Relationship between summer rainfall anomalies and sub-seasonal oscillation intensity in the ChangJiang Valley in China     

《Dynamics of Atmospheres and Oceans》2015

Sub-seasonal variability of summer (May–October) rainfall over the ChangJiang Valley exhibits two dominant timescales, one with a quasi-biweekly (QBW) period (10–20 days) and the other with an intraseasonal oscillation (ISO) period (20–60 days). A significant positive correlation (at a 99% confidence level) was found between the summer precipitation anomaly and the intensity of the QBW and ISO modes in the region. By examining the composite structure and evolution characteristics, we note that the QBW mode is characterized by a northwest–southeast oriented wave train pattern, moving southeastward. The perturbations associated with the ISO mode propagate northwestward in strong ISO years but southeastward in weak ISO years. A marked feature is the phase leading of low-level moisture to convection in both the QBW and ISO mode. When the summer rainfall is strong in the ChangJiang Valley, large-scale atmospheric conditions in the strong QBW/ISO activity region are characterized by deeper moist layer, convectively more unstable stratification and greater ascending motion. Such mean conditions favor the growth of the QBW and ISO perturbations. Thus, a significant positive correlation between the summer precipitation and the strength of sub-seasonal variability arises from the large-scale control of the summer mean flow to perturbations.  相似文献   

日本海中尺度涡旋时空变化特征研究     

杨霄  张永垂  夏长水  董昌明  胡楠  汪浩笛  陈诗尧 《海洋学报》2022,44(6):22-36

本文利用1993–2019年基于海表面高度异常的涡旋数据集和高度计数据统计分析了日本海区域中尺度涡旋的大小、极性、生命周期、振幅、传播等表面特征的时空变化规律。27年间,共探测到1 429个涡旋,气旋和反气旋数量基本相当,其中气旋675个,反气旋754个。两种极性涡旋均具有较强的季节变化:秋季较多,冬季次之,春季最少。郁陵盆地、大和盆地等为涡旋多发区域呈现西南–东北向带状分布。其中,南部海域反气旋占优,靠近津轻海峡的北部海域气旋占优。西部和南部受东韩暖流和对马暖流的驱动,涡旋移动方向与流场基本一致,北部涡旋与黎曼寒流以及副极地锋流有关。研究表明,动力学不稳定是涡旋在秋冬季大量产生的重要原因。此外,半封闭盆地、局地流场以及复杂的海气相互作用等都可能会对涡旋的产生和消亡造成一定影响。  相似文献   

Influence of sequential tropical cyclones on phytoplankton blooms in the northwestern South China Sea     

Wang  Tongyu  Zhang  Shuwen  Chen  Fajin  Ma  Yonggui  Jiang  Chen  Yu  Jie 《中国海洋湖沼学报》2021,39(1):14-25

Upper ocean responses to the passage of sequential tropical cyclones over the northwestern South China Sea(SCS) in 2011 were investigated using satellite remote sensing data,Argo reanalysis data,and an array of mooring data.We found that the sea surface low temperature region lasted for more than 38 days and two phytoplankton blooms occurred after the passage of sequential tropical cyclones.The upper ocean cooling reached 2-5℃ with a right-side bias was observed along the typhoon track to about 200 km.The maintenance of low temperature region and the two phytoplankton blooms were mainly driven by upwelling and near-inertial turbulence mixing induced by the sequential tropical cyclones.The first phytoplankton bloom appeared on the 7~(th) day after the passage of the three tropical cyclones,and the chlorophyll-a(chl-a) concentration increased by 226%,which may be mainly driven by typhoons induced upwelling.The second phytoplankton bloom occurred on the 30~(th) day,the chl-a concentration increased by290%.Further analysis suggested that only the typhoons with similar characteristics as Nesat and Nalgae can induce strong near-inertial oscillation(NIO).Strong turbulent mixing associated with the near-inertial baroclinic shear instability lasted for 26 days.The measured mean eddy diffusivity in the upper ocean was above 10~(-4) m~2/s after typhoon Nesat.Enhancement of the turbulent mixing in the upper ocean helped to transport nutrient-rich cold waters from the deep layer to the euphotic layer,and is a maj or mechanism for the long-term maintenance of low temperature region as well as the second phytoplankton bloom.  相似文献   

QuikSCAT卫星散射计矢量风检验及南海月平均风场特征分析   总被引：4，自引：1，他引：3  

王慧鹏  王春明  项杰  李健  刘春霞 《气象科学》2014,34(1):54-59

采用中国科学院南海海洋研究所2008年建设的,西沙海洋观测研究站上的自动气象站实测数据,对亚太数据研究中心提供的近实时QuikSCAT卫星遥感风场资料(2008年4月6日—12月31日)进行了检验和统计特征分析,得出:这两者风速的相关系数为0.86,平均偏差为-1.50 m/s,均方根误差为1.71 m/s,表明QuikSCAT卫星遥感风场资料在南海具有很高的适用性。在此基础上,利用QuikSCAT卫星遥感的月平均风场资料分析了南海月平均风场特征。结果表明:(1)南海季风10月到次年3月盛行东北风,6—8月盛行西南风,4、5、9月为季风转换季节;(2)存在两个平均风速大值中心,一个位于南海南部(10°N,108°E)附近,另一个位于台湾海峡附近,其位置和强度会随着季节变化而变动。  相似文献   

Parsivel激光雨滴谱仪观测较强降水的可行性分析和建议   总被引：3，自引：2，他引：1  

胡子浩  濮江平  张欢  张小鹏 《气象科学》2014,34(1):25-31

为了研究OTT-Parsivel激光雨滴谱仪(简称Parsivel)在较强降水观测中应用的可行性,用南京地区2012年6—7月份4个典型的降水个例,对Parsivel和SL3-1翻斗式雨量计(简称雨量计)的累积降水量、降水强度观测资料进行对比分析,并与人工雨量筒观测作以比较。结果表明:Parsivel测值是可信的,在累积降水量观测上,与雨量计具有很好的相关性,但测值始终偏高,该现象主要是粒子相互遮挡造成的。雨量计的反应时间,明显滞后于Parsivel。雨量计测值接近人工测值;而Parsivel与人工测值的偏差明显大于雨量计。结合实验分析与业务应用,提出3点使用建议:(1)仪器应架设在无遮蔽物的开阔地带。(2)采样周期应随着降水强度(地理位置)的不同而改变。(3)对降水微物理参量特征以及粒子谱分析时,可剔除直径过大、速度很低的粒子。  相似文献   

西北太平洋海域风浪、涌浪、混合浪波浪能资源特征   总被引：1，自引：0，他引：1  

郑崇伟  游小宝  陈晓斌  李燕 《气象科学》2014,34(4):408-413

用ECMWF的ERA-40海浪再分析资料,应用波浪能流密度计算方法,对西北太平洋海域的风浪能、涌浪能、混合浪能展开研究。结果表明:(1)波浪能流密度呈现出显著季节性差异。混合浪能流密度表现为冬高夏低;春、夏、秋季的涌浪能流密度明显大于风浪能流密度,冬季相反;(2)混合浪能流密度的大值区主要分布于阿留申群岛附近海域,高值中心可达60 kW/m以上;近海的大值区主要分布于琉球群岛—巴士海峡—传统的南海大风区一带,年平均值在4 kW/m以上,南海北部可达12 kW/m以上;(3)黄渤海的涌浪和混合浪能流密度峰值出现在8—9月,波谷出现在6月。风浪能流密度峰值出现在11月—次年3月,波谷出现在6—8月,均呈现双峰型月变化特征。东海、南海北部、南海中南部海域能流密度的月变化特征相似,都为双峰型,12月—次年4月的能流密度整体较高,波峰出现在12月,波谷出现在5—7月;(4)2 kW/m以上混合浪能流密度出现的频率较高,近海低于大洋;(5)0.5 m以上有效波高出现的频率都非常高,中国近海稍低于大洋;(6)涌浪能流密度的稳定性明显好于风浪能流密度;大洋的能流密度稳定性明显强于近岸。1月份能流密度的稳定性最好,4月和7月次之,10月的稳定性最差。  相似文献   

Variability of tropical cyclone in high frequent occurrence regions over the western North Pacific   总被引：1，自引：0，他引：1  

Yuxing Yang  Fei Huang  Faming Wang 《中国海洋大学学报(英文版)》2014,13(3):347-355

In this study, three high frequent occurrence regions of tropical cyclones(TCs), i.e., the northern South China Sea(the region S), the south Philippine Sea(the region P) and the region east of Taiwan Island(the region E), are defined with frequency of TC's occurrence at each grid for a 45-year period(1965–2009), where the frequency of occurrence(FO) of TCs is triple the mean value of the whole western North Pacific. Over the region S, there are decreasing trends in the FO of TCs, the number of TCs' tracks going though this region and the number of TCs' genesis in this region. Over the region P, the FO and tracks demonstrate decadal variation with periods of 10–12 year, while over the region E, a significant 4–5 years' oscillation appears in both FO and tracks. It is demonstrated that the differences of TCs' variation in these three different regions are mainly caused by the variation of the Western Pacific Subtropical High(WPSH) at different time scales. The westward shift of WPSH is responsible for the northwesterly anomaly over the region S which inhibits westward TC movement into the region S. On the decadal timescale, the WPSH stretches northwestward because of the anomalous anticyclone over the northwestern part of the region P, and steers more TCs reaching the region P in the greater FO years of the region P. The retreating of the WPSH on the interannual time scale is the main reason for the FO's oscillation over the region E.  相似文献   

北京一次大暴雨的水汽收支和微物理过程数值分析   总被引：1，自引：1，他引：0  

岳甫璐  王春明  王慧鹏 《气象科学》2014,34(6):692-699

利用NCEP1°×1°再分析资料和常规气象观测资料,使用WRF模式对2012年7月21日发生在北京地区的一次特大暴雨天气过程进行数值模拟。在模拟结果的基础上,分析了此次暴雨过程的形势演变和水汽条件,并分别计算了暴雨发生过程中北京全市范围内的水汽输送、水汽收支、大气可降水量和空中各相态水物质的量值大小、空间分布情况及其相互转化关系。结果发现:这次降水主要受高空槽、低涡和地面切变线的影响。有东南、西南两条水汽输送通道,计算区域上空水汽收支变化与地面雨强的演变对应很好。中低层持续而强烈的水汽净输入,为暴雨的发生发展提供了很好的水汽条件。北京各站点大气可降水量普遍超过历史极值,反映了降水的极端性。降水发展不同阶段,云内微物理过程存在差异,降水量初期以暖雨为主,降雨量不大,之后冷雨过程增强,降水量迅速增大。  相似文献   

斜压罗斯贝变形半径优化的误差相关尺度及其对最优插值效果的改进   总被引：2，自引：0，他引：2  

王公杰  张韧  陈建  王辉赞  王璐华 《海洋学报》2014,36(1):109-118

利用最优插值方法进行三维温盐场重构时,如何正确估算背景场误差协方差至关重要。针对背景场误差协方差主要取决于误差相关尺度的问题,本文提出了用中国东部海域及其附近海域的最新的高分辨率气候态数据进行斜压罗斯贝变形半径优化其误差相关尺度计算的研究方案和技术途径;对比分析了均一化相关尺度方案和法国ISAS系统尺度方案,讨论了变形半径对最优插值的影响。结果表明:均一化相关尺度方案的均方根误差小于ISAS方案,但温度场过于平滑,难以刻画一些重要的物理现象;相比而言,本文提出的基于变形半径的相关尺度方案在取2倍变形半径时,不仅均方根误差在各水平层较小,且温度场能够更好地刻画四国海盆海域涡旋及黑潮影响的温度场三维结构。由于实际海洋中各层物理过程的尺度存在差异,实际应用时各层的最优尺度设置也应有所不同。  相似文献   

Impact of recirculation on the East Greenland Current in Fram Strait: Results from moored current meter measurements between 1997 and 2009     

《Deep Sea Research Part I: Oceanographic Research Papers》2014

  相似文献