Does the HadGEM3-GC3.1 GCM overestimate land precipitation at high resolution? A constraint based on observed river discharge

• Autores: Müller, Omar Vicente; Vidale, Pier Luigi; Vannière, Benoît; Schiemann, Reinhard; McGuire, Patrick C.
• Año de publicación: 2021
• Idioma: inglés
• Tipo de recurso: artículo
• Materia: GLOBAL CLIMATE MODELS; RESOLUTION; GLOBAL RIVER DISCHARGE; GLOBAL LAND PRECIPITATION
• Institución: Consejo Nacional de Investigaciones Científicas y Técnicas

Previous studies showed that high-resolution GCMs overestimate land precipitation when compared against observation-based data. Particularly, high-resolution HadGEM3-GC3.1 shows a significant precipitation increase in mountainous regions, where the scarcity of gauge stations increases the uncertainty of gridded observations and reanalyses. This work evaluates such precipitation uncertainties indirectly through the assessment of river discharge, considering that an increase of ~10% in land precipitation produces ~28% more runoff when the resolution is enhanced from 1° to 0.25°, and ~50% of the global runoff is produced in 27% of global land dominated by mountains. We diagnosed the river flow by routing the runoff generated by HadGEM3-GC3.1 low- and high-resolution simulations. The river flow is evaluated using a set of 344 monitored catchments distributed around the world. We also infer the global discharge by constraining the simulations with observations following a novel approach that implies bias correction in monitored rivers with two methods, and extension of the correction to the river mouth, and along the coast. Our global discharge estimate is 47.4 ± 1.6 × 103 km3 yr−1, which is closer to the original high-resolution estimate (50.5 × 103 km3 yr−1) than to the low-resolution (39.6 × 103 km3 yr−1). The assessment suggests that high-resolution simulations perform better in mountainous regions, either because the better-defined orography favors the placement of precipitation in the correct catchment, leading to a more accurate distribution of runoff, or the orographic precipitation increases, reducing the dry runoff bias of coarse-resolution simulations. However, high-resolution slightly increases wet biases in catchments dominated by flat terrain. The improvement of model parameterizations and tuning may reduce the remaining errors in high-resolution simulations.
Fil: Müller, Omar Vicente. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; Argentina. Universidad Nacional del Litoral. Facultad de Ingenieria y Ciencias Hidricas. Centro de Estudios de Variabilidad y Cambio Climatico.; Argentina. University Of Reading. Departament Of Meteorology; Reino Unido
Fil: Vidale, Pier Luigi. University Of Reading. Departament Of Meteorology; Reino Unido
Fil: Vannière, Benoît. University Of Reading. Departament Of Meteorology; Reino Unido
Fil: Schiemann, Reinhard. University Of Reading. Departament Of Meteorology; Reino Unido
Fil: McGuire, Patrick C.. University Of Reading. Departament Of Meteorology; Reino Unido