Spatial and temporal seasonal trends in coastal upwelling off Northwest Africa, 1981–2012     

《Deep Sea Research Part I: Oceanographic Research Papers》2014

Seasonal coastal upwelling was analyzed along the NW African coastline (11–35°N) from 1981 to 2012. Upwelling magnitudes are calculated by wind speed indices, sea-surface temperature indices and inferred from meteorological station, sea-surface height and vertical water column transport data. A permanent annual upwelling regime is documented across 21–35°N and a seasonal regime across 12–19°N, in accordance with the climatology of previous studies. Upwelling regions were split into three zones: (1) the Mauritania–Senegalese upwelling zone (12–19°N), (2) the strong permanent annual upwelling zone (21–26°N) and (3) the weak permanent upwelling zone (26–35°N). We find compelling evidence in our various indices for the Bakun upwelling intensification hypothesis due to a significant coastal summer wind speed increase, resulting in an increase in upwelling-favorable wind speeds north of 20°N and an increase in downwelling-favorable winds south of 20°N. The North Atlantic Oscillation plays a leading role in modifying interannual variability during the other seasons (autumn–spring), with its influence dominating in winter. The East Atlantic pattern shows a strong correlation with upwelling during spring, while El Niño Southern Oscillation and Atlantic Multi-decadal Oscillation teleconnections were not found. A disagreement between observationally-based wind speed products and reanalysis-derived data is explored. A modification to the Bakun upwelling intensification hypothesis for NW Africa is presented, which accounts for the latitudinal divide in summer wind regimes.  相似文献   

2009/2010年冬季云南严重干旱原因的进一步分析   总被引：8，自引：2，他引：6       下载免费PDF全文

宋洁  杨辉  李崇银 《大气科学》2011,35(6):1009-1019

为了揭示2009/2010年冬季云南出现严重干旱灾害的原因,本文利用NCEP/NCAR再分析资料以及云南省台站降水资料计算得到的云南冬季降水指数,讨论了在北半球冬季(12～2月)北大西洋涛动(North Atlantic Oscillation,简称NAO)和云南省降水(旱涝)之间的联系.分析结果表明,在1961/19...  相似文献   

Evaluation of the Forecast Performance for North Atlantic Oscillation Onset     

Guokun DAI  Mu MU  Zhina JIANG 《大气科学进展》2019,(7):753-765

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环状模概念   总被引：1，自引：0，他引：1  

李晓峰 《地球科学进展》2015,30(3):1-384

"环状模"(Annular Mode)是大气遥相关领域一个新兴的气候学概念,目前已被广泛接受并应用。它表征热带外地区中纬度和高纬度间大气质量的"跷跷板"现象,为热带外地区最主要的大气变率,影响包括我国在内的中高纬度地区、甚至部分热带地区的近地层气候。它对整个北半球气候的影响之大,从根本上改变了气候学家对北极气候模型的理解,也被称为"北极厄尔尼诺"。可见,"环状模"概念的提出具有重要的科学意义。然而,"环状模"这一气候学概念的提出和推广过程并不平顺。多派学者曾围绕这一新兴概念,展开过近年来气候学领域内少有、激烈和精彩的辩论。而这场辩论是"环状模"概念提出和发展过程中的重要一环,它最终促使更多的学者了解并接受了"环状模"这一新兴的气候学概念。这场辩论的焦点主要围绕"‘环状模’是否真实存在"、"‘环状模’信号是否源自于平流层"和"‘北半球环状模’与‘北大西洋涛动’究竟谁更适合于代表北半球热带外行星尺度扰动最主要的模态"等3个问题。辩论的具体过程,不仅展示了相关的学者们高超的研究水平和技巧,还折射出他们对真理不懈追求的科学精神;而辩论的最终结果,不但增强了人们对"环状模"概念的理解,还催生了人们对大气环流基本活动规律认识的突破。厘清这场辩论的主要思路和观点,不仅可以增强我们对"环状模"概念以及基本大气环流过程的理解,而且对分析和解决其他类似的科学问题同样具有重要的启示性作用。因此,力图通过综述的方式,围绕"环状模"概念的由来和争论,与读者一起回顾"环状模"这一重要气候学概念的提出和推广过程。  相似文献   

The influences of the Southern and North Atlantic Oscillations on climatic surface variables in Turkey     

M. aatay Karabrk  Ercan Kahya  Mehmet Karaca 《水文研究》2005,19(6):1185-1211

In this study, Turkish climatic variables (precipitation, stream flow and maximum and minimum temperatures) were first analysed in association with both the Southern Oscillation (SO) and the North Atlantic Oscillation (NAO). The relationships between Turkish maximum and minimum monthly temperatures and the extreme phases of the SO (El Niño and La Niña events) were examined. The results of this analysis showed that relationships between Turkish monthly maximum temperatures and El Niño and La Niña contain some complexity still to be identified, because both events produce a signal indicating a correspondence with cold anomalies in the aggregate composites. A relationship between turkish minimum temperatures and El Niño was detected in western Anatolia, whereas there was no significant and consistent signal associated with La Niña. Moreover a series of cross‐correlation analyses was carried out to demonstrate the teleconnections between the climatic variables and both the NAO and SO. The NAO during winter was found to influence precipitation and stream‐flow patterns. In contrast temperature patterns appeared to be less sensitive to the NAO. Furthermore, lag‐correlation results indicated a prediction potential for both precipitation and stream‐flow variables in connection with the NAO. Simultaneous and time‐lag correlations between the climatic variables and the SO index, in general, indicated weaker relationships in comparison with those for the NAO. These analyses also showed that the influences of the SO on Turkish temperature data are negligible. The outcomes were presented in conjunction with an explanation regarding physical mechanisms behind the implied teleconnections. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

1951—2016年中亚努尔苏丹与乌鲁木齐寒潮过程频数变化及其主要影响因子对比分析   总被引：1，自引：1，他引：0  

段均泽  毛炜峄  黄迤静  陈静  迪丽努尔·托列吾别克  姚俊强  沈永平 《冰川冻土》2021,43(4):1060-1072

利用1951—2016年努尔苏丹和乌鲁木齐的逐日最低气温资料, 以当年7月到翌年6月为统计年, 对比分析了中亚地区的努尔苏丹与乌鲁木齐的寒潮、 强寒潮和超强寒潮过程频数气候变化特征, 并初步分析了冬季北极涛动（AO）、 北大西洋涛动（NAO）与中亚两个城市同期寒潮活动关系。结果显示： 努尔苏丹的年平均寒潮过程频数（15.7次·a^-1）是乌鲁木齐（4.1次·a^-1）的3.88倍, 强寒潮和超强寒潮过程频数分别是乌鲁木齐的5.91倍和7.55倍; 努尔苏丹的超强寒潮过程频数月分布呈单峰型, 1月最多, 乌鲁木齐的呈双峰型, 峰值分别出现在11月和4月。努尔苏丹的寒潮过程持续日数普遍比乌鲁木齐短。65 a来, 努尔苏丹与乌鲁木齐的春季寒潮过程频数之间的相关关系显著。努尔苏丹和乌鲁木齐的年寒潮过程频数的线性递减率分别为-0.111次·（10a）^-1和-0.445次·（10a）^-1; 两城市秋、 冬、 春季寒潮、 强寒潮和超强寒潮过程频数线性趋势大多以递减为主, 但是努尔苏丹冬季和乌鲁木齐春季的超强寒潮过程频数均呈递增趋势。努尔苏丹的年超强寒潮过程频数在近5 a最多。努尔苏丹的年寒潮过程频数序列有31 a、 20 a左右的显著周期, 乌鲁木齐的年寒潮过程频数序列有39 a、 8 a左右显著周期。北大西洋涛动（NAO）与努尔苏丹和乌鲁木齐寒潮过程的关联程度比北极涛动（AO）与它们之间的关联程度更为密切; 努尔苏丹的寒潮过程频数受NAO以及AO的影响程度更深。  相似文献   

2000-2020年格陵兰冰盖夏季表面温度变化及其对物质平衡的影响北大核心CSCD     

方振祥  王宁练  李想  张玉杰  邰雪楠 《冰川冻土》2022,44(3):872-884

基于MODIS温度产品,着重分析了2000-2020年格陵兰冰盖夏季表面温度和表面融化范围的年际变化趋势;联合IMBIE(冰盖物质平衡对比实验)数据分析表面温度对于冰盖物质平衡的影响;进一步讨论了大气环流对于格陵兰冰盖表面温度变化的影响。结果表明:格陵兰冰盖夏季表面温度和融化范围趋势较为一致,2000年初期呈现出显著的上升趋势,2012年达到峰值,随后波动下降;整个研究阶段北部区域是增温速率最大的区域,高于其他任何区域两倍,东南部和西南部是温度最高的区域却具有最小的增长率;格陵兰冰盖夏季表面温度、融化范围以及物质平衡之间都具有显著的相关性,同时格陵兰冰盖夏季表面温度每上升1℃,会导致其物质损失增加74.29Gt·a;最后,经过对北大西洋涛动(NAO)和格陵兰阻塞指数(GBI)指数的分析得到,格陵兰冰盖夏季表面温度受到GBI的影响要强于NAO的影响,冰盖夏季表面温度和NAO呈现出负相关(r=-0.64,P<0.05),和GBI呈现出正相关(r=0.77,P<0.05)。  相似文献   

近67a影响山东台风频数的变化特征及其与若干气候因子的关系   总被引：3，自引：2，他引：1  

高晓梅  江静  刘畅  马守强 《气象科学》2018,38(6):749-758

利用1949—2015年台风年鉴资料、NCEP/NCAR再分析资料、NOAA资料等对近67 a影响山东的台风频数特征及其与相关气候因子的关系进行了分析。结果表明:(1)影响山东的6类台风中沿海北上类最多,登陆填塞类最少。8月和8月上旬是主要月份和旬份。台风年代际变化明显,并存在显著的26 a年代际尺度和5 a年际尺度的周期变化。(2)台风频数与同年份的东亚槽位置、亚洲区极涡面积指数分别呈显著的负、正相关关系。Ni1o3. 4区海温对台风频数存在超前的显著负相关,超前影响分别在1、2、3、4月。台风频数与冬季北大西洋涛动(NAO)指数、太平洋年代际振荡(PDO)指数分别存在显著的正、负相关关系。春、夏、秋季和年PDO冷位相时台风频数偏多,PDO暖位相时台风频数偏少,这与西太平洋副热带高压和低层水汽条件关系密切。(3)冷、暖位相年台风频数与太平洋海温分别存在显著的相关区,特别是冬季暖位相时赤道中东太平洋显著负相关区域较大。年PDO冷位相与夏季的显著相关区较相似,暖位相与秋季相似。(4)太平洋海温与台风频数相关性较好的海域主要有3个关键区:赤道中东太平洋、北太平洋中部和西太平洋暖池。其中赤道中东太平洋的的显著性表现在冬季,北太平洋中部的显著性表现在年、春、夏、秋季,西太平洋暖池的显著性表现在夏、秋季。  相似文献   

Comparative analysis of statistical tools to identify recruitment-environment relationships and forecast recruitment strength   总被引：1，自引：0，他引：1  

Megrey  Bernard A.; Lee  Yong-Woo; Macklin  S. Allen 《ICES Journal of Marine Science》2005,62(7):1256-1269

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Regional variation in distribution pattern, population structure and growth rates of Meganyctiphanes norvegica and Thysanoessa longicaudata in the Irminger Sea, North Atlantic     

R.A. Saunders  A. Ingvarsdttir  J. Rasmussen  S.J. Hay  A.S. Brierley 《Progress in Oceanography》2007,72(4):313-342

Euphausiids are a key component of the northern North Atlantic marine ecosystem and Meganyctiphanes norvegica and Thysanoessa longicaudata are dominant both numerically and in terms of biomass. The Irminger Sea is remote and experiences often-hostile weather conditions. Consequently, few studies have been conducted there, and detailed information on the seasonal distribution, abundance and growth of euphausiids is limited. Here we explore patterns of abundance and spatial and temporal variation in length–frequency distribution in order to determine regional growth rates for both species in the Irminger Basin. Regional composite length–frequency distributions for spring, summer and winter were devised by aggregating discrete net haul data according to the results of a multivariate cluster analysis of length conducted on spring and summer net sample data. Three biologically distinct regions within the Irminger basin were apparent (Central Irminger Sea, Northern Irminger Sea and East of Greenland Shelf). These regions corresponded broadly with distinct physical zones within the basin. Modes in the composite length–frequency distributions were determined by fitting multiple normal distributions, and regional differences in growth were investigated by tracking modes between seasons. The results provide some evidence for regional variability in growth and population dynamics. The population structure and growth of M. norvegica was similar in the open ocean regions of the Northern and Central Irminger Basin, but different in the region around the East Greenland Shelf. There was a distinct absence of larger individuals (+I-group) in the open ocean regions compared to East Greenland Coast region, and growth rates were marginally higher. A similar pattern in population structure was also observed for T. longicaudata. Variability in growth and abundance are discussed in relation to prevailing environmental characteristics such as temperature and food availability.  相似文献