Fig. 7

Count of cycle slips calculated from the HKOH (red line with stars), HKPC (green line with triangles), and HKST (blue line with squares) stations from 14 September to 12 October 2013 on the GPS L1 (a) and L2 (b) signals. The life cycle of the Usagi was from 16 to 24 September 2013, as represented by the gray background area between two vertical red dashed lines. The vertical red solid line denotes the TC’s landfall near Hong Kong on 22 September 2013