Measurements at the high‐elevation Lamar Observatory in the Mantaro Valley (MV) in the Central Andes of Peru demonstrate a diurnal cycle of precipitation characterized by convective rainfall during the afternoon and nighttime stratiform rainfall with embedded convection. Wet season data (2016–2018) reveal long‐duration (6–12 hr) shallow precipitating systems (LDPS) that produced about 17% of monsoon rainfall in 2016 and 2018 associated with El Niño and La Niña, respectively. The LPDS fraction of monsoon rainfall doubles to 35% with weekly recurrence in 2017 under El Niño Costero (coastal) conditions. LDPS occur under favorable moisture conditions dictated by the South America (SA) Low‐Level Jet (SALLJ) and Cold Air Intrusions (CAIs). Backward trajectory analysis shows that precipitable water sustains >80% of seasonal precipitation and ties the LPDS to particular moisture source regions in the eastern Andes foothills 1–2 days in advance, enhanced by increased moisture supply in the midtroposphere. Higher frequency of CAIs and enhanced midlevel moisture convergence along CAI fronts explain the increased LDPS frequency during the 2017 El Niño Costero. These findings highlight the functional role of the Andes morphology in organizing moisture supply to high‐elevation precipitation systems on the orographic envelope. Analysis of the Global Precipitation Measurement (GPM) mission satellite‐based radar observations points to challenges to precipitation detection and estimation in this region as the GPM clutter‐free height (~1–2 km AGL) exceeds the depth of shallow precipitation systems in the MV.

中文翻译：

---

秘鲁中部安第斯山脉的高空季风降水过程

在秘鲁中部安第斯山脉中部Mantaro谷（MV）的高海拔Lamar天文台进行的测量显示，降水的昼夜周期具有下午的特征，而下午和夜间的层状降雨则带有对流。湿季数据（2016-2018年）显示，长时间持续（6-12小时）的浅层降水系统（LDPS）分别产生了与厄尔尼诺现象和拉尼娜现象有关的2016年和2018年季风降雨的17％。在厄尔尼诺·科斯特罗（沿海地区）的条件下，2017年季风降雨的LPDS比例翻了一番，达到35％，每周出现一次。LDPS发生在南美（SA）低空急流（SALLJ）和冷空气入侵（CAI）规定的有利湿度条件下。向后的轨迹分析表明，可降水量维持> 80％的季节性降水将LPDS提前1-2天与安第斯山脉东部丘陵的特定水分源区域联系起来，而对流层中层的水分供应增加了这种情况。在2017年厄尔尼诺·科斯特罗（ElNiñoCostero）期间，CAI的频率较高，且沿CAI前沿的中层水分汇聚增加，这说明LDPS频率增加。这些发现突显了安第斯山脉形态在组织向地形封盖层上的高海拔降水系统供应水分方面的功能性作用。对全球降水测量（GPM）任务卫星雷达观测的分析指出，该区域的降水检测和估计面临挑战，因为GPM的无杂波高度（〜1-2 km AGL）超过了该区域浅层降水系统的深度。 MV