Measurement report: Geostationary satellite and ground-based video observations of cloud brightness variations triggered by the 2022 Hunga Lamb wave

Abstract. The eruption of the Hunga volcano on 15 January 2022 generated a Lamb wave, an atmospheric pressure perturbation propagating horizontally at the speed of sound. A recent regional study uncovered variations in the reflectance of liquid clouds triggered by the wave’s temperature perturbations, most notably a transient darkening during the first minor-arc wave passage across the Caribbean. The present expanded analysis—combining ground-based video footage, surface pressure records, and geostationary satellite imagery—reveals that the Lamb wave-induced cloud reflectance variations were globally detectable for ~6 days. Reflectance anomalies traced temperature anomalies on timescales as short as a few seconds to 1 min and persisted at the 2 % level even after 3 days of propagation. The relative magnitudes of cloud darkening and brightening changed upon each crossing of the antipode or the epicenter due to the caustic phase shift. Brightening dominated during the second minor-arc wave passage because of a polarity inversion. The observed lifetime of the Lamb wave compares well with early theoretical estimates.