Decadal convection-permitting irrigation impacts across the European Continent

The interest in the role of irrigation in the Earth system has grown in the last years due to the fact that various land surface and atmospheric modeling studies have established a well-documented and solid impact of irrigation on weather forecasting. Variables that are certainly affected are soil moisture, energy fluxes, relative humidity and temperature. Aside from very few studies, most of the previous research has been focused on lower/medium horizontal resolutions simulations combined with short-term case studies. Thus, the community still needs long-term simulations integrated with high-resolution to better understand the irrigation's wider impact in climate modeling. This study addresses that gap by conducting multi-year  convection-permitting irrigation simulations with the operational ICON-nwp in Limited Area Mode over the EURO-CORDEX domain. We adapted and implemented the CHANNEL scheme developed by Valmassoi et al. (2020) for the WRF model to the operational ICON-nwp coupled with the land surface model TERRA. For greater flexibility, we opted to include this parameterization in the land surface and atmosphere interface of the ICON-NWP version 2.6.6-nwp3c. Analogous to the original parameterization, the irrigation amount is a fixed value calculated within the simulation. The scheme computes the irrigation amount based on soil type characteristics such as field capacity and permanent wilting point, a root depth of 0.81 cm and a depletion fraction of 0.65. The irrigation settings consist of an irrigation frequency of 12 days,  with the first irrigation event taking place on  May 1st of each year and the last irrigation event on August 17th. All of these events include an irrigation start time at 5 UTC and an irrigation length of 5 hours. The model set-up for the control and irrigation simulations is 3 km resolution, 75 vertical levels and the boundary and initial conditions come from the new global reanalyses ICON-DREAM. These experiments have a simulation time period from 2010 to 2022. Initial findings on the differences between the irrigation experiment and control run demonstrate that ICON effectively captures the impact of irrigation on soil moisture, energy fluxes and 2-meter temperature, primarily in Southern Europe. The verification includes a comparison between the experiments and observations for variables such as 2-meter temperature and relative humidity.