡及附近测点均出现明显的转换面波,坡顶点处波形转换最显著。数值模拟结果进一步验证了龙头山集镇依坡而建的房屋建筑破坏严重是由局部地形地震动放大效应与地震动差动共同作用引起的。  相似文献   

Under the surface: Pressure-induced planetary-scale waves,volcanic lightning,and gaseous clouds caused by the submarine eruption of Hunga Tonga-Hunga Ha'apai volcano     

David A. Yuen  Melissa A. Scruggs  Frank J. Spera  Yingcai Zheng  Hao Hu  Stephen R. McNutt  Glenn Thompson  Kyle Mandli  Barry R. Keller  Songqiao Shawn Wei  Zhigang Peng  Zili Zhou  Francesco Mulargia  Yuichiro Tanioka 《地震研究进展（英文）》2022,2(3):100134

We present a narrative of the eruptive events culminating in the cataclysmic January 15, 2022 eruption of Hunga Tonga-Hunga Ha'apai Volcano by synthesizing diverse preliminary seismic, volcanological, sound wave, and lightning data available within the first few weeks after the eruption occurred. The first hour of eruptive activity produced fast-propagating tsunami waves, long-period seismic waves, loud audible sound waves, infrasonic waves, exceptionally intense volcanic lightning and an unsteady volcanic plume that transiently reached—at 58 ?km—the Earth's mesosphere. Energetic seismic signals were recorded worldwide and the globally stacked seismogram showed episodic seismic events within the most intense periods of phreatoplinian activity, and they correlated well with the infrasound pressure waveform recorded in Fiji. Gravity wave signals were strong enough to be observed over the entire planet in just the first few hours, with some circling the Earth multiple times subsequently. These large-amplitude, long-wavelength atmospheric disturbances come from the Earth's atmosphere being forced by the magmatic mixture of tephra, melt and gasses emitted by the unsteady but quasi-continuous eruption from 0402±1–1800 UTC on January 15, 2022. Atmospheric forcing lasted much longer than rupturing from large earthquakes recorded on modern instruments, producing a type of shock wave that originated from the interaction between compressed air and ambient (wavy) sea surface. This scenario differs from conventional ideas of earthquake slip, landslides, or caldera collapse-generated tsunami waves because of the enormous (～1000x) volumetric change due to the supercritical nature of volatiles associated with the hot, volatile-rich phreatoplinian plume. The time series of plume altitude can be translated to volumetric discharge and mass flow rate. For an eruption duration of ～12 ?h, the eruptive volume and mass are estimated at 1.9 ?km³ and ～2 900 ?Tg, respectively, corresponding to a VEI of 5–6 for this event. The high frequency and intensity of lightning was enhanced by the production of fine ash due to magma—seawater interaction with concomitant high charge per unit mass and the high pre-eruptive concentration of dissolved volatiles. Analysis of lightning flash frequencies provides a rapid metric for plume activity and eruption magnitude. Many aspects of this eruption await further investigation by multidisciplinary teams. It represents a unique opportunity for fundamental research regarding the complex, non-linear behavior of high energetic volcanic eruptions and attendant phenomena, with critical implications for hazard mitigation, volcano forecasting, and first-response efforts in future disasters.  相似文献   

绕射波逆时偏移成像方法研究     

王晓毅  陈玺  杨振  张江杰 《地球物理学报》2022,65(1):320-332

地震剖面中的绕射点反应地下断层、尖灭、溶洞等不连续体的位置信息,因此绕射波对于实现小尺度构造的精细成像具有重要意义.基于逆时偏移的绕射波成像方案包括乘法成像条件法和倾角域拾取法.乘法成像条件利用正\负倾角构造剖面相乘实现绕射点的定位,倾角域拾取法则根据绕射波能量在角度域的特征进行拾取.其中,通过Hilbert变换和伴随波场的延拓可以实现波场的方向分解,从而实现单一倾向构造的成像并改善倾角道集的质量.本文也对无需方向分解的正\负倾角构造成像公式进行了推导.逆时偏移作为一种全波成像方法,所得剖面本身包含绕射点信息,因此本文通过图像处理方法提取绕射点位置.这一方法具有成本低、扩展性强、可对剖面做局部化处理的特点.  相似文献   

地下浅部异质体对表面波场谱扰动分析     

柴华友  柯文汇  柴扬斐  朱红西  王贤达  刘欢 《岩土力学》2022,43(6):1683-1693

均匀半无限体中表面源激发近表面波场由瑞利波主导,当浅部存在异质体,前行瑞利波发生散射,异质体周围表面波场响应谱发生变化。当异质体长度相对波长较大时,由异质体上方表面质点响应谱提取绕射波频散曲线可分析异质体与周围介质刚度差异对绕射波传播特性的影响。与含软层或硬层半无限体中瑞利波特性比较,可以发现绕射波具有与瑞利波类似的传播特性。异质体上方谱变化特征与异质体和周围介质间刚度差异有关,本研究基于异质体绕射波与入射瑞利波位移结构差异解释谱变化现象。结果表明：异质体上方谱与周围谱明显不同,在偏移距−波长域,相对于前方波场,软质体上方谱密度整体呈减弱趋势,硬质体上方谱密度整体呈增强趋势。根据谱密度变化对应偏移距、波长及谱密度强弱,可以预估异质体在传播方向的位置、埋深,并识别异质体类型。  相似文献   

全球海啸地震震源机制解及海啸成因探讨     

贾仲佳  朱俊江  欧小林  张升升  黄畅  陈瑞雪  张绍玉  李三忠  贾永刚  刘永江 《地学前缘》2022,29(5):203-215

海啸作为五大海洋自然灾害之一,严重威胁着人类生命财产安全。近些年来,国内外学者对地震海啸进行了大量研究,主要针对海啸的生成、传播、爬高和淹没的数值模拟,以及古海啸沉积物进行研究,但是对于海啸地震震源机制的研究还比较欠缺,尤其是缺乏对震级小于6.5的海啸地震的研究。针对我国的地震海啸研究现状,强调震级小于6.5地震引发海啸的问题不容忽视。本文归纳整理了全球766次地震海啸,利用三角图分类基本法则对海啸地震震源机制解进行分类,并对其中341个发生在1976年后的海啸地震进行震源机制解分析,对其中633次海啸浪高进行统计学方法分析研究。本文认为逆冲型、正断型、走滑型和奇异型机制地震均能引发海啸,逆冲型地震引发的海啸占比最大,震级小于6.5级地震引发的海啸的浪高也有高达10 m的情况,也能产生巨大破坏性。逆冲型、正断型、奇异型地震可直接引起海底地形垂向变化,进而引发海啸,而走滑型地震引发海啸则可能有两种原因,一种是走滑型地震并非纯走滑型而是带有正断或逆冲分量从而引发海啸,另外一种是走滑型地震引发海底滑坡导致海底地形变化进而产生海啸。从海啸地震震源深度分析,能产生海啸的地震震源深度97%以上都是浅源地震,主要集中在30 km深度以内,但是也有中深源地震海啸。本文综合海啸地震的震源特点、我国地理位置以及以往海啸发生的情况,认为未来我国沿海地区威胁性的地震海啸主要集中在马尼拉海沟和台湾海峡区域,在今后海啸预警方面需要格外重视这些区域,通过建立完善海啸预警系统来减少损失。  相似文献