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Abstract The submarine volcano Hunga Tonga–Hunga Ha’apai erupted explosively on January 15, 2022, offering a unique opportunity to investigate interactions between the atmosphere and ionosphere caused by Lamb and Pekeris waves. However, the resonance of Pekeris waves has not been previously detected. In this study, we applied a multi-point monitoring approach focusing on the lower ionosphere and atmospheric electric field. Here we show observed oscillations of 100–200 s in manmade transmitter signals and the magnetic and atmospheric electric fields, which were caused by Pekeris waves. However, no corresponding changes with the period of 100–200 s in atmospheric pressure due to Pekeris waves were observed on the ground. A simulation of neutral wind revealed Pekeris waves oscillating near the mesopause, suggesting resonance. Therefore, the oscillation in atmospheric electric field is interpreted that the resonance in the lower ionosphere was projected onto the Earth's surface via a global electric circuit.

A rotating shadow-band spectroradiometer system is a powerful tool for surveying light in an environment. It can provide the following spectral components of the solar irradiance without using any traditional solar tracking tool: direct normal irradiance (spDNI), diffuse horizontal irradiance (spDHI), and global horizontal irradiance (spGHI). Both irradiances, spDNI and spDHI, are derived from the combination of spGHI observations at different shadow-band positions. The shadow-band system induces basic errors caused by the imperfect corrections of the diffuse irradiance shadowed by band. To restrict the basic errors to < 2 %, the band slant-angle should be < 72° for a usual operating condition of the MS-700 spectroradiometer manufactured by EKO Instruments Co., Ltd., with the MB-20 shadow-band system for MS-700. The errors in the spDNI and spDHI estimation are evaluated quantitatively by using realistic models that consider instrumental and atmospheric conditions. Estimates of spDNI can result in optical depth errors. The relative error in this estimation is described by using a correction coefficient Cfwd defined by the ratio of the true diffuse irradiance simulated by the shadowed irradiance to the approximate value observed. The value of Cfwd depends on the magnitude of the aerosol optical depth as well as the aerosol type. This error analysis should help in improving the accuracy of this system of measurements. [ABSTRACT FROM AUTHOR]