This study examines the implications of Tropical Montane Forests (TMFs) loss on orographic precipitation in the Eastern slopes of the Andes (EADS). The focus is on moist processes for synoptic regimes associated with significant EADS precipitation: (1) monsoon rainfall for weak and strong South America Low-Level Jet (LLJ) conditions and (2) heavy rainfall associated with cold air intrusions (CAI) in the dry season. High-resolution simulations using the Weather Research and Forecasting (WRF) model were conducted for realistic and modified land-cover resulting from the conversion of TMFs to savanna. The deforestation scenarios result in 50–100% decrease (up to ∼400 J kg–1) in Convective Available Potential Energy (CAPE) spatially organized by land-cover change along the EADS. Analysis of the differences in simulated frequency distributions of rainfall intensity shows robust daytime increases in light rainfall (<2 mm h–1) and decreases in moderate rainfall rates (2–10 mm h–1) in the altitudinal band 500–2,000 m where orographic enhancement is dominant. Whereas there are negligible changes in the spatial patterns of precipitation and hydrologic response for monsoon conditions, rainfall accumulations decrease for all cases, and the precipitation maxima shift downslope into the Amazon lowlands. Changes in rainfall amount and intensity result in runoff decreases of 5–10% at the event-scale for the CAI case. Sensitivity simulations for lower initial soil moisture conditions indicate a strong positive feedback of forest loss to hydrologic drought along the EADS foothills in the austral spring when CAIs play a key role in the tropical EADS dry season hydrometeorology.

中文翻译：

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森林砍伐对热带安第斯山脉地形降水的影响

本研究考察了热带山地森林 (TMF) 损失对安第斯山脉东坡 (EADS) 地形降水的影响。重点是与重要 EADS 降水相关的天气状况的潮湿过程：(1) 弱和强南美洲低空急流 (LLJ) 条件下的季风降雨和 (2) 与冷空气入侵 (CAI) 相关的强降雨旱季。使用天气研究和预测 (WRF) 模型进行了高分辨率模拟，用于模拟由 TMF 转换为稀树草原的真实和修改后的土地覆盖。森林砍伐情景导致沿 EADS 的土地覆盖变化在空间上组织的对流可用势能 (CAPE) 减少 50-100%（最多约 400 J kg-1）。对降雨强度模拟频率分布差异的分析表明，在海拔 500-2,000 m 的海拔带中，白天小雨（<2 mm h-1）强劲增加，中等降雨率（2-10 mm h-1）减少，其中地形增强占主导地位。尽管季风条件下降水和水文响应的空间格局变化可以忽略不计，但所有情况下的降水积累都会减少，并且降水最大值沿着斜坡向下移动到亚马逊低地。对于 CAI 案例，降雨量和强度的变化导致径流在事件尺度上减少 5-10%。