Technical note: A physically based correction of WRF temperature using atmospheric lapse rates for high-resolution hydrological simulations in a glacierized catchment

Abstract

This technical note presents a physically based post-processing workflow for correcting coarse-resolution regional climate model output used to force high-resolution hydrological models in high-elevation, glacierized catchments. The Weather Research and Forecasting (WRF) model was used to dynamically downscale the 20th Century Reanalysis Version 3 (20CRv3; 1° × 1°, 3-hourly) to a spatial resolution of 2 km and an hourly temporal resolution for the period 1969–2015. Evaluation of WRF output in the upper Kauner Valley (Austria) revealed a pronounced cold bias in the diagnosed 2 m temperature at elevations above 2600 m above sea level, which was attributed to the coarse representation of snow- and ice-covered surfaces and their influence on land-atmosphere interactions. To address this limitation, we developed a novel post-processing workflow that derives hourly temperature lapse rates directly from the WRF atmosphere using temperature and geopotential height fields from multiple eta levels. These lapse rates are subsequently used to reconstruct near-surface temperatures from the first atmospheric model level, thereby reducing the influence of surface-related biases. In addition, a sequential thermodynamically consistent correction of relative humidity was applied using the corrected temperature fields. The proposed approach was evaluated against observations from four meteorological stations spanning an elevation gradient of nearly 900 m and through hydrological simulations with the physics-based WaSiM model. Corrected hourly temperatures showed substantially improved agreement with observations, whereas simulations driven by uncorrected WRF data failed to adequately reproduce observed cryospheric and hydrological dynamics. The temperature correction significantly improved the simulation of snow accumulation and melt, glacier mass balance, snow cover dynamics, and streamflow. Furthermore, the thermodynamically consistent correction of relative humidity enhanced late-summer streamflow during periods of maximum glacier melt. Evaluation against homogenized station observations demonstrated that the corrected temperature product preserves long-term regional warming trends over a period of 42 years, indicating its suitability for climate impact assessments. The results show that the proposed workflow effectively reduces temperature biases associated with coarse-resolution land-cover representation while maintaining physical consistency among meteorological variables. Because the method relies on atmospheric lapse rates derived from the regional climate model itself rather than long-term local observations, it provides a transferable alternative to empirical bias-correction approaches and a robust framework for hydrological and climate impact studies in glacierized mountain environments.