���������񵴼���ģ�ļ���   总被引：1，自引：0，他引：1  

杨兆  孙和平  雷湘鄂 《大地测量与地球动力学》2007,27(4):38-43

??????????????????(Runge??Kutta)????????PREM??????????????????λ??????????????????????????????200 s??????????????????ε??????????????????????????????????仯???????????????о??????λ???????е?仯?????????????:??????????????????????????????仯?????, 20???????????????μ????????????Dziewonski??Anderson??????, ?????????????0.25%?????  相似文献   

利用双阳台水管观测资料检测地球自由振荡   总被引：2，自引：2，他引：0  

邓娜  刘冰冰  杨耀文  蒋翠荣  范金梅  任佳 《大地测量与地球动力学》2009,29(Z1):41-44

基于双阳台水管倾斜仪的数字化观测资料，利用功率谱密度估计方法，在没有对资料进行去固体潮处理的情况下，准确获得了2004年12月26日苏门答腊大地震激发的0S3～0S31基频球型自由振荡。并与PREM模型的理论自由振荡周期进行了对比，发现实测振荡周期与PREM预测的振荡周期相吻合，除0S3、0S4振型的观测周期和PREM模型理论周期的相对误差大于0.3%外，其他振型的观测周期和PREM模型理论周期的相对误差大都集中在0.1%左右。同时还检测到了5个谐频球型振荡和8个环型振荡。  相似文献   

The impact of overfishing and El Niño on the condition factor and reproductive success of Peruvian hake, Merluccius gayi peruanus   总被引：1，自引：1，他引：0  

Michael Balln  Claudia Wosnitza-Mendo  Renato Guevara-Carrasco  Arnaud Bertrand 《Progress in Oceanography》2008,79(2-4):300

In this study we examine physiological responses of Peruvian hake (Merluccius gayi peruanus) to changes in their population structure and physical environment during the period 1971–2004. In particular, we assess the relative investment of energy in growth and/or reproduction of small (20–35 cm) and large (35–50 cm) hake. We calculated the (i) condition (Fulton’s K), (ii) gonad and (iii) gut fullness indices for 42,761 female hakes sampled from commercial landings; these indices indicate fish somatic, reproductive and feeding condition, respectively. Using Generalized Additive Models we then examined potential relationships between these indices and sea surface temperature anomalies and date. Drastic energy exhaustion and a decrease in female hake fecundity were observed during El Niño events. The long-term trend showed a general increase in condition factor and a decrease in gonad index for large hake between 1971 and 2004. Small hake exhibited a different trend with an increase in reproductive activity, which was accompanied by an earlier maturation. We hypothesise that the observed low investment of energy in reproduction by large female hake might be related to the lack of large males, due to a sex-selective fishery and the impact of El Niño. We suggest that fishing diminished hake reproductive capacity, modified the sex ratio in favour of females and increased population vulnerability to environmental stress, in particular to the El Niño. The impact of multidecadal variability and predators like the squid, Dosidicus gigas, remain unresolved until longer time series become available.  相似文献   

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何晓业  何晓红 《大地测量与地球动力学》2007,27(2):122-124

?????????????????????????????????е???????,???????????????????????????????????????????????????????????????HLS???????????????????  相似文献   

应用MJO制作长江流域月降水预测的试验研究   总被引：1，自引：0，他引：1  

张礼平  张乐飞 《气象》2013,39(9):1217-1220

用MJO指数RMM1、RMM2、振幅 1—25日平均代替月平均,用上月月平均RMM1和RMM2、振幅构造为右场,下月长江流域降水场为左场,SVD分析两场的关联,借助最优化技术,在降水场预测距平与实况距平同号总站数最大意义下确定系数,建立估计公式,由右场时间系数估计左场时间系数,最后反演降水场。尽管多数的月第一模态相关并不显著,但实际预测效果较好。  相似文献   

亚洲夏季风季节内振荡对云南主汛期降水的影响Ⅱ:云南主汛期季节内振荡活动过程及其对MJO活动的响应     

李汀  琚建华 《高原气象》2013,32(3)

利用NCEP OLR、风场再分析资料和日本APHRO_MA_V1003R1降水资料,针对云南主汛期季节内振荡(ISO)活跃年分析了对应低频对流场、环流场和降水的异常特征,以及热带印度洋大尺度振荡MJO分别激发孟加拉湾西南季风ISO和南海热带季风ISO,从而对云南主汛期ISO和降水产生的影响.在云南主汛期ISO活跃年,低频对流场和环流场在云南ISO波动的1～3位相和4～6位相呈反位相特征,这主要由热带印度洋低频对流东传、北传和副热带西太平洋低频对流西传造成的.热带印度洋的低频对流在发展过程中,一方面沿孟加拉湾西岸向西南-东北方向传播,激发了孟加拉湾西南季风ISO活跃并继续向云南传播;另一方面沿孟加拉湾以南继续东传到南海,激发了南海热带季风ISO活跃并北传到副热带中国东部地区,再沿副热带西传至云南,越过云南后与沿孟加拉湾西岸从东北方向传来的低频对流在孟加拉湾以北地区交汇,完成了一个经纬向接力传播的周期.云南主汛期降水在1～3位相由于副热带低频对流西传和孟加拉湾低频对流东北向传播而处于正距平(第2位相降水最多);在4～6位相,由于副热带低频对流抑制区西传和孟加拉湾低频对流抑制区东北向传播而降水减少(第5位相降水最少),云南主汛期降水与当地低频对流有较好的对应关系.当热带印度洋MJO较强时,4-7月以两条路径向云南的三次传播增强和提前,使得云南主汛期ISO活动也加强,对应产生三次低频对流活跃期,这种MJO由热带印度洋向云南的传播需要30～40天的时间.因此,正是热带印度洋MJO分别对孟加拉湾西南季风ISO和南海热带季风ISO的激发,使得东亚夏季风和南亚夏季风这两个亚洲夏季风系统共同作用于云南主汛期ISO,影响当地降水.  相似文献   

Resonance of baroclinic waves in the tropical oceans: The Indian Ocean and the far western Pacific     

《Dynamics of Atmospheres and Oceans》2020

The Indian Ocean has a particularity, its width is close to half the wavelength of a Rossby wave of biannual frequency, this coincidence having been capitalized on by several authors to give the observations a physical basis. The purpose of this article is to show that this is not the case since the resonance of tropical baroclinic waves occurs in all three oceans. This is because the westward-propagating Rossby wave is retroflexed at the western boundary to form off-equatorial Rossby waves dragged by countercurrents before receding and turning back as a Kelvin wave. Thus a quasi-stationary baroclinic wave is formed, whose mean period is tuned to the forcing period. Two independent basin modes resonantly forced are highlighted – 1) a nearly symmetric zonal 1/2-yr period Quasi-Stationary Wave (QSW) that is resonantly forced by the biannual monsoon. It is formed from first baroclinic mode equatorial-trapped Rossby and Kelvin waves and off-equatorial Rossby waves at the western antinode. This QSW controls the Equatorial Counter Current at the node. The Indian Ocean Dipole (IOD) results from a subharmonic mode locking resulting from the coupling of this QSW and the 2nd, 3rd and 4th baroclinic modes - 2) a 1-yr period QSW formed from an off-equatorial baroclinic Rossby wave, which is induced from the southernmost current of the Indonesian Throughflow through the Timor passage, propagating in the southern and northern hemispheres: the drivers are south-easterlies in the southern hemisphere and monsoon wind in the northern hemisphere.  相似文献   

大气季节内振荡对夏季登陆广东台风的影响     

叶烁旎  凌征 《广东气象》2020,(2):1-6

基于热带气旋最佳路径资料和向外长波辐射数据,结合高斯滤波、经验正交函数分解和合成分析等方法,探讨了20~90 d周期的MJO(Madden-Julian Oscillation)和10~20 d周期的QBWO(Quasi-Biweekly Oscillation)两类大气季节内振荡对夏季(5-9月)登陆广东台风的影响。结果表明:MJO和QBWO对登陆广东台风个数、强度、位置和运动方向均有显著影响:当MJO和QBWO的对流中心(抑制中心)靠近广东沿岸时,登陆广东的台风数量多(少)、强度大(小)、登陆位置偏东(西)、登陆后东向运动的台风数量偏多(少)。在此基础上,还进一步探讨了MJO和QBWO对生成于南海和西北太平洋的这两类登陆广东台风的影响及两者对登陆广东台风的共同影响。  相似文献   

1991、1998和2016年三个大水年长江中下游夏季降水季节内特征的对比     

黄桢  李双林  张超 《热带气象学报》2020,36(1):13-24

针对长江中下游三个大水年1991、1998和2016年,利用NCEP/NCAR大气环流再分析资料和CMAP降水资料,对比了夏季降水的季节内特征,分析了引起降水季节内变化的大气环流季节内振荡ISO演变及源地。小波分析表明,三年季节内降水周期差异明显,分别为20~30 d、20~40 d和10~20 d。随之,以东亚季风区季节内振荡指数及热带外Rossby波活动通量,诊断了引起三年季节内活动异常的热带和中纬度ISO变率特点。结果显示影响三年季节内降水的ISO差异较大。1991年受到来自印度洋10~30 d和中纬度高层Rossby波10~30 d的ISO共同影响,造成周期为20~30 d的低频降水;1998年ISO来源路径单一,受中北太平洋30~60 d和10~30 d的ISO西传叠加作用,降水表现为20~40 d的振荡;引起2016年季节内降水异常的ISO源地较多,既有来自印度洋向东北传播30~60 d的ISO,又有来自太平洋向西北传播10~30 d的ISO,还有来自热带外10~30 d的ISO,三者在长江中下游汇合,引起降水10~20 d的振荡。研究结果对认识长江中下游夏季集中降水的形成有重要意义。   相似文献   

卑尔根气候模式中大西洋热盐环流年代际与年际变率的气候影响   总被引：12，自引：3，他引：9  

周天军  Helge DRANGE 《大气科学》2005,29(2):167-177

利用一个全球海气耦合模式--卑尔根气候模式的积分结果,揭示了与大西洋热盐环流(THC)年代际和年际振荡相对应的气候异常型.年代际振荡发生在全海盆尺度,伴有亚速尔高压的增强、冰岛低压的加深;年际振荡发生在局地尺度,伴有亚速尔高压的减弱.这两种海平面气压异常型都反映了北大西洋涛动(NAO)活动中心的强度变化,两种变率型对应的拉布拉多海对流活动都加剧.但伴随局地尺度的THC调整,伊尔明格海的对流活动减弱.蒸发异常对拉布拉多海表层盐度异常的影响较为显著.分析表明,局地尺度的THC振荡主要是对大气强迫的被动响应,而海盆尺度THC振荡的实质是反映整个输送带的强度变化,其气候意义要大于THC的局地振荡.  相似文献