Abstract
In this study, a technique facilitating the enhanced detection of airborne volcanic ash (VA) has been developed, which is based on the use of visible (VIS), near-infrared (NIR), and infrared (IR) bands by meteorological satellite systems. Channels with NIR and IR bands centered at ~3.8, 7.3, 8.7, 10.5, and 12.3 μm are utilized, which enhances the accuracy of VA detection. The technique is based on two-band brightness temperature differences (BTDs), two-band brightness temperature ratios (BTRs), and background image BTDs. The physical effects of the observed BTDs and BTRs, which can be used to distinguish VA from meteorological clouds based on absorption differences, depend on the channel and time of day. The Advanced Meteorological Imager onboard the GEOKOMPSAT-2A (GK-2A) satellite has several advantages, including the day- and nighttime detection of land and ocean. Based on the GK-2A data on several volcanic eruptions, multispectral data are more sensitive to volcanic clouds than ice and water clouds, ensuring the detection of VA. They can also be used as an input to provide detailed information about volcanoes, such as the height of the VA layer and VA mass. The GK-2A was optimized, and an improved ash algorithm was established by focusing on the volcanic eruptions that occurred in 2020. In particular, the 3.8 μm band was utilized, the threshold was changed by division between day and night, and efforts were made to reduce the effects of clouds and the discontinuity between land and ocean. The GK-2A imagery was used to study volcanic clouds related to the eruptions of Taal, Philippines, on 12 January and Nishinoshima, Japan, from 30 July–2 August to demonstrate the applicability of this product during volcanic events. The improved VA product of GK-2A provides vital information, helping forecasters to locate VA as well as guidance for the aviation industry in preventing dangerous and expensive interactions between aircrafts and VA.
Highlights
During volcanic eruptions, excessive amounts of volcanic ash (VA), aerosols, and gases are released into the atmosphere, presenting both human health and aviation issues.The primary concern is the risk of an engine shutdown due to the melting of VA particles within the engine of an aircraft
We focused on volcanic events that occurred in 2020 in East Asia because the GK-2A satellite data are available for this year and can be optimized based on specific cases
We studied six volcanoes that erupted in 2020 and characterized the atmosphere after each eruption
Summary
Excessive amounts of volcanic ash (VA), aerosols, and gases are released into the atmosphere, presenting both human health and aviation issues.The primary concern is the risk of an engine shutdown due to the melting of VA particles within the engine of an aircraft. The VA particles can generate extensive damage to the frame of an aircraft due to scraping [1]. They pose severe hazards to high-altitude jet aircrafts along major air routes adjacent to active volcanoes. The reflectance signal decreases close to the critical reflectance due to changes in the aerosol loading. It decreases with increasing AOD and the surface reflectance is larger than the critical reflectance [33,34]. The accurate calculation of the background field can lead to an increase in the accuracy of the VA detection. The aerosol fluctuation was the smallest, which reduces the limitations due to the change in the season
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