两种形态ENSO对南半球热带外气候变化特征的影响          下载免费PDF全文

万伟杰张召儒  刘海龙周朦 钟贻森 《极地研究》2018,30(4):376-390

本研究利用1979—2012年欧洲中期天气预报中心(ECMWF)的ORAP5(Ocean Reanalysis Pilot 5)海洋/海冰再分析资料和ERA-Interim气象再分析资料,采用回归分析方法,分1979—1998年和1999—2012年两个时间段探讨了南半球热带外地区气候变化对两种不同形态ENSO的响应特征。结果表明,南半球热带外区域气候在1999年前后两个时段对ENSO的响应表现出了较大的年代际变化特征。1979—1998年南半球热带外气候变量对Nio3指数在时间上的相关性和空间上的响应强度都普遍大于Nio4指数,说明这一时段东部型ENSO对南半球热带外区域气候变化的影响要更强一些。在1999—2012年,不同形态ENSO与气候变量的相关性大小并无明显的规律,而且空间响应场的差异性并不大。海平面气压、风场和气温对ENSO变化的响应在南半球冬季表现最为强烈,在夏季最弱。三者在1999—2012年秋季对Nio3指数和Nio4指数的响应场中出现了纬向三波数结构。1999—2012年冬季,有异于海平面气压和风场,在罗斯海和阿蒙森海海域海表气温对Nio4变化的正响应明显强于对Nio3的响应,该特征在混合层温度中也有体现,表明海表气温随ENSO的变化受海洋特征变化影响较大。混合层深度和混合层温度的响应场之间存在很大的相关性,混合层温度响应在秋季表现最强,春季最弱,混合层深度响应与之相反。在1979—1998年,海冰密集度对不同Nio指数变化的响应差异主要出现在海冰结冰季节,而海冰厚度对不同Nio指数变化的响应差异在夏季表现较强。海冰密集度和厚度对Nio3变化响应的年代际差异在秋冬季节更加明显,对Nio4变化响应的年代际差异在秋、冬、春季都较明显。  相似文献   

中国东北地区冬季气温趋势及反相模态分析   总被引：3，自引：0，他引：3  

徐迪  任保华  郑建秋  董祝雷  卢国阳 《气象科学》2017,37(1):127-133

利用1951—2010年我国东北地区共97个台站的逐月气温资料,应用trend-EOF和EOF分析方法研究了我国东北地区冬季气温的趋势模态和反相模态及其影响因子。trend-EOF的结果表明,东北地区均为一致型的趋势变化,trend-PC1有明显的年代际周期变化和更长期的上升趋势变化特征。去除全球变暖信号后的EOF分析结果表明:第一模态仍为全区一致型的空间分布,而第二模态的空间分布呈现南北反相型的分布特征,是东北冬季气温变化模态中极为重要的一部分,对应的时间序列有明显的年际周期变化,前两个模态可以解释总方差80%以上的变化。东北地区全区一致的上升趋势是在全球变暖大背景下发生的,既是对全球变暖的局地响应,同时全球变暖也使大气环流发生了变化,西伯利亚高压减弱,纬向环流增强,导致了东北地区冬季气温全区的上升趋势。赤道东太平洋的异常海温对第二模态的出现具有一定的预示意义,当太平洋出现典型的厄尔尼诺年海温距平场分布特征时,东北南部较常年偏暖,北部地区却较常年偏冷。  相似文献   

CMIP5模式中El Ni?o-EAWM关系的模拟对东亚冬季风模拟的影响     

尹依雯  郭品文  张攀全  沈沉 《气象科学》2017,37(2):205-212

本文利用统计学的方法,评估了17个参加第五次国际耦合模式比较计划(CMIP5)的海气耦合模式对东亚冬季风(EAWM)年际变化的模拟。结果表明:多数模式对东亚冬季风的年际变化有一定的模拟能力,其中对东亚大槽年际变化的模拟最好;模式对东亚冬季主要系统的年际变化在空间上的模拟好于强度,对强度的模拟以偏弱为主;通过综合评估得到模拟能力好的模式有:bcc-csm1-1,CCSM4,HadCM3,NorESM1-M。针对模式间对冬季风年际变化模拟能力差别较大的现象,选取了4个模拟能力最好的模式和5个最差的进行讨论;通过评估El Ni?o对东亚冬季环流的影响,发现模式对El Ni?o与EAWM之间相互关系(El Ni?o-EAWM)的模拟能力是模式间对冬季风年际变化模拟偏差较大的原因之一,即对El Ni?o-EAWM模拟好的模式对东亚冬季风年际变化的模拟也好。  相似文献   

2015年11月浙江省降水异常成因分析   总被引：1，自引：1，他引：0  

陈练  王阔  李进  李栋梁 《气象科学》2017,37(4):542-552

利用NCEP/NCAR大气环流资料、NOAA ERSST.V3b海温资料以及浙江省66个台站1971年以来的降水资料,分析了浙江省11月降水偏多对应的高低层大气环流异常特征以及与热带海温异常的联系,并在此基础上对2015年11月浙江省降水异常偏多的事实进行梳理和个例诊断。结果显示,2015年11月浙江省处于降水偏多的气候背景,同时北半球北极涛动正位相异常偏强、中高纬地区经向环流偏弱,西北太平洋副热带高压强度异常偏强、位置偏西是造成降水异常偏多的主要原因;统计分析表明巴尔喀什湖地区500 hPa高度场和西太平洋副热带高压强度与浙江省11月份降水具有显著相关;厄尔尼诺是导致浙江省11月降水偏多的重要外强迫因子之一,2015年11月Niño3.4指数达历史峰值,是造成浙江省同期降水异常偏多的主要原因。  相似文献   

Why Was the Strengthening of Rainfall in Summer over the Yangtze River Valley in 2016 Less Pronounced than that in 1998 under Similar Preceding El Niño Events?——Role of Midlatitude Circulation in August     

Chaofan LI  Wei CHEN  Xiaowei HONG  Riyu LU 《大气科学进展》2017,34(11):1290-1300

It is widely recognized that rainfall over the Yangtze River valley (YRV) strengthens considerably during the decaying summer of El Niño, as demonstrated by the catastrophic flooding suffered in the summer of 1998. Nevertheless, the rainfall over the YRV in the summer of 2016 was much weaker than that in 1998, despite the intensity of the 2016 El Niño having been as strong as that in 1998. A thorough comparison of the YRV summer rainfall anomaly between 2016 and 1998 suggests that the difference was caused by the sub-seasonal variation in the YRV rainfall anomaly between these two years, principally in August. The precipitation anomaly was negative in August 2016——different to the positive anomaly of 1998. Further analysis suggests that the weaker YRV rainfall in August 2016 could be attributable to the distinct circulation anomalies over the midlatitudes. The intensified "Silk Road Pattern" and upper-tropospheric geopotential height over the Urals region, both at their strongest since 1980, resulted in an anticyclonic circulation anomaly over midlatitude East Asia with anomalous easterly flow over the middle-to-lower reaches of the YRV in the lower troposphere. This easterly flow reduced the climatological wind, weakened the water vapor transport, and induced the weaker YRV rainfall in August 2016, as compared to that in 1998. Given the unique sub-seasonal variation of the YRV rainfall in summer 2016, more attention should be paid to midlatitude circulation——besides the signal in the tropics——to further our understanding of the predictability and variation of YRV summer rainfall.  相似文献   

Fire activity in Borneo driven by industrial land conversion and drought during El Niño periods, 1982–2010     

《Global Environmental Change》2017

Tropical rainforests, naturally resistant to fire when intact, are increasingly vulnerable to burning due to ongoing forest perturbation and, possibly, climatic changes. Industrial-scale forest degradation and conversion are increasing fire occurrence, and interactions with climate anomalies such as El Niño induced droughts can magnify the extent and severity of fire activity. The influences of these factors on fire frequency in tropical forests has not been widely studied at large spatio-temporal scales at which feedbacks between fire reoccurrence and forest degradation may develop. Linkages between fire activity, industrial land use, and El Niño rainfall deficits are acute in Borneo, where the greatest tropical fire events in recorded history have apparently occurred in recent decades. Here we investigate how fire frequency in Borneo has been influenced by industrial-scale agricultural development and logging during El Niño periods by integrating long-term satellite observations between 1982 and 2010 – a period encompassing the onset, development, and consolidation of its Borneo’s industrial forestry and agricultural operations as well as the full diversity of El Niño events. We record changes in fire frequency over this period by deriving the longest and most comprehensive spatio-temporal record of fire activity across Borneo using AVHRR Global Area Coverage (GAC) satellite data. Monthly fire frequency was derived from these data and modelled at 0.04° resolution via a random-forest model, which explained 56% of the monthly variation as a function of oil palm and timber plantation extent and proximity, logging intensity and proximity, human settlement, climate, forest and peatland condition, and time, observed using Landsat and similar satellite data. Oil-palm extent increased fire frequency until covering 20% of a grid cell, signalling the significant influence of early stages of plantation establishment. Heighted fire frequency was particularly acute within 10 km of oil palm, where both expanding plantation and smallholder agriculture are believed to be contributing factors. Fire frequency increased abruptly and dramatically when rainfall fell below 200 mm month⁻¹, especially as landscape perturbation increased (indicated by vegetation index data). Logging intensity had a negligible influence on fire frequency, including on peatlands, suggesting a more complex response of logged forest to burning than appreciated. Over time, the epicentres of high-frequency fires expanded from East Kalimantan (1980’s) to Central and West Kalimantan (1990’s), coincidentally but apparently slightly preceding oil-palm expansion, and high-frequency fires then waned in East Kalimantan and occurred only in Central and West Kalimantan (2000’s). After accounting for land-cover changes and climate, our model under-estimates observed fire frequency during ca. 1990–2002 and over-estimates it thereafter, suggesting that a multi-decadal shift to industrial forest conversion and forest landscapes may have diminished the propensity for high-frequency fires in much of this globally significant tropical region since ca. 2000.  相似文献   

2000—2019年秦岭南北实际蒸散发时空变化特征   总被引：1，自引：0，他引：1  

李双双  张玉凤  张立伟  王婷  延军平 《地理科学进展》2021,40(11):1900-1910

基于遥感数据全面认识复杂地形单元实际蒸散发时空规律,对区域可持续水资源管理具有重要的意义。论文基于MODIS实际蒸散发(ET)数据,对2000—2019年秦岭南北ET时空变化特征进行分析,探究不同分区ET对植被变化的响应关系,进而识别ET趋势和年代变化的高相关海气环流因素。结果表明：① 在变化趋势上,以1000 m等高线为界,即秦岭地区北亚热带和山地暖温带的分界线,低海拔河谷地带为ET显著增加区,山地高海拔地区为ET下降区;② 除城市、乡镇周边地区,研究期间秦岭南北下垫面相对稳定,转为生态用地的活跃区主要分布在山地1000 m过渡带,其是ET与NDVI变化显著相关区,而1000 m以上高海拔地区两者相关性较低;③ ENSO、青藏高原北部气压异常,与秦岭山地、汉江谷地ET的趋势变化和年代波动显著相关,而西太平洋副热带高压与ET的趋势显著相关,与年代波动特征相关较弱。即发生中部型厄尔尼诺事件时,西太平洋副热带高压偏强,对流层低层形成异常反气旋,导致中国东部雨带北移,秦岭山地和汉江谷地降水偏少,气温偏高,ET往往偏大。研究结果启示：秦岭南北科学适应气候变化时,应关注秦岭山地、汉江谷地ET变化显著相关的环流信号;应深刻理解秦岭高海拔地区蒸散发下降趋势对区域水资源管理的影响。  相似文献   

Contrasting Regional Responses of Indian Summer Monsoon Rainfall to Exhausted Spring and Concurrently Emerging Summer El Ni?o Events     

E.K.KRISHNA KUMAR  S.ABHILASH  SANKAR SYAM  P.VIJAYKUMAR  K.R.SANTOSH  A.V.SREENATH 《大气科学进展》2023,40(4):697-710

The inverse relationship between the warm phase of the El Ni?o Southern Oscillation(ENSO) and the Indian Summer Monsoon Rainfall(ISMR) is well established. Yet, some El Ni?o events that occur in the early months of the year(boreal spring) transform into a neutral phase before the start of summer, whereas others begin in the boreal summer and persist in a positive phase throughout the summer monsoon season. This study investigates the distinct influences of an exhausted spring El Ni?o(springtime)...  相似文献   

Sulfur speciation with high performance liquid chromatography as a tool for El Chichón volcano,crater lake monitoring     

《Journal of South American Earth Sciences》2016

The monitoring of sulfur species in crater lakes has proven to be useful for forecasting episodes of volcanic unrest in certain active volcanoes, including Poás, Costa Rica; Kusatsu-Shirane, Japan; and Mt. Ruapehu, New Zealand. In this study, we have improved the current geochemical monitoring of El Chichón volcano through the setting of optimal high-performance liquid chromatography conditions (HPLC) for the analysis of S²⁻, SO₃²⁻, S₂O₃²⁻, S₄O₆²⁻ and SO₄²⁻ using a common chromatographic system. The procedure was applied to the analysis of lake samples taken in March, July and October of 2014 and April of 2015. The results were promising, since nearly all species were detected (with the exception of S₂O₃²⁻) in measurable amounts, including S²⁻ (<0.85–5.05 mg/L), SO₃²⁻ (<2.77–26.1 mg/L), S₄O₆²⁻ (108.27–303.82 mg/L) and SO₄²⁻ (489.58–676.26 mg/L). The spatial distribution of these species along the lakeshore showed zones of increased concentrations to the east and southeast of the lake, which provides information on the distribution of faults or cracks that feed hydrothermal fluids to the lake. This method thus provides additional information linked to the volcanic and hydrothermal activity of the volcano.  相似文献   

近年来厄尔尼诺期间北赤道流输运的年际变化   总被引：1，自引：0，他引：1       下载免费PDF全文

吴国丽  王庆业  翟方国  胡敦欣 《海洋科学》2016,40(2):118-127

为了研究近年来厄尔尼诺期间北赤道流输运的年际变化,本文利用海洋客观分析数据MOAA GPV(Grid Point Value of the Monthly Objective Analysis)以及P-vector方法计算了北太平洋绝对地转流,探讨了2001~2013年期间厄尔尼诺与北赤道流输运之间的关系。在此期间发生的4次厄尔尼诺事件中,北赤道流输运在2002~2003、2006~2007、2009~2010年的厄尔尼诺成熟期都出现了明显的增强,但是在2004~2005年的厄尔尼诺成熟期并没有明显的增强。进一步分析发现,在2002~2003年、2006~2007年、2009~2010年的厄尔尼诺成熟期,10°N以南的热带西北太平洋区域出现了负的海面高度异常和气旋式环流异常,这主要是由热带环流区域出现的西风异常和正的Ekman抽吸通过Rossby波西传到热带西太平洋区域所致;但是在2004~2005年厄尔尼诺成熟期,海面温度异常的分布明显不同,西风异常和正的Ekman抽吸异常明显北移,导致负的海面高度异常和气旋式环流异常出现在了10°N以北的西北太平洋区域,使得北赤道流输运在2004~2005年的厄尔尼诺成熟期没有明显的增强。  相似文献