2012年南极长城站气象和海冰特征分析   总被引：1，自引：0，他引：1       下载免费PDF全文

杨清华  张本正李明 孟上 《极地研究》2013,25(3):268-277

基于中国第28次南极科学考察长城站越冬期间获取的常规气象和海冰观测资料,结合统计的1985—2010年气候值,对比分析了长城站2012年的气象及海冰特征。气象分析表明,该年平均气压和气温偏低,N—W风向频率显著偏低,E—SE风向频率显著偏高;雾日偏少,降雪量、吹雪及雪暴显著偏多;针对观测期间某些月份比较明显的气象要素和天气现象异常,从大气环流角度进行了分析解释。海冰观测表明,长城湾冰情变化受大气动力作用影响大,冰情稳定性差,外围海域海冰极不稳定,2012年4月至2012年11月冰情几经进退,先后交替出现3个完全冰冻和3个部分冰冻期。  相似文献   

Pre-processing of data-driven river flow forecasting models by singular value decomposition (SVD) technique     

Nastaran Chitsaz  Ali Azarnivand  Shahab Araghinejad 《水文科学杂志》2013,58(12):2164-2178

ABSTRACT

An appropriate streamflow forecasting method is a prerequisite for implementation of efficient water resources management in the water-limited, arid regions that occupy much of Iran. In the current research, monthly streamflow forecasting was combined with three data-driven methods based on large input datasets involving 11 precipitation stations, a natural streamflow, and four climate indices through a long period. The major challenges of rainfall–runoff modelling are generally attributed to complex interacting processes, the large number of variables, and strong nonlinearity. The sensitivity of data-driven methods to the dimension of input/output datasets would be another challenge, so large datasets should be compressed into independently standardized principal components. In this study, three pre-processing techniques were applied: singular value decomposition (SVD) provided more efficient forecasts in comparison to principal component analysis (PCA) and average values of inputs in all networks. Among the data-driven methods, the multi-layer perceptron (MLP) with 1-month lag-time outperformed radial basis and fuzzy-based networks. In general, an increase in monthly lag-time of streamflow forecasting resulted in a decline in forecasting accuracy. The results reveal that SVD was highly effective in pre-processing of data-driven evaluations.  相似文献   

The catastrophe structure of thermohaline convection in a two-dimensional fluid model and a comparison with low-order box models     

Olivier Thual  James C. Mcwilliams 《地球物理与天体物理流体动力学》2013,107(1-4):67-95

Abstract

We impose a surface forcing on the 2D, Boussinesq, thermohaline equations in a rectangular domain, in the form of equatorially symmetric cosine distributions of salinity flux and temperature. This system may be seen as an idealization of the ocean thermohaline circulation on the global scale over intervals of centuries or millenia. Multiple steady states are found numerically. They reflect the competition between the opposite signs of the temperature and salinity-driven equatorially symmetric circulations. There are also pole-to-pole, equatorially asymmetric circulations. In the control space of the temperature and salinity-flux forcing amplitudes, these equilibria form two cusp catastrophes, and transitions between stable equilibria occur through several distinct bifurcations. These catastrophes can be reproduced in simple box models connecting stirred reservoirs through capillary pipes. This steady-state analysis may provide a framework for a better understanding of climatic transitions between different stable regimes of the ocean-atmosphere system.  相似文献   

Historical aspects of soil erosion in the Mejerda catchment,Tunisia     

Sihem Jebari  Ronny Berndtsson  Fethi Lebdi  Akissa Bahri 《水文科学杂志》2013,58(5):901-912

Abstract

Agricultural use and related water erosion may lead to significant changes in the sedimentological and hydrological characteristics of watersheds, and therefore negative consequences for rural development. This research aimed to put present-day soil erosion of the important Mejerda catchment into a historical context. The catchment of Wadi Mejerda in northern Tunisia has experienced soil erosion due to weather and human impacts for thousands of years. We used historical texts and results from archaeological research that go back to 1000 BC, as well as data collected during the last century. Soil erosion from different types of agricultural landscape management was analysed together with information on the soils' production potential, the hydrographic network and flood frequency. The results showed that water erosion has increased the hydrographic network by 65 km and increased the deltaic plain by as much as 15 km²/century. However, soil productivity has decreased significantly. Moreover, due to in channel sedimentation and river choking, the number of flooding occurrences has multiplied over the last century. Finally, it is shown that water erosion follows a specific cycle of degradation throughout the watershed. These findings should be considered for better water and soil management in the context of semi-arid areas.

Editor Z.W. Kundzewicz

Citation Jebari, S., Berndtsson, R., Lebdi, F., and Bahri, A., 2012. Historical aspects of soil erosion in the Mejerda catchment. Hydrological Sciences Journal, 57 (5), 901–912.  相似文献   

Simulation of streamflow with statistically downscaled daily rainfall using a hybrid of wavelet and GAMLSS models     

Md. Mamunur Rashid  Simon Beecham 《水文科学杂志》2013,58(11):1327-1339

ABSTRACT

A rainfall–streamflow model is proposed, in which a downscaled rainfall series and its wavelet-based decomposed sub-series at optimum lags were used as covariates in GAMLSS (Generalized Additive Model in Location, Scale and Shape). GAMLSS is applied in climate change impact assessment using CMIP5 general climate model to simulate daily streamflow in three sub-catchments of the Onkaparinga catchment, South Australia. The Spearman correlation and Nash-Sutcliffe efficiency between the observed and median simulated streamflow values were high and comparable for both the calibration and validation periods for each sub-catchment. We show that the GAMLSS has the capability to capture non-stationarity in the rainfall–streamflow process. It was also observed that the use of wavelet-based decomposed rainfall sub-series with optimum lags as covariates in the GAMLSS model captures the underlying physics of the rainfall–streamflow process. The development and application of an empirical rainfall–streamflow model that can be used to assess the impact of catchment-scale climate change on streamflow is demonstrated.  相似文献   

Climatic variations of general atmospheric circulation, precipitation and river flow of the territory of Kazakhstan     

Vitaly Salnikov  Galina Turulin  Svetlana Polyakov  Marat Moldahmetov  Lyazzat Mahmudova 《寒旱区科学》2013,5(1):0109-0113

Methods of calculating the basic hydrological characteristics of a water resource assessment, as well as the planning and management of their long-term use are based upon the concept of stationarity of long-term flow fluctuations. However, data of researches by hydrologists and climatologists clearly indicate that there are long-period changes in the characteristics of precipitation and river flow. This article discusses the variations of annual precipitation and river flow in the Ishim River Basin in Kazakhstan, based on the W, C and E classification developed by G.Y. Vangengeim who analyzed the long-term variability of anomalies by the number of days with some form of atmospheric circulation. From this study, the largest anomaly of the macro-circulation processes was revealed, and a comparative analysis of the number of days with various forms of atmospheric circulation and precipitation anomalies was made. It was demonstrated that the nature of atmospheric circulation depends on the distribution of precipitation; however, precipitation is also highly dependent on local physiographic conditions. The analysis of anomalous precipitation during the maximum number of days of positive anomalies with various forms of atmospheric circulation was also carried out. This study presents some results from the preliminary analysis of annual river flow linked with forms of atmospheric circulation.  相似文献   

Tameike灌溉池塘农业文化遗产:以大分县国东半岛为例（英文）     

Kazem VAFADARI 《资源与生态学报(英文版)》2013,4(3):220-230

本文以于2013年5月被认定为全球重要农业文化遗产(GIAHS)试点的国东半岛为例,探讨了日本tameike灌溉池塘成为农业文化遗产的潜力。"tameike"是这个地区主要用来储存泉水或者短小急流的一种小型池塘。国东的tameike建造与当地的水稻种植和林业发展关系密切。许多现存的灌溉池塘均建于江户时期(1603–1867),直到战后这些池塘都是通过传统农业技术进行管理。然而,随着经济发展,这些灌溉池塘的用途和生态系统功能迅速减少。目前,灌溉池塘的总数只有明治维新前的近三分之一。GIAHS项目试图重新评估这些灌溉池塘的生态系统功能和相关知识体系以振兴当地农业。本文基于文献调查和实地研究,提出合理管理灌溉池塘可以成功使这种资源循环利用的文化恢复生机,而这正是国东地区作为农业文化遗产的意义。  相似文献   

岷县漳县6.6级地震前区域地壳运动变形背景与断层形变异常特征          下载免费PDF全文

王双绪  蒋锋云  李宁  刘立炜  张四新 《地震工程学报》2013,35(3):503-512

利用甘肃岷县漳县6.6级地震区所在的青藏块体东北缘地区的区域水准、GPS、流动重力和跨断层短测线等地形变监测资料,结合地质构造、动力环境和已往的研究结果,分析了不同类型资料反映的震前区域性地壳变形背景、断层形变异常特征和可能的机理.结果认为：（1）岷县漳县6.6级地震前西秦岭、六盘山等构造区不同程度地存在着GPS水平挤压闭锁高应变积累、垂直隆升异常高梯度带和重力升、降差异剧烈变化等中长期背景;（2）震前到震时发震断裂附近及其外围相关构造区域断层形变异常在空间和时间上的起伏波动变化显著,尤其是汶川地震以来的波动变化在一定程度上反映了与本区构造比邻的龙门山断裂带剧烈右旋错动对本区的影响,与本次岷县6.6级地震过程有关;（3）本区有地形变监测资料积累以来缺乏6级以上震例,虽然存在不同程度的中长期形变背景异常,但何时进入短期-短临阶段确实很难把握,需要不断积累总结和探索提高.  相似文献   

AVO analysis with partial stacking to detect gas anomalies in the GÜEPAJÉ-3D project     

Juan C. Mosquera  Alfredo Ghisays  Luis Montes 《Geofísica Internacional》2013,52(3):249-260

We applied analysis AVO with partial stacking to an onshore gas field in order to detect gas at the top of the Ciénaga de Oro formation (FCO), by using seismic gathers of the Güepajé-3D project. The technique was supported by petrophysical analysis of the Ayombe-1 well.The sensitivity of seismic response to changes in the saturating fluid was evaluated by fluid substitution technique in an interval of the Ayombe-1 well. As a result, a class I AVO anomaly at the top of the FCO was observed, even though the gas and water responses were similar. After applying AVO with partial stack technique at the top of FCO, AVO class I anomalies were observed in the Ayombe-1 and Güepajé-1 gas wells and none in the dry Güepajé-3 well. In spite of being reported with gas, the results in the Güepajé-2 well indicated any to an incipient class I anomaly related to a weak seismic response associated to gas.When the technique was applied to the seismic volume of the Güepajé-3D Project, a map of the direct gas indicator was obtained. The map shows a high correlation with the structural surface at top of FCO. Lithic factors such as compaction, cementation and carbonate overlaying the FCO and variable thickness of partial and full saturated layers, may cause anomalies in zones unlikely to contain gas.  相似文献   

沉降监测数据的非等间距GM(1,1)模型插补应用     

宁卫远 《测绘与空间地理信息》2013,36(6):167-170

科学、准确、及时地分析和预报建筑物的沉降状况,对其施工和运营极为重要,沉降监测的研究成果也是检验设计和施工的重要手段。由于自然环境的多变性、施工现场的复杂性等各种主、客观因素影响,监测数据有时会出现间断,为了分析沉降规律,需要对缺失数据进行插补。考虑到沉降监测非等时间间隔的特点,建立非等间距GM(1,1)模型及优化背景值的GM(1,1)模型,应用于沉降监测缺失资料的插补工作中,取得了较满意的监测间断数据插补值。  相似文献