长江中下游冬季两类冷空气活动事件的环流差异及其与急流的关系          下载免费PDF全文

朱璇  张耀存  尹婧楠 《气象科学》2023,43(3):326-336

利用1981—2020年台站观测的降水和最低气温资料,从长江中下游地区冬季冷空气活动事件中分出"降温有降水"和"降温无降水"两类事件(简称为"冷湿"和"冷干"事件),结合再分析资料,分析两类事件的冷暖空气活动特征和大气环流差异,进而探讨其与急流的联系。结果发现,长江中下游冷空气活动事件发生频次逐年减少,其中冷干事件发生频次逐年减少,冷湿事件发生频次显著增加,且冷湿事件的降温幅度大于冷干事件。冷湿事件发生时,高层副热带急流北移、极锋急流偏弱,中层存在倾斜槽脊、副热带高压偏西,低层西伯利亚高压增强,有来自西南的暖湿气流在长江中下游地区辐合上升;冷干事件发生时,高层副热带急流偏弱、极锋急流偏强,中层槽脊倾斜程度偏弱、副热带高压偏东,低层西伯利亚高压南移,有来自北方的偏干气流在长江中下游地区辐散下沉。此外,与冷湿事件相比,冷干事件过程中急流强度指数和经向风位置指数的波动更加频繁,冷空气活动持续时间更短。  相似文献   

Analysis of resonant curves and phase portrait in the earth–moon system by using its unperturbed solution and earth’s equatorial ellipticity     

《New Astronomy》2022

In this research article, we have investigated resonant curves due to the rate of change of earth’s equatorial ellipticity parameter $\left(\dot{\gamma }\right)$, steady-state value of the angular velocity of the moon $\left({\dot{\theta }}_{mo}\right)$, and angular velocity of barycenter $\left(\dot{{\alpha }_0}\right)$ in the Earth-Moon system. Equations of motion of the moon are determined in a spherical coordinate system with the help of the gravitational potential of the earth. By using the unperturbed solution, equations of motion of the moon reduced into the second-order differential equation. From the solution it is observed that resonance occurs due to the frequencies $\dot{\gamma }$, ${\dot{\theta }}_{m0}$, and $\dot{{\alpha }_0}$ at the resonant points ${\dot{\theta }}_{m0}=2\dot{\gamma }$, $3{\dot{\theta }}_{m0}=2\dot{\gamma }$, ${\dot{\theta }}_{m0}=\dot{\gamma }$, ${\dot{\theta }}_{m0}={\dot{\alpha }}_0$. Finally, we have analyzed the phase portrait and phase space by method of Poincaré section when the system is free from forces.  相似文献   

北方盛夏台风暴雨的天气型及其年际变率   总被引：18，自引：5，他引：18       下载免费PDF全文

仇永炎 《气象》1997,23(7):3-9

１９４９－１９９６年的４８个盛夏期间，我国北方地区共有１０次过程雨量最大值大于４００ｍｍ的台风暴雨实例。从台风与西风槽相互作用的观点对这１０例进行分类。根据实践经验可以把台风槽、可套西风槽、日本海渤海高压、上海地区８５０ｈＰａ东南风急流以及弱冷空气入侵台风等５因子作为分型的判据。结果指出，１０例中只有发生于１９５０、１９６３、１９７５、１９８４和１９９６年８月上旬的５例属于相互作用型，其他５例不是  相似文献