The first offline land carbon simulation over Europe driven by the atmospheric forcing of a global storm-resolving climate model

Abstract. This study is motivated by the hypothesis that the drizzle problem of coarse-resolution climate models, whereby convective precipitation preferentially falls as light precipitation rather than short-lived and intense storms, leads to low gross primary productivity (GPP). To test this hypothesis, we perform an offline land carbon simulation over Europe using a terrestrial biosphere model driven by atmospheric forcing from a global km-scale climate simulation with explicitly resolved convection. This simulation is compared with a coarse-resolution simulation derived by atmospheric forcing from a coarse-resolution climate model with parameterized convection. The km-scale forcing leads, on average, to higher GPP. We find that shorter, more intense daily precipitation events when convection is explicitly resolved allow for stronger downward shortwave radiation on rainy days, thereby enhancing photosynthesis. At the same time, differences in the precipitation climatology between the two atmospheric forcing datasets, with a deficit of precipitation over eastern Europe in the km-scale forcing, result in soil moisture falling below the wilting point and reduced GPP in that region. Consistent with these GPP changes, autotrophic respiration is larger in the km-scale simulation, whereas heterotrophic respiration is smaller, the latter due to drier conditions.