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Tornadoes are among the most extreme hazardous weather phenomena. Several recent studies have assessed their important impact also in mid-latitudes European countries. An update climatology of the EF1+ tornadoes in Italy confirms that the central Tyrrhenian (CT) and the South-Eastern (SE) regions of the Italian peninsula represent two of the areas most affected by tornadoes in the Mediterranean. Two recent works, in particular, analyzed some case studies affecting these two regions: Avolio and Miglietta (2021) studied four tornado-spawning supercells over SE regions, that hit the same (Ionian) areas and that were characterized by similar synoptic conditions; in a more recent work (Avolio and Miglietta, 2022; under review), the same authors performed a synoptic/mesoscale analysis of the main patterns associated to the most intense tornadoes in the CT regions, also analyzing a significant event hitting the surroundings of Rome. Aim of this work is to propose a comparative analysis between these two tornado hotspots: the possible causes that generate these events in relation to the peculiarities of the two areas are analyzed by using upper air observations, radar images, ERA5 reanalysis, and high resolution WRF simulations. While for tornadoes in southeastern Italy the synergy of orographic forcing and air-sea interaction in a strongly sheared environment appears fundamental, in the Tyrrhenian regions the genesis is mainly related to the presence of convergence lines over the sea.

We apply extreme value theory (EVT) to study the daily precipitation and temperature extremes in the Calabria region (southern Italy) mainly considering a long-term observational dataset (1990–2020) and also investigating the possible use of the ERA5 (ECMWF Reanalysis v5) fields. The efficiency of the EVT applied on the available observational dataset is first assessed—both through a punctual statistical analysis and return-level maps. Two different EVT methods are adopted, namely the peak-over-threshold (POT) approach for the precipitation and the block-maxima (BM) approach for the temperature. The proposed methodologies appear to be suitable for describing daily extremes both in quantitative terms, considering the punctual analysis in specific points, and in terms of the most affected areas by extreme values, considering the return-level maps. Conversely, the analysis conducted using the reanalysis fields for the same time period highlights the limitations of using these fields for a correct quantitative reconstruction of the extremes while showing a certain consistency regarding the areas most affected by extreme events. By applying the methodology on the observed dataset but focusing on return periods of 50 and 100 years, an increasing trend of daily extreme rainfall and temperature over the whole region emerges, with specific areas more affected by these events; in particular, rainfall values up to 500 mm/day are predicted in the southeastern part of Calabria for the 50-year-return period, and maximum daily temperatures up to 40 °C are expected in the next 100 years, mainly in the western and southern parts of the region. These results offer a useful perspective for evaluating the exacerbation of future extreme weather events possibly linked to climate change effects.

On 20 August 2018 a flash flood affected the Raganello Creek (southern Italy) causing 10 casualties. The rainfall event was so highly localized that the spatial coverage of rain gauges were inadequate to measure it, while radar products showed a storm cell with rain peaks of about 70–100 mm h−1. This scientific report provides a preliminary hydro-meteorological analysis of the event and evaluates the forecasting skills of a system based on the WRF–WRF-Hydro models, using both one-way and fully coupled approaches. The first results show a reasonable simulation of the event in terms of both rainfall and hydrological impact.

Coastal areas are more and more exposed to the effects of climatic change. Intense local rainfalls increases the frequency of flash floods and/or flow-like subaerial and afterward submarine landslides. The overall phenomenon of flash flood is complex and involves different phases strongly connected: heavy precipitations in a short period of time, soil erosion, fan deltas forming at mouth and hyperpycnal flows and/or landslides occurrence. Such interrelated phases were separately modelled for simulation purposes by different computational models: Partial Differential Equations methods for weather forecasts and sediment production estimation and Cellular Automata for soil erosion by rainfall and subaerial sediment transport and deposit. Our aim is to complete the model for the last phase of final sediment outcome. This research starts from the results of the previous models and introduces the processes concerning the demolition of fan deltas by sea waves during a sea-storm and the subsequent transport of and sediments in suspension by current at the sea-storm end and their deposition and eventual flowing on the sea bed. A first reduced implementation of the new model SCIDDICA-ss2/w&c1 was applied on the partial reconstruction of the 2016 Bagnara case regarding the meteorological conditions and the flattening of Sfalassa’s fan delta.

In this paper we study the sensitivity of the quantitative precipitation forecast (QPF) to different physical parameterization schemes and configuration settings of WRF (Weather Research and Forecasting) model for a catastrophic event occurred in Calabria, Southern Italy. The event lasted four days, from 30 October 2015 to 2 November 2015, and affected mostly the eastern side of the peninsula. Several raingauges measured >500 mm for the whole event, with the maximum recorded in Chiaravalle (739 mm for the whole event, which is about half of the yearly rainfall). Damages to railway, roads and properties were extensive. To show the sensitivity of the QPF to the model settings and physical parameterization schemes, twelve configurations of WRF are considered, in addition to the control run ( CC ), which is the configuration used for the operational forecast at ISAC-CNR in Lamezia Terme. In particular, we tested the sensitivity of the QPF to four different microphysical schemes, three Planetary Boundary Layer (PBL) schemes (non-local and local), two cumulus parameterization schemes, two different horizontal resolutions (1 km vs 3 km), and different initial and boundary conditions. The QPF is verified both by quantitative measures and qualitative scores, using the observations of 156 raingauges quite uniformly distributed over Calabria. The analysis refers to 12 h and 24 h rainfall, but some details are given also for shorter time scales. Results show that most of the WRF configurations are able to predict most of the features of the precipitation field. However, there are differences at the local scale (few tens of kilometers) that are important for several purposes, including civil protection. In particular, using a non-local PBL closure scheme was fundamental to correctly simulate the heavy precipitation close to the sea for this case, while other configurations predicted the rainfall more anchored to mountain peaks. The good performance of non-local PBL scheme confirms the findings of a previous study over Calabria. The results of this paper show the sensitivity of the QPF at the local scale for different WRF configurations and an ensemble approach is envisaged to improve the prediction of such catastrophic events.

The sensitivity of boundary layer variables to five (two non-local and three local) planetary boundary-layer (PBL) parameterization schemes, available in the Weather Research and Forecasting (WRF) mesoscale meteorological model, is evaluated in an experimental site in Calabria region (southern Italy), in an area characterized by a complex orography near the sea. Results of 1 km × 1 km grid spacing simulations are compared with the data collected during a measurement campaign in summer 2009, considering hourly model outputs. Measurements from several instruments are taken into account for the performance evaluation: near surface variables (2 m temperature and relative humidity, downward shortwave radiation, 10 m wind speed and direction) from a surface station and a meteorological mast; vertical wind profiles from Lidar and Sodar; also, the aerosol backscattering from a ceilometer to estimate the PBL height. Results covering the whole measurement campaign show a cold and moist bias near the surface, mostly during daytime, for all schemes, as well as an overestimation of the downward shortwave radiation and wind speed. Wind speed and direction are also verified at vertical levels above the surface, where the model uncertainties are, usually, smaller than at the surface. A general anticlockwise rotation of the simulated flow with height is found at all levels. The mixing height is overestimated by all schemes and a possible role of the simulated sensible heat fluxes for this mismatching is investigated. On a single-case basis, significantly better results are obtained when the atmospheric conditions near the measurement site are dominated by synoptic forcing rather than by local circulations. From this study, it follows that the two first order non-local schemes, ACM2 and YSU, are the schemes with the best performance in representing parameters near the surface and in the boundary layer during the analyzed campaign.

The understanding of the atmospheric processes in coastal areas requires the availability of quality datasets describing the vertical and horizontal spatial structure of the Atmospheric Boundary Layer (ABL) on either side of the coastline. High-resolution Numerical Weather Prediction (NWP) models can provide this information and the main ingredients for good simulations are: an accurate description of the coastline and a correct subgrid process parametrization permitting coastline discontinuities to be caught. To provide an as comprehensive as possible dataset on Mediterranean coastal area, an intensive experimental campaign was realized at a near-shore Italian site, using optical and acoustic ground-based remote sensing and surface instruments, under different weather characteristic and stability conditions, the campaign is also fully simulated by a NWP model. Integrating information from instruments responding to different atmospheric properties allowed for an explanation of the development of various patterns in the vertical structure of the atmosphere. Wind LiDAR measurements provided information of the internal boundary layer from the value of maximum height reached by the wind profile, a height between 80 and 130 m is often detected as an interface between two different layers. The NWP model was able to simulate the vertical wind profiles and the eight of the ABL.

The analysis of a severe convective storm, occurred in northwestern Italy during late summer 2012, is presented here. The event was characterized by heavy precipitation, hail and intense wind gusts, causing injuries and damages to trees, buildings and infrastructures. The description of the case study draws upon a wide palette of observational data. Surface and upper-air observations helped characterize the event, emphasizing the rapid changes in the meteorological parameters in the study area; satellite data highlights the presence of deep moist convection, associated with strong updrafts; Doppler radar allows the identification of the main features of the event in terms of storm-motion, hail detection/probability and the possible presence of a mesocyclone. A high-resolution (3 km inner grid spacing) simulation with the WRF (Weather Research and Forecasting) model was performed to study the atmospheric conditions conducive to convection, as well as to estimate the main instability parameters. The main features of the storm were well reproduced with WRF; furthermore, the high values of the simulated instability parameters denote the presence of favourable conditions for severe convection. The analysis of this event shows that supercells can develop also in a pre-alpine environment, characterized by a complex orography, in particular in the sub-regions where the local morphology creates conditions favourable for severe weather development.

In this paper, we study the impact of lightning and radar reflectivity factor data assimilation on the precipitation VSF (Very Short-term Forecast, 3 hours in this study) for two relevant case studies occurred over Italy. The first case refers to a moderate localised rainfall over Central Italy happened on 16 September 2017. The second case, occurred on 09 and 10 September 2017, was very intense and caused damages in several parts of Italy, while nine people died around Livorno, in Tuscany. The first case study was missed by most operational forecasts over Italy, including that performed by the model used in this paper, while the Livorno case was partially predicted by operational models. We use the RAMS@ISAC model (Regional Atmospheric Modelling System at Institute for Atmospheric Sciences and Climate of the Italian National Research Council), whose 3D-Var extension to the assimilation of RADAR reflectivity factor is shown in this paper. Results for the two cases show that the assimilation of lightning and radar reflectivity factor, especially when used together, have a significant and positive impact on the precipitation forecast. The improvement compared to the control model, not assimilating lightning and radar reflectivity factor, is systematic because occurs for all the Very Short-term Forecast (VSF, 3h) of the events considered. For specific time intervals, the data assimilation is of practical importance for Civil Protection purposes because it transforms a missed forecast of intense precipitation (> 40 mm/3h) in a correct forecast. While there is an improvement of the rainfall VSF thanks to the lightning and radar reflectivity factor data assimilation, its impact is reduced by the increase of the false alarms in the forecast assimilating both types of data.

The knowledge of water vapour distribution is a key element in atmospheric modeling and considerable information, also at the local scale, can be derived from the GPS-ZTD (global positioning system-Zenith total delay) data.

Phenological investigations that adopt aerobiological monitoring methodologies are frequently used for species that rely on the wind for pollen grain dispersion, such as the olive in the Mediterranean basin. The present study of olive flowering dates was carried out in the Calabria region (southern Italy). These were calculated on the basis of a phenological study of pollen levels in the atmosphere in three typical olive-growing areas over an 11 year study period (1999–2009). This phenological method provides olive flowering maps that are based on temperatures (as the growing degree days: GDDs), which are highly correlated with the release of the pollen grains. According to the model developed, the average GDDs corresponding to the flowering dates were calculated for the baseline period of 1981–2000. Moreover, with the use of meteorological data derived from the Intergovernmental Panel on Climate Change scenarios, the future olive flowering dates are estimated for the 20 year period from 2081 to 2100. The close relationships between the spring temperature trends and the reproductive phenological phases in the olive are highly sensitive to climatic change, which has implications in terms of potential latitude and altitude shifts in the olive cultivation areas. In some cultivation areas in southern Italy, the present particular combination of microclimate, soil status and level of erosion is considered as limiting to regular vegetative plant development. However, the use of olive cultivars that are specifically adapted to extremely stressful environments, in terms of high temperatures and water deficit, might represent the main solution for the mitigation of the consequences of climatic change.

A four-dimensional data assimilation (FDDA) scheme based on a Newtonian relaxation (or “nudging”) was tested using observational asynoptic data collected at a coastal site in the Central Mediterranean peninsula of Calabria, southern Italy. The study is referred to an experimental campaign carried out in summer 2008. For this period a wind profiler, a sodar and two surface meteorological stations were considered. The collected measurements were used for the FDDA scheme, and the technique was incorporated into a tailored version of the Regional Atmospheric Modeling System (RAMS). All instruments are installed and operated routinely at the experimental field of the CRATI-ISAC/CNR located at 600 m from the Tyrrhenian coastline. Several simulations were performed, and the results show that the assimilation of wind and/or temperature data, both throughout the simulation time (continuous FDDA) and for a 12 h time window (forecasting configuration), produces improvements of the model performance. Considering a whole single day, improvements are sub-stantial in the case of continuous FDDA while they are smaller in the case of forecasting configuration. En-hancements, during the first six hours of each run, are generally higher. The resulting meteorological fields are finalised as input into air quality and agro-meteorological models, for short-term predictions of renew-able energy production forecast, and for atmospheric model initialization.

This brief communication introduces a new quality-controlled precipitation database for Calabria, shows the precipitation trend for the period considered, and correlates daily rainfall with some common teleconnection patterns. The database consists of daily accumulated precipitation collected by 61 rain gauges from 1 January 1970 to 31 December 2006. The 37-year trend in yearly rainfall shows a decrease of 4.7 mm/y, with a 17% reduction in the yearly mean value. The correlation of the daily rainfall with large-scale patterns shows that the Mediterranean Oscillation Index (MOI a/c) is a useful predictor of daily precipitation over Calabria.

This paper presents first exploratory results and analyses performed on a 30-year (1978–2007) homogeneous precipitation database that has been created for the Calabria peninsula, southern Italy. The database consists of complete time series of daily values of precipitation from 88 stations distributed over the region. The database temporal resolution is one day while its spatial resolution is about 10 km. Calabria offers an interesting scenario for mesoclimatic studies in spatial and temporal rainfall variability. The region is located in the Central Mediterranean Basin, which has a strong seasonal variability that mirrors in large precipitation differences among seasons. The complex orography of the region leads to different exposures of the territory to the rain-bearing air masses and large differences in rainfall can occur in few tens of kilometers. Different kinds of Mediterranean storms are important for Calabria: a) storms originating in the lee of the Alps; b) storms that enter the Basin or develop in the western Mediterranean (Gulf of Lyon, Rhone valley, Iberia, Gibraltar); c) storms from northern Africa; d) storms moving over the central Mediterranean from Balkans and eastern Europe. Again, their interaction with local orography determines complex rainfall patterns and variability. In this paper, the maps of average values of precipitation, rain frequency, rain rate, persistence of rainfall and length of dry periods are presented. Precipitation spatial structure shows that the orography and the sea have a major role, while the seasonal dependence of rainfall unequivocally reveals the influence of the synoptic scale conditions. A large number of cast-studies of heavy precipitation events have been investigated in the past and several of them refer to the east side of Calabria. The results shown here confirm this issue in a climatological sense: despite the fact that yearly precipitation is larger on the west side of the peninsula, most intense rainstorms affect mainly the east side, which is favorably exposed to these storms. The current database represents a foundation for further investigations.

Olives are one of the largest crops in the Mediterranean and in central and southern Italy. This work investigates the correlation of the Olea europaea L. pollen season in Perugia, the capital city of the region of Umbria in central Italy, with atmospheric parameters. The aim of the study is twofold. First, we study the correlation between the pollen season and the surface air temperature of the spring and late spring in Perugia. Second, the correlation between the pollen season and large-scale atmospheric patterns is investigated. The average surface temperature in the spring and late spring has a clear impact on the pollen season in Perugia. Years with higher average temperatures have an earlier onset of the pollen season. In particular, a 1 degrees C higher (lower) average surface temperature corresponds to an earlier (later) start of the pollen season of about 1 week. The correlation between the pollen season and large-scale atmospheric patterns of sea level pressure and 500-hPa geopotential height shows that the cyclonic activity in the Mediterranean is unequivocally tied to the pollen season in Perugia. A larger than average cyclonic activity in the Mediterranean Basin corresponds to a later than average pollen season. Larger than average cyclonic activity in Northern Europe and Siberia corresponds to an earlier than average pollen season. A possible explanation of this correlation, that needs further investigation to be proven, is given. These results can have a practical application by using the seasonal forecast of atmospheric general circulation models.

This paper reports preliminary results of a Limited area model Ensemble Prediction System (LEPS), based on RAMS, for eight case studies of moderate-intense precipitation over Calabria, the southernmost tip of the Italian peninsula. LEPS aims to transfer the benefits of a probabilistic forecast from global to regional scales in countries where local orographic forcing is a key factor to force convection. To accomplish this task and to limit computational time, in order to implement LEPS operational, we perform a cluster analysis of ECMWF-EPS runs. Starting from the 51 members that forms the ECMWF-EPS we generate five clusters. For each cluster a representative member is selected and used to provide initial and dynamic boundary conditions to RAMS, whose integrations generate LEPS. RAMS runs have 12 km horizontal resolution. Hereafter this ensemble will be referred also as LEPS_12L30. To analyze the impact of enhanced horizontal resolution on quantitative precipitation forecast, LEPS_12L30 forecasts are compared to a lower resolution ensemble, based on RAMS that has 50 km horizontal resolution and 51 members, nested in each ECMWF-EPS member. Hereafter this ensemble will be also referred as LEPS_50L30. LEPS_12L30 and LEPS_50L30 results were compared subjectively for all case studies but, for brevity, results are reported for two "representative" cases only. Subjective analysis is based on ensemble-mean precipitation and probability maps. Moreover, a short summary of objective scores. Maps and scores are evaluated against reports of Calabria regional raingauges network. Results show better LEPS_12L30 performance compared to LEPS_50L30. This is obtained for all case studies selected and strongly suggests the importance of the enhanced horizontal resolution, compared to ensemble population, for Calabria, at least for set-ups and case studies selected in this work.

At Crati Scrl an operational version of RAMS 4.3 (Regional Atmospheric Modeling System) was implemented in January 2001. This paper aims to give a first assessment of model performances for quantitative precipitation forecast (QPF). In essence, the effects of enhanced horizontal grid resolution over Calabria, using a 6km spacing domain nested in a 30km resolution parent grid, is studied. To cope with this problem two integrations sets are discussed using two model resolutions. Integrations are performed daily for six months. ECMWF 12:00UTC forecast cycle is used for initial and dynamic boundary conditions. Performances are evaluated by scores computed from model outputs and raingauge measurements coming from Calabrian regional network.

This paper shows the results of a tailored version of a previously published methodology, designed to simulate lightning activity, implemented into the Regional Atmospheric Modeling System (RAMS). The method gives the flash density at the resolution of the RAMS grid scale allowing for a detailed analysis of the evolution of simulated lightning activity. The system is applied in detail to two case studies occurred over the Lazio Region, in Central Italy. Simulations are compared with the lightning activity detected by the LINET network. The cases refer to two thunderstorms of different intensity which occurred, respectively, on 20 October 2011 and on 15 October 2012. The number of flashes simulated (observed) over Lazio is 19435 (16231) for the first case and 7012 (4820) for the second case, and the model correctly reproduces the larger number of flashes that characterized the 20 October 2011 event compared to the 15 October 2012 event. There are, however, errors in timing and positioning of the convection, whose magnitude depends on the case study, which mirrors in timing and positioning errors of the lightning distribution. For the 20 October 2011 case study, spatial errors are of the order of a few tens of kilometres and the timing of the event is correctly simulated. For the 15 October 2012 case study, the spatial error in the positioning of the convection is of the order of 100 km and the event has a longer duration in the simulation than in the reality. To assess objectively the performance of the methodology, standard scores are presented for four additional case studies. Scores show the ability of the methodology to simulate the daily lightning activity for different spatial scales and for two different minimum thresholds of flash number density. The performance decreases at finer spatial scales and for higher thresholds. The comparison of simulated and observed lighting activity is an immediate and powerful tool to assess the model ability to reproduce the intensity and the evolution of the convection. This shows the importance of using computationally efficient lightning schemes, such as the one described in this paper, in forecast models.

The purpose of this paper is to study the development of the coastal flow i.e. its micro-scale characteristics within the surface layer at the sea-land transition and to investigate the development of inland formation of cloudiness during merging of sea/land and valley- mountain breeze regimes. The area is the mountainous southern tip of Italy, about 50 km wide and 300 km long, in the Central Mediterranean Basin. Here, thermal meso-scale circulations and cloud formations on the mountains are pronounced because of their peculiar elongated shape. Upslope flow is very strong, due to the steepness of Apennines, and sea-breeze circulation is supported by the thermally forced meso-scale flows. Here, we present preliminary results from a case study during six consecutive days where sea/land breeze circulation was well developed and discuss the effect on the formation of inland clouds. Sea breeze days are selected by a sodar and surface meteorological station measurements. Cloud development is analyzed by subjective inspection of METEOSAT MSG images in the visible channel. The WRF (Weather Research and Forecasting) model is used to analyze the meteorological situation. The Institute of Atmospheric Sciences and Climate CNR-ISAC in house modular Multi-Tone Sodar system (PC-MTSodar) and the surface meteorological station are installed and operated at a coastal site located at about 300 m from the coastline. Preliminary results show that the methodology is viable to study the development of thermally forced meso-scale circulations over Calabria at micro and large scale and that these circulations can be intense over the peninsula thanks to its peculiar shape. It is shown that the formation of afternoon cumulus clouds, which may result in rainfall, is modulated by synoptic scale conditions. Further development will be a climatic assessment of the role of breezes on local climate.

In this study we conduct a numerical analysis of an intense and destructive storm that occurred over Calabria, southern Italy, on 10–12 December 2003. More than 250 mm of precipitation was recorded over a large area in southern Calabria and one station reported about 660 mm in two days (more than half of the yearly climatological value). Precipitation fell mainly during 11 and 12 December. The storm was characterized by the entrance of an Atlantic upper-level trough associated with a deep surface low that advected humid marine air toward steep Calabrian orography. The steep mountain ridges favoured landslides, which were reported in several villages. Property damage was extensive. We study the storm at the mesoscale by means of the Regional Atmospheric Modeling System (RAMS). The model was successful at representing the observed accumulated rainfall patterns. This justifies our use of RAMS for further analysis of the physical and dynamic factors involved in the storm event. In particular, we use RAMS to evaluate the roles of Calabrian orography, surface latent heat flux, and upper level forcing. The key role of a potential vorticity (PV) streamer, which forced the entire meteorological system from the upper levels is assessed by the PV inversion technique in a Limited Area Model Ensemble Prediction System (LEPS) framework. Results show that the roles of Calabrian orography and surface latent heat flux are important in our simulations. Indeed, humid marine air masses were advected by the synoptic flow toward Calabrian steep coastal mountain ranges determining intense and abundant rainfall.

This study investigates the atmospheric pattern circulations associated with heavy rainfall (HR) days in Calabria, southern Italy, and contributes to the understanding of the dynamical mechanisms that produce those events. Heavy rainfall days are extracted from the raingauge database of the "Protezione Civile Regionale", which has more than a hundred pluviometric stations for the period 1999–2007 (eight years). To study the synoptic atmospheric circulations associated with HR we use the Regional Atmospheric Modeling System (RAMS) gridded data field of 925 hPa and 500 hPa geopotential height. First the number of variables is reduced by principal component analysis (PCA), then a cluster analysis (CA) is applied on those new atmospheric variables and eleven atmospheric patterns are obtained. Clear associations emerged between each of the circulation types and rainfall patterns over Calabria for HR days. These associations can be explained by the interaction between the complex orography of the region, the sea and the synoptic scale flow.