The mineralogy and possible sources of spring dust particles over Beijing   总被引：2，自引：0，他引：2  

邵龙义  李卫军  肖正辉  孙珍全 《大气科学进展》2008,25(3):395-403

A severe Asian Dust Storm （ADS） event occurred on 16-17 April 2006 in northern China. The mineral compositions of dust samples were analyzed using X-ray diffraction （XRD）. The results indicated that dust particles of the ＂17 April 2006＂ dust storm were dominated by quartz （37.4%） and clay （32.9%）, followed by plagioclase （13.7%）, with small amounts of calcite, K-feldspar, dolomite, hornblende and gypsum （all less than 10%）. The clay fractions with diameter less than 2 μm were separated from the dust storm particles by centrifuging and were further analyzed by XRD. The results revealed that the clay species were mainly illite/smectite mixed layers （I/S） （49%） and illite （34%）, with small amount of kaolinite （8%） and chlorite （9%）.
In order to evaluate the feasibility of using the mineralogy to trace the sources of dust particles, the XRD results of the ＂17 April 2006＂ dustfall particles were compared with the dust particles over past years. The results confirmed that the finer dust particles represented by the ADS PM10 displayed a smaller quartz/clay ratio than the dustfall particles. The dust storm particles, either from the ADS PM10 or from the ＂17 April 2006＂ dustfall, showed a lower level of dolomite contents and lower dolomite/clay ratios compared with the non-dust storm dustfall particles. This implies that dolomite could be used to distinguish between the dust contributions from local and non-local sources. Similar trends were found for the gypsum and the gypsum/clay ratio. Moreover, the two dustfall samples had a lower level of illite/smectite mixed layers and a higher level of illite than airborne PM10, implying that the dustfall particles tend to be enriched with illite in its clay fraction.  相似文献   

Cyclone life cycle characteristics over the Northern Hemisphere in coupled GCMs   总被引：4，自引：1，他引：3  

Ulrike Löptien  Olga Zolina  Sergey Gulev  Mojib Latif  Vladimir Soloviov 《Climate Dynamics》2008,31(5):507-532

Cyclone activity and life cycle are analysed in the coupled GCMs ECHAM5/OM and ECHAM4/OPYC3. First, the results for the present climate (1978–1999) are compared with ERA-40 and NCEP/NCAR reanalyses, showing a drastic improvement in the representation of cyclone activity in ECHAM5/OM compared to ECHAM4/OPYC3. The total number of cyclones, cyclone intensity, propagation velocity and deepening rates are found to be much more realistic in ECHAM5/OM relative to ECHAM4/OPYC3. Then, changes in extra tropical cyclone characteristics are compared between present day climate and future climate under the emission-scenario A1B using ECHAM5/OM. This comparison is performed using the 20-year time slices 1978–1999, 2070–2090 and 2170–2190, which were considered to be representative for the various climate conditions. The total number of cyclones does not undergo significant changes in a warmer climate. However, regional changes in cyclone numbers and frequencies are evident. One example is the Mediterranean region where the number of cyclones in summer increases almost by factor 2. Some noticeable changes are also found in cyclone life cycle characteristics (deepening rate and propagation velocity). Cyclones in the future climate scenario tend to move slower and their deepening rate becomes stronger, while cyclone intensity does not undergo significant change in a warmer climate. Generally, our results do not support the hypothesis of enhanced storminess under future climate conditions.  相似文献   

Human fatalities from wind-related tree failures in the United States, 1995–2007     

Thomas W. Schmidlin 《Natural Hazards》2009,50(1):13-25

There were 407 deaths from wind-related tree failures in the United States, 1995–2007. The most common cause of the deadly fallen tree was a thunderstorm (41%), followed by nonconvective high winds (35%), tropical cyclones (14%), tornadoes (7%), and snow and ice (3%). Most (62%) of the deaths were males while the median age was 44 years. The most common location of the fatality was in a vehicle struck by the tree or a vehicle that crashed into a downed tree on the road (44%), followed by persons outdoors (38%), in mobile homes (9%), and in frame houses (9%). Persons killed by wind-related tree failures during tropical cyclones and tornadoes were more commonly at home (40%) when struck than those killed at home by thunderstorm and nonconvective high winds (13%). Seasonality of the deaths varied by weather type with deaths in thunderstorms clustered during May–August, nonconvective high winds October–April, tropical cyclones August–October, tornadoes in April and November, and snow and ice December–April. Regional patterns result from frequency of the wind events, population density, and tree cover. Suggestions are made for hazard reductions.  相似文献   

Research Progress of Coastal Dunes Response to Storm   总被引：1，自引：0，他引：1  

Yang Lin  Dong Yuxiang  Du Jianhui 《地球科学进展》2017,32(7):716-722

The major areas of world coastal dunes have been frequently attacked by storms. The storm, as a high energy influential factor for the formation and evolution of coastal dunes, is also one of the important research contents on the surf zone-beach-dune interaction. The research progress are reviewed from the following aspects: Coastal dune morphological response to storms, coastal dune sediments response to storms, mechanisms of coastal dunes in response to storms, and the research methods and techniques used in the research on coastal dunes to storms. Finally, open questions and future developments were suggested.  相似文献   

Further evidences of deep convective vertical transport of water vapor through the tropopause   总被引：2，自引：0，他引：2  

Pao K. Wang  Martin Setvk  Walter Lyons  Willi Schmid  Hsin-Mu Lin 《Atmospheric Research》2009,94(3):400-408

A few years ago, we identified a deep convective transport mechanism, of water vapor through the tropopause, namely, storm top gravity wave breaking, such that tropospheric water substance can be injected into the lower stratosphere via this pathway. The main evidence presented previously was taken from the lower resolution AVHRR images of the storm anvil top cirrus plumes obtained by polar orbiting satellites. Recent observations have provided further supporting evidence for this important cross-tropopause transport mechanism. There are now many higher resolution satellite images, mainly from MODIS instrument, that show more definitely the existence of these plumes, many of which would probably be unseen by lower resolution images.Furthermore, a thunderstorm movie taken in Denver (USA) area during STEPS2000 field campaign and another thunderstorm movie taken by a building top webcam in Zurich also demonstrate that the jumping cirrus phenomenon, first identified by T. Fujita in 1980s, may be quite common in active thunderstorm cells, quite contrary to previous belief that it is rare. We have used a cloud model to demonstrate that the jumping cirrus is exactly the gravity wave breaking phenomenon that transports water vapor through the tropopause.These additional evidences provide increasing support that deep convection contributes substantially to the troposphere-to-stratosphere transport of water substance. This corroborates well with recent studies of the stratospheric HDO/H₂O ratio which is much highly than it would be if the transport is via slow ascent. The only explanation that can be used to interpret this observation at present is that water substance is transported through the tropopause via rapid vertical motion, i.e., deep convection.  相似文献   

北大西洋海表面温度锋与大西洋风暴路径及大气大尺度异常的关系研究   总被引：1，自引：0，他引：1  

周雅娟  钟霖浩  华丽娟 《气候与环境研究》2016,21(4):449-466

运用NCEP、Had ISST再分析资料,北大西洋涛动(NAO)月指数序列,探讨了海表面温度(SST)锋的时空变化特征,揭示了北大西洋SST锋的主要气候变率及其与北大西洋风暴轴和大气大尺度环流异常的关系。研究表明,剔除季节循环后的SST锋显示其最主要变率为锋区的向南/北摆动,其对应的风暴轴发生相应的西南/东北移动,并同时在北大西洋上空对应一个跨海盆的位势高度负/正异常。这种环流异常可引起高纬度海平面气压(SLP)的反气旋/气旋式环流,这有利于增强海表面风对大洋副极地环流的负/正涡度异常输入,进一步减弱/加强了高纬度上层冷水向SST锋区的输送。北大西洋SST锋的另一主要模态为锋区在南北方向的分支和合并。当SST锋异常在40°N~45°N以单支形式加强时,对流层位势高度场和SLP南北梯度增大,对应NAO正位相,此时风暴轴也为单支型;同时SLP异常场促使冰岛附近具有气旋式风应力异常,亚速尔地区具有反气旋式风应力异常,导致副极地环流和副热带环流均加强,增加高纬度冷水和低纬度暖水在锋区的输入,从而进一步增强40°N~45°N附近的SST锋区。当SST锋异常在40°N~45°N纬带南北发生分支时,风暴轴也同时出现北强南弱的南北分支,此时对应了负位相NAO,来自北南的冷暖水输送减弱,SST锋也发生减弱分支。此外,位于大洋内区的SST锋东端也存在一个偶极子型的模态,尽管其解释方差相对较小,但仍与偏东北的NAO型具有显著相关。谱分析表明,北大西洋SST锋与风暴轴具有1~3年和年代际共振,与中高纬大尺度环流也存在周期1~3年的共变信号,其中准一年共变信号体现了SST锋和NAO之间的对应关系。进一步诊断分析表明,SST锋上空的近表层大气斜压性和经向温度梯度随着SST锋的增强而增强,经向热通量的向北输送导致涡动有效位能的增加;海洋的非绝热加热产生更强的垂直热量通量,这有利于涡动有效位能释放成为涡动动能,从而表现为该区域的风暴轴加强,并进一步影响风暴轴中的天气尺度扰动与下游大尺度环流异常的相互作用过程。  相似文献   

2004年安徽省梅汛期三次暴雨过程的大气低频振荡背景          下载免费PDF全文

陈晓红  张娇 《应用气象学报》2005,16(6):753-762

对2004年夏季安徽省降水以及850 hPa涡度、水汽通量散度场进行Morlet小波分析，结果发现:6月中下旬，三者都存在着2~6 d，7~15 d以及18~30 d的振荡周期，并且三者的各频带的低频分量与实际降水距平的对应关系较好。其中18~30 d低频涡旋系统和水汽通量散度具有源自孟加拉湾和中南半岛自西南向安徽省传播特征；7~15 d低频涡旋系统主要是沿着中纬度地区自西向东传入安徽省，低频水汽通量散度则由低纬度地区自南向北传入安徽省。6月中下旬赤道西太平洋地区沿东南-西北向移动的7~15 d低频气旋和反气旋波列，以及安徽省附近低层流场的2~6 d高频变化，为其6月中下旬的三次强降水过程提供了有利条件。  相似文献   

近年来我国海洋灾害损失及防灾减灾策略   总被引：2，自引：0，他引：2  

王爱军 《江苏地质》2005,29(2):98-101

我国是世界上海洋灾害最为严重的少数国家之一。近年来，由风暴潮、灾害性海浪、赤潮、海冰、海平面上升等海洋灾害带来的经济损失和人员伤亡越来越严重，其中，风暴潮是影响我国沿海地区最为严重的海洋灾害。通过建立海岸生态防护网、提高沿海地区防潮工程标准、开发海洋灾害监测和预报系统、实行海洋数据资料和信息共享等方法，降低海洋灾害发生的机率，减少海洋灾害损失。  相似文献   

Impact of natural (storm) and anthropogenic (trawling) sediment resuspension on particulate organic matter in coastal environments   总被引：1，自引：0，他引：1  

A. Pusceddu  A. Grmare  K. Escoubeyrou  J.M. Amouroux  C. Fiordelmondo  R. Danovaro 《Continental Shelf Research》2005,25(19-20):2506

In order to assess the impact of natural and anthropogenic sediment resuspension on quantity, biochemical composition and bioavailability of particulate organic matter (POM), two field investigations were carried out in two shallow coastal areas of the Mediterranean Sea. In the Gulf of Lions, we investigated the impact of a storm resuspension of sediment, whereas in the Thermaikos Gulf we investigated the impact of bottom trawling.Resuspension in the Gulf of Lions determined the increase of sedimentation rates, modified the composition of the organic fraction of settling particles and decreased the labile fraction of POM, as indicated by a drop in the enzymatically hydrolysable amino acid fraction. The increase in the refractory fraction, following short-term storm-induced resuspension, increased also the contribution of glycine and decreased the contribution of aspartic acid contents to the total amino acid pools.Trawling activities in Thermaikos Gulf determined a significant increase in suspended POM concentrations and important changes in its biochemical composition. After trawling, the protein to carbohydrate ratio decreased (as a result of a major input of sedimentary carbohydrates at the water–sediment interface) and the fraction of enzymatically hydrolysable biopolymeric C decreased by ≈30%, thus reducing the bioavailability of resuspended organic particles. Results of the present study indicate that changes in suspended POM, induced by storms and trawling activities, can have similar consequences on benthic systems and on food webs. In fact, the potential benefit of increased organic particle concentration for suspension feeders, is depressed by the shift of suspended food particles towards a more refractory composition.  相似文献   

Estimating groundwater recharge induced by engineering systems in a semiarid area (southeastern Spain)   总被引：2，自引：0，他引：2  

W. Martín-Rosales  J. Gisbert  A. Pulido-Bosch  A. Vallejos  A. Fernández-Cortés 《Environmental Geology》2007,52(5):985-995

The scarcity of water resources in semiarid regions is usually accompanied by brief periods of quite intense precipitation that can generate potentially catastrophic floods. In such regions, the use of runoff water for aquifer recharge can contribute to both flooding prevention and effective management of water resources. This paper presents the results of a study undertaken in southeastern Spain focusing on the recharge induced by a number of engineering structures (check dams) and gravel pits. The current network of check dams consists of 107 dams, of which 64 are located over permeable substrates and so we can induce recharge of the storm runoff retained therein. The hydrological model was performed using the curve number method (CN) of the Service for the Conservation of Soils, utilizing code HEC-HMS. Results indicate that the proportion of runoff infiltrated through the check dams varies from 3% to more than 50%, according to the effective volume of water dammed and the substrate. In addition, hydrological modelling was carried out in a subbasin taking advantage of the presence of one of a number of gravel pits. The gravel pits are situated in the apical sectors of alluvial fans that overlie hydrogeological units that are widely overexploited, and so they are well positioned for use for artificial recharge. In this case, we conclude that a pit is capable of retaining and infiltrating the combined runoff volumes for various return periods (5, 25, 50, and 100 years). Furthermore, the simulation carried out suggests that the recharge processes in these environments are intimately linked to episodic storm events. The incorporation of hydrogeological criteria in the design and construction of check dams could therefore be very useful for the optimum management of water resources in semiarid zones.  相似文献