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NCEP/NCAR再分析资料中北半球夏季海平面气压的年代际变化 总被引:1,自引:0,他引:1
NCEP/NCAR再分析资料集中1948—2005年北半球夏季海平面气压(sea level pressure,SLP)场具有明显的年代际变化特征,主要在东亚和北非大陆地区以及极地地区。20世纪60年代中后期和70年代中后期夏季SLP场有两次跃变过程。对于北半球夏季SLP的这次年代际变化过程而言,20世纪60年代末首先于北欧地区出现距平变化,然后逐渐向东南方向移动,70年代早期贝加尔湖地区开始出现正距平信号,之后这种正距平信号开始往南移,70年代中期东亚大陆出现正距平中心。另外,20世纪60年代中期西北大西洋SLP距平也开始了转变,之后分别向南、北移动,于70年代早期加强了北欧的正距平强度,同时非洲北部也开始了SLP距平的转变。 相似文献
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采用1980-2004年5-8月NCEP/NCAR逐日再分析资料,将105°E和125°E越赤道气流增强过程按一定标准进行取样,并对增强过程中越赤道气流的变化特点及其相应的南、北半球环流特征进行分析,结果表明:越赤道气流的增强往往对应着通道南侧或北侧从热带到副热带地区的环流调整,而这种环流调整在南半球主要指澳洲冷空气活动,在北半球主要为辐合带的变化,二者是影响越赤道气流的主要环流因子;北半球辐合带的变化与西太平洋副高的东西振荡有密切关系,前者的分布形态在一定程度上决定了南半球环流及越赤道气流变化对北半球热带外环流的影响情况;125°E越赤道气流比105°E越赤道气流的增强过程通常更为显著,这与它们对应的南、北半球环流调整的差异有关。 相似文献
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It is generally thought that the influence of comparable track typhoons is approximately similar,
but in fact their wind and especially their rainstorm distribution are often very different. Therefore, a
contrastive analysis of rainstorms by tropical cyclones (TCs) Haitang (0505) and Bilis (0604), which are of
a similar track, is designed to help understand the mechanism of the TC rainstorm and to improve
forecasting skills. The daily rainfall of TC Haitang (0505) and Bilis (0604) is diagnosed and compared.
The result indicates that these two TCs have similar precipitation distribution before landfall but different
precipitation characteristics after landfall. Using NCEP/GFS analysis data, the synoptic situation is
analyzed; water vapor transportation is discussed regarding the calculated water vapor flux and divergence.
The results show that the heavy rainfall in the Zhejiang and Fujian Provinces associated with Haitang
(0505) and Bilis (0604) before landfall results from a peripheral easterly wind, a combination of the
tropical cyclone and the terrain. After landfall and moving far inland of the storm, the precipitation of
Haitang is caused by water vapor convergence carried by its own circulation; it is much weaker than that in
the coastal area. One of the important contributing factors to heavy rainstorms in southeast Zhejiang is a
southeast jet stream, which is maintained over the southeast coast. In contrast, the South China Sea
monsoon circulation transports large amounts of water vapor into Bilis – when a water-vapor transport belt
south of the tropical cyclone significantly strengthens – which strengthens the transport. Then, it causes
water vapor flux to converge on the south side of Bilis and diverge on the north side. Precipitation is much
stronger on the south side than that on the north side. After Bilis travels far inland, the cold air guided by a
north trough travels into the TC and remarkably enhances precipitation. In summary, combining vertical
wind shear with water vapor transportation is a good way to predict rainstorms associated with landing
tropical cyclones. 相似文献
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用一个带有地形项的β平面准地转正压涡度方程,进行2组积分时间长度为48h的试验,分析旋转大气中地形对多涡自组织的影响。地球旋转作用的引入主要会引起以下的差别:无旋转大气中,多涡自组织的特征是准终态涡将初始多涡全部吸收或全部组织起来;旋转大气中,多涡自组织的特征是准终态涡将初始多涡部分吸收或部分组织起来,差别较明显。中尺度地形对准终态涡位置的影响不同。无旋转大气中,中尺度地形对准终态涡位置的影响较小,有无地形的两个准终态涡中心之间的距离约100km;旋转大气中,中尺度地形对准终态涡位置的影响较大,有无地形的两个准终态涡中心之间的距离约200km,两者相差一倍左右。 相似文献
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研究了北半球初秋500hPa高度场的6个遥相关型特征及其与冬季遥相关型的区别,和其强度与我国初秋气温场的关系。指出我国大部地区的气温场特征与其中4个环流型强度的关系密切。 相似文献