La prévision du climat : de l'échelle saisonnière à l'échelle décennale     

Jean-Claude Andr  Jean-Yves Caneill  Michel Dqu  Philippe Rogel  Laurent Terray  Yves Tourre 《Comptes Rendus Geoscience》2002,334(16):1115

The atmosphere and the ocean are subject to many dynamical instabilities, which limit the time during which their behaviour can be deterministically forecasted. At longer timescales, the atmosphere can be predicted at best using statistical methods, as a response to external forcing linked to sea- and land-surface anomalies. Climate being defined as the mean of atmospheric states, it appears that it can be predicted up to a few months in advance, which is the characteristic time of the so-called slow components of the climate system. Forecasting can sometimes be extended to longer time ranges, especially when the coupled ocean–atmosphere system exhibits internal variability modes, with characteristic times of a few years. Seasonal climate forecasting is most often based upon Monte-Carlo simulations, where the various realisations correspond to slightly different initial conditions. The present sate-of-the-art in Europe (ECMWF) and/or in the USA (IRI) allows to forecast such major phenomena, as El Niño, up to six months in advance. Finally, some parameters may exhibit predictability at still longer time-ranges (inter-annual to decadal), but only for certain regions. The example of electricity production is used to underline the potentially large economical benefit of seasonal climate forecasting. To cite this article: J.-C. André et al., C. R. Geoscience 334 (2002) 1115–1127.

Résumé

L'atmosphère et l'océan sont le siège d'instabilités dynamiques, qui limitent la durée pendant laquelle il est possible d'en prévoir l'évolution de façon déterministe. Au-delà, l'atmosphère n'est plus prévisible, au mieux, que de façon statistique, en fonction du forçage externe qu'exerce(nt) sur elle l'océan et/ou la surface des continents. Le climat (au sens d'une moyenne des états atmosphériques) se révèle ainsi prévisible jusqu'à des échéances temporelles de quelques mois, échelle de temps caractéristique des composantes dites « lentes » du système climatique. La prévision peut s'étendre à des échéances parfois plus longues, dans le cas où le système couplé océan–atmosphère posséderait des modes de variabilité temporelle de périodes caractéristiques de quelques années. La prévision climatique saisonnière est très souvent construite à partir de simulations de type Monte-Carlo, avec des ensembles de réalisations utilisant des conditions initiales légèrement différentes. Dans l'état actuel de ces prévisions, qu'elles soient réalisées en Europe (CEPMMT) ou aux États-Unis (IRI), il est possible de prévoir environ six mois à l'avance un certain nombre de phénomènes climatiques, en particulier ceux liés aux épisodes dits « El Niño », pour lesquels l'amplitude des variations est suffisamment importante. Il existe, par ailleurs, une prévisibilité à encore plus longue échéance (inter-annuelle à décennale), mais seulement pour certains paramètres et certaines régions. L'exemple de la production d'électricité montre l'importance économique potentielle très grande de la prévision climatique saisonnière. Pour citer cet article : J.-C. André et al., C. R. Geoscience 334 (2002) 1115–1127.  相似文献   

Multi-scale wavelet separation of aeromagnetic anomaly and study of faults in Beijing area     

张先 赵丽刘天佑  杨宇山 《地震学报(英文版)》2006,19(5):542-551

Introduction As the capital of China, Beijing is a major political, economic and cultural center. In 2008, it will host the Olympic Games. Therefore, Beijing is of great importance in our national undertak-ing in guarding against earthquakes and reducing their damages. The Chinese Capital Circle re-gion has always been attached great importance in monitoring earthquakes by the China Earth-quake Administration, and as the kernel of the Capital Circle region, Beijing is the key area for ea…  相似文献   

综合物探技术在石家庄凹陷地热勘查中的应用   总被引：1，自引：0，他引：1  

许德树  冯创业 《物探与化探》2007,31(5):440-443

在岩石密度、磁性、电性综合分析的基础上,提出用重力资料反演广义新生界基底,利用航磁资料研究太古宇、下元古界结晶基底的研究思路.根据大地电磁测深资料,对新生界、中生界和古生界垂向分布进行了深入研究,结合重力剖面反演进一步予以证实.工作结果在石家庄凹陷内发现槐底低凸起存在,是寻找寒武系、奥陶系灰岩类型的地热远景有利地区;发现石家庄市区内存在南北、东西2个新生界深洼槽,分别为石家庄火车站至永壁深洼槽和永壁至二十里铺深洼槽.  相似文献   

西安地区部分古遗址考古地磁研究          下载免费PDF全文

孟昭秦 《地质科学》1998,33(4):489-493

通过对陕西耀州窑遗址内4个古窑,临潼兵马俑一号坑,西铜一级公路经过黄堡工地开挖的两个五代窑,以及耀州窑博物馆仓库工地内开挖的一个金代窑和一个春秋窑遗址的古地磁研究,初步得出了西安地区古地磁场变化的规律,为鉴定从春秋到金代西安地区的古遗址、古文物提供了考古地磁学上的一个粗略的标准。  相似文献   

航磁ΔT解析信号确定线性构造隐伏形态的算法及阿尔金的应用   总被引：2，自引：0，他引：2  

张明华  蔺启忠 《物探化探计算技术》1998,20(3):199-204

本文研究了模拟线性地质构造具有普遍意义的有限延深薄板状体ΔＴ的解析信号强度与其几何参数之间的超定方程关系,运用奇异值分解和广义逆技术求解超定方程,获得了高精度的理论反演方法,同时给出了定性解释板状体产状的辅助方法。对阿尔金地区隐伏断裂形态的反演结果,为西藏地体的“北推东移”提供了定量化的地球物理解释证据。文章还勾画了阿尔金与塔里木的深部界线。  相似文献   

The role of anthropogenic activities in karst spring discharge volatility          下载免费PDF全文

Jing Wu  Jian Yin  Yonghong Hao  Yan Liu  Yonghui Fan  Xueli Huo  Youcun Liu  Tian‐Chyi J. Yeh 《水文研究》2015,29(13):2855-2866

The traditional hydrological time series methods tend to focus on the mean of whichever variable is analysed but neglect its time‐varying variance (i.e. assuming the variance remains constant). The variances of hydrological time series vary with time under anthropogenic influence. There is evidence that extensive well drilling and groundwater pumping can intercept groundwater run‐off and consequently induce spring discharge volatility or variance varying with time (i.e. heteroskedasticity). To investigate the time‐varying variance or heteroskedasticity of spring discharge, this paper presents a seasonal autoregressive integrated moving average with general autoregressive conditional heteroskedasticity (SARIMA‐GARCH) model, whose the SARIMA model is used to estimate the mean of hydrological time series, and the GARCH model estimates its time‐varying variance. The SARIMA‐GARCH model was then applied to the Xin'an Springs Basin, China, where extensive groundwater development has occurred since 1978 (e.g. the average annual groundwater pumping rates were less than 0.20 m³/s in the 1970s, reached 1.20 m³/s at the end of the 1980s, surpassed 2.0 m³/s in the 1990s and exceeded 3.0 m³/s by 2007). To identify whether human activities or natural stressors caused the heteroskedasticity of Xin'an Springs discharge, we segmented the spring discharge sequence into two periods: a predevelopment stage (i.e. 1956–1977) and a developed stage (i.e. 1978–2012), and set up the SARIMA‐GARCH model for the two stages, respectively. By comparing the models, we detected the role of human activities in spring discharge volatility. The results showed that human activities caused the heteroskedasticity of the Xin'an Spring discharge. The predicted Xin'an Springs discharge by the SARIMA‐GARCH model showed that the mean monthly spring discharge is predicted to continue to decline to 0.93 m³/s in 2013, 0.67 m³/s in 2014 and 0.73 m³/s in 2015. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

现代藻类磷酸盐埋藏学实验——对磷酸盐化球状化石研究的启示     

张神功  钟振华  陈雷  刘慧渊  杨锋杰 《地质学报》2023,97(12):4035-4043

产于贵州瓮安埃迪卡拉系陡山沱组磷块岩中的“瓮安生物群”是认识早期生命起源与演化的重要窗口。因为其特殊的磷酸盐化作用,其中的球状化石内部保存了大量精细的细胞甚至亚细胞结构,但保存这些化石的磷酸盐化作用机理尚不清楚。因此,本文采用绿藻门下团藻和空球藻为实验对象,通过改变pH、温度、氧气含量等实验条件,探索藻类在不同埋藏环境下的保存状况,为早期磷酸盐化化石的埋藏机制提供证据。实验结果显示藻类在不同实验条件下的保存潜力差距较大,相同环境下两种藻类所体现的保存潜力也不一致,但都具备足够的保存潜力;空球藻细胞在埋藏过程中出现褶皱变形,但在不同条件下的形态学差异并不明显;团藻的繁殖体形态与瓮安生物群中的一类多细胞球状化石的细胞分裂形式十分相似;早期状态一致的同种藻类不管在相同还是不同的实验条件下其个体直径大小均表现出较强的差异性。本次实验模拟自然状态下的埋藏环境,因此实验现象可能在现实埋藏过程中重现,通过实验得出以下结论：磷酸盐化的埋藏环境中藻类具备足够的保存潜力;磷酸盐化会导致生物获得自身以外的形态学信息;在不同的埋藏学环境下保存的磷酸盐化球状化石的直径大小会有差异;胚胎状化石与磷酸盐化的现生藻类...  相似文献   

Land use change and its ecological effect in Qian'an County of Jilin Province     

ZHONG Linsheng  ZHANG Yongmin  ZHAO Shidong  Karl E. Ryavec 《地理学报》2003,13(4):423-428

Based on GIS and statistical methods, with the help of searching historical literatures and calculating the landscape indices, the land use changes of Qian'an County in both spatial and temporal aspects from 1945 to 1996 has been analyzed in this paper. And the driving forces of land use changes and their ecological effects are discussed too. The main findings of this study are as follows: (1) Land use changed greatly in Qian'an during 1945-1996, characterized by a decrease in grassland, wetland and water bodies, and an increase in cultivated land, saline-alkali land, and the land for housing and other construction purposes. Grassland decreased by 175,828.66 ha, and cultivated land increased by 102,137.23 ha over the half century. Accordingly, the main landscape type changed from a steppe landscape to a managed agricultural ecosystem. (2) Results of correlation analysis show that the land use change in the study area was mainly driven by the socioeconomic factors.　(3) The ecological effects of land use change in the area are characterized by serious salinization, degression of soil fertility and the weakening of landscape suitability.  相似文献   

珠江口盆地航磁局部构造异常     

张永军  刘振军  周坚鑫 《物探与化探》2010,34(1):8-13

珠江口盆地存在丰富的油气资源,勘探前景受到越来越多的关注。局部磁异常往往与含油气局部构造密切相关。通过对珠江口盆地大比例尺高精度航磁资料处理和分析,识别出5种航磁局部构造异常:基岩凸起局部构造异常、与基性侵入岩有关的局部构造异常、与中酸性侵入岩有关的局部构造异常、与火山岩有关的局部构造异常、与沉积层有关的局部构造异常。对各种局部构造异常进行了较细致的描述,并结合地震、重力、钻孔等资料对典型异常进行了地质解释,为油气勘探提供了依据。  相似文献   

福建永安丰门坑多金属矿地质特征及找矿前景     

张进高 《福建地质》2010,29(2):83-88

永安丰门坑多金属矿呈似层状、层状、透镜状,贮存在寒武系林田组下段钙质碎屑岩中,矿床具明显的层控和热液叠加改造特征,为沉积-热液改造型多金属矿床。该多金属矿床的发现,为我省在寒武系林田组中寻找该类矿床提供新的目标。  相似文献