A new ash concentration estimation method using polarimetric data: The RMA observation of the 2015 Calbuco eruption

Abstract

The Chilean volcano Calbuco erupted twice in 2015. The first eruption occurred at 21:04 UTC April 22nd, and the second at 04:00 UTC April 23rd. The ash cloud elevated to stratospheric levels, and extended hundreds of kilometers to the North East reaching Argentina. The RMA0, a polarimetric Doppler weather radar (located at San Carlos de Bariloche airport in Argentina, 124 km to the East) detected both clouds. The movement of the ash cloud could be followed in detail, and the height is reached, about 25 km, allowed an estimation of the total mass ejected: (4.4±0.7)×1011 kg for the first eruption and (1.9±0.3)×1012kg for the second. These estimates suggest this eruption should be classified by a VEI 4 or 5. A new formulation was developed to allow the use of Kdp and Zdr polarimetric radar variables to quantify the concentration of volcanic ash. Also ρhv is used to infer the change of behavior between early and later stages of the eruption.