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991.
992.
广州城市暴雨内涝时空演变及建设用地扩张的影响 总被引：2，自引：0，他引：2
暴雨内涝是城市常见的“城市病”。本研究通过收集20世纪80年代、90年代,以及2000年之后广州市主城区严重暴雨内涝资料,探索改革开放后广州市暴雨内涝时空演变特征,分析城市建设用地扩张对暴雨内涝的影响。结果表明,20世纪80年代至今,广州市主城区暴雨内涝点在时间和空间2个尺度上有显著的变化。早期内涝点主要集中于市中心的越秀区,随着城市化进程的推进逐渐在白云、天河等城市化较快的区域出现。从1990-2010年,广州市城乡建设用地扩张显著,城市不透水面密度与暴雨内涝点核密度呈正相关。其相关性随城市化发展逐渐增强,表明改革开放后广州市城市的快速扩张,对主城区暴雨内涝点的时空演变有较大的影响。因此,城市暴雨内涝的防治应重视城市不透水面格局的优化和调整。 相似文献
993.
华北地区寒武系中发育有大量的风暴沉积,对于此类沉积物的成因前人意见趋于统一,但对其沉积环境的认识仍存在较多争议。在野外细致观察、实测的基础上,结合室内沉积学描述和分析,在北京西山下苇甸剖面寒武系第三统和芙蓉统内识别出5种沉积相类型,并根据沉积环境将其归入3种相组合,分别形成于浅海碳酸盐缓坡潮下带、深潮下带和页岩盆地环境。在研究地层内,共识别出了49层风暴沉积,基于沉积结构和构造特征,这些风暴沉积层可归入4个风暴沉积大类(原地未破碎风暴沉积、原地破碎风暴沉积、近源风暴沉积、远源风暴沉积)和12个亚类,这些风暴沉积类型形成于不同的环境。根据风暴沉积亚类在地层中的分布规律及其所指示的环境类型,恢复了北京西山寒武纪中晚期相对海平面的变化历史。通过与用不同方法恢复的北京西山和鲁西地区同时期海平面变化曲线进行对比,发现利用风暴沉积类型所恢复的海平面变化曲线与使用正常沉积类型恢复的海平面变化曲线具有相同的变化趋势。因此,风暴沉积类型可以用于恢复长时间尺度的海平面变化趋势。 相似文献
994.
通过若干实例,本文讨论了地磁数据分析中的一些方法.这些方法包括时间序列的多项式拟合,相关性分析,频谱分析和小波分析等.在Matlab和AutoSignal软件下实现了以上方法,并基于这些方法研究了地磁场形态和地磁现象的频谱特征.我们分析了Surlari观测台（余纬45.3°,经度26.3°）的地磁时间序列,并与Ottawa（余纬44.6°,〖JP2〗经度284.5°）,Canberra（余纬125.3°,经度149.3°）, Kakioka（余纬53.8°,经度140.2°）,Vernadsky〖JP〗（余纬155.3°,经度295.7°）等台站的结果进行了对比分析,讨论了Fourier变换时间窗和小波基函数选取的影响,有限长时间序列引起的边缘效应,以及小波尺度和Fourier频率的关系等问题.我们采用谱分析和小波分析处理了2007年两个台站的地磁数据,研究了地磁场形态和地磁现象的频谱特征,并讨论了Fourier变换和小波变换的优缺点. 相似文献
995.
This paper reviews the progress in our understanding of the atmospheric response to midlatitude oceanic fronts and eddies,emphasizing the Kuroshio-Oyashio Extension(KOE)region.Oceanic perturbations of interest consist of sharp oceanic fronts,temperature anomalies associated with mesoscale eddies,and to some extent even higher-frequency submesoscale variability.The focus is on the free atmosphere above the boundary layer.As the midlatitude atmosphere is dominated by vigorous transient eddy activity in the storm track,the response of both the time-mean flow and the storm track is assessed.The storm track response arguably overwhelms the mean-flow response and makes the latter hard to detect from observations.Oceanic frontal impacts on the mesoscale structures of individual synoptic storms are discussed,followed by the role of oceanic fronts in maintaining the storm track as a whole.KOE fronts exhibit significant decadal variability and can therefore presumably modulate the storm track.Relevant studies are summarized and intercompared.Current understanding has advanced greatly but is still subject to large uncertainties arising from inadequate data resolution and other factors.Recent modeling studies highlighted the importance of mesoscale eddies and probably even submesoscale processes in maintaining the storm track but confirmation and validation are still needed.Moreover,the atmospheric response can potentially provide a feedback mechanism for the North Pacific climate.By reviewing the above aspects,we envision that future research shall focus more upon the interaction between smaller-scale oceanic processes(fronts,eddies,submesoscale features)and atmospheric processes(fronts,extratropical cyclones etc.),in an integrated way,within the context of different climate background states. 相似文献
996.
Lanqiang BAI Zhiyong MENG Ruilin ZHOU Guixing CHEN Naigeng WU Wai-Kin WONG 《大气科学进展》2022,39(5):802-818
This study presents the radar-based characteristics and formation environment of supercells spawned by the tornadic landfalling Typhoon Mujigae(2015)in October 2015.More than 100 supercells were identified within a 24-hour period around the time of the typhoon’s landfall,of which three were tornadic with a rotational intensity clearly stronger than those of non-tornadic supercells.The identified supercells were concentrated within a relatively small area in the northeast quadrant beyond 140 km from the typhoon center.These supercells were found more likely to form over flat topography and were difficult to maintain in mountainous regions.During the study period,more supercells formed offshore than onshore.The mesocyclones of the identified supercells were characterized by a small diameter generally less than 5 km and a shallow depth generally less than 4 km above ground level.An environmental analysis revealed that the northeast quadrant had the most favorable conditions for the genesis of supercell in this typhoon case.The nondimensional supercell composite parameter(SCP)and entraining-SCP(E-SCP)were effective in separating supercell from non-supercell environment.Even though the atmosphere in the typhoon’s northeast quadrant was characterized by an E-SCP/SCP value supportive of supercell organization,orography was an impeditive factor for the supercell development.These findings support the use of traditional parameters obtained from midlatitude supercells to assess the supercell potential in a tropical cyclone envelope. 相似文献
997.
Huayanpeng boulder beach is located at the Cape of Putuo Island, southeast coast of China. From 6000 years ago, sea level
changed little and turned steady, which was prone to forming the boulder beach. Since then, numerous storm surges propagated
from the West Pacific Ocean have imposed on the bedrock of the eastern coast of Putuo Island, resulting in a large amount
of rocks fallen from the hill-slope onto the beach. The similarity of rock lithology between the bedrock and the boulders
of the study area supports the hypothesis of Holocene steady sea-level controls on the formation of the beach. Long-term littoral
currents, including storm weather and normal weather conditions, have greatly sorted the boulder beach vertically and transversely.
From east to west, the beach turns wider and gradient becomes gentler, and the boulders reduce its size, from, on average,
1.0 m to 0.5 m, with a decrease in flattening and an increase in sphericity and psephicity. The sizes of the boulders and
flattening turn bigger from supra-littoral to inter-littoral zone, while sphericity and psephicity turn smaller and lower.
These basal characteristics of boulders highlight the linkage of beach formation to the high-storm energy propagated from
the open seas during the typhoon season. 相似文献
998.
Since G.Kelling put forward tempestite in 1973,the study has been developed quickly;especially the storm flow theory is known to be a milestone of sedimentology and the geology development as turbidite theory established in 1950s.This paper makes reviews on the development of tempestite theory:the origin and definitions,methods of the study,and its formation environment,scales,sedimentary characters,structures,sequences,model,and hummocky bedding were commented.It also explores the significance of the research on Tempestite of the Xingwen World Geopark. 相似文献
999.
湘西北江坪地区志留系小河坝组发育了大量与风暴作用有关的沉积构造,如渠模、风暴丘状体、波状侵蚀面、介壳层、递变层理和振荡波痕等。在垂向厚度不足5,m的地层中连续发育了3期垂向结构特征不尽相同的风暴岩序列:Ⅰ.具波状侵蚀面的风暴丘状体序列;Ⅱ.具渠模构造的递变层理段+块状层理段:Ⅲ.具波状侵蚀面的递变层理段+水平层理段。上述风暴沉积都具有原地或近原地特点。该套风暴沉积的发现进一步证实了早志留世小河坝期湘西北地区的古地理环境为古海水深度相对较小、接近于正常浪基面的临滨环境。 相似文献
1000.