Glacial and Holocene terrestrial temperature variability in subtropical east Australia as inferred from branched GDGT distributions in a sediment core from Lake McKenzie     

Martijn Woltering  Pia Atahan  Kliti Grice  Henk Heijnis  Kathryn Taffs  John Dodson 《Quaternary Research》2014

Branched glycerol dialkyl glycerol tetraether (GDGT) distributions observed in a sediment core from Lake McKenzie were utilized to quantitatively reconstruct the pattern of mean annual air temperature (MAAT) from coastal subtropical eastern Australia between 37 and 18.3 cal ka BP and 14.0 cal ka BP to present. Both the reconstructed trend and amplitude of MAAT changes from the top of the sediment core were nearly identical to a local instrumental MAAT record from Fraser Island, providing confidence that in this sediment core branched GDGTs could be used to produce a quantitative record of past MAAT. The reconstructed trend of MAAT during 37 to 18.3 cal ka BP and timing of the Last Glacial Maximum (LGM) in the Lake McKenzie record were in agreement with previously published nearby marine climate records. The amplitude of lower-than-present MAAT during the LGM potentially provides information on the latitude of separation of the Tasman Front from the East Australian current in the subtropical western Pacific. The Lake McKenzie record shows an earlier onset of near modern day warm temperatures in the early Holocene compared to marine records and the presence of a warmer than present day period during the mid-Holocene.  相似文献   

东亚与北美东部降水和环流季节演变差异及其可能机理分析   总被引：1，自引：0，他引：1  

常炉予  何金海  祁莉  温敏 《气象学报》2013,71(6):1074-1088

利用NCEP/ NCAR 再分析资料和CMAP、GPCP卫星反演降水资料,对比分析了东亚与北美东部地区降水和大尺度大气环流季节演变特征的差异。结果显示,东亚和北美东部地区冬季环流形势较为相似,而夏季差异则较大,这正是东亚为季风区,北美为非季风区的表现。此外,基于季风的两大特征量“风”和“雨”,分析了两地降水和低空风场季节变化的显著差异：东亚副热带地区降水季节变率大,呈“夏湿冬干”的季风降水特征,低层盛行风向随季节逆转,冬季盛行偏北风,夏季盛行偏南风,具有显著的副热带季风区特征。北美东部副热带地区全年雨量分配均匀,低层常年盛行偏西风,呈现非季风区特征。进一步的分析发现,作为季风基本推动力的海、陆热力差异在东亚和北美东部地区有着显著的区别：东亚地区的经向和纬向温度梯度随季节反转的特征显著;而北美东部地区虽有纬向温度梯度的季节反转但幅度很小,且经向海、陆热力差异随季节反转不明显。此外,与青藏高原和落基山脉相伴的纬向环流也存在显著差异。鉴于此,提出经向和纬向海、陆热力梯度反转特征的不同以及青藏高原和落基山脉地形的不同作用很可能是造成东亚副热带季风气候而北美东部非季风气候的主要原因,上述结论还有待于数值试验的进一步证实。  相似文献   

2013年夏季长江中下游地区降水异常与MJO的可能联系          下载免费PDF全文

刘蕾  高辉  李鸾  周晶 《气象与减灾研究》2018,41(2):126-132

利用国家气象信息中心提供的753站降水资料,澳大利亚气象局提供的RMM MJO指数资料和NECP/NCAR逐日再分析资料,分析了2013年夏季长江中下游地区降水持续异常与MJO位相异常的可能联系。结果表明：2013年夏季长江中下游地区持续干旱期间,MJO位相分布明显异常,MJO东传停滞,长时间维持在第1、8位相;西太平洋副热带高压偏北偏强。当MJO位于第1、8位相时,东亚高纬度地区的环流距平场呈现“西高东低”的分布特征,不利于西伯利亚地区的冷空气南下至长江中下游地区;当MJO位于第1位相时,副热带高压西北侧水汽主要输送至长江中下游地区,第8位相时,输送至长江中下游地区的水汽异常偏少。总之,当MJO位于第1、8位相时,冷空气活动较弱,冷暖空气无法在长江中下游地区交汇,同时该地区深厚的下沉运动从近地面一直延伸至对流层上层,不利于降水的发生,导致2013年夏季降水持续偏少。  相似文献   

Modulation of Madden-Julian Oscillation Activity by the Tropical Pacific-Indian Ocean Associated Mode     

Lifeng LI  Xin LI  Xiong CHEN  Chongyin LI  Jianqi ZHANG  Yulong SHAN 《大气科学进展》2020,37(12):1375-1388

In this study, the impacts of the tropical Pacific–Indian Ocean associated mode (PIOAM) on Madden–Julian Oscillation (MJO) activity were investigated using reanalysis data. In the positive (negative) phase of the PIOAM, the amplitudes of MJO zonal wind and outgoing longwave radiation are significantly weakened (enhanced) over the Indian Ocean, while they are enhanced (weakened) over the central and eastern Pacific. The eastward propagation of the MJO can extend to the central Pacific in the positive phase of the PIOAM, whereas it is mainly confined to west of 160°E in the negative phase. The PIOAM impacts MJO activity by modifying the atmospheric circulation and moisture budget. Anomalous ascending (descending) motion and positive (negative) moisture anomalies occur over the western Indian Ocean and central-eastern Pacific (Maritime Continent and western Pacific) during the positive phase of the PIOAM. The anomalous circulation is almost the opposite in the negative phases of the PIOAM. This anomalous circulation and moisture can modulate the activity of the MJO. The stronger moistening over the Indian Ocean induced by zonal and vertical moisture advection leads to the stronger MJO activity over the Indian Ocean in the negative phase of the PIOAM. During the positive phase of the PIOAM, the MJO propagates farther east over the central Pacific owing to the stronger moistening there, which is mainly attributable to the meridional and vertical moisture advection, especially low-frequency background state moisture advection by the MJO’s meridional and vertical velocities.  相似文献   

The influence of the Madden-Julian oscillation on high-latitude surface air temperature during boreal winter     

《Dynamics of Atmospheres and Oceans》2020

By analyzing NCEP-NCAR reanalysis daily data for 1979–2016, the modulation by Madden-Julian Oscillation (MJO) of the wintertime surface air temperature (SAT) over high latitude is examined. The real-time multivariate MJO (RMM) index, which divides the MJO into eight phases, is used. It is found that a significantly negative SAT anomaly over the northern high latitude region of (180°–60 °W, 60°–90 °N) lags the MJO convection for 1∼2 weeks in phase 3, in which the enhanced convective activity exists over the Indian Ocean. While a significantly positive SAT anomaly appears over the same region following the MJO phase 7, as the tropical heating shows an opposite sign. Analysis of the anomalous circulation indicates that the observed SAT signal is probably a result of the northeastward propagating Rossby wave train triggered by MJO-related tropical forcing through Rossby wave energy dispersion. By using an anomalous atmospheric general circulation model (AGCM), the significant effect of tropical forcing on organizing the extratropical circulation anomaly is confirmed. Analysis of a temperature tendency equation further reveals that the intraseasonal SAT anomaly is primarily attributed to the advection of the mean temperature by the wind anomaly associated with the anomalous circulation of the MJO-related variability.  相似文献   

基于交叉小波分析方法的西太平洋副热带高压年际变率与热带海温及大气环流异常的相关性研究     

洪梅  刘科峰  张栋  张韧  葛晶晶 《热带气象学报》2020,36(2):166-179

西太平洋副热带高压的年际变率受热带多个关键海区的海-气相互作用过程调控, 但彼此间的因果关联和影响机制尚不清楚。为揭示西太平洋副热带高压的年际变率与热带海温及大气环流异常之间的内在关联特性, 定义了三个关键海区以及赤道纬向西风区的特征指数, 并分别与西太平洋副热带高压强度、脊线指数进行了交叉小波和相干小波分析。研究发现:西太平洋副热带高压指数存在显著的2~3年和准5年的周期振荡, 20世纪八九十年代后, 由于暖池区海温及赤道纬向西风区的Hadley环流强迫加强, 致使副热带高压特征指数的2~3年周期振荡加强; 从位相关系看, 先是西太平洋副热带高压减弱南撤导致纬向西风加强, 其后影响赤道东太平洋海温升高, 同时暖水向东传, 使赤道中太平洋以及暖池区海温逐渐升高, 在Hadley环流作用下使副高加强北抬。基于上述西太平洋副热带高压的年际变率与热带海温及大气环流异常变化相关性诊断研究, 进一步探讨了造成这种相关性的影响机理和因果关联, 为揭示西太平洋副热带高压年际变率与热带海温及大气环流异常的相关性做探索研究。   相似文献   

Effects of desertification on the body temperature, activity and water turnover of Angora goats     

R.S. Hetem  B.A. de WittL.G. Fick  A. FullerS.K. Maloney  L.C.R. MeyerD. Mitchell  G.I.H. Kerley 《Journal of Arid Environments》2011,75(1):20-28

Globally, pastoral practices have transformed habitats, which often lead to desertification. With climate change predicted to exacerbate desertification, adaptation provides the best survival strategy for agriculturally important herbivores. We investigated body temperature, water turnover, physical activity and microclimate selection of Angora goats inhabiting transformed and intact sites in the Eastern Cape Province, South Africa. Although goats on both sites responded similarly under most environmental conditions, when goats were subjected to a thermal stress, imposed by shearing, those inhabiting the transformed site had a faster rate of rise in abdominal temperature (0.38 versus 0.31 °C h⁻¹, P = 0.0009), displayed an increased 24-h abdominal temperature amplitude (1.8 versus 1.6 °C, P = 0.01) and were generally less active (3.9 versus 5.2 activity units) compared to goats inhabiting the intact site. Post-shearing, goats inhabiting the transformed site had higher water turnover rates (P < 0.0001) and selected more variable microclimates (P < 0.0001) than goats inhabiting the intact site, despite obtaining less water from their diet (P = 0.01). Goats inhabiting the transformed site were more water dependent and more susceptible to thermal stresses in their environment than were those inhabiting the intact site. Coping with thermal challenges will be essential for Angora goats if the mohair industry is to thrive under future climate change scenarios.  相似文献   

大气振荡与副高活动及四川盆地旱涝的关系     

李跃清  章基嘉 《成都信息工程学院学报》1993,(4)

本文分析了1982年5～9月热带西太平洋地区,尤其是我国南海、菲律宾和印度尼西亚上空30～50天大气振荡与太平洋副高活动及四川盆地夏季旱涝的关系。结果表明:热带西太平洋上空大气低频振荡对太平洋副高有明显影响;四川盆地东、西部夏季降水30～50天振荡呈反位相变化;东(西)部降水低频振荡与热带西太平洋上空大气低频振荡呈反(同)位相关系。热带西太平洋上空大气低频振荡,通过引起太平洋副高中心、西伸脊点东西变动影响盆地夏季旱涝异常。  相似文献   

MJO对华南前汛期降水的影响及其可能机制   总被引：12，自引：2，他引：10  

李文铠  何金海  祁莉  陈伯民 《热带气象学报》2014,30(5):983-989

利用站点降水资料、实时多变量MJO(Madden-Julian Oscillation)指数、向外长波辐射(OLR)资料和NCEP/NCAR再分析资料,采用合成分析方法研究了MJO对华南前汛期降水的影响,并讨论其可能机制。结果表明,(1)在MJO不同位相,华南前汛期降水异常有明显的差异,并且这种差异随滞后时长而发生变化。第2~3位相和第6~7位相分别是影响华南前汛期降水的典型"湿位相"和"干位相"。(2)华南前汛期降水对MJO的响应需要一定时间,滞后时长约为1~2候。(3)MJO活跃(受抑)对流可通过激发Rossby波影响华南前汛期降水。当MJO活跃(受抑)对流中心位于赤道印度洋附近时,非绝热加热作用激发的Rossby波到达并影响华南地区,华南地区出现水汽供应的增强(减弱),从而促进(抑制)华南前汛期降水。  相似文献   

广东地区雷电活动的气候分布特征   总被引：27，自引：14，他引：27  

张敏锋  刘欣生  张义军  樊灵孟  钟定珠  周良才 《热带气象学报》2000,16(1):46-53

利用地闪定向仪(DF)和时间到达法(TOA)定位技术,1997年3月～1998年6月在研究范围内共计得到404431次地闪资料.分析了地闪的雷电流强度、回击数的气候概率分布特征以及雷电参数的日变化及其空间分布的气候规律.正闪占总闪的比例仅为5.03%,正负闪密度的高值中心均在(114.E,23.N)附近.总体日变化特征明显,全天有两个高值时段,分别为00～06时和12～18时.与北方地区的雷电特征不同.结果表明雷电活动特征可以基本揭示本地区天气活动的时空分布的规律.  相似文献