The 2022-23 hydrological year in the Lake Titicaca, Desaguadero River, and Lake Poopó hydrological system (TDPS) over the South American Altiplano constituted a historically dry period. This drought was particularly severe during the pre-wet season (October–December), when the TDPS and the adjacent Andean-Amazon region experienced as much as 60% reductions in rainfall. Consequently, Titicaca Lake water levels decreased by 0.05 m from December to January, which is part of the rising lake level period of normal conditions. Such conditions have not been seen since the El Niño-related drought of 1982-83. Using a set of hydroclimatic, Sea Surface Temperature (SST) and atmospheric reanalysis datasets, we find that this new historical drought was associated with enhanced southerly moisture flux anomalies, reducing the inflow of moisture-laden winds from the Amazon basin to the TDPS. Such anomalies in moisture transport were not seen since at least the 1950s. The atmospheric dynamics associated with this drought are related to La Niña SST anomalies via subtropical teleconnections associated with Rossby wave trains towards South America, further extended by subtropical Atlantic Ocean SST anomalies. This feature reduced the atmospheric moisture inflow from the Amazon and weakened the development of the Bolivian High in the upper troposphere. These results document a new atmospheric mechanism related to extreme droughts in the TDPS associated with La Niña SST anomalies during the pre-wet season. This goes beyond the traditional understanding of El Niño events, especially the strongest ones, being associated with dry conditions in the TDPS during the wet season (December–March).

中文翻译：

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2022-23 年南美高原干旱：ENSO 对雨季前亚马逊西部水分通量的影响


2022-23水文年，南美高原上的的喀喀湖、德萨瓜德罗河和波波湖水文系统（TDPS）构成历史干旱期。这种干旱在雨季前（10 月至 12 月）尤为严重，当时 TDPS 和邻近的安第斯-亚马逊地区的降雨量减少了 60%。因此，的的喀喀湖水位从12月到1月下降了0.05米，属于正常情况湖水上升期的一部分。自 1982-83 年厄尔尼诺现象引发的干旱以来，还没有出现过这样的情况。使用一组水文气候、海面温度 (SST) 和大气再分析数据集，我们发现这次新的历史干旱与南风水分通量异常增强有关，从而减少了从亚马逊盆地流入 TDPS 的富含水分的风。至少自 20 世纪 50 年代以来，这种水分输送异常现象就没有出现过。与这次干旱相关的大气动态与拉尼娜海温异常有关，通过与南美罗斯贝波列相关的副热带遥相关，并通过副热带大西洋海温异常进一步延伸。这一特征减少了来自亚马逊的大气水汽流入，削弱了对流层上层玻利维亚高压的发展。这些结果记录了与湿季前拉尼娜海温异常相关的 TDPS 极端干旱相关的新大气机制。这超出了对厄尔尼诺事件（尤其是最强厄尔尼诺事件）的传统理解，因为厄尔尼诺事件与雨季（12 月至 3 月）期间 TDPS 的干燥条件有关。