A DYNAMIC MODE FOR RELATIONSHIP BETWEEN FLOOD/DROUGHT IN YANGTZE RIVER VALLEY AND LOW FREQUENCY WAVE ORIGINATED FROM TROPICAL SEA AREA

According to statistic analysis on sea surface temperature(SST)anomaly features in theNorth Pacific in winters and springs prior to the summer flood/drought in the middle and lowerreaches of the Yangtze River(hereafter referred to as MLRY),a strong signal SST key area thataffects local flood/drought is put forward,that is the equatorial eastern Pacific.The response ofgeneral circulation in the Northern Hemisphere to SST anomaly in the key area is furtherinvestigated. The low frequency wave train structure of correlation between the eastern PacificSST and the height at 500 hPa in the Northern Hemisphere is also studied,which reflects thedynamic features of teleresponse of local flood/drought at extratropics to tropical SST anomaly.Through introducing SST anomaly in the strong signal area in numerical experiments,the flood inYangtze River Valley is successfully simulated and the similar wave train pattern in the flow field isobtained too.Altogether,the physical picture and dynamic mode of the flood in the Yangtze RiverValley are described in this work.     

A high-resolution diatom reconstruction between 21,000 and 17,4000 14C yr BP from the southern Bolivian Altiplano (18–23°S)

A diatom study of lacustrine sediments in the southern part of the Bolivian Altiplano (Salar of Coipasa) provides a continuous record of the period 21,000–17,500 ¹⁴C yr BP. Constrained by seven AMS ¹⁴C dates, this record provides evidence that the Coipasa basin was filled by a shallow body of water during this time. Diatom/salinity and diatom/ionic composition transfer functions indicate that the lake was saline, dominated by sodium-chloride throughout all the period.A comparison with regional data shows that Lake Titicaca could not have overflowed towards the southern Bolivian Altiplano at that time. As this dry phase was not registered in Lake Coipasa, this lake was probably supplied by winter precipitation originating from the Pacific. But, recent data from the deep basin of Lake Titicaca show that the lake-level was higher during this time interval, and the question arises whether precipitation from Atlantic and Amazonia sources could have played an important role on the Altiplano during the Last Glacial Maximum (LGM). This hypothesis needs to match other available paleoclimatic data from the lowlands of tropical South America, where there is evidence that during the LGM, conditions were drier than today. Global climate simulations suggest a positive P-E on the Altiplano, due to a strong cooling, reducing evaporative demand more than any increase in precipitations. An increase of winter precipitation from the Pacific is in agreement with data from the Chilean coast showing a northward locations of the Westerlies during the LGM. This paleoclimatic hypothesis is also in agreement with a coupled ocean-atmosphere model, which indicates weaker summer precipitation and stronger winter precipitation in the tropical areas.     

CELLULOSE DECOMPOSTION IN TROPICAL PEAT SWAMPS

Given that organic soil is a complex substrate and there are many environmental factors which directly or indirectly control its decomposition processes, the use of standard substrate simplify the system in that the effect of substrate quality could be eliminated and influence of certain environmental conditions such as edaphic factors, acidity and moisture could be focused on. In addition to the forest floor, decomposition potential down the peat profile can also be examined. Cotton strip assay was used to estimate decomposition potentials in tropical peat swamp occupied by different Shorea Albida peat swamp forest communities, The 'Alan Batu' , the ' Alan Bunga' , the 'Alan Padang' and the ' mixed Alan' forest communities.Greatest decay rates on the peat surface took place during the wet period. The moist condition of the wet months appeared to favour the growth and stimulate activities of decomposer population and soil invertebrates. Generally, 50% of cotton tensile loss is achieved after four weeks     

Climatological characteristics of the tropics in China: climate classification schemes between German scientists and Huang Bingwei

Reviewing some important German scientists who have developed climatic regionalization schemes either on a global or Chinese scale, their various definitions of the tropical climate characteristics in China are discussed and compared with Huang Bingwei's climate classification scheme and the identification of the tropical climate therein. It can be seen that, due to different methodological approaches of the climatic regionalization schemes, the definitions of the tropics vary and hence also their spatial distribution in China. However, it is found that the tropical climate type occupies only a peripheral part of southern China, though it firmly represents a distinctive type of climate that is supsequently associated with a great economic importance for China. As such, the tropical climate type was mostly identified with its agro-climatological significance, that is by giving favourable growing conditions all-year round for perennial crops with a great heat demand. Tropical climate is, hence, conventionally regarded to be governed by all-year round summer conditions "where winter never comes".     

渭干河流域"2002·7"特大洪水分析

渭干河是塔里木河流域第六大源流, 位于天山西部南麓, 渭干河干流起点有新疆最大的流域性控制工程--克孜尔水库. 2002年7月下旬天山中西部山区出现大暴雨(雪)过程, 渭干河流域山区降水持续时间长达30 h以上, 山区降水量50 mm左右, 导致5条支流和渭干河干流出现有水文记录以来的最大洪峰, 流量超过警戒流量和危险流量的2～3.5倍, 暴雨(雪)过程结束之后, 融雪型洪峰长时间居高不下. 洪水过程中, 各支流以及暴雨与融雪等多种洪峰遭遇现象很明显. 克孜尔水库入库洪峰流量达3 660 m3*s-1, 经水库调洪错峰, 出库峰值流量为1 000 m3*s-1, 削峰率72.7%.     

浙江桐庐晚奥陶世晚期沉积层序和沉积环境分析

文昌组上段顶部是一套潮汐层理非常发育的泥质砂岩或砂质泥岩,存在双向交错层理,层面有雨痕,应为潮坪沉积。潮坪沉积由小型层序构成,小型层序又是由砂、泥质单层组成。砂质单层底部通常为岩性突变面或侵蚀面,砂质纹层较厚,其中可见对称波痕或泥砾;向上砂质纹层变薄,过渡到泥质单层。砂质单层形成于暴风浪时期,泥质单层是风浪衰减后恢复正常的潮汐沉积。因此,小型层序从成因上说是一风暴层序。碎屑成份、砾石成份分析表明沉积物均来自华夏古陆的沉积岩和变质岩基底。物源一致,岩层产状变化不大,反映文昌组沉积环境稳定。岩性、粒度分析表明文昌组是一向上变细、由浅海高能环境向近岸低能环境过渡的沉积层序。文昌组下段为浅海砂岩沉积,上段顶部为潮坪沉积。二者之间是一套夹砾岩透镜体的泥质粉细砂岩,其沉积环境应介于浅海和滨岸之间,为水下岸坡沉积。砾岩层只是大的沉积旋回中出现的事件性水下冲积物。     

Water and sediment outbursts from advanced Franz Josef Glacier,New Zealand

The Franz Josef Glacier, Westland, New Zealand, has a history of catastrophic sediment‐laden outburst ?oods associated with extreme rainfall events when the glacier toe is advanced over its own sediments. Consideration of these events and inspection of recent sediment deposits suggest that there are three distinct modes of outburst. The ?rst is associated with fans fed by over?ow along the glacier margin. As the glacier has advanced across its own fore?eld gravels, it is inferred that the primary drainage conduit has developed a reach of negative slope. In high ?ows massive boulders can block the conduit, trapping lesser clasts. The resulting backup of water causes over?ows through marginal moulins, producing the fan type of deposit. The second type of outburst deposits massive imbricated boulders at a greater or lesser distance from the glacier portal. In this case, pressure buildup drives the blockage out of the portal where the boulders deposit. Smaller materials are generally carried away. The third type consists of very shallow ?ows, and produces massive gravel deposits of uncertain provenance. In this condition, the excess pressure in the conduit results in slight uplift of the glacier and widespread discharge of water and sediment below the glacier snout; gravels and smaller sediments are laid down in a massive deposit across the fore?eld. The massive, boulder‐veneered deposit from the December 1995 outburst is interpreted in the light of the above mechanisms as a hyperconcentrated ?ow deposit from hydraulic jacking, overlain by boulders emplaced by a subsequent conduit outburst. A possible association of outbursts with the present advanced position of the glacier is suggested. Copyright © 2003 John Wiley & Sons, Ltd.     

Quantifying Storm Tide Risk in Cairns

The United Nations International Decade for Natural Disaster Reduction (IDNDR)gave rise to an increasing level of attention to the risks posed by a range of naturalhazards and the development of strategies by which to reduce those risks. It waswidely recognised that in order to evaluate risk treatment strategies it was necessaryto `measure' the level of risk that already existed and the level of risk that would beencountered with the treatment strategy(s) in place.This paper outlines the methodology developed under the AGSO (now GeoscienceAustralia) Cities Project to quantify the risk associated with storm tide inundation. It includes the methodology for `measuring' the level of community exposure to storm tide hazards and the methodology for `measuring' community vulnerability. The Far North Queensland city of Cairns is used as the case study to demonstrate the application of these methods.     

Community Vulnerability to Tropical Cyclones: Cairns, 1996–2000

This paper is a partial discussion of a four-year study that investigated the vulnerability of the people living in the Cairns region to the tropical cyclone hazard. The longitudinal case study, focussing on the Cairns Northern Beaches area, was unique in that it included a social and societal `pre-cyclone impact' evaluation of various resident communities within the region, and then two consecutive `post-cyclone impact' studies. The primary research method supported an inductive qualitative approach to the collection and analysis of survey data. Some quantitative methods were invoked to support qualitative research findings. Survey data was collected in five separate questionnaire-based social surveys that were administered between 1996 and 2000. During the study, residents experiencedthe direct impact of two land-falling tropical cyclones. In addition to this, targeted andfocussed tropical cyclone awareness education was made increasingly available withinthe community. The social and demographic attributes that influence the individual'sperception of risk and contribute to our understanding of community vulnerability were examined and evaluated. Changes in the residents' attitudes, cyclone preparednessbehaviours and willingness to respond to cyclone warnings were monitored and measured. Analysis of early survey data indicated that community residents generally had some knowledge of cyclones but a limited understanding of cyclone processes and very little direct personal experience of the cyclone hazard. Individually and collectively, residents frequently demonstrated a biased perception of the risks associated with cyclones. The resident community was shown to be fragmented, with limited support being available to individual households. Initially, residents were found to be poorly prepared for cyclones and unlikely to respond to warnings appropriately. It appeared that, in the event of a land-falling tropical cyclone impacting the area, the community was highly vulnerable to unnecessary loss of property, livelihood and – in extreme circumstances – life. By 2000, Cairns community residents were somewhat better informed about cyclones and certainly more experienced. This paper provides some insight into how cyclone experience and education may synergisticly have contributed to a change in risk perceptions and a reduction in the vulnerability of Cairns residents to the tropical cyclone and storm surge hazards.     

北京一次大风和强降水天气过程形成机理的数值模拟

利用3维强风暴冰雹分档模式(IPA—HBM)对2001年8月23日北京的一次伴有大风、暴雨和冰雹的强对流天气过程进行模拟和分析，并与部分观测资料进行了比较分析。结果表明，该模式对此次强风暴的生命史、降水分布、降雹的大小等要素做了较好的模拟，并能够模拟出伴随强风暴过程所产生的强下沉气流和及地面强风速切变(下去暴流)。从云微物理学角度分析了此次局地性大风的形成原因，认为由高空冰雹粒子的拖曳产生的负浮力作用是促发强下沉气流产生的主要原因，其次是冰雹的融化和雨水蒸发冷却对下沉气流起加速作用，冰雹的拖曳和融化作用对下沉气流具有决定性作用。强风暴所产生的爆发性强下沉气流最终导致了局地大风的形成。