Conference Agenda

Clouds are a crucial regulator of the Earth’s radiation budget (ERB), making the detection and characterization of their properties essential for meteorological research. However, observing clouds in the Antarctic region is challenging: direct in situ data are limited by extreme environmental conditions, while satellites face difficulties in distinguishing clouds from the underlying snow or ice (Cossich et al., 2021). The scarcity of reliable measurements also contributes to the poor representation of Antarctic clouds in General Circulation Models (GCMs), where cloud microphysics parameterizations are often based on mid-latitude or tropical data (Lachlan-Cope, 2010; Bromwich et al., 2012).

This study aims at characterizing in detail the properties of Antarctic clouds by analyzing their seasonal variability and correlation with surface variables, and to develop a parameterization of ice cloud effective dimensions as a function of the thermodynamic conditions of the layer. To achieve this, we use an extensive dataset of spectrally resolved downwelling radiances in the far- and mid-infrared spectral range (200–1000 cm^-1), collected by the REFIR-PAD spectroradiometer (Radiation Explorer in the Far Infrared – Prototype for Applications and Development) installed at Concordia Research Station, Antarctica, spanning 2013–2020.

The radiances are processed using the Cloud Identification and Classification (CIC) algorithm (Maestri et al., 2019; Donat et al., 2024) to identify cloud layers and classify their phase (ice or mixed). These spectra are then used as input to the Simultaneous Atmospheric and Cloud Retrieval (SACR) algorithm (Di Natale et al., 2020), which retrieves cloud optical depth, effective dimensions, and atmospheric profiles of water vapor and temperature. Retrievals are further constrained by a-priori information on cloud-base and cloud-top heights, obtained from the Polar Threshold (PT) algorithm (Van Tricht et al., 2014) applied to collocated lidar backscatter profiles.

Results indicate that, despite strong seasonal temperature variations (213–257 K in summer; ~195–245 K in other seasons), the occurrence of both ice and mixed-phase clouds is consistently associated with relatively warmer near-surface air. Seasonal analysis further reveals a pronounced semi-annual cycle in cloud occurrence and ice cloud optical depth, superimposed on the expected annual variability. Finally, a parameterization of ice cloud effective diameters as a function of layer temperature and ice water content is developed and evaluated against existing literature.

The LUCE mission, formerly CALIGOLA, is an advanced multi-purpose space lidar mission, exploiting elastic (Rayleigh-Mie), depolarized, Raman and fluorescent lidar echoes from atmospheric and ocean constituents, with a focus on atmospheric and oceanic observation aimed at characterizing the Ocean-Earth-Atmosphere system and the mutual interactions within it. This mission has been conceived by the Italian Space Agency (ASI) with the aim to provide the international scientific community with an unprecedented dataset of geophysical parameters capable of increasing scientific knowledge in the areas of atmospheric, aquatic, terrestrial, cryospheric and hydrological sciences. The Italian Space Agency is partnering with NASA on this exciting new space lidar mission. The mission is planned to be launched in 2032, with an expected lifetime of 3-5 years. Scientific studies in support of the mission are ongoing, commissioned by the Italian Space Agency to University of Basilicata and ISMAR-CNR. A Phase A study, commissioned by the Italian Space Agency to Leonardo S.p.A. and focusing of the technological feasibility of the lidar payload, was carried out starting in October 2022 and has recently bridged into a Phase A/B1 study (kick-off in March 2025). Phase A/B1 activities for the platform and the end-to-end system, commissioned by the Italian Space Agency to Thales Alenia Space, have also started, with kick-off in March 2025. In September 2023, NASA-LARC initiated a pre-formulation study to assess the feasibility of a possible contribution to the LUCE mission focused on development of the detection system and sampling chain and the implementation of data down link capabilities. The pre-formulation study ended in September 2024, and, after a successful Mission Concept Review, a phase A/formulation study started in January 2025. This presentation will provide details on current status and future steps of this groundbreaking multidisciplinary lidar mission.

In anticipation of the forthcoming launch of ESA’s 9th Earth Explorer, the Far-infrared Outgoing Radiation Understanding and Monitoring (FORUM) satellite, substantial effort is being devoted to the development of advanced algorithms and databases to fully exploit the mission spectrally resolved radiance measurements across the 100–1600 cm-1 interval.

Within this framework, we present recent advances in the sigma-FORUM fast radiative transfer model [Masiello et al., 2024], designed to provide accurate and computationally efficient simulations of FIR radiances under cloudy-sky conditions. A key new feature is the implementation of a temperature-dependent optical property dataset for column aggregate ice particles [Ren et al., 2025], covering the 160–270 K range. This addition enables a more consistent treatment of the radiative impact of ice clouds in the far-infrared, where sensitivity to ice particle microphysics is significant.

The relevance of the new dataset for the interpretation of FORUM observations is assessed through multiple-scattering simulations of far-infrared outgoing longwave radiation, performed across a range of representative ice cloud conditions.

Finally, the performance of the iota retrieval scheme (Martinazzo, Maestri et al., in prep.), integrating sigma-FORUM with a Tang Chou adjustment scheme [Tang et al., 2019], are evaluated both on simulated and measured cloudy-sky observations from the Infrared Atmospheric Sounding Interferometer, IASI.

This study investigates the relationship between Air Temperature (AT), tree canopy cover, and imperviousness in Rome, Italy, using a novel approach based on low-cost sensors mounted on public buses. The system operates autonomously, requiring no on-site personnel, and provides continuous mea- surements across the entire urban area and at all hours of the day. Data were collected over 53 clear-sky summer days under stable meteorological condi- tions and aggregated onto a 500 m grid after quality control and normaliza- tion. Results show a strong linear correlation between AT and canopy cover during morning hours, with an estimated cooling potential of up to −1.6°C at 100% cover. This effect disappears after the onset of the sea breeze, high- lighting the role of wind in suppressing local cooling. At night, AT exhibits a strong linear increase with imperviousness, with differences up to 3.6°C be- tween fully urbanized and non-urbanized areas. The diurnal cycle of Urban Heat Island (UHI) intensity, derived from the imperviousness-based method, is consistent with theory and previous studies, showing negligible values dur- ing daytime and peaks of 3–4°C at night. By leveraging automated, citywide measurements with low-cost sensors, this study provides new insights into the spatial and temporal variability of urban heat and supports the development of targeted adaptation strategies.

Accurate air temperature measurements in environmental monitoring networks are essential for various applications in meteorology, hydrology, climatology and ecology. Hence, manufacturers of weather stations have been continuously introducing new improvements to take advantage of technological progress and achieve precise measurements and, as much as possible, unaffected by spurious effects. However, while electronic temperature sensors have reached very high levels of accuracy and reliability, radiation shields (RS) remain the most critical component affecting measurement quality. In the last decades, following the increasing diffusion of electronic systems worldwide, the traditional Stevenson screens, as well as their American counterpart, the Cotton Regional Shelter (CRS), have been widely replaced either by Passive Radiation Shields (PRSs), i. e. shields that do not include any active device to prevent sensor overheating, or by Forces Aspiration Radiation Shields (FARS), which instead include systems ensuring suitable sensor ventilation. This study presents a field intercomparison of four of the most advanced PRSs commonly used in operational meteorological applications. During eight months (April-November 2024), identical temperature sensors, protected by different shields, were installed in an experimental field in Friuli Venezia Giulia (Italy). The resulting data were compared using objective statistical analyses based on multiple criteria. Results indicate that the BAR-3, while highly responsive, is prone to overcooling in wet conditions and overheating at low solar elevations. The RAD10 offers good moisture protection and balanced performance, particularly in humid climates, but responds more slowly. The SMART provides reliable behavior in most conditions, especially in dry or temperate climates, with good responsiveness and limited moisture retention. The COMET shows the best nighttime performance and strong moisture shielding, but is the most susceptible to daytime overheating and has the lowest responsiveness due to its thermal inertia. Results from this study provide scientific support for the identification of possible new reference instruments for operational air temperature measurements, as far as traditional shelters are no longer a global standard.

How does climate change impact extreme events and which is the future change of their dynamics? How will the ongoing and future changing climate control the evolution and intensification of severe storms? The Hail Hazard in the Mediterranean (H2Med) project tackles these open issues by investigating hailstorms in the Mediterranean region through the synergistic application of satellite observations, meteorological reanalysis and climatic modelling. Extending and refining the preliminary 22-year climatology proposed in Laviola et al. (2022; 2023) at daily scale, the large-scale and mesoscale atmospheric scenarios that trigger hail events in some regions of the central Mediterranean area are investigated through a cluster analysis using ERA5 reanalysis data. Hail-prone conditions associated with the optimization of a hail-proxy index (based on reanalysis products) are also investigated through the ensemble of climate model projections to outline the future evolution of hail events over the Mediterranean Basin.

The results of this project offer a new paradigm of knowledge and operative tools for better understanding the effects of climate change on hailstorms by using hail-bearing convective systems as a driver for evaluating the potential impact of future changes in the Mediterranean basin. Thus, a new vulnerability map, where past events, current occurrences and future scenarios will be stressed, will be generated to serve the scientific community, operational forecasters, stakeholders such as insurance companies and policymakers.

References

Hail Hazard in the Mediterranean (H2Med) website: https://h2med.isac.cnr.it

Laviola, S., G. Monte, E. Cattani, and V. Levizzani, 2022: Hail climatology in the Mediterranean Basin using the GPM constellation (1999–2021), Remote Sens., 14(17), 4320, https://doi.org/10.3390/rs14174320.

Laviola, S., G. Monte, E. Cattani, and V. Levizzani, 2023: How hail hazards are changing around the Mediterranean, Eos, 104, https://doi.org/10.1029/2023EO230070. Published on 27 February 2023.