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11.
利用澳大利亚气象局MJO(Madden-Julian Oscillation)指数(1979—2015年)资料、NCEP/NCAR全球再分析格点资料和中国气象局上海台风研究所台风资料,分析了MJO不同位相、强度与7—10月影响海南岛的热带气旋活动的关系。结果表明:7—10月影响海南岛的热带气旋活跃期和沉寂期与MJO的位相和强度有关,但7—8月和9—10月的热带气旋活跃期和沉寂期对应的MJO位相和强度有所不同。在7、8月,当MJO处于强的第3、6位相或弱的第4位相时有利于热带气旋影响海南岛,当MJO处于强的第1、2、8位相时则不利于热带气旋影响海南岛。在9、10月,当MJO处于7位相时有利于热带气旋影响海南岛,当MJO处于1位相时则不利于热带气旋影响海南岛。无论是7、8月还是9、10月,有利于热带气旋偏多和偏少的MJO位相对应的环流形势基本相反。 相似文献
12.
ABSTRACTA detailed analysis is performed on an inland-penetrating atmospheric river (AR) driven by and coupled to a Colorado cyclone in the first week of February 2016. This winter weather system was initiated by a trough of low pressure moving across the Rocky Mountains from the California coast. The low-level jet ahead of the trough was capable of extracting water vapour from the Gulf of Mexico to feed a cyclone on the lee side of the Rocky Mountaains, and the jet stream eventually transformed into a powerful AR. The warm, moist flow from the south produced a narrow band of heavy precipitation along the major axis of the AR across the central and eastern United States and generated significant freezing rain in parts of the northeastern United States and eastern Canada as the AR flowed over the warm front. It is suggested that, in an operational weather forecasting and warning environment, ARs can be easily identified by using the vertically integrated horizontal water vapour transport, and the major AR contribution to heavy precipitation can be estimated from the horizontal moisture convergence. It is demonstrated that the AR analysis in this case can assist operational meteorologists in understanding and conceptualizing winter storm development and the associated high-impact weather pattern. The operational predictability of this winter storm and its possible teleconnection with the Madden–Julian Oscillation (MJO) are also investigated. Our lagged composite analysis reveals that a statistically significant increase in water vapour transport from the Gulf of Mexico over the North American continent could occur about 10–20 days after the MJO-related convection anomaly reaches the tropical Indian Ocean. 相似文献
13.
福建前汛期持续性强降水的大气低频特征分析 总被引：1，自引：0，他引：1
本文采用福建1979—2010年66个气象站逐日降水资料和NCEP再分析资料和OLR资料,揭示了福建前汛期降水的低频特征,分析了福建前汛期持续性强降水同期的大气低频特征以及前期低频信号的演变特征,结果表明:(1)福建前汛期降水存在显著的低频周期,出现频率较高的前三个低频周期分别为:10~20、30~60和20~30 d;约63%的年份出现两种以上显著的低频周期;10~90 d低频变化占前汛期降水总方差的20%~30%;(2)前汛期总雨量与降水低频信号的强度呈显著正相关关系,持续性强降水的强度和持续时间与降水的低频特征关系密切,以BWO(ISO)为主的年份,持续性强降水的持续时间较短(长)。(3)福建前汛期持续性强降水期间日本以东、索马里以东和南海三个关键区皆为低频反气旋,日本至渤海湾南下的冷空气与索马里越赤道气流、南海南部越赤道气流在福建上空持续相遇形成低频气旋,导致福建上空低层低频辐合、高层低频辐散,对流活跃。(4)福建前汛期持续性强降水与热带及副热带大气低频变化密切相关,热带MJO的东传以及东亚西北太平洋地区低频信号的北传对福建持续性强降水过程的延伸期预报具有一定的指示意义。 相似文献
14.
IAP9L AGCM中大气季节内振荡的时空特征 总被引：4，自引：1，他引：3
根据IAP9LAGCM10年积分850hPa纬向风的逐日输出结果,应用Morlet小波分析方法,研究了该模式中的大气季节内振荡(MJO),结果表明该模式能抓住热带MJO的基本时空特征,模式中MJO的显著周期为36天;另外还分析了16～64天重构信号的时间经度剖面图,发现该MJO为东传,这与实际较一致;最后用EOF方法分析了模式大气中850hPa5天平均速度势,揭示出该MJO在全球表现为行星尺度1波和2波的特征。 相似文献
15.
This study evaluates the ability of four versions BCC (Beijing Climate Center or National Climate Center) models (BCC_AGCM2.1, BCC_AGCM2.2, BCC_CSM1.1 and BCC_CSM1.1m) in simulating the MJO phenomenon using the outputs of the AMIP (Atmospheric Model Intercomparison Project) and historical runs. In general, the models can simulate some major characteristics of the MJO, such as the intensity, the periodicity, the propagation, and the temporal/spatial evolution of the MJO signals in the tropics. There are still some biases between the models and the observation/reanalysis data, such as the overestimated total intraseasonal variability, but underestimated MJO intensity, shorter significant periodicity, and excessive westward propagation. The differences in the ability of simulating the MJO between AMIP and historical experiments are also significant. Compared to the AMIP runs, the total intraseasonal variability is reduced and more realistic, however the ratio between the MJO and its westward counterpart decreases in the historical runs. This unrealistic simulation of the zonal propagation might have been associated with the greater mean precipitation over the Pacific and corresponded to the exaggeration of the South Pacific Convergence Zone structure in precipitation mean state. In contrast to the T42 versions, the improvement of model resolution demonstrate more elaborate topography, but the enhanced westward propagation signals over the Arabia Sea followed. The underestimated (overestimated) MJO variability over eastern Indian Ocean (Pacific) was assumed to be associated with the mean state. Three sets of sensitive experiments using BCC_CSM1.1m turn out to support this argument. 相似文献