Atmospheric circulation over the Bolivian Altiplano during dry and wet periods and extreme phases of the southern oscillation
Atmospheric circulation over the Bolivian Altiplano during dry and wet periods and extreme phases of the southern oscillation
复制标题
DOI：
10.1002/(sici)1097-0088(19991130)19:14
复制
发表时间：
1999-11
期刊：
影响因子：
--
通讯作者：
M. Vuille
中科院分区：
文献类型：
--
作者：
M. Vuille
利用智利萨尔塔安托法加斯塔的探空资料，研究了玻利维亚高原在干湿复合期和南方涛动高、低指数位相的大气环流（阿根廷）、利马（秘鲁）和拉巴斯（玻利维亚），玻利维亚/智利边界在18°和19°S之间的每日降水数据和每月NCEP（美国国家环境预测中心）1960年至1998年的再分析数据。在南半球夏季（DJF）的大气在潮湿的时期的特点是东风异常对流层中上部的高原，导致增加的水分从大陆内部的高原表面附近的流入。玻利维亚高压增强并向南移动。另一方面，在干燥的夏季，西风通常占主导地位，阻止来自东部的水汽输送到达西部高原。降水往往是不足的西部玻利维亚高原在低指数的夏季和高于平均水平在高和低+1夏季，但这种关系是弱的，统计上不显着。低夏季的大气环流异常特征与干旱期大致相似，可以被视为延长的干旱期或干旱事件发生增加的夏季。夏季的高气压区和低气压+1区的低气压区的特征大致相反，玻利维亚高气压区位于更远的南方，在高原上空有东风异常。在冬季（JJA）降水事件是罕见的，这些都与增加偏北和西风分量，降低压力和温度，并增加比湿度在整个高原。低气压期间的大气环流异常在南半球冬季（JJA）不如夏季明显，但通常具有相似的变化（温度升高和对流层垂直扩张）。然而，这些异常的重要性，特别是关于风的模式，取决于站和压力水平。因此，南半球冬季的降水与南方涛动的极值没有关系。版权所有© 1999年皇家气象学会
The atmospheric circulation over the Bolivian Altiplano during composite WET and DRY periods and during HIGH and LOW index phases of the Southern Oscillation was investigated using daily radiosonde data from Antofagasta (Chile), Salta (Argentina), Lima (Peru) and La Paz (Bolivia), daily precipitation data from the Bolivian/Chilean border between 18° and 19°S and monthly NCEP (National Centers for Environmental Prediction) reanalysis data between 1960 and 1998. In austral summer (DJF) the atmosphere during WET periods is characterized by easterly wind anomalies in the middle and upper troposphere over the Altiplano, resulting in increased moisture influx from the interior of the continent near the Altiplano surface. The Bolivian High is intensified and displaced southward. On the other hand, westerly winds usually prevail during DRY summer periods, preventing the moisture transport from the east from reaching the western Altiplano. Precipitation tends to be deficient over the western Bolivian Altiplano during LOW index summers and above average during HIGH and LOW+1 summers, but the relation is weak and statistically insignificant. LOW summers feature broadly similar atmospheric circulation anomalies as DRY periods and can be regarded as an extended DRY period or as a summer with increased occurrence of DRY episodes. HIGH summers, and to a lesser degree LOW+1 summers, are characterized by broadly opposite atmospheric characteristics, featuring a more pronounced Bolivian High located significantly further south, and easterly wind anomalies over the Altiplano. In winter (JJA) precipitation events are rare; these are associated with increased northerly and westerly wind components, reduced pressure and temperature, and increased specific humidity over the entire Altiplano. Atmospheric circulation anomalies during LOW periods are less pronounced in austral winter (JJA) than in summer, but generally feature similar changes (increased temperatures and a vertically expanded troposphere). However, the significance of these anomalies, especially with regard to the wind pattern, varies depending on station and pressure level. Accordingly, precipitation during austral winter shows no relationship with the extremes of the Southern Oscillation. Copyright © 1999 Royal Meteorological Society