Snowfall over the Andes: a convection-permitting climate model

The Andes has the longest mountain range in the world, stretching over 7000 kilometres from Colombia in the tropics to the bottom of Chile in the extratropics. Millions of people depend on water supply from the Andes for their consumption, agriculture, hydropower, and ecosystem services. Often, this water comes from snow and glacier melt, and these water stores can be especially important in times of drought, or during dry seasons for regions with strong annual cycles of precipitation. The inaccessibility of the higher regions in Andes makes setting up weather stations difficult, and the extremely complex topography leads to sharp gradients in weather and climate with varying altitudes of snowline, therefore requiring very high-resolution models to accurately capture the small-scale processes occurring. Due to these challenges, snowfall and snowcover in the Andes remain poorly understood and difficult to model, which are critical to address in the face of a changing climate, with potential for future precipitation occurring in fewer, more extreme snowfall events. Here we present initial work optimising a high-resolution climate model over the Andes from Peru to the bottom of Chile. We have determined the best setup to model snowfall over the Andes in the Weather Research and Forecasting Model. The results of a sensitivity study with multiple different setups are compared to observations from weather stations and satellite data. We also show the capability of the model to represent extreme snowfall events at different latitudes. This model setup will be used to create both hindcasts and future projections of snowfall across the Andes mountain range, to better understand the implications for changing water resources in the Andes