两次典型极端低温过程低频特征分析
Low-Frequency Features during the Two Typical Extreme Cold Events in China
查看参考文献34篇
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文摘
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对1960年1月至2016年2月NCEP/NCAR再分析资料进行Butterworth带通滤波,保留周期为30~ 60天的低频信号,采用低频天气图方法分析了2008年初低温雨雪冰冻灾害和2016年“霸王级”寒潮的低频特征,揭示典型极端低温事件中低频系统的特征及其生成、演变过程。结果表明: 2008年初环流系统具有明显的30~ 60天低频振荡,位势高度正(负)距平对应低频流场的低频高(低)压,纬向风速正距平与低频风速大值区一致。过程期间北极涛动(Arctic Oscillation,AO)为正位相,有利于中东急流的加强和阻塞高压的维持,进而造成持续低温。2016年初环流系统的30~ 60天低频特征不明显,但低频低压能反映极涡的生成、演变。此外低频天气图能反映寒潮前后AO位相的转变,AO由12月下旬的正位相转变为1月初的负位相,中纬度纬向环流减弱而经向环流增强,极涡中心的冷空气在阻塞高压脊前偏北气流的引导下入侵中国,可能是造成剧烈降温的主要原因。两次过程中,低频低压、高压的分布和冷空气南下路径不同,但低频流场均落后天气过程2天左右表现出AO位相的转变,通过追踪和判断低频信号的路径,结合数值预报产品,可为类似的极端低温过程的延伸期预报提供参考。 |
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其他语种文摘
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Keeping oscillation of low frequency of 30~60 days,Butterworth band-pass filter method was used to process the NCEP /NCAR reanalysis data. Based on the application of the low-frequency synoptic map (LFSM), low frequency features of the two extreme low temperature events including durative low temperature,snow fall and freezing weather in early 2008 and“overlord”-level cold wave in 2016 were analyzed in order to reveal the characteristics,forming and evolution of the low frequency systems during these two events. The results are as follows: During durative low temperature,snow fall and freezing weather in early 2008,large-scale atmospheric systems including blocking-high and upper-level jet stream all featured a distinct 30~60 days oscillation. The positive (negative) anomaly of geopotential height was closely coincided with the low frequency high (low) pressure of the low frequency systems,and the center of positive zonal wind anomaly was consistent with the high value center of low frequency zonal wind. During this event,the positive phase of the Arctic Oscillation (AO) favored the strengthening of the Middle East jet and the maintenance of the blocking high,resulting in durative low temperature in south China. The 30~60 days oscillation features of the weather systems including upper-level jet and blocking high were not so obvious during“overlord”-level cold wave in 2016 as that during early 2008. However,the low pressure of low frequency can describe the generating and developing of the polar vortex. Meanwhile the low-frequency synoptic map reflected the phase transition of AO before and after the cold wave. The phase of AO was positive in later December 2015 while negative in early January 2016,which led to the weakened latitudinal circulations of the middle latitudes and the strengthen longitudinal circulations. Then under north air stream at the front of blocking high ridge guidance,the strong cold air in the middle of polar vortex invaded southern China. These can be concluded as the main cause of the sharp drop in temperature. Although the position distribution of low-frequency low pressure,high pressure and the south path of cold air are different,the low-frequency flow field showed the phase transition of AO lagging behind the synoptic flow field about two days during the two events. By tracking and estimate the path of such low-frequency signal in the LFSM. This result can provide reference for extended-range weather forecast of similar extreme cold events by using the numerical forecast products. |
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来源
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高原气象
,2018,37(5):1341-1352 【核心库】
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DOI
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10.7522/j.issn.1000-0534.2018.00035
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关键词
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低频天气图
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低温雨雪冰冻
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“霸王级”寒潮
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极涡
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地址
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兰州大学大气科学学院, 甘肃省干旱气候变化与减灾重点实验室, 甘肃, 兰州, 730000
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语种
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中文 |
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文献类型
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研究性论文 |
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ISSN
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1000-0534 |
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学科
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大气科学(气象学) |
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基金
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国家自然科学基金项目
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兰州大学中央高校基本科研业务费专项基金
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文献收藏号
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CSCD:6349215
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