Evaluating the ALADIN-climate model reanalysis over Central Europe

Abstract

Reanalysis is a well-established tool for monitoring the state of the atmosphere. This study aims at validating the ALADIN-Climate (AC) model reanalysis over Europe with a focus on Central Europe. The AC model is based on the ALARO model configuration and belongs to convection permitting models. Its horizontal resolution is 2.3 km. We evaluated a 25-year long period (1990-2014) and we performed the validation process using measurements from ground-based meteorological data over Europe to assess the ability of the AC model to simulate temperature, precipitation, relative humidity, wind speed, and global radiation. The AC model reanalysis tends to overestimate minimum daily temperature and underestimate maximum daily temperature, with larger differences observed during summer. Winter precipitation totals are overestimated by nearly 50 %, partly due to an overestimation of wet days, while summer precipitation is less overestimated (by 13 %). Relative humidity is consistently overestimated across the model domain in winter, whereas in summer it is variable. Wind speed is overestimated in both summer and winter, and global radiation is also overestimated, especially in winter. Although some variables, like winter precipitation, exhibit significant biases, the overall differences between the AC model reanalysis and station data are consistent with other reanalyses, such as CERRA and ERA5. Biases in the AC model reanalysis are not only caused by the model's imperfections and errors, but also by potential systematic errors at measuring stations. Given its high spatial resolution, this AC regional reanalysis offers a valuable source for further climate studies in Central Europe.