Calbuco Ash Over Buenos Aires 04-24-2015 The most northern ash plume from the Calbuco eruption passed directly over Buenos Aires yesterday, impacting air travel into and out of the airport there; here's the VIIRS RGB and OMPS AI over VIIRS RGB The largest AI value on 23 April was over 29, indicating an extremely high cloud; Calipso lidar measurements confirmed the altitude of the initial cloud was 18 km! Since the largest AI value yesterday was "only" a little over 7, the cloud looked to be bit lower down.