Thermal remote sensing of sea surface temperature

Sea surface temperature has been an important application of remote sensing from space for three decades. This chapter first describes well-established methods that have delivered valuable routine observations of sea surface temperature for meteorology and oceanography. Increasingly demanding requirements, often related to climate science, have highlighted some limitations of these ap-proaches. Practitioners have had to revisit techniques of estimation, of characterising uncertainty, and of validating observations—and even to reconsider the meaning(s) of “sea surface temperature”. The current understanding of these issues is reviewed, drawing attention to ongoing questions. Lastly, the prospect for thermal remote sens-ing of sea surface temperature over coming years is discussed

SATELLITE AND IN SITU GROUND TEMPERATURE

Ground thermal anomalies in volcanic-hydrothermal systems, where the outflow of hot fluids gives rise to fumarolic fields, soil degassing, and hot soils, have, up to now, rarely been investigated by using satellite. Here we report a comparison between surface temperature derived by satellite data and a large data set of measured soil temperatures and CO2 fluxes for a volcanic-hydrothermal system, the Solfatara of Pozzuoli (Campi Flegrei, Italy). Surface temperatures derived from ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) data are compared with soil temperatures and CO2 fluxes from four surveys performed in 2003, 2010, and in 2014. The good match between the spatial distributions of computed and measured temperatures suggests the adequacy of satellite data to describe the Solfatara thermal anomaly, while the correspondence between temperatures and CO2 fluxes, evidences the link between degassing and heating processes. The ASTER derived surface temperatures (14–37°C) are coherent with those measured in the soil (10–97°C at 10 cm depth), considering the effect of the thermal gradients which characterize the degassing area of Solfatara. This study shows that satellite data can be a very powerful tool with which to study surface thermal anomalies, and can provide a supplementary tool to monitor thermal evolution of restless volcanoes

Operational volcanic ash monitoring during Etna volcanic crises

Operational systems able to monitor volcanic ash in real time and provide both critical eruption parameters and useful warnings to emergency responders and government agencies should be implemented in most volcanic observatories worldwide. Over the past ten years, more than fifty lava fountains occurred at Mt. Etna (Italy) that produced eruption columns more than 10 km a.s.l. and generated large tephra fallout around the volcano flanks. For civil protection purposes, there was the need to improve the already existing monitoring systems daily run at the Istituto Nazionale di Geofisica and Vulcanologia, mainly based on eruption scenarios (weak and strong plume scenarios). We present a new upgraded system that has multiple objectives: i) to have a fast system able to best identify the type of eruptive scenario; ii) to forecast the tephra deposit in near real time, i.e. within a few hours from the eruptive event; iii) to determine the area impacted by clasts larger than 5 cm that could severely injure hikers, guides, and volcanologists and damage infrastructures in proximity of Etna summit craters. This new system is based on the real-time estimate of column height from the analysis of images taken by SEVIRI satellite and by new calibrated cameras and using meteorological parameters obtained by local models.PublishedVienna , Austria6V. Pericolosità vulcanica e contributi alla stima del rischi

Airborne LiDAR and Hyperspectral Data to Support the Seismic Vulnerability of Urban Environments

The seismic vulnerability analysis of urban environments is an operational issue that concerns the comprehensive knowledge of both building structural features and soils geophysical parameters, especially when considering areas that are prone to hydrogeological and seismic disasters. The protection of such environments, together with the population growth and the urbanization processes, requires a multi-disciplinary approach aiming at providing both an effective assessment of urban resources and synthetic parameters for managing post crisis events, restoration activities and search & rescue operations. Within such a framework, airborne Light Detection and Ranging (LiDAR) and Hyperspectral sensors have demonstrated to be powerful remote sensing instruments, whose jointly use allow providing meaningful parameters to describe both the topographic settings of urbanized areas and the buildings properties, in terms of geometrical, spectral and structural features. Based on this rationale, in this study, the operational benefits obtained by combining airborne LiDAR and Hyperspectral measurements are provided to support the seismic vulnerability assessment of urban seismic areas. The digital elevation model as well as the building height and the shape of the observed area are gathered by using airborne LiDAR measurements. Spectral and structural information of urban buildings are provided through the supervised classification of IMSpectorV10E VNIR (wavelength range between 400 and 1000nm subdivided into 503 bands) measurements acquired by the IPERGEO sensor. The objective is to combine the different products provided by LiDAR and Hyperspectral image processing analysis within a Geographic Information System (GIS) platform, to evaluate the intrinsic properties of buildings (e.g. perimeter, covered area, height and type of roofs) together with the topographic features of the surrounding area (e.g. the surface height and slope) for providing synthetic parameters and thematic maps useful for seismic assessment and mitigation purposes, such as: (i) the identification of steep slope areas, (ii) the analysis of building roof typology for supporting the evaluation of structural load conditions, (iii) the detection of critical structures (e.g. asbestos buildings), (iv) the identification of primary roads (in terms of escape or access routes) for supporting search and rescue operations, (v) the analysis of main road conditions after building collapses. Meaningful experimental results, gathered for the historical center of Cosenza city (Italy), allow demonstrating the benefits of the proposed approach for both seismic assessment and mitigation purposes. The present work is supported and funded by Ministero dell'Universita, dell'Istruzione e della Ricerca (MIUR) under the project PON01-02710 "MASSIMO" - "Monitoraggio in Area Sismica di SIstemi MOnumentali"

Near-Real-Time Tephra Fallout Assessment at Mt. Etna, Italy

During explosive eruptions, emergency responders and government agencies need to make fast decisions that should be based on an accurate forecast of tephra dispersal and assessment of the expected impact. Here, we propose a new operational tephra fallout monitoring and forecasting system based on quantitative volcanological observations and modelling. The new system runs at the Istituto Nazionale di Geofisica e Vulcanologia, Osservatorio Etneo (INGV-OE) and is able to provide a reliable hazard assessment to the National Department of Civil Protection (DPC) during explosive eruptions. The new operational system combines data from low-cost calibrated visible cameras and satellite images to estimate the variation of column height with time and model volcanic plume and fallout in near-real-time(NRT). The new system has three main objectives: (i) to determine column height in NRT using multiple sensors (calibrated cameras and satellite images); (ii) to compute isomass and isopleth maps of tephra deposits in NRT; (iii) to help the DPC to best select the eruption scenarios run daily by INGV-OE every three hours. A particular novel feature of the new system is the computation of an isopleth map, which helps to identify the region of sedimentation of large clasts (≥5 cm) that could cause injuries to tourists, hikers, guides, and scientists, as well as damage buildings in the proximity of the summit craters. The proposed system could be easily adapted to other volcano observatories worldwide.Publishedid 29876V. Pericolosità vulcanica e contributi alla stima del rischioJCR Journa

A new way to reduce the impact from tephra fallout during Etna explosive eruptions

The frequent number of explosive events at Mt. Etna, in Italy, over the last ten years, has made necessary the improvement of volcanic ash monitoring and forecasting system at the Istituto Nazionale di Geofisica e Vulcanologia, Osservatorio Etneo (INGV-OE). Tephra fallout produced during Etna lava fountains largely impact the population living on the volcano flanks. In addition, during one of the most powerful paroxysms, large clasts fell in proximal areas injured tourists and hikers. To reduce risk, the Italian Department Civil Protection (DPC) asked and funded INGV-OE to do a research project finalized to three specific objectives. First, identify the plume scenario (i.e. weak plume scenario (WPS) and strong plume scenarios (SPS)) based on 1-D plume model. Second, forecast characteristics of tephra deposition using near real time observations. Third, identify the region possibly impacted by large clasts (>5 cm). Two algorithms were developed to measure the column height. One from the calibrated images of two visible cameras installed on the S and W flanks of the volcano, respectively; and the other one from satellite data using a procedure based on the computation of the volcanic plume-top brightness temperature at 10.8 mm. The analysis of lava fountains that occurred between 2011 and 2015 provided the opportunity to differentiate between weak, transitional and strong plumes. The uncertainty associated with eruption source parameters, while maintaining a fixed plume height, was also assessed. In the near future the implementation of these products into the INGV-OE - monitoring room will guarantee a better and timely information to civil protection authorities charged of risk prevention at different levels of responsibility.PublishedNapoli6V. Pericolosità vulcanica e contributi alla stima del rischi

IDENTIFICAZIONE DI ANOMALIE TERMICHE IN AREE NATURALI ED URBANE ATTRAVERSO SERIE STORICHE DI DATI SATELLITARI NELL’INFRAROSSO TERMICO

Le attuali missioni satellitari che forniscono immagini nella regione spettrale dell'infrarosso termico (TIR) e con una risoluzione spaziale di 60-100 metri, permettono la stima della temperatura del suolo (LST) e sono capaci di evidenziare anomalie termiche, aree cioè dove la temperatura superficiale ha un valore significativamente diverso da quella di background. Le anomalie termiche sono potenzialmente legate a fonti di energia presenti nel sottosuolo o ad una modifica dell’uso e della sua copertura come ad esempio le aree urbane dove è possibile osservare il fenomeno delle isole di calore (UHI). Il presente lavoro di dottorato vuole analizzare a questi due campi. Sono stati condotte due tipi di analisi su due casi di studio. La prima è l’individuazione di anomalie termiche su aree geotermicamente attive (vulcaniche e non). La seconda è focalizzata sull’identificazione dell’UHI. Entrambe le analisi sono basate sulle serie storiche di LST ottenute da dati satellitari. Nel primo studio, le serie storiche dei sensori ASTER e TIRS/Landsat 8 sono state elaborate utilizzando due diverse metodologie: l’algoritmo Temperature and Emissivity Separation (TES) per ASTER e il Single Channel Algorithm (SCA) per Landsat 8. Sono state ottenute due serie storiche LST e i risultati sono stati confrontati e validati con misure a terra. TES e SCA sono metodologie note e sono state applicate su due siti con differenti caratteristiche geologiche: l'area vulcanica dei Campi Flegrei e l'area geotermica del Parco delle Biancane. Il secondo caso di studio ha riguardato la caratterizzazione dell’UHI della città di Modena. L'analisi è basata sull’utilizzo delle serie temporali di LST di immagini TIRS / Landsat 8 ottenute tramite la metodologia SCA. In entrambi i casi di studio l’identificazione dell’anomalia termica è basata sull’analisi delle componenti principali (PCA) sulle serie temporali di LST. Nello studio dell’UHI è stato inoltre considerato un secondo metodo, la Differenza Normalizzata delle temperature. I risultati ottenuti da questi studi hanno fornito alcune importanti considerazioni: - Le metodologie usate per ottenere la stima di LST producono una buona stima di temperatura anche in aree molto particolari dove sono presenti anomalie geotermiche e sono utilizzabili per l’analisi dell’andamento di temperatura dell’aria vicino al suolo; - L’individuazione delle anomalie termiche basate sull’analisi delle serie storiche di LST sono spesso affette da un trend stagionale. Il metodo della PCA offre una buona e facile soluzione per evitare questo problema producendo una mappa molto ben dettagliata delle anomalie termiche in entrambe le aree geotermiche e nelle aree urbane (UHI); - I due casi di studio rappresentano due ulteriori dimostrazioni della potenzialità delle osservazioni satellitari nella regione dell’infrarosso termico per applicazioni di tipo ambientale.Current satellite missions, providing imagery in the Thermal InfraRed (TIR) spectral region at 60-100 meters of spatial resolution, give the possibility to estimate the land surface temperature (LST) and highlight the main surface thermal anomalies, i.e. areas where the surface temperature has a value significantly different from the background. Thermal anomalies are potentially related to the underground energy sources or to land use and coverage variations as urban areas where the urban heat island (UHI) phenomenon can be observed. This work wants to fit in these two fields. Two separate analysis on two case studies were carried out. The first is the detection of thermal anomalies on geothermal active areas (volcanic or not). The second focuses on the detection of UHI. Both the analyses are based on remote sensing LST time series. In the first study, ASTER and TIRS/Landsat 8 time series have been processed using two different methodologies: Temperature and Emissivity Separation (TES) algorithm for ASTER and Single Channel Algorithm for Landsat 8 (SCA). Two LST time series have been obtained and results are cross-compared and validated with ground measurements. TES and SCA are well-known methodologies and have been used to evaluate LST on two different test sites with different geological features: the volcanic area of Campi Flegrei and the geothermal area of Parco delle Biancane. The second case study has been addressed to the characterization of the UHI of the city of Modena. The analysis is based on TIRS/Landsat 8 image time series processed using the SCA methodology. In both the case studies the thermal anomaly detection is based on the principal component analysis (PCA) of the LST time series. In the UHI study a second method, the Normalized Temperature Difference, has been also considered. The results of these studies furnished some important consideration: - The methodologies used to obtain LST produce good temperature estimates also in the very particular case of geothermal anomalies and usable for near ground air temperature trends analysis; - Thermal anomalies detection based on LST time series is often affected by seasonal trends. The PCA method offers a good and easy way to avoid this problem producing very detailed maps of thermal anomalies both in geothermal areas and in urban areas (UHI); - The two case studied represent two more demonstration of the potentiality of satellite observations in TIR for environmental applications