我国东部海域不同类型的登陆再发展变性台风的统计分析     

谢骏  朱先德  高大鲁  田天 《海洋与湖沼》2018,49(2):251-262

本文对1982年以来我国东部海域登陆再发展台风进行统计分析,选取其中15个个例进行对比分析,根据其移动路径和增强幅度分为3类,研究表明:台风如果移向东北方向则再发展较弱,而向北移动则发展较深,且向北越深发展越强,这与副热带高压(副高)的位置和强度以及上游高空槽存在一定的关系(整体偏向于正相关),在北上的过程中,如果与高空正位涡发生耦合,则增强越大,但非绝热加热所占的比重越小。同时动能收支分布显示,台风加强越深,动能转换越强,两者成正比,但在能量转化的方向和位置上,三者又存在差异。  相似文献   

Changes of coral communities over 35 years: Integrating in situ and remote-sensing data on Saint-Leu Reef (la Réunion, Indian Ocean)     

J. Scoplitis  S. Andrfouët  S. Phinn  P. Chabanet  O. Naim  C. Tourrand  T. Done 《Estuarine, Coastal and Shelf Science》2009,84(3):342-352

Monitoring coral reef communities at a decadal scale is necessary to understand and project their dynamics to provide a basis for reef management in light of disturbances and climate change. Complementing infrequent and localised in situ observations, time-series of aerial photographs and remotely sensed satellite images provide a means of monitoring the position and extent of reef-top coral communities, vegetation and abiotic substrata at the whole reef scale. The aim of the present study was to map such changes on Saint-Leu Reef (La Réunion) between 1973 and 2007. The period included two cyclones (1989, 2002) and one severe bleaching event (2002). Vertical images of the reef were recorded in five aerial photographs (1973, 1978, 1989, 1997, and 2003) and two Quickbird satellite images (2002, 2006) during that time. Quantitative in situ observations of parts of the reef-top were also available both to document ecological and substratum characteristics that produce the color and texture observable in the photos and satellite images. Coral communities were mapped on all images using manual delineation of polygons identified according to color and texture contrast. The 2006 Quickbird image was used as the mapping base and 15 types of coral communities were identified from a reef survey conducted in 2007. This hierarchical typology used coral growth forms, live and dead coral cover, macro-algae, substratum (sand, rubble and platform) and, to a lesser extent, coral taxonomy. The polygons at date t were over-laid onto image t − 1 across the whole series and their boundaries were manually edited to match the pattern on the earlier image. Labelling of polygons was guided by field-survey data and maps. For coral-dominated patches, six successive pairs of maps from 1973 to 2006 were compared to produce ‘coral community change maps’ for that period. Despite the multiple disturbance events, the coral community distribution and composition in 2006 on Saint-Leu Reef did not display major differences compared to 1973. This suggests a high degree of coral resilience at the site, led by rapid recovery of compact branching corals. The mapping techniques overcame challenges due to different image quality and the sparsity of in situ observations in time and space. Our results demonstrate the potential for further application of reef monitoring protocols based on complementary in situ and remote-sensing data to help understand the dynamics of reef-top coral reef communities and geomorphology over years to decades.  相似文献   

大尺度环流系统对西北太平洋变性TC频数影响的气候诊断分析     

钟颖旻  徐明 《成都信息工程学院学报》2007,22(3):374-378

基于中国热带气旋年鉴资料,从气候学角度出发,对西北太平洋TC(热带气旋)发生温带变性的频数与大尺度环流系统间的关系进行了诊断和分析.研究发现变性TC多发生于夏、秋两季,通过对NCEP月平均再分析资料的500hPa高度场进行EOF分解,发现西北太平洋TC变性的频数与65°N附近强冷高压系统在夏、秋两季都存在着正相关关系,且相关性在秋季高于夏季;与30°N附近强副热带高压系统存在负相关关系,夏季副热带高压系统的作用更大;与30°N以南西北太平洋多台风活动区域的弱低压存在显著的负相关,低压越弱,对流越弱,则TC的生成数越少,其中发生变性的TC数也会减少.500hPa高度场EOF分解的第一特征向量所对应的时间函数分布在20世纪70年代中期前后出现了反号,较好地对应了变性TC年频数的年际变化趋势,70年代中期之前变性TC呈总体偏多,之后变性TC的频数总体偏少,呈明显下降趋势.  相似文献   

变化环境下中国东南沿海致灾气旋及其人口暴露度研究     

陈雪  苏布达  温姗姗  姜彤  王艳君  高梦竹 《海洋通报》2020,39(2):241-248

本文基于气象观测站的逐日气压、风速和降水量确定致灾气旋阈值,结合区域气候模式COSMO-CLM (CCLM)输出,研究中国东南沿海地区2021—2050年RCP2.6、4.5、8.5情景下致灾气旋的时空变化特征。并采用人口-发展-环境分析模型(PDE),预测共享社会经济路径SSP2下东南沿海地区人口发展趋势,揭示了致灾气旋人口暴露度演变。研究表明:(1) RCP2.6情景,东南沿海地区平均每年发生致灾气旋6.3次,风速和降水量较基准期(1986—2005年)分别增加9%和15%,72%区域致灾气旋人口暴露度有所增加。暴露在超基准期最大影响面积和最强风速下的致灾气旋人口分别增加2.1亿和0.1亿。(2) RCP4.5情景,致灾气旋年均发生7次,风速和降水量较基准期分别上升16%和32%,89%地区致灾气旋暴露人口增加。暴露在超基准期最大影响面积和最强风速下的致灾气旋人口分别增加2.6亿和0.5亿。(3) RCP8.5情景,致灾气旋年均发生5.8次,风速和降水量较基准期分别增加32%和50%,65%区域致灾气旋暴露人口度有所增加。暴露在超基准期最大影响面积和最强风速下的致灾气旋人口分别增加5.7亿和1.9亿。(4)相比RCP2.6,RCP8.5情景致灾气旋风速和降水量高出23%和35%,暴露于超基准期最大影响面积和最强风速的致灾气旋人口分别多3.6亿和1.8亿。控制温室气体浓度对降低致灾气旋的不利影响具有重要意义。  相似文献   

On the Interrelation between Spring Bihemispheric Circulations at Middle and High Latitudes     

Chuhan LU  Zhaoyong GUAN 《大气科学进展》2019,36(12):1371-1380

Bihemispheric atmospheric interaction and teleconnection allow us to deepen our understanding of large-scale climate and weather variability. This study uses 1979-2017 spring NCEP reanalysis to show that there is interrelation between bihemispheric circulations at the extratropics. This is regarded as a significant negative correlation between the Antarctic and the Arctic regional surface air pressure anomalies, which is induced by interhemispheric oscillation (IHO) of the atmospheric mass. The spatial pattern of IHO is characterized by antiphase extratropical airmass anomalies and geopotential height anomalies from the troposphere to stratosphere between the Southern and Northern Hemisphere. IHO is closely related to stronger bihemispheric low-frequency signals such as Antarctic Oscillation and Arctic Oscillation,thereby demonstrating that IHO can be interpreted as a tie in linking these two dominant extratropical circulations of both hemispheres. IHO is associated with a strong meridional teleconnection in zonal winds from the middle-high troposphere to the lower stratosphere, with the wind anomalies in the form of alternate positive-negative wavy bands extending from the Antarctic to Arctic region, which act as a possible approach to interactions between the bihemispheric atmospheric mass. It is argued that IHO-related omega angular momentum anomalies led by the extratropical atmosphere cause the meridional teleconnection of relative angular momenta, thereby giving rise to the zonal wind anomalies. The modeling of GFDL and UKMO as components of the CMIP5 project have been verified, achieving the related IHO structure shown in the present paper.  相似文献   

“浣熊”强度变化的环境背景和卫星观测分析   总被引：1，自引：1，他引：0  

李勋  李泽椿  赵声蓉  王勇  赵大军 《气象》2009,35(12):21-29

利用实况观测定位和强度资料、NCEP的1°×1°全球最终分析资料、NOAA周平均1°×1°海温再分析资料和FY卫星水汽图像,分析台风浣熊(0801)的环境背景条件和内核结构演变与强度变化的关系.结果表明:(1)环境风垂直切变增大至10m·s~(-1)左右与南海北部海表温度逐步减小导致最大可能强度不断降低是"浣熊"快速发展过程中断并减弱的重要外部条件;(2)卫星水汽图像显示内核结构存在眼壁破裂和复原现象,该现象精确地反映其强度变化.眼壁破裂(复原)过程导致"浣熊"减弱(增强).  相似文献   

2006年超级台风“桑美”强度与结构变化的数值模拟研究   总被引：2，自引：1，他引：1  

曾智华  陈联寿  王玉清  高志球 《气象学报》2009,67(5):750-763

使用一个高分辨率、非静力数值模式WRF模式对2006年超级台风Saomei强度和结构进行了数值模拟研究.首先,评估了Makin的粗糙度长度公式对台风Saomei强度和结构变化的影响,结果表明,采用新参数后,使得模拟的台风强度变化与实况最佳路径资料的强度变化更一致,对超级台风Saomei强度预报有改进;但对台风路径的影响不大.通过QuikSCAT、雷达和TRMM非常规资料的验证,进一步表明模拟的台风Saomei的结构与实况很接近,可以再现台风内核区域的部分"双眼墙"和"Annular"结构.其次,通过对台风Saomei边界层过程模拟的改进,表明在平均风速大于40 m/s时边界层各物理量明显改善,使得模式最大强度比传统的简单外推插值方案有显著改进,特别是在台风最强阶段,当台风Saomei眼墙区域的海表面拖曳系数C_d的相对变小,使得其眼墙区域的平均切向风速、径向风速、垂直风速、温度距平、涡旋动能和绝对角动量等物理量均有增强.表明台风Saomei眼墙氏域(20-40 km)各物理量的贡献对其强度和结构变化的影响十分重要.最后,在此基础上进一步分析模式海温和大尺度环境垂直风切变对台风Saomei强度和结构变化的可能影响,讨论了台风Saomei在其增强和消弱阶段中,大尺度环境垂直风切变对其强度变化的负反馈作用.  相似文献   

ANALYSIS OF RAINSTORMS ASSOCIATED WITH SIMILAR TRACK TROPICAL CYCLONES HAITANG (0505) AND BILLS (0604)     

YU Zhen-shou  CHEN Xuan-miao  NI Dong-hong  JI Chun-xiao  XIE Hai-hua 《热带气象学报(英文版)》2009,15(1)

It is generally thought that the influence of comparable track typhoons is approximately similar,but in fact their wind and especially their rainstorm distribution are often very different. Therefore,a contrastive analysis of rainstorms by tropical cyclones (TCs) Haitang (0505) and Bilis (0604),which are of a similar track,is designed to help understand the mechanism of the TC rainstorm and to improve forecasting skills. The daily rainthll of TC itaitang (0505) and Bills (0604) is diagnosed and compared.The result indicates that these two TCs have similar precipitation distribution before landtall but different precipitation characteristics after landthll. Using NCEP/GFS analysis data,the synoptic situation is analyzed; water vapor transportation is discussed regarding the calculated water vapor flux and divergence.The results show that the heavy rainfall in the Zhejiang and Fujian Provinces associated with Haitang (0505) and Bitis (0604) before landlhll results ti'om a peripheral easterly wind,a combination of the tropical cyclone and the terrain. After landthll and moving far inland of the storm,the precipitation of Haitang is caused by water vapor convergence carried by its own circulation; it is much weaker than that in the coastal area. One of the important contributing thctors to heavy rainstorms in southeast Zhejiang is a southeast jet stream,which is maintained over the southeast coast. In contrast,the South China Sea monsoon circulation transports large amounts of water vapor into Bills - when a water-vapor transport belt south of the tropical cyclone significantly strengthens - which strengthens the transport. Then,it causes water vapor flux to converge on the south side of Bilis and diverge on the north side. Precipitation is much stronger on the south side than that on the north side. After Bilis travels far inland,the cold air guided by a north trough travels into the TC and remarkably enhances precipitation. In summary,combining vertical wind shear with water vapor transportation is a good way to predict rainstorms associated with landing tropical cyclones.  相似文献   

A CLIMATOLOGY OF EXTRATROPICAL TRANSITION OF TROPICAL CYCLONES IN THE WESTERN NORTH PACIFIC   总被引：1，自引：1，他引：0  

钟霖浩  华丽娟  冯士德 《热带气象学报(英文版)》2009,15(2):130-147

Based on best-track data and JRA-25 reanalysis, a climatology of western North Pacific extratropical transition (ET) of tropical cyclone (TC) is presented in this paper. It was found that 35% (318 out of 912) of all TCs underwent ET during 1979–2008. The warm-season (June through September) ETs account for 64% of all ET events with the most occurrence in September. The area 120°E–150°E and 20°N–40°N is the most favorable region for ET onsets in western North Pacific. The TCs experience ET at latitudes 30°N–40°N and have the greatest intensity in contrast to other latitude bands. The distribution of ET onset locations shows obviously meridional migration in different seasons. A cyclone phase space (CPS) method was used to analyze the TC evolution during ET. Except for some cases of abnormal ET at relatively high latitudes, typical phase evolution paths—along which TC firstly showed thermal asymmetry and an upper-level cold core and then lost its low-level warm core—can be used to describe the main features of ET processes in western North Pacific. Some seasonal variations of ET evolution paths in CPS were also found at low latitudes south of 15°N, which suggests different ET onset mechanisms there. Further composite analysis concluded that warm-season ETs have generally two types of evolutions, but only one type in cold season (October through next May). The first type of warm-season ETs has less baroclinicity due to long distance between the TC and upper-level mid-latitude system. However, significant interactions between a mid-latitude upper -level trough and TC, of either approaching or being absorbed into the trough, and TC’s relations with downstream and upstream upper-level jets, are the fingerprints for both a second type of warm-season ETs and almost all the cold-season ETs. For each type of ETs, detailed structural characteristics as well as precipitation distribution are illustrated by latitude.  相似文献   

Effect of tropospheric temperature change on the zonal mean circulation and SH winter extratropical cyclones   总被引：1，自引：1，他引：0  

Eun-Pa Lim  Ian Simmonds 《Climate Dynamics》2009,33(1):19-32

This study aims to understand the mechanisms which cause an overall reduction of SH extratropical cyclone activity with a slight increase in the high latitudes in a warmer climate simulated in general circulation models (GCMs) with increasing CO₂. For this purpose, we conducted idealized model experiments by forcing warm temperature anomalies to the areas where climate change models exhibit local maximum warming—the tropics in the upper troposphere and the polar regions in the lower troposphere—simultaneously and separately. The Melbourne University atmospheric GCM (R21) coupled with prescribed SST was utilized for the experiments. Our results demonstrate that the reduction of SH extratropical cyclone frequency and depth in the midlatitudes but the slight increase in the high latitudes suggested in climate change models result essentially from the tropical upper tropospheric warming. With this tropical warming, the enhanced static stability which decreases baroclinicity in the low and midlatitudes turns out to be a major contributor to the decrease of cyclone activity equatorward of 45°S whereas the increased meridional temperature gradient in the high latitudes seems an important mechanism for the increase of cyclone activity over 50°–60°S.  相似文献