Are urban impacts on heavy rainfall amplified in mountainous regions?

Abstract Global evidence indicates that orography can exert a strong influence on rainfall, thereby giving rise to natural hazards such as flooding in mountain areas. Alongside orographic influences, urban areas can also act to intensify storms, but their impact on heavy rainfall in high elevations has not yet been investigated in detail. Here, we quantify the contribution of a high-altitude city to both rainfall intensification and its daytime and nighttime patterns, focusing on the city of Cuenca in the Ecuadorian Andes. Modeling several observed storms with and without the city suggests that the urban area can enhance downstream precipitation by over 20% over a pre-existing hotspot of orographically induced precipitation. This urban-induced rainfall intensification seems to exceed that observed for cities of comparable size outside mountainous regions. This may be explained by Cuenca’s valley setting and its high humidity compared to its surroundings, suggesting that high-altitude cities with similar morphologies could amplify combined orographic-dynamic and urban-thermodynamic effects.