Falconieri Alfredo, Marchese Francesco, Ciancia Emanuele, Genzano Nicola, Mazzeo Giuseppe, Pietrapertosa Carla, Pergola Nicola, Plank Simon, Filizzola Carolina
Institute of Methodologies for Environmental Analysis, National Research Council, 85050 Tito Scalo, Italy.
Department of Architecture, Built Environment and Construction Engineering (ABC), Politecnico di Milano Via Ponzio 31, 20133 Milan, Italy.
Sensors (Basel). 2025 Mar 7;25(6):1658. doi: 10.3390/s25061658.
Every year about fifty volcanoes erupt on average, posing a serious threat for populations living in the neighboring areas. To mitigate the volcanic risk, many satellite monitoring systems have been developed. Information from the medium infrared (MIR) and thermal infrared (TIR) bands of sensors such as the Moderate Resolution Imaging Spectroradiometer (MODIS) and the Visible Infrared Imaging Radiometer Suite (VIIRS) is commonly exploited for this purpose. However, the potential of daytime shortwave infrared (SWIR) observations from the Sea and Land Surface Temperature Radiometer (SLSTR) aboard Sentinel-3 satellites in supporting the near-real-time monitoring of thermal volcanic activity has not been fully evaluated so far. In this work, we assess this potential by exploring the contribution of a normalized hotspot index (NHI) in the monitoring of the recent Home Reef (Tonga Islands) eruption. By analyzing the time series of the maximum NHI value, computed over the Home Reef area, we inferred information about the waxing/waning phases of lava effusion during four distinct subaerial eruptions. The results indicate that the first eruption phase (September-October 2022) was more intense than the second one (September-November 2023) and comparable with the fourth eruptive phase (June-August 2024) in terms of intensity level; the third eruption phase (January 2024) was more difficult to investigate because of cloudy conditions. Moreover, by adapting the NHI algorithm to daytime SLSTR SWIR data, we found that the detected thermal anomalies complemented those in night-time conditions identified and quantified by the operational Level 2 SLSTR fire radiative power (FRP) product. This study demonstrates that NHI-based algorithms may contribute to investigating active volcanoes located even in remote areas through SWIR data at 500 m spatial resolution, encouraging the development of an automated processing chain for the near-real-time monitoring of thermal volcanic activity by means of night-time/daytime Sentinel-3 SLSTR data.
平均每年约有五十座火山喷发,对居住在邻近地区的居民构成严重威胁。为了降低火山风险,人们开发了许多卫星监测系统。为此,通常会利用中分辨率成像光谱仪(MODIS)和可见红外成像辐射仪套件(VIIRS)等传感器的中红外(MIR)和热红外(TIR)波段信息。然而,哨兵 - 3 卫星搭载的海陆表面温度辐射计(SLSTR)进行的白天短波红外(SWIR)观测在支持热火山活动近实时监测方面的潜力,迄今尚未得到充分评估。在这项工作中,我们通过探索归一化热点指数(NHI)在监测汤加群岛霍姆礁近期火山喷发中的作用来评估这一潜力。通过分析在霍姆礁区域计算得到的最大 NHI 值的时间序列,我们推断出了四次不同的陆上喷发期间熔岩喷发的增减阶段信息。结果表明,第一个喷发阶段(2022 年 9 月至 10 月)比第二个阶段(2023 年 9 月至 11 月)更强烈,在强度水平上与第四个喷发阶段(2024 年 6 月至 8 月)相当;由于多云天气,第三个喷发阶段(2024 年 1 月)更难进行调查。此外,通过使 NHI 算法适用于白天的 SLSTR SWIR 数据,我们发现检测到的热异常补充了由业务二级 SLSTR 火灾辐射功率(FRP)产品识别和量化的夜间热异常。这项研究表明,基于 NHI 的算法可能有助于通过 500 米空间分辨率的 SWIR 数据调查甚至位于偏远地区的活火山,这鼓励开发一种利用夜间/白天哨兵 - 3 SLSTR 数据进行热火山活动近实时监测的自动化处理链。