2014年夏季青藏高原南部降水10-20天低频振荡特征

【作者】 段丽君； 段安民；

【机构】 成都信息工程大学； 中科院大气物理研究所；

【摘要】 根据中国气象局台站观测资料、JRA-55逐日再分析资料以及GPCP全球降水逐日观测资料,对2014年7、8月高原南缘狮泉河站、林芝站的低频特征进行分析,并重点讨论了10-20d低频降水干、湿位相期间相关要素场低频分量的异常分布及传播特征,结果表明:(1)2014年7、8月高原西南部狮泉河站、东南部林芝站降水均存在10-20天低频振荡,且两站存在低频振荡的时段相同。(2)500h Pa环流场、水汽通量场10-20d低频分量的分布在降水干、湿位相期间的配置正好相反。在降水干(湿)位相期间,印度北部和我国华南地区存在一个低频反气旋(气旋),受印度北部低频反气旋(气旋)北侧的偏北(南)气流和华南地区低频反气旋东南部的偏东(西)气流共同影响,高原南缘为低频水汽辅散(辐合)区,高原中东部由于受到华南地区反气旋(气旋)西部的偏南(北)气流的影响为水汽辅合(辐散)区。(3)在低频降水的干、湿位相期间,热源的10-20d低频分量配置正好相反。在干位相期间,高原南缘、印度北部以及中南半岛为低频热汇区,高原中东部为低频热源区;湿位相,热源、热汇低频分量的分布与干位相相反。(4)沿狮泉河至林芝的降水、200h Pa散度场、整层积分水汽通量场斜线剖面图中可以看出,该低频振荡无经向传播,狮泉河站(林芝站)降水、200h Pa散度场纬向传播自西向东(自东向西),水汽通量散度自东向西(无传播)。因此,狮泉河站与林芝站在同一时段分别存在两种起源不同的季节内振荡。更多还原

【Abstract】 The characteristics of precipitation low-frequency oscillation over the southern Tibetan Plateau(TP) and especially the abnormal distribution and propagation of the 10-20 day filtered fields between dry and wet phases of precipitation low-frequency oscillation are investigated using daily JRA-55 reanalysis data、GPCP global precipitation daily data and station observation data in 2014. The results are shown as follows:(1)Shiquanhe station in southwestern plateau and Linzhi station in southeastern plateau precipitation are existed main periods of oscillation of 10-20 day, and two station have same period of low-frequency oscillation.(2)The distribution of circulation filed and moisture flux filed over 10-20 d low-frequency oscillation period have reversed shape. During the dry(wet) phase, there is a low-frequency anticyclone(cyclone) to the north side of India and south China, the south TP is influenced both by the northerly(southerly) winds of the north India anticyclone(cyclone) and the easterly(westerly) winds of the south China anticyclone(cyclone),and it is the low-frequency moisture divergence(convergence) area. There have reversed distribution in the eastern of TP.(3)The heat source over 10-20 d low-frequency oscillation period have reversed shape. During dry phase, the southern TP, north India and Indo-China are all low-frequency heat sink areas, mid-eastern TP is heat source area, but the 10-20 d filtered heat source/sink fields are opposite in the wet phase.(4)From cross section pictures we can know that this 10-20 d low-frequency oscillation have two different propagated passages about two stations. Precipitation、high level divergence field and moisture field at Shiquanhe station are all propagating from west to east. However, Linzhi station are all propagating from east to west. So, during the same periods, there are two different origin waves at these two stations.更多还原