Moisture variability over the South American Altiplano during the South American Low Level Jet Experiment (SALLJEX) observing season
Moisture variability over the South American Altiplano during the South American Low Level Jet Experiment (SALLJEX) observing season
复制标题
南美低空急流实验（SALLJEX）观测季期间南美高原的湿度变化
DOI：
10.1029/2005jd006152
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发表时间：
2005
影响因子：
--
通讯作者：
R. Garreaud
中科院分区：
文献类型：
--
作者：
M. Falvey;R. Garreaud
[1] 在南半球夏季，南美高原高海拔高原的降水表现出明显的季节内变化，这与高原西部山脉附近地面站观测到的潮湿和干燥条件的交替有关。在这项研究中，利用南美低空急流实验（SALLJEX）的观测数据以及全球定位系统、中分辨率成像光谱仪和无源微波辐射计仪器对可降水量（PW）的卫星估计，对2002年至2003年夏季在高原西缘的一个站观测到的潮湿（湿）和干燥（干）事件的特征进行了检查。我们发现，在潮湿的日子里，整个高原普遍处于平均潮湿状态（PW大于10毫米）。这种水分显然是由大陆盆地上方类似高度的空气持续向西平流带到高原的，并穿过高原传播，以湿润高原以西相当远距离（>1000公里）的太平洋上空的大气。相反，在干旱事件期间，主要在西部山脉和高原南部上空观察到边界层显着干燥。没有证据表明高原北部有强烈的中层干燥空气平流，北部盆地和高原东部山脊的湿度保持恒定且较高。因此，降水和对流云量与高原西部山脉沿线的水分关系最为密切。人们发现，水分的显着日变化在高原的外坡上最为强烈。几乎没有迹象表明，高原东坡的白天上坡流在潮湿时期向高原输送水分方面发挥了主要作用。
[1] During the austral summer, precipitation over the high-altitude plateau of the South American Altiplano exhibits a marked intraseasonal variability which has been associated with alternating moist and dry conditions observed at surface stations near the Altiplano western cordillera. In this study the characteristics of humid (wet) and dry (dry) episodes observed at a station on the western rim of the Altiplano during the summer of 2002–2003 are examined using observational data from the South American Low Level Jet Experiment (SALLJEX) and satellite-based estimates of precipitable water (PW) from Global Positioning System, Moderate Resolution Imaging Spectrometer, and Passive Microwave Radiometer instruments. We find that on wet days, mean moist conditions (PW greater than 10 mm) prevail across the entire plateau. This moisture is apparently brought to the Altiplano by sustained westward advection of air at similar altitude above the continental basin and propagates across the Altiplano to moisten the atmosphere over the Pacific Ocean a considerable distance (>1000 km) west of the plateau. In contrast, during dry events, significant drying of the boundary layer is observed mainly along the western mountain range and over the southern Altiplano. There is no evidence of strong midlevel advection of dry air across the northern Altiplano, and moisture remains constant and high over the northern basin and along the Altiplano eastern ridge. Consequently, precipitation and convective cloudiness show the strongest relation to moisture along the western cordillera of the Altiplano. Significant diurnal variability of moisture is found to occur most strongly on the outer slopes of the Altiplano. There is little indication that daytime upslope flow on the eastern slope of the Altiplano plays a major role in the transport of moisture to the Altiplano during wet episodes.