Evolution of the flux ratio ℜ between the NE and SW images of PKS 1830−211(marked symbols for each spectral window in our ALMA observations), overlaid over the γ-ray light curve (in grey) retrieved from the Fermi-LAT public archive. The dotted lines mark the time when the submillimeter flare begins to be seen in each image, according to the model by Martí-Vidal et al. (2013).