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ABSTRACTThe Pan-Eurasian Experiment Modelling Platform (PEEX-MP) is one of the key blocks of the PEEX Research Programme. The PEEX MP has more than 30 models and is directed towards seamless environmental prediction. The main focus area is the Arctic-boreal regions and China. The models used in PEEX-MP cover several main components of the Earth’s system, such as the atmosphere, hydrosphere, pedosphere and biosphere, and resolve the physical-chemical-biological processes at different spatial and temporal scales and resolutions. This paper introduces and discusses PEEX MP multi-scale modelling concept for the Earth system, online integrated, forward/inverse, and socioeconomical modelling, and other approaches with a particular focus on applications in the PEEX geographical domain. The employed high-performance computing facilities, capabilities, and PEEX dataflow for modelling results are described. Several virtual research platforms (PEEX-View, Virtual Research Environment, Web-based Atlas) for handling PEEX modelling and observational results are introduced. The overall approach allows us to understand better physical-chemical-biological processes, Earth’s system interactions and feedbacks and to provide valuable information for assessment studies on evaluating risks, impact, consequences, etc. for population, environment and climate in the PEEX domain. This work was also one of the last projects of Prof. Sergej Zilitinkevich, who passed away on 15 February 2021. Since the finalization took time, the paper was actually submitted in 2023 and we could not argue that the final paper text was agreed with him.

ABSTRACTThe oceanographic forecast capability in coastal seas is often limited by the capacity of the numerical models in correctly reproducing the complex morphology of the coastline and the exchange processes between the shelf and the open seas. In the marginal Adriatic Sea this task is of uppermost importance due to the presence of several coastal water bodies and rivers. We present here a new operational oceanographic system, called Tiresias, based on the unstructured grid model SHYFEM and representing the whole Adriatic Sea together with the lagoons of Marano-Grado, Venice and Po Delta. The novelty of this oceanographic system resides in the very high-resolution, up to 10 m, of the numerical mesh, and in the high spatial and temporal resolution of the forcing and boundary conditions that drive the forecasts. The forecast results are evaluated against sea temperature and salinity profiles, mean circulation fields derived from a regional ocean model, tide gauges and drifter trajectory. The presented results highlighted the capacity of Tiresias in forecasting the general circulation in the Adriatic Sea, as well as several relevant coastal dynamics, such as saltwater intrusion, storm surge and riverine waters dispersion.

We introduce the latest version of the RegCM regional climate modeling system, RegCM5. Compared to the previous model version (RegCM4) the main new development is the inclusion of the non‐hydrostatic dynamical core from the weather prediction model MOLOCH, which is more accurate and much more computationally stable and efficient than the previous one. In particular, the new dynamical core is best designed for use at convection‐permitting resolutions of a few km. Several physics schemes and coupled model components have also been upgraded compared to the previous version of the model. A set of test simulations for present day climate conditions at parameterized convection and convection permitting resolutions over different European domains is presented for illustrative purposes. Overall, for these simulations RegCM5 exhibits a better performance than RegCM4 for the majority of statistics analyzed, especially at convection‐permitting resolutions. However, this performance depends on the physics schemes used, and further optimization work is under way to fully test the model in different climate settings and reduce current biases. RegCM5 is a freely available, computationally efficient, flexible, and portable Regional Earth System model designed for community use, so that prospective model users are welcome to access its code and use it for different applications. We introduce the latest version of the RegCM regional climate modeling system, RegCM5, in which the main new development, in addition to some physics upgrades, is the inclusion of the non‐hydrostatic dynamical core from the weather prediction model MOLOCH. This makes the model more accurate and much more computationally efficient than the previous version, especially at convection‐permitting resolutions of a few km. A set of test simulations for present day climate conditions at parameterized convection and convection permitting resolutions over different European domains is presented for illustrative purposes. Overall, these simulations show that RegCM5 mostly exhibits a better performance than RegCM4 for most statistics analyzed, especially at convection‐permitting resolutions, although this performance depends on the physics schemes used. Further optimization work is under way to fully test the model in different climate settings and reduce current biases. RegCM5 is a freely available, computationally efficient, flexible, and portable Regional Earth System model designed for community use, so that prospective model users are welcome to access its code and use it for different applications. The fifth version of the regional climate modeling system RegCM, has been developed and releasedIllustrative experiments show that the model overall performs better and is much more computationally efficient than the previous versionThe model is a community resource so that prospective users are encouraged to access it and use it The fifth version of the regional climate modeling system RegCM, has been developed and released Illustrative experiments show that the model overall performs better and is much more computationally efficient than the previous version The model is a community resource so that prospective users are encouraged to access it and use it

The response of the ozone column across Europe to the extreme 2020 Arctic ozone depletion was examined by analyzing ground‐based observations at 38 European stations. The ozone decrease at the northernmost site, Ny‐Ålesund (79°N) was about 43% with respect to a climatology of more than 30 years. The magnitude of the decrease declined by about 0.7% deg−1moving south to reach nearly 15% at 40°N. In addition, it was found that the variations of the ozone column at each of the selected stations in March‐May were similar to those observed at Ny‐Ålesund but with a delay increasing to about 20 days at mid‐latitudes with a gradient of approximately 0.5 days deg−1. The distributions of reconstructed ozone column anomalies over a sector covering a large European area show decreasing ozone that started from the north at the beginning of April 2020 and spread south. Such behavior was shown to be similar to that observed after the Arctic ozone depletion in 2011. Stratospheric dynamical patterns in March–May 2011 and during 2020 suggested that the migration of ozone‐poor air masses from polar areas to the south after the vortex breakup caused the observed ozone responses. A brief survey of the ozone mass mixing ratios at three stratospheric levels showed the exceptional strength of the 2020 episode. Despite the stronger and longer‐lasting Arctic ozone loss in 2020, the analysis in this work indicates a similar ozone response at latitudes below 50°N to both 2011 and 2020 phenomena. The winter polar vortex isolates a huge volume of air from external impacts that, in the absence of the sunlight, leads to a great deal of cooling and the formation of polar stratospheric clouds. Chemical reactions taking place in these clouds contribute to ozone destruction. Such spring‐time ozone depletions are regularly observed in Antarctica, but usually do not occur in the Arctic where the vortex is much less intense. However, in the past three decades several similar episodes occurred in the Arctic and the most marked of them took place in the 2011 and 2020 springs. The response of the ozone layer over Europe to the 2020 episode was studied here by analyzing the data from 38 ground measurement stations. It was found that there was a nearly 43% decrease in ozone in the Arctic, and, as it spread southward, a reduction of 15% in mid‐latitudes 15–20 days later. This spread was attributed to the transport of ozone‐poor air from the Arctic to the south after the vortex breakup. Despite the stronger depletion in 2020 and some differences in the movement of air, the response of the ozone layer was quite similar in the springs of both 2011 and 2020. The 2020 ozone depletion in the Arctic was found to impact the ozone in the mid‐latitude European areasThe magnitude of ozone decrease in the southern regions declined with respect to that in the Arctic and occurred with a delay up to 20 daysSuch a response was similar to that observed in 2011 and both were considered a result of ozone‐poor air masses transported southward The 2020 ozone depletion in the Arctic was found to impact the ozone in the mid‐latitude European areas The magnitude of ozone decrease in the southern regions declined with respect to that in the Arctic and occurred with a delay up to 20 days Such a response was similar to that observed in 2011 and both were considered a result of ozone‐poor air masses transported southward

The present study discusses the effect of the ozone depletion that occurred over the Arctic in 2020 on the ozone column in central and southern Europe by analysing a data set obtained from ground-based measurements at six stations placed from 79 to 42°N. Over the northernmost site (Ny-Ålesund), the ozone column decreased by about 45% compared to the climatological average at the beginning of April, and its values returned to the normal levels at the end of the month. Southwards, the anomaly gradually reduced to nearly 15% at 42°N (Rome) and the ozone minimum was detected with a delay from about 6 days at 65°N to 20 days at 42°N. At the same time, the evolution of the ozone column at the considered stations placed below the polar circle corresponded to that observed at Ny-Ålesund, but at 42°–46°N, the ozone column turned back to the typical values at the end of May. This similarity in the ozone evolutional patterns at different latitudes and the gradually increasing delay of the minimum occurrences towards the south allows the assumption that the ozone columns at lower latitudes were affected by the phenomenon in the Arctic. The ozone decrease observed at Aosta (46°N) combined with predominantly cloud-free conditions resulted in about an 18% increase in the erythemally weighted solar ultraviolet irradiance reaching the Earth’s surface in May.