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181.
The Gold Coast sandy beaches of Queensland (Australia) are exposed to energetic wave conditions. Storms, particularly tropical
cyclones, have a high potential of destruction. The Gold Coast has not experienced excessive erosive events over the past
30 years. However, some climate indicators suggest that cyclone frequency is likely to increase in response to global climate
change within the near future. Over a 2-month period in early 2006, beach surveys were undertaken with a theodolite total
station at four different sites. Offshore wave conditions were provided by SWAN regional wave modelling. During this study,
the Gold Coast was exposed to three major storms, the first one being the second most energetic over the past 30 years. Results
show a substantial variability of the beach response to these events along the Gold Coast, and that engineering structures
do not have marked effects. Easterly swells have the greatest impact on the Gold Coast sub-aerial beach morphology. When low
wave-energy conditions prevail, the southern Gold Coast beaches recover more quickly than the northern ones, as they are sheltered
from high SE waves and draw advantage from the artificial sand bypassing system. Nevertheless, the data show that the Gold
Coast beaches are exceedingly fragile. For instance, the early March decadal event considerably weakened the beaches, which
resulted in surprisingly high erosion rates all along the Gold Coast during the two following annual wave events. This study
suggests that the Gold Coast beaches would not be able to withstand the impact of an increased frequency of extreme events
similar in scale to those of 1967. 相似文献
182.
通过盆栽试验探讨了红壤施用不同浓度的硼、钼微肥对圆叶决明(Chamaecrista rotundifolia)植株生长和叶肉细胞超显微结构的影响.结果表明,施用1.0、3.0、7.0mg·kg^-1的硼酸或0.5、1.0、4.0mg·kg^-1的钼酸铵都能增加圆叶决明的株高、分枝数、干物质重和硼/钼元素的吸收,稳定细胞壁、细胞膜、叶绿体膜的结构,增加叶绿体的数量;其中以3.0mg·kg^-1的硼酸或4.0mg·kg^-1的钼酸铵为最佳施用量.本研究证实了在施用的硼、钼浓度范围内,施用较高浓度的硼酸(7.0mg·kg^-1)会对植株产生一定的毒害,而施用高量(4.0mg·kg^-1)的钼酸铵并没有表现出明显的毒害症状. 相似文献
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185.
Backcasting long-term climate data: evaluation of hypothesis 总被引:1,自引:0,他引:1
Bahram?SaghafianEmail author Sara?Ghasemi?Aghbalaghi Mohsen?Nasseri 《Theoretical and Applied Climatology》2018,132(3-4):717-726
Most often than not, incomplete datasets or short-term recorded data in vast regions impedes reliable climate and water studies. Various methods, such as simple correlation with stations having long-term time series, are practiced to infill or extend the period of observation at stations with missing or short-term data. In the current paper and for the first time, the hypothesis on the feasibility of extending the downscaling concept to backcast local observation records using large-scale atmospheric predictors is examined. Backcasting is coined here to contrast forecasting/projection; the former is implied to reconstruct in the past, while the latter represents projection in the future. To assess our hypotheses, daily and monthly statistical downscaling models were employed to reconstruct past precipitation data and lengthen the data period. Urmia and Tabriz synoptic stations, located in northwestern Iran, constituted two case study stations. SDSM and data-mining downscaling model (DMDM) daily as well as the group method of data handling (GMDH) and model tree (Mp5) monthly downscaling models were trained with National Center for Environmental Prediction (NCEP) data. After training, reconstructed precipitation data of the past was validated against observed data. Then, the data was fully extended to the 1948 to 2009 period corresponding to available NCEP data period. The results showed that DMDM performed superior in generation of monthly average precipitation compared with the SDSM, Mp5, and GMDH models, although none of the models could preserve the monthly variance. This overall confirms practical value of the proposed approach in extension of the past historic data, particularly for long-term climatological and water budget studies. 相似文献
186.
Pierre-Henri Blard Jérôme Lave Kenneth A. Farley Victor Ramirez Nestor Jimenez Léo C.P. Martin Julien Charreau Bouchaïb Tibari Michel Fornari 《Quaternary Research》2014
This work presents the first reconstruction of late Pleistocene glacier fluctuations on Uturuncu volcano, in the Southern Tropical Andes. Cosmogenic 3He dating of glacial landforms provides constraints on ancient glacier position between 65 and 14 ka. Despite important scatter in the exposure ages on the oldest moraines, probably resulting from pre-exposure, these 3He data constrain the timing of the moraine deposits and subsequent glacier recessions: the Uturuncu glacier may have reached its maximum extent much before the global LGM, maybe as early as 65 ka, with an equilibrium line altitude (ELA) at 5280 m. Then, the glacier remained close to its maximum position, with a main stillstand identified around 40 ka, and another one between 35 and 17 ka, followed by a limited recession at 17 ka. Then, another glacial stillstand is identified upstream during the late glacial period, probably between 16 and 14 ka, with an ELA standing at 5350 m. This stillstand is synchronous with the paleolake Tauca highstand. This result indicates that this regionally wet and cold episode, during the Heinrich 1 event, also impacted the Southern Altiplano. The ELA rose above 5450 m after 14 ka, synchronously with the Bolling–Allerod. 相似文献
187.
Karel Hron Peter Filzmoser Patrice de Caritat Eva Fišerová Alžběta Gardlo 《Mathematical Geosciences》2017,49(6):797-814
The log ratio methodology converts compositional data, such as concentrations of chemical elements in a rock, from their original Aitchison geometry to interpretable real orthonormal coordinates, thereby allowing meaningful statistical processing and visualization. However, it must be taken into account that the original concentrations can be flawed by detection limit or imprecision problems that can severely affect the resulting coordinates. This paper aims to construct such orthonormal log ratio coordinates, called weighted pivot coordinates, that capture the relevant relative information about an original component and treat the redundant information in a controlled manner. Theoretical developments are supported by a thorough simulation study. Weighted pivot coordinates are then applied to the geochemical mapping of catchment outlet sediments from the National Geochemical Survey of Australia illustrating their advantage over possible alternatives. 相似文献