Abstract ID: 3.12225 | Accepted as Talk | Talk/Oral | TBA | TBA

Orographic rain shadows play an important role in shaping regional climates, ecosystems, and water resources in the Andes. As moist air from the Amazon/the Pacific rises over the Andes, it generates significant rainfall and snowfall on the windward side, replenishing glaciers, lakes, and river systems that support agriculture, hydropower, and drinking water supplies for local communities, while leaving the leeward side significantly drier. Given that orographic precipitation serves as a vital freshwater source in this region, improving our understanding and prediction of its response to climate change is crucial.
However, characterizing how orographic precipitation responds to climate change in the Andes remains challenging, due to the complexity of warming’s effects on orographic processes. In addition to thermodynamic changes (increased atmospheric moisture), warming could raise freezing levels, causing a shift from snow to rain, resulting in less snowpack, faster runoff, and higher flood risk. Shifts in wind patterns and static stability could alter atmospheric moisture transport and mountain wave dynamics, affecting where and how much precipitation falls. Current global and regional climate models applied in studying the Andes often struggle to accurately represent the fine-scale topography and atmospheric dynamics involved in orographic precipitation. Previous research (mostly Western U.S. focused) on orographic rain shadows’ response to warming—primarily relying on idealized simulations or lower resolution climate models that cannot fully capture convection—found higher fractional increases in precipitation extremes on the climatological leeward slope compared to the windward slope, indicating a future weakening of orographic rain shadows in midlatitude mountain ranges.
In this study, we assess how orographic rain shadows respond to climate change across the different climate zones of the Andes. We present results comparing a contemporary time period (2000-2024) with a future time period (2140-2050) from convection-permitting (4km) simulations conducted with the Weather Research and Forecasting model (version 4.6) over the entire Andes. We further investigate the role played by various physical factors in determining changes in orographic precipitation extremes. Given the Andes’ role as water towers for South America, understanding and adapting to shifts in orographic rain shadows is crucial for ensuring long-term water security.