Intensity distribution during pre-phase of recurrent jets at the base of each jet in AIA 131 Å. The location of the jet base of each jet is displayed in Fig. 2 (see the red squares). In each panel, the blue arrow indicates the peak phase of the main jet. The small intensity peaks before each main jet are related to small jet ejections (10 Mm height) from the same location. The two vertical dashed red lines in each panel show the duration of the pre-jet intensity oscillation that is used for the wavelet analysis.