Fig. 4

a Filtered time series of range change (for pixel highlighted in white in Fig. 3c) for the CSK satellite corrected for atmosphere using a standard APS approach (spatio-temporal filtering). Grey bars indicate period of reversed LOS. b Example of observed absolute wet delay across Nabro caldera on a given date. c Time series of wet (blue) and hydrostatic (red) delays of the summit pixel with respect to the reference pixel (black star Fig. 2c), relative to the first day of acquisition. d Time series of range increase corrected using ERA-I data (red), APS spatio-temporal filtering (black) and a linear-with-height relationship (green)