Assessment of temperature and precipitation variability over a complex terrain. Multi-resolution model evaluación.

Mountain regions are particularly vulnerable to climate change, as warming reduces snow and ice reserves, thus amplifying positive temperature feedbacks. These processes also have consequences for the hydrological cycle and, therefore, leading to wide-ranging impacts on society by altering ecosystem services and products. This highlights the importance of understanding how climate change affects mountain areas. However, the limited availability of long-term climate records at high elevations, due to adverse weather conditions, makes high-resolution regional climate models essential for studying complex terrain.

The CIMAs (Climate Research Initiative for Iberian Mountain Areas) project focuses on analyzing climate variability and the impact of climate change on the Central System of the Iberian Peninsula. The studied area is the largest mountain range of the peninsula, reaching 2.592 m at its highest point (Almanzor Peak) and includes surrounding areas with lower altitudes.

CIMAS observational data, gathered from several institutions in Portugal and Spain, was used to assess the accuracy of regional models over the domain of interest. Model simulations were produced with the WRF and HCLIM models spanning the period 1990-2025, using two nested domains at 12 and 4 km resolution and a nestdown strategy to produce a 1 km resolution simulation domain over the Central System. The domains at 4 and 1 km resolution were configured as convection-permitting. Both models were driven by the same boundary conditions provided by the ERA5 reanalysis, which was also used as a reference to evaluate the added value of increased resolution by each regional model. Specifically, temperature and precipitation variability at daily temporal resolution were used to evaluate model output against observations.

Results show how increasing resolution improves the simulation of temperatura and precipitation at high elevations and allows for better understanding of the climatology in complex terrain. The comparison of the WRF and HCLIM temperature simulations with observations highlights differences, mostly in the reproduction of extremes. Regarding the precipitation, 1 km resolution tends to overestimate the total accumulations due to an excess of simulated wet days.