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Water vapor variability in the Atacama desert during the 20th century
Global and Planetary Change ( IF 3.9 ) Pub Date : 2020-07-01 , DOI: 10.1016/j.gloplacha.2020.103192
Christoph Böhm , Mark Reyers , Jan Herbert Schween , Susanne Crewell

Abstract This study focuses on integrated water vapor (IWV) which is the main source for precipitation, fog and dew formation in the Atacama Desert in northern Chile. In order to study its long-term variability, a consistent meteorological record is needed. Here, we utilize the European Centre for Medium-Range Weather Forecasts' reanalysis ERA-20C which provides IWV among other atmospheric variables over the course of the entire 20th century (1900–2010). In this two fold study, we first present a validation of ERA-20C IWV for the Atacama and the bordering southeast Pacific region. Comparisons to satellite observations, i.e. the Hamburg Ocean Atmosphere Parameters and Fluxes from Satellite data record and the Moderate Resolution Imaging Spectroradiometer measurements, for overlapping time periods prove the suitability of ERA-20C to study IWV variability. Assessment of the observation feedback in ERA-20C reveals a higher uncertainty for the beginning of the 20th century when fewer observations are assimilated. Nevertheless, departures of the assimilated observations do not show a systematic bias in space or time supporting suitability of ERA-20C for long-term investigations. In the second part of the study, we describe the IWV variability over the course of the 20th century. Deviations from the long-term mean greater than 30% are found on an inter-annual time scale over the continental Atacama. Furthermore, we investigate potential drivers of the IWV variability such as the Pacific Decadal Oscillation (PDO) and the El Nino Southern Oscillation (ENSO) phenomenon. The relationship between the local IWV and these large scale indices depends on region and season. For instance, during austral summer, La Nina conditions yield overall greater IWV variability in the Atacama allowing both drier and even more pronounced wetter extremes than El Nino conditions.

中文翻译:

20 世纪阿塔卡马沙漠的水汽变化

摘要 本研究的重点是综合水汽(IWV),它是智利北部阿塔卡马沙漠降水、雾和露水形成的主要来源。为了研究其长期变化,需要一致的气象记录。在这里,我们利用欧洲中期天气预报中心的再分析 ERA-20C,它提供了整个 20 世纪(1900-2010 年)期间其他大气变量中的 IWV。在这项双重研究中,我们首先展示了对阿塔卡马和毗邻的东南太平洋地区的 ERA-20C IWV 的验证。与卫星观测的比较,即来自卫星数据记录的汉堡海洋大气参数和通量以及中分辨率成像光谱仪测量值,重叠时间段证明 ERA-20C 适合研究 IWV 变异性。对 ERA-20C 中观测反馈的评估揭示了 20 世纪初当吸收的观测较少时具有更高的不确定性。然而,同化观测的偏离并未显示支持 ERA-20C 长期调查适用性的空间或时间系统偏差。在研究的第二部分,我们描述了 20 世纪过程中的 IWV 变化。在阿塔卡马大陆的年际时间尺度上发现与长期平均值的偏差超过 30%。此外,我们调查了 IWV 变化的潜在驱动因素,例如太平洋年代际涛动 (PDO) 和厄尔尼诺南方涛动 (ENSO) 现象。当地 IWV 与这些大尺度指数之间的关系取决于地区和季节。例如,在南方夏季,拉尼娜条件在阿塔卡马产生了更大的 IWV 变化,允许比厄尔尼诺条件更干燥甚至更明显的潮湿极端情况。
更新日期:2020-07-01
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