Field Measurements and Numerical Simulations of the 2004 Tsunami Impact on the East Coast of Sri Lanka     

J. J. Wijetunge 《Pure and Applied Geophysics》2009,166(4):593-622

This paper employs a numerical model of tsunami propagation together with documented observations and field measurements of the evidence left behind by the tsunami in December 2004, to identify and interpret the factors that have contributed to the significant spatial variability of the level of tsunami impact along the coastal belt of the eastern province of Sri Lanka. The model results considered in the present analysis include the distribution of the amplitude of the tsunami and the pattern of wave propagation over the continental shelf off the east coast, while the field data examined comprise the maximum water levels measured at or near the shoreline, the horizontal inundation distances and the number of housing and other buildings damaged. The computed maximum amplitude of the tsunami at water points nearest the shoreline along the east coast shows considerable variation ranging from 2.2 m to 11.4 m with a mean value of 5.7 m; moreover, the computed amplitudes agree well with the available field measurements. We also show that the shelf bathymetry off the east coast, particularly the submarine canyons at several locations, significantly influences the near-shore transformation of tsunami waves, and consequently, the spatial variation of the maximum water levels along the coastline. The measured values of inundation also show significant variation along the east coast and range from 70 m to 4560 m with a median value of 700 m. Our analyses of field data also show the dominant influence of the coastal topography and geomorphology on the extent of tsunami inundation. Furthermore, the measured inundation distances indicate no apparent correlation with the computed tsunami heights at the respective locations. We also show that both the computed tsunami heights and the measured inundation distances for the east coast closely follow the log-normal statistical distribution.  相似文献   

Late Tertiary paleoclimatic interpretation from lacustrine rhythmites in the Gray Fossil Site,northeastern Tennessee,USA     

Aaron J. Shunk  Steven G. Driese  John A. Dunbar 《Journal of Paleolimnology》2009,42(1):11-24

The Gray Fossil Site (GFS) includes a small (<2 ha) paleosinkhole lake fill with an exceptionally well-preserved record of sedimentation and fossils from the latest Miocene to earliest Pliocene. The uppermost lacustrine stratigraphy is characterized by rhythmites that regularly alternate between coarse-grained and organic-rich (A) laminae and fine-grained, silty clay (B) laminae. Both the A and B components are almost exclusively comprised of exogenic sediment (including organic matter). Periodicities of 24 and 4.4 are recorded within a continuous 96 interpreted year sequence of rhythmite sediment. In a small lake with a poorly oxygenated bottom, the presence of laterally continuous laminated sediment that includes well-known periodicities in rhythmite thickness is interpreted as representing annually generated varves that correspond to seasonal variations in sedimentation. The distinctly larger fraction of medium sand-size quartz grains present within the A laminae, as well as the abrupt transitions between A and B components suggest that the rhythmites represent deposition during alternating high-energy and lower-energy seasons, which is consistent with a monsoonal precipitation pattern. The seasonal climate may relate to changes in the ocean circulation pattern prior to 4.6 Ma that resulted in an increased temperature and atmospheric pressure gradient between the east coast of North America and the Atlantic Ocean, but this climate phase seems to be only a temporary condition, as underlying and overlying sediment are both consistent with drier conditions. The periodicity at 24 interpreted years is consistent with the well-known Hale solar cycle. The 4.4 interpreted-year periodicity occurs within the ENSO frequency band, and if this documentation of ENSO-like interannual climate change is correct, then it suggests that ENSO operated at times during the warm Earth conditions characterizing the late Tertiary.  相似文献   

THE RELATIONSHIP OF THE PRECEDING WINTER MJO ACTIVITIES AND THE SUMMER PRECIPITATION IN YANGTZE-HUAIHE RIVER BASIN OF CHINA   总被引：2，自引：0，他引：2  

李汀  琚建华  甘薇薇 《热带气象学报(英文版)》2012,18(1):32-44

The first two series(RMM1 and RMM2) of RMM Index(all-Season Real-time Multivariate MJO Index) are computed to obtain the interannual variation of the preceding winter(preceding December to current February) MJO strength,according to which active(or inactive) years of preceding winter MJO are divided.By utilizing the data provided by NCEP/NCAR,CMAP and China’s 160 stations from 1979 to 2008,we studied the preceding winter MJO strength and discovered that the summer precipitation in the basin are of significantly negative correlation,i.e.when the preceding winter MJO is relatively active,the summer precipitation in the basin decreases,and vise verse.We also analyzed the causes.When the preceding winter MJO is relatively active,its release of potential heat facilities Inter-Tropical Convergence Zone(ITCZ) to strengthen and locate northward in winter and propagate northeastward.This abnormal situation lasts from winter to summer.In mid-May,ITCZ jumps northward to the South China Sea,the western Pacific subtropical high withdraws eastward,and the South China Sea summer monsoon sets off and strengthens.In summer,ITCZ propagates to South China Sea-subtropical western Pacific,the zonal circulation of subtropical Pacific strengthens,and a local meridional circulation of the South China Sea to the basin area forms,giving rise to the East Asia Pacific teleconnection wave-train.An East Asian monsoon trough and the Meiyu front show opposite features from south to north,the East Asian summer monsoon strengthens and advances northward.As a result,the summer monsoon is weakened as the basin is controlled by the subtropical high continually,with less rain in summer.On the contrary,when the preceding winter MJO is inactive,ITCZ weakens and is located southward,the subtropical high is located southward in summer,and the basin is in a region of ascending airflow with prevailing southwest wind.The East Asian monsoon trough and EASM weaken so that summer monsoon is reduced in the basin where precipitation increases.  相似文献   

The Relationship between Precipitation and Airflow over the Tibetan Plateau in Boreal Summer          下载免费PDF全文

LI Fei  FENG Juan 《大气和海洋科学快报》2012,5(3):176-182

Based on the observation data and the reanalysis datasets, the variability and the circulation features influencing precipitation in the Tibetan Plateau (TP) are investigated. Taking into account the effects of topography, surface winds are deconstructed into flow-around and flow-over components relative to the TP. Climatologically, the flow-around component mainly represents cyclonic circulation in the TP during the summer. The transition zone of total precipitation in the summer parallels the convergence belt between the southerlies and the northerlies of the flow-over component. The leading mode of rainfall anomalies in the TP has a meridional dipole structure, and the first principal component (PC1) mainly depicts the variation of rainfall in the southern TP. The wet southern TP experiences strengthened flow-over, which in turn mechanistically favors intensified ascent forced by the flow-over component. In addition, variations in the Indian summer monsoon (ISM) have an important role in influencing the flow over the southern TP, and the ISM ultimately impacts the precipitation over southern TP.  相似文献   

Hydrography and Circulation in the Eastern Tropical Indian Ocean during April-May 2011   总被引：2，自引：0，他引：2       下载免费PDF全文

XUAN Li-Li  QIU Yun  XU Jin-Dian  HE Yun-Kai 《大气和海洋科学快报》2012,5(4):284-289

The distribution of hydrography and circulation in the eastern tropical Indian Ocean(ETIO) during April-May 2011 were analyzed using cruise observations,satellite observations,and historic hydrographic data.It was observed that warm water(28℃) occupies the upper 50-m layer in the ETIO.Low-salinity surface water was observed at the mouth of the Bay of Bengal(BOB),which further extends to the Arabian Sea and off Sumatra via the Sri Lanka coast and the eastern bay mouth.Arabian Sea high-salinity water(ASHSW) is carried eastward along the equator to around 90°E by the equatorial undercurrent(EUC).It also runs south of Sri Lanka(north to 3°N) and in the western bay mouth(west to 87°E) but is much shallower than its counterpart at the equator.It is suggested to be the residual of the ASHSW,which intrudes into the BOB during the preceding southwest monsoon.Our results also show that,in the south of Sri Lanka,just below this subsurface high-salinity water,very-low-salinity water(about 34.8) occurs at depths of 100-200 m.Further analysis suggests that this low-salinity water comes from the BOB.  相似文献   

Projected Changes in Asian Summer Monsoon in RCP Scenarios of CMIP5   总被引：2，自引：0，他引：2       下载免费PDF全文

BAO Qing 《大气和海洋科学快报》2012,5(1):43-48

Responses of the Asian Summer Monsoon(ASM) in future projections have been studied based on two core future projections of phase five of the Coupled Model Intercomparison Project(CMIP5) coordinated experiments with the IAP-coupled model FGOALS_s2(the Flexible Global Ocean-Atmosphere-Land System Model).The projected changes of the ASM in climatological mean and interannual variability were respectively reported.Both the South Asian Summer Monsoon(SASM) and the East Asian Summer Monsoon(EASM) were intensified in their climatology,featuring increased monsoon precipitation and an enhanced monsoon lower-level westerly jet flow.Accordingly,the amplitude of the annual cycle of rainfall over East Asia(EA) is enhanced,thereby indicating a more abrupt monsoon onset.After the EA monsoon onset,the EASM marched farther northward in the future scenarios than in the historical runs.In the interannual variability,the leading pattern of the EASM,defined by the first multi-variable EOF analysis over EA,explains more of the total variances in the warmest future scenario,specifically,Representative Concentration Pathway(RCP8.5).Also,the correlation coefficients analysis suggests that the relationship between the EASM interannual variations and ENSO was significantly strengthened in the future projections,which may indicate improved predictability of the EASM interannual variations.  相似文献   

Study on the association of green house gas (CO2) with monsoon rainfall using AIRS and TRMM satellite observations     

《Physics and Chemistry of the Earth》2015

Monsoon water cycle is the lifeline to over 60 per cent of the world’s population. Throughout history, the monsoon-related calamities of droughts and floods have determined the life pattern of people. The association of Green House Gases (GHGs) particularly Carbon dioxide (CO₂) with monsoon has been greatly debated amongst the scientific community in the past. The effect of CO₂ on the monsoon rainfall over the Indian–Indonesian region (8–30°N, 65°–100°E) is being investigated using satellite data. The correlation coefficient (R_xy) between CO₂ and monsoon is analysed. The R_xy is not significantly positive over a greater part of the study region, except a few regions. The inter-annual anomalies of CO₂ is identified for playing a secondary role to influencing monsoon while other phenomenon like ENSO might be exerting a much greater influence.  相似文献   

西南印度洋真光层海水中固氮细菌多样性     

谢尚微  杨俊毅  张东声  王春生 《海洋学研究》2015,33(3):54-61

本文通过构建克隆文库和基因测序的方法研究了西南印度洋真光层海水中固氮细菌nifH基因的多样性。从构建的2个nifH基因克隆文库中共获得76条有效序列,其中46条来自CTD13-30 m文库,分属10个OTUs;30条来自CTD13-125 m文库,分属8个OTUs。系统发育分析结果显示,研究站位nifH基因序列主要分布于Cluster I和Cluster III两个分支,其中Cluster I中包含蓝细菌和变形菌两个分支,蓝细菌以Group B为优势类群,并未获得束毛藻和Group A的nifH基因序列。此外还有少数nifH基因序列分布于Cluster II。总体来看,西南印度洋固氮生物基因与大西洋的亲缘关系更近;固氮生物的多样性较为丰富,受环境条件的影响,群落结构与其它热带、亚热带寡营养海域具有明显的不同。  相似文献   

一次西南印度洋热带气旋过程发展机制的数值研究     

王彬  郭敬天  曹永正  张薇  刘桂艳 《海洋与湖沼》2017,48(4):695-702

本文利用尽可能多的观测资料和WRF-3.4.1模式(Weather Research and Forecasting Model)对2012年1月19日至28日发生在西南印度洋上空的1次强热带气旋进行了研究,并分析其时空结构和发展机制。对该热带气旋的移动路径、强度及内部结构的数值模拟结果与实际符合较好。分析表明,感热和凝结潜热贯串于热带气旋发展的整个过程,其中感热对气旋发展的影响较弱,凝结潜热是气旋发展的主要能量来源,CISK机制可解释该热带气旋的发展过程。  相似文献   

Contrasting hydrography and phytoplankton distribution in the upper layers of cyclonic eddies in the Mozambique Basin and Mozambique Channel     

T Lamont  RG Barlow 《African Journal of Marine Science》2017,39(3):293-306

Hydrographic data collected in cyclonic eddies in the Mozambique Channel and Basin revealed notable differences in temperature and salinity at a depth of 100 m, the upper mixed layer, the nitracline depths, and vertical distribution of chlorophyll-a (Chl-a). Differences in temperature and salinity did not show any consistent patterns. In contrast, the differences in the upper mixed layer, nitracline depths and the vertical Chl-a profile appeared to be driven by combined effects of eddy dynamics (i.e. shoaling of isopleths) and the seasonal variation in light availability and mixing conditions in the upper layers. Cyclonic eddies studied during austral spring and summer in the Mozambique Channel exhibited shallower upper mixed layers and nitracline depths, and deeper euphotic zones. Distinct subsurface Chl-a maxima (SCM) were associated with the stratified conditions in the upper layers of these eddies. In contrast, a cyclonic eddy studied during mid-austral winter in the Mozambique Basin had a shallower euphotic zone, deeper upper mixed layer and uniform Chl-a profiles. Another eddy sampled in the Mozambique Basin toward the end of winter showed a less pronounced SCM and roughly equal euphotic zone and upper mixed layer depths, suggestive of a transition from a well-mixed upper layer during winter to stratified conditions in summer.  相似文献