【作者】 岳彩军；

【导师】 陆维松；

【作者基本信息】 南京气象学院 ， 气象学， 2003， 博士

【摘要】 本文利用925hPa NCEP／NCAR再分析风场资料替代FSU风场资料对Zebiak—Cane海气耦合模式(简称ZC耦合模式)的初始强迫风场进行了改进，结合模拟资料与观测资料对1997／1998 El Nino事件进行了诊断分析，提出了1997／1998 El Nino发生、发展的一种新的可能机制，进而对El Nino成因机制进行了进一步完善，最后尝试对改进初始强迫风场后的ZC耦合模式的大气模式中的潜热加热计算的参数化方案进行了改进。结果表明： (1)80、90年代925hPaNCEP／NCAR再分析风应力距平(以下简称NCEP风应力距平)较FSU风应力距平与观测的SSTA匹配更为合理。NCEP风应力距平不仅较FSU风应力距平对ZC海洋模式初始化的效果好，尤其在90年代更为显著，而且以NCEP风应力距平替代FSU风应力距平作为ZC耦合模式的初始强迫风场提高了该耦合模式的预报能力，可以提前6—8个月成功地预报出1997／1998 El Nino事件。改进初始强迫风场后的ZC耦合模式(以下简称ZCW耦合模式)没有表现出明显的“春季预报”障碍现象，但对冷事件的预报能力仍然有限。 (2)对1997／1998 El Nino事件进行热力诊断分析表明，NINO4区纬向平流项与经向平流项对SSTA增加的贡献相当，且都大于垂直上翻流对SSTA增加的贡献；NINO3区经向平流项对SSTA增加的贡献最大，纬向平流项与垂直上翻流对SSTA增加的贡献相当；NINO1+2区，仍然是经向平流项对SSTA增加的贡献最大，而纬向平流项对SSTA增加的贡献小于垂直上翻流对SSTA增加的贡献。总的看来，经向平流项对SSTA增加的贡献最大，纬向平流项与垂直上翻流对SSTA增加的贡献相当。从NINO4区到NINO1+2区，纬向平流项对SSTA增加的贡献基本呈减小趋势，而经向平流项和垂直上翻流对SSTA增加的贡献却是呈上升趋势。在整个过程中热力阻尼项对SSTA变化基本都是起抑制作用，且从NINO4到NINO1+2区抑制作用依次增强。 (3)在1997／1998 El Nino事件期间，西太平洋暖池海表温度变化及异常西风和东太平洋暖池海表温度变化及异常北风两者都与NINO3指数变化密切相关。将东、西太平洋暖池及异常北风、西风一并结合起来考虑，提出1997／1998 El Nino事件发生、发展的一种新的可能机制：异常西风激发东传的暖Kelvin波对东太平洋的冷上翻流有抑制作用，从而有利于东太平洋海表温度增加；异常西风驱动西太平洋暖池东端暖水向东伸展直接有利于东太平洋海表温度增加；东传的异常西风可以通过埃克曼漂流效应将赤道两侧的海表暖水向赤道辐合从而加强了赤道附近的下沉流，也有利于东太平洋赤道附近海表温度增加。几乎与此同时，北风距平通过产生北风吹流将东太平洋暖池暖水由北向南输送至赤道附近直接导致NINO3区海表温度增加。上述增温因素的叠加作用共同导致了1997／1998 El Nino事件迅速发生、异常强大。此外，还初步分析了1997／1998 El Nino事件期间异常西风、北风的来源。 (4)东太平洋暖池气候平均海表温度存在明显的季节变化特征且与El Nino事件春季发生、夏季发展、秋季达到成熟及冬季衰亡的成长过程非常相似，同时结合对异常经向风的分析结果，提出了东太平洋暖池及经向风异常对ENSO事件发生。发展作用的概念模型：北风距平爆发通过产生北风吹洋流的作用将东太平洋暖池暖水由北向南输送至赤道附近从而有利于NINO3区海表温度上升，与此同时，东太平洋暖池赤道上异常经向风辐合不仅能导致北来的暖水在赤道附近堆积而且辐合的风场对赤道附近的冷上翻流有抑制作用，从而有利于NffeO3区海表温度的增加，上述增温因素都有利于（不利于）EI Nino事件（La Nina）事件的发生、发展。因此，将东太平洋暖池及异常经向风和西太平洋暖池及异常西风一并结合起来考虑，则对EI Nino事件成因机制作了进一步完善。进一步分析表明，东太平洋暖池及异常经向风仅对日 Nino（La Nina）事件发生、发展起促进（抑制）作用而不起决定作用。此外，对 80、90年代日 Nino事件的特性差异进行了初步分析。 （5）数值试验结果表明，改变（去除、增加）东太平洋暖池区气候平均海表温度。经向洋流、经向风及异常经向洋流、经向风对ZCW耦合模式预报ENSO事件的能力能产生不同的影响。进一步结合 1997／1998 EI Nino事件对东太平洋暖池区海、气状况进行数值试验发现，改变（去除、增加）东太平洋暖地区气候平均海表温度能对 ZCW耦合模式预报 1997／1998 EI Nino事件能力产生显著的影响，而分别改变该区气候平均北经向洋流、北经向风则对耦合模式预报该暖事件的能力几乎没有影响：改变（去除、增加）东太平洋暖地区北经向洋流距平能明显地改变ZCW耦合模式在发展阶段之前对 1997／1998 EI Nino事件的预报效果，而在各个阶段改变东太平洋暖池区经向北风距平都能明显改变耦合模式对该暖事件强度的预报效果，甚至能影响耦合模式提前成功预报出该暖事件的起始时间。数值试验结果间接验证了基于观测资料分析所得到的结论：东太平洋暖池及北风异常二者对 1997／1998 EI Nino事件发生、发展起重要的促进作用。 （6）利用Wears关于计算潜热加热的参数化方案替代ZCW耦合模式的大气模式中的?更多还原

【Abstract】 Using 925hPa NCEP/NCAR reanalysis wind data to replace FSU wind data improves initialization impact wind field of Zebiak-Cane ocean-atmosphere coupled model (hereafter referred to as ZC coupled model). Subsequently, 1997/1998 El Nino is analyzed on the base of simulated and observed data, and a new possible mechanism for the evolution of the 1997/1998 El Nino is advanced. Then genesis mechanism for ENSO is perfected further. At last, the parameterization scheme for latent heat calculation included in atmosphere model of ZC coupled model with revised initialization impact wind is modified. The results are as follows:(1) The 925hPa NECP/NCAR reanalysis wind stress anomaly (hereafter referred to as NECP wind stress anomaly) is more fit to observed SSTA than the FSU wind stress anomaly both in 1980s and in 1990s. Employing the former to take the place of the latter as the initialization impact wind not only make the ZC ocean model have a better skill, especially in 1990s but also improve the forecast ability of the ZC coupled model, which can succeed in predicting 1997/1998 El Nino before 6 to 8 months. The ZC coupled model with the revised initialization impact wind (hereafter referred to as ZCW coupled model) is not clearly confronted with "spring forecast barrier" but has limited capability to forecast cold event.(2) The thermodynamic analysis of 1997/1998 El Nino shows that in NINO4 the contribution of the zonal and the meridional advection to the SSTA increase are equivalent and both bigger than that of the vertical upwelling flow; in NINO3 the contribution of the meridional advection to SSTA increase is the most and the counterparts of the zonal advection and vertical upwelling flow are equivalent; in NINO 1+2 it is still the most that the contribution of the meridional advection to SSTA increase, and the counterpart of the zonal advection is less than that of the vertical upwelling flow. In a whole, the contribution of the meridional advection to the SSTA increase is the most and the counterparts of the zonal advection and upwelling flow are equivalent. From NINO4 to NINO 1+2 the contribution of the zonal advection to SSTA increase decreases approximately in such a way that the counterparts of the meridional advection and vertical upwelling flow increase. In the whole process the thermodynamic damping suppresses basically the SSTA increase, and the suppression becomes strong gradually.(3) During the 1997/1998 El Nino we find western Pacific warm pool (WPWP) SST variation, abnormal west wind, eastern Pacific warm pool (EPWP) SST variation and abnormal north wind are associated with the NINO3 index change. Based on the EPWP and WPWP in conjunction with abnormal north and west wind, a new possibleiiimechanism is provided for the evolution of the 1997/1998 El Nino. To be specific, the warm Kelvin wave propagating to east excited by the abnormal west wind can suppress the cold upwelling flow in the eastern Pacific, which, in turn, is favorable to the eastern Pacific SST increase; abnormal west wind can make the warm water of the WPWP east edge extend to east, which is conductive directly to eastern Pacific SST increase; the abnormal west wind propagating to east can make the sea surface warm water near two equatorial laterals converge to the equator by Ekman drifting, which, in rum, strengthens the downwelling flow near the equator, leading to eastern Pacific SST increase. Almost meanwhile, the north wind anomaly brings EPWP warm water to equatorial vicinity by producing north ocean flow, which causes directly NINO3 SST increase. As a result, such factors favoring to SST increase give rise to 1997/1998 El Nino quick occurrence and abnormal strength. Furthermore, the origins of abnormal west and north wind during the 1997/1998 El Nino are explored primarily.(4) The EPWP climatologic SST has a clear intraseasonal variability, which is very similar to El Nino growth process, i.e., occurring in spring, developing in summer, maturing in autumn and decaying in winter. Based on the analysis of meri更多还原