Rol of the seasonal cycle and interseasonal variability on the interannual variability of the climate system.

季节周期和季节间变率对气候系统年际变率的作用。

基本信息

批准号：
05452077
负责人：
YASUNARI Tetsuzo
金额：
$ 3.2万
依托单位：
University of Tsukuba
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1993
资助国家：
日本
起止时间：
1993 至 1995
项目状态：
已结题

项目摘要

The convective activities at the tropical western Pacific is the major source of atmospheric energy which controls the global climate system. This study has investigated the role of the interseasonal variability, seasonal cycle, and interannual variability of the convective activities there upon the activities in Asian monsoon and the atmosphere-ocean interactions at the tropical Pacific.The result of this study may be summarized as follows :1) An abrupt shift of the active convection area in conjunction with the anomalous interseasonal variability is found. This jump is related to the onset of monsoonal circulation in Asia and the onset of Baiu in Japan.2) The jump of the active convection area is related to the seasonal change of sea surface temperature and is controlled by the intensity of the convection activities through the land-sea interactions.3) The interannual variability is resulted from the intensity of the unusual behavior of the interseasonal variability associated with the jump of the active convection area.On the other hand, a simple barotropic model experiment is carried out to examine the cause of the interseasonal and interannual variabilities. The forced annual cycle is expected to excite its harmonics and subharmonics by the internal nonlinear dynamic modulationwhich tern out to be interseasonal and internnual variabilities. The results, however, show that the spectral features with and without the forced annual cycle are not altered by the inclusion of the annual cycle, except for the isolated spectral peak associated with the annual cycle forcing.We suggest from the results of this numerical experiment that the harmonics and subharmonics, such as semiannual and biennial oscillations, are not excited by the nonlinear dynamic modulation of the forced annual cycle. Namely, the low-frequency variabilities, such as the semiannual and biennial oscillations, must be excited by the external forcing of the atmosphere rather than the internal dynamics.

热带西太平洋的对流活动是控制全球气候系统的主要大气能量来源。本研究探讨了该地区对流活动的季节变化、季节周期和年际变化对亚洲季风活动和热带太平洋大气-海洋相互作用的作用。研究结果可概括如下： 1）发现活跃对流区突然发生变化，并伴有异常的季节间变化。这种跳跃与亚洲季风环流的爆发和日本白雨的爆发有关。 2）对流活跃区的跳跃与海面温度的季节变化有关，并受对流活动强度的控制，通过3）年际变率是由与活跃对流区跳跃相关的季际变率异常行为的强度引起的。另一方面，进行了简单的正压模型实验。检查季节间和年际变化的原因。强制年周期预计会通过内部非线性动态调制激发其谐波和分谐波，从而产生季节间和年间变化。然而，结果表明，除了与年循环强迫相关的孤立光谱峰值外，有和没有强迫年循环的光谱特征不会因包含年循环而改变。我们从这个数值实验的结果中建议谐波和次谐波，例如半年和两年振荡，不会被强制年周期的非线性动态调制所激发。也就是说，低频变化，例如半年一次和两年一次的振荡，一定是由大气的外部强迫而不是内部动力激发的。