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利用NCEP/NCAR提供的再分析资料和NOAA提供的海温资料分析太平洋年代际振荡(Pacific Decadal Oscillation,PDO)不同位相的年代际背景下北半球海气耦合关系的异常与风暴轴协同变化的联系,主要结果如下:1)冬季太平洋年代际振荡与北半球两大洋风暴轴协同变化之间存在显著的相关关系,当PDO暖位相时,对应两大洋风暴轴南北位置反向的异常变化,其中北太平洋风暴轴偏南且中东部减弱,北大西洋风暴轴偏北且中东部增强,PDO冷位相时相反。2)PDO为暖位相时,对应El Niňo型海温异常,北大西洋海温呈三极型,平均槽脊加强,经向环流增强,极涡收缩,北太平洋风暴轴南压,大西洋风暴轴则北抬,此时欧亚大陆北部和北美大陆大部分地区温度异常升高,亚洲南部、非洲北部及巴伦支海以北的高纬温度异常降低,北美西南部和格陵兰岛附近温度也为异常降低,PDO冷位相时相反。 相似文献
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Yu Liu Qiu‐Li Li Guo‐Qiang Tang Xian‐Hua Li 《Geostandards and Geoanalytical Research》2020,44(3):421-437
A combined geochronological and geochemical investigation for the same domain of zircon provides valuable information on timing and genesis, particularly in the case of multi‐growth metamorphic zircon. A high spatial resolution concurrent analytical method for zircon U‐Pb age and rare earth element content was successfully achieved in this study, using a multi‐collector secondary ion mass spectrometer (SIMS) at a ~ 8 μm diameter scale. Special instrument parameters were employed, including a high mass resolution of approximately 15000 applied to replace the previous energy filter method, and a dynamic multi‐collector mode used to reduce the measurement time to 18 min per analysis. Six zircon reference materials yielded precise and accurate 206Pb/238U ages, which are comparable to those obtained by the ordinary mono‐collector method, but with 2–3 times higher spatial resolution. All zircon grains measured in this study showed enriched heavy‐REE (HREE) contents consistent with previously reported values determined by LA and solution ICP‐MS methods. The light‐REE (LREE) mass fractions measured using both SIMS and LA‐ICP‐MS methods in this study, although with quite different volume, show consistent results within uncertainties. 相似文献
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随着网络地理信息服务技术的发展,如何基于负载均衡实现地理信息服务资源的智能化调度,从而提高服务系统的并发访问能力是当前研究的重点。提出一种动态负载均衡算法,首先将不同的地理信息服务类型与对应的服务器组相匹配,将RED算法与双阈值方法有效结合判定服务节点的负载状态,并在一定周期内对服务进行了基于加权概率的调度。最后搭建了一个基于服务器集群的实验系统,实验验证了本文方法的有效性。 相似文献
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Explanatory analysis of the relationship between atmospheric circulation and occurrence of flood‐generating events in a coastal city
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Helena L. A. Åström Maria Sunyer Henrik Madsen Dan Rosbjerg K. Arnbjerg‐Nielsen 《水文研究》2016,30(16):2773-2788
The aim of this study is to enhance the understanding of the occurrence of flood‐generating events in urban areas by analysing the relationship between large‐scale atmospheric circulation and extreme precipitation events, extreme sea water level events and their simultaneous occurrence, respectively. To describe the atmospheric circulation, we used the Lamb circulation type (LCT) classification and re‐grouped it into Lamb circulation classes (LCC). The daily LCCs/LCTs were connected with rare precipitation and water‐level events in Aarhus, a Danish coastal city. Westerly and cyclonic LCCs (W, C, SW and NW) showed a significantly high occurrence of extreme precipitation. Similarly, for extreme water‐level events westerly LCCs (W and SW) showed a significantly high occurrence. Significantly low occurrence of extreme precipitation and water‐level events was obtained in easterly LCCs (NE, E and SE). For concurrent events, significantly high occurrence was obtained in LCC W. We assessed the change in LCC occurrence frequency in the future based on two regional climate models (RCMs). The projections indicate that the westerly directions in LCCs are expected to increase in the future. Consequently, simultaneous occurrence of extreme water level and precipitation events is expected to increase in the future as a result of change in LCC frequencies. The RCM projections for LCC frequencies are uncertain because the representation of current LCCs is poor; a large number of days cannot be classified and the frequencies of the days that can be classified differ from the observed time series. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
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天然水体中泥沙组成具有非恒定性和非均匀性,而不同粒径泥沙的吸附能力差异很大.因此.讨论天然水体中泥沙对重金属污染物的自净能力,必须研究不同粒径泥沙共存(即非均匀沙)的吸附模式.通过系统室内静态试验,研究了不同粒径泥沙共存吸附的吸附动力学模式.它表明,不同粒径泥沙共存吸附体系各粒径之间不存在竞争和干扰,共存体系单位重量泥沙的吸附量等于各粒径泥沙单独存在,在相同条件下单位重量泥沙的吸附量乘以其在共存体系中所占份额的和.这在一定程度上解决了天然河流水体泥沙吸附量的计算问题. 相似文献
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Catherine O. de Burgh-Day Claire M. Spillman Craig Stevens Oscar Alves Graham Rickard 《新西兰海洋与淡水研究杂志》2019,53(2):201-221
We present a first assessment of the Sea Surface Temperature (SST) and 300m Heat Content (HC) ensemble mean skill of the Australian Community Climate and Earth-System Simulator-Seasonal v1.0 (ACCESS-S1) around New Zealand on seasonal timescales, using a set of retrospective ensemble forecasts for 1990-2012. This was verified against Reynolds AVHRR analysis and Bluelink ReANalysis 3.5 (BRAN3.5). For inshore areas with depth <300m, the model shows skill forecasting for summer at a lead time of 0 months, with 66% and 65% of model grid cells having correlation coefficients exceeding 0.6 for SST and 300m HC respectively. Regions of lower skill seem to be associated with the model representation of the complex and variable frontal systems around New Zealand, and an overly-strong response to the El Niño Southern-Oscillation (ENSO). Nevertheless, the skill of ACCESS-S1 around New Zealand suggests there is potential for the development of useful seasonal forecast products for the region. 相似文献
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利用ERA-Interim再分析资料,采用滤波和合成分析等统计方法,分析了冬季东亚高空急流的季节内协同变化以及对我国东部降水的影响,结果表明:在季节内尺度(10~90天)中,东亚地区冬季300 hPa逐日纬向风主要表现为准双周振荡(10~30天)。300 hPa低频纬向风异常整体向东传播,高纬的低频纬向风异常向南传播,低纬低频纬向风没有明显经向传播特征。伴随低频纬向西风从里海附近开始向东移动至西北太平洋上空,温带急流向东再向东南移动并且强度先增强再减弱,副热带急流位置没有明显变化,强度演变特征与温带急流变化相反。降水异常对300 hPa风场低频振荡有显著响应,低频降水主要出现在我国东部,随时间向东移动,移至西太平洋附近消失;受低频风场影响,温带急流偏强,副热带急流偏弱时,我国东部高空辐合,地面表现为低频高压,整层有较强下沉气流,地面为东北风控制,不易产生降水;温带急流偏弱,副热带急流偏强时,青藏高原北侧整层一致东风异常,南侧整层一致西风异常,使我国东部高空辐散,地面受低频低压控制,我国东部产生整层上升运动,并且有西南风水汽输送,水汽辐合,我国东部出现低频降水正异常。 相似文献