Radar image of the May 17, 2018 eruption of ash from Halema‘uma‘u

Radar image of the May 17, 2018 eruption of ash from Halema‘uma‘u Crater. This image is a slice through the cloud at an altitude of 14,000 ft (4 km) above sea level at 4:12 a.m., HST. The colors scale is radar reflectivity, a measure of the size of the particles and their concentration within the ash cloud. Colors indicate the different echo intensities or reflectivity. Reflectivity is the amount of transmitted power returned to the radar receiver, and because it occurs over a wide range, a logarithmic (or decibel, dBZ) scale is used. Data could also be displayed in cross section to estimate the height of the cloud.