Search

In this paper we coupled a crop growth model to the Weather Research and Forecasting model with its land surface model Noah‐MP and demonstrated the influence of the weather driven crop growth on land‐atmosphere (L‐A) feedback. An impact study was performed at the convection permitting scale of 3 km over Germany. While the leaf area index (LAI) in the control simulation was the same for all cropland grid cells, the inclusion of the crop growth model resulted in heterogeneous crop development with higher LAI and stronger seasonality. For the analyses of L‐A coupling, a two‐legged metric was applied based on soil moisture, latent heat flux and convective available potential energy. Weak atmospheric coupling is enhanced by the crop model, the terrestrial coupling determines the regions with the L‐A feedback. The inclusion of the crop model turns regions with no L‐A feedback on this path into regions with strong positive coupling. The number of non‐atmospherically controlled days between April and August is increased by 10–15 days in more than 50% of Germany. Our work shows that this impact results in a reduction of both cold bias and warm biases and thus improves the metrics of distributed added value of the monthly mean temperatures. The study confirms that the simulation of the weather driven annual phenological development of croplands for the regional climate simulations in mid‐latitudes is crucial due to the L‐A feedback processes and the currently observed and expected future change in phenological phases., Key Points: Coupling a crop growth model with the Weather and Research Forecasting model significantly improves the simulation of the leaf area index. Land‐atmosphere coupling strength is enhanced by weather dependent crop growth simulation. The distributed added value metric shows a reduction in temperature biases of up to 80% in croplands throughout the season in Germany., Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659, https://opendata.dwd.de/climate_environment/CDC/grids_germany/daily/Project_TRY/air_temperature_mean/, https://doi.org/10.5281/zenodo.6501984, http://land.copernicus.eu/pan-european/corine-land-cover/clc-2006/view, https://doi.org/10.1594/WDCC/WRF_NOAH_HWSD_world_TOP_SOILTYP

International audience; The present study investigates the initiation of precipitating deep convection in an ensemble of convection-resolving mesoscale models. Results of eight different model runs from five non-hydrostatic models are compared for a case of the Convective and Orographically-induced Precipitation Study (COPS). An isolated convective cell initiated east of the Black Forest crest in southwest Germany, although convective available potential energy was only moderate and convective inhibition was high. Measurements revealed that, due to the absence of synoptic forcing, convection was initiated by local processes related to the orography. In particular, the lifting by low-level convergence in the planetary boundary layer is assumed to be the dominant process on that day. The models used different configurations as well as different initial and boundary conditions. By comparing the different model performance with each other and with measurements, the processes which need to be well represented to initiate convection at the right place and time are discussed. Besides an accurate specification of the thermodynamic and kinematic fields, the results highlight the role of boundary-layer convergence features for quantitative precipitation forecasts in mountainous terrain.

The goal of the present study is to investigate the variability of simulated convective precipitation by three convection-resolving models using different setups and initial and boundary conditions. The COSMO, MM5 and WRF models have been used to simulate the atmospheric situation on 12 July 2006, when local convection occurred in central Europe under weak synoptic forcing. The focus of this investigation is on the convective precipitation in the Northern Black Forest in South-West Germany. The precipitation fields from the nine model simulations differ considerably. Six simulations capture the convective character of the event. However, they differ considerably in the location and timing of the intense convective cells. Only one model simulation captures the early onset of precipitation; in all other simulations, the onset of convective precipitation is delayed by up to five hours. All model simulations significantly underpredict the amount of surface precipitation compared to gauge-adjusted radar observations. The simulated diurnal cycles show maximum CAPE and minimum CIN values in the early afternoon. The different onset times of precipitation in the model simulations are shifted in accordance to the simulated diurnal cycles of CAPE and CIN. In the simulations with an early onset of precipitation also maximum CAPE and minimum CIN values appear early. The amount of simulated precipitation, however, does not correlate with CAPE or CIN.