Work Packages

Production of a daily hail climatology (1999-2021) from satellite observations for the Mediterranean Basin (Leader CNR). The aim of the WP is to obtain daily maps of H and SH occurrences at 1°x1° spatial resolution covering the period 1999-2021. The premise of this WP is the hail dataset (“hail season” from April to November) obtained from the passive microwave (PMW) observations of the GPM satellite constellation (Laviola et al., 2022). The working dataset covers the last 22 years of hail season by gathering hail events in two hail categories: large Hail (H; diameter [2, 10] cm) and Super Hail (SH; diameter > 10 cm).

The activity of this WP aims to calculate a level 2 product where all 22 years of hail data are regridded to compose a new daily hail map on a regular grid box. Thus, the whole Mediterranean basin will be redefined following the concept of hail day where intense hail events (H) and extreme hail events (SH), are remapped in space and time to be consistent with the large scale of the explored domain. Even though the contrast between the typical scale of hail events and the resolution of the hail days.

This WP aims at identify the atmospheric types that promote hail and super hail events in the Mediterranean Basin, and develop a hail-proxy index based on environmental variables. This WP will characterise the atmospheric scenarios that trigger the H and SH in the Central Mediterranean area. The input for this activity will be the 1°x1° spatial resolution daily climatology produced by WP1. The research activities will be firstly devoted to identify the main H and SH spatial pattern for the period 1999-2021 using a multivariate statistical approach based on Principal Component Analysis and cluster analysis. Subsequently, using several basic atmospheric fields and stability indices provided by ERA5 dataset, the large scale and mesoscale atmospheric circulation schemes associated with the H and SH spatial pattern will be identified.

This analysis will provide a new synoptic climatology of H and SH events, consisting of a set atmospheric types that will be used as a benchmark to reconstruct the hail favouring environment conditions in the previous 40 years (1959-1998 period). In addition, the results of this research activity will be the basis for the development of a hail proxy index based on an optimal combination of environmental variables extracted from ERA5 and additional regional reanalysis products. Finally, the outcomes of the haily proxy index will be exploited to select the most relevant case studies that will be used to evaluate the nowcasting performance of the MASHA technique provided by WP4.

WP3 is aimed at analysing future changes of the occurrence of large hail events over the Mediterranean region based on the proxy variables and hail index identified in WP2. The latest CMIP6 climate model output adopted by the IPCC will be exploited to construct daily fields of the hail proxy variables and seek for hail favourable synoptic conditions in the historical period which are consistent with those identified in WP2. Hail favourable conditions and hail index results will be compared to a correlative analysis of meteoclimatic extremes based on the ETCCDI/ETSCI standardised indices, including extreme temperature, extreme precipitation, wet/dry spells and heat/cold waves.

The analysis will allow estimating and characterising the fraction of precipitation extreme events that lead to hail precipitation, identify and investigate the models that better reproduce what found in WP2, and understand how to upgrade the current extreme indices suite to include hail. The analysis will be extended to projections for the 21st century under different SSPs scenarios, to provide estimates of the expected changes in hail occurrence in the Mediterranean basin over the next decades. The analysis will be performed exploiting the ESMValTool suite of metrics developed for CMIP and gridded data and adopted by the IPCC: the hail index and associated hail proxy parameters will be introduced in an ad-hoc metric component and proposed for inclusion in the ESMValTool package.

This WP aims at identify the atmospheric types that promote hail and super hail events in the Mediterranean Basin, and develop a hail-proxy index based on environmental variables. This WP will characterise the atmospheric scenarios that trigger the H and SH in the Central Mediterranean area. The input for this activity will be the 1°x1° spatial resolution daily climatology produced by WP1. The research activities will be firstly devoted to identify the main H and SH spatial pattern for the period 1999-2021 using a multivariate statistical approach based on Principal Component Analysis and cluster analysis. Subsequently, using several basic atmospheric fields and stability indices provided by ERA5 dataset, the large scale and mesoscale atmospheric circulation schemes associated with the H and SH spatial pattern will be identified.

This analysis will provide a new synoptic climatology of H and SH events, consisting of a set atmospheric types that will be used as a benchmark to reconstruct the hail favouring environment conditions in the previous 40 years (1959-1998 period). In addition, the results of this research activity will be the basis for the development of a hail proxy index based on an optimal combination of environmental variables extracted from ERA5 and additional regional reanalysis products. Finally, the outcomes of the haily proxy index will be exploited to select the most relevant case studies that will be used to evaluate the nowcasting performance of the MASHA technique provided by WP4.