## 3 Results
### Seasonality Analysis
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline  & & \multicolumn{2}{c}{**N**} & \multicolumn{2}{c}{**E**} & \multicolumn{2}{c}{**U**} \\  & & \multicolumn{2}{c}{**GNSS/GRACE**} & \multicolumn{2}{c}{**GNSS/GRACE**} & \multicolumn{2}{c}{**GNSS/GRACE**} \\ \cline{2-10}
**Station** & \multicolumn{2}{c}{
\begin{tabular}{c} **Phase** \\ **(DOY)** \\ \end{tabular} } & \multicolumn{2}{c}{**Amplitude**} & \multicolumn{2}{c}{**CC**} & \multicolumn{2}{c}{**Phase**} & \multicolumn{2}{c}{**Amplitude**} & \multicolumn{2}{c}{**CC**} \\  & **(DOY)** & **(mm)** & **CC** & **(DOY)** & **(mm)** & **CC** & **(DOY)** & **(mm)** & \\ \hline SCMB & 112/130 & 1.84/0.90 & 0.63/0.94 & 24/131 & 1.76/0.65 & 0.28/0.94 & 169/115 & 7.01/3.63 & 0.85/0.95 \\ SCML & 81/127 & 1.44/1.02 & 0.35/0.96 & 360/46 & 2.10/0.57 & 0.67/0.94 & 142/113 & 11.55/4.95 & 0.93/0.96 \\ SCMN & 101/131 & 1.62/1.07 & 0.63/0.95 & 24/67 & 0.94/0.53 & 0.23/0.93 & 150/117 & 7.18/4.66 & 0.90/0.96 \\ SCPZ & 92/140 & 1.71/0.96 & 0.73/0.94 & 202/67 & 1.22/0.68 & 0.20/0.95 & 156/123 & 8.46/5.44 & 0.90/0.96 \\ SCSM & 103/150 & 1.71/0.42 & 0.63/0.91 & 226/117 & 1.41/0.23 & 0.57/0.52 & 153/145 & 7.85/1.66 & 0.89/0.84 \\ SCXC & 86/106 & 2.01/0.91 & 0.65/0.96 & 240/19 & 1.86/0.49 & 0.85/0.94 & 30/88 & 6.92/4.31 & 0.89/0.96 \\ SCXD & 102/132 & 2.01/1.07 & 0.66/0.95 & 216/93 & 1.20/0.56 & 0.28/0.93 & 136/119 & 7.69/4.63 & 0.84/0.96 \\ SCYY & 95/132 & 2.23/1.01 & 0.77/0.95 & 117/51 & 1.17/0.62 & 0.14/0.94 & 144/117 & 19.65/19 & 0.89/0.96 \\ XIAG & 99/125 & 1.91/1.08 & 0.53/0.95 & 275/75 & 2.79/0.76 & 0.60/0.96 & 146/111 & 9.50/6.42 & 0.84/0.97 \\ YNCX & 92/135 & 2.37/0.86 & 0.61/0.92 & 160/87 & 1.62/0.82 & 0.29/0.96 & 153/123 & 10.13/6.09 & 0.89/0.96 \\ YNDC & 87/149 & 1.71/0.87 & 0.58/0.91 & 197/127 & 1.83/0.74 & 0.46/0.95 & 128/130 & 7.89/5.15 & 0.86/0.95 \\ YNLC & 83/122 & 2.38/0.95 & 0.76/0.94 & 15/96 & 2.00/0.74 & 0.51/0.95 & 145/145 & 11.18/3.78/0.87 & 0.87/0.97 \\ YNJJ & 92/119 & 2.56/1.07 & 0.66/0.96 & 23/53 & 1.23/0.66 & 0.59/0.96 & 148/100 & 8.79/5.71 & 0.86/0.97 \\ YNMJ & 87/120 & 1.40/0.73 & 0.51/0.87 & 166/95 & 1.52/0.87 & 0.41/0.96 & 151/120 & 10.63/6.73 & 0.92/0.96 \\ YNME & 102/138 & 1.72/0.54 & 0.47/0.79 & 175/126 & 1.75/0.91 & 0.52/0.96 & 89/126 & 7.66/5.18 & 0.84/0.93 \\ YNRL & 77/135 & 2.11/1.08 & 0.63/0.96 & 173/143 & 1.88/0.43 & 0.45/0.86 & 140/113 & 11.16/8.93 & 0.92/0.98 \\ YNSD & 96/123 & 1.90/1.22 & 0.62/0.96 & 26/94 & 1.48/0.64 & 0.33/0.94 & 139/109 & 0.97/0.84 & 0.94/0.98 \\ YNTC & 89/124 & 1.76/1.35 & 0.57/0.97 & 253/109 & 1.63/0.52 & 0.01/0.92 & 145/108 & 13.01/8.29 & 0.91/0.98 \\ YNTH & 92/140 & 1.79/0.65 & 0.67/0.84 & 181/116 & 1.24/0.85 & 0.59/0.96 & 143/128 & 8.04/5.61 & 0.84/0.94 \\ YNVA & 84/136 & 1.85/0.92 & 0.75/0.94 & 297/77 & 1.25/0.77 & 0.35/0.96 & 150/122 & 8.73/5.82 & 0.87/0.96 \\ YNYL & 96/119 & 2.37/1.24 & 0.82/0.97 & 356/71 & 1.44/0.65 & 0.29/0.95 & 142/102 & 12.11/6.77 & 0.85/0.97 \\ YNYM & 94/142 & 1.68/0.88 & 0.40/0.93 & 210/85 & 1.67/0.74 & 0.49/0.95 & 157/126 & 9.37/5.68 & 0.80/0.96 \\ YNYS & 101/127 & 2.75/0.99 & 0.82/0.95 & 215/57 & 1.00/0.69 & 0.23/0.96 & 135/111 & 9.26/5.49 & 0.90/0.97 \\ YNZD & 89/107 & 2.22/1.01 & 0.62/0.97 & 326/30 & 2.15/0.58 & 0.44/0.95 & 150/85 & 7.99/5.04 & 0.78/0.96 \\ \hline Mean Value & 93/130 & 1.96/0.95 & 0.63/0.93 & 170/85 & 1.59/0.66 & 0.41/0.93 & 139/115 & 9.21/5.72 & 0.87/0.96 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Phase, amplitude and CC of seasonal variations of GNSS and GRACE time series for each station. On comparing the N component of GNSS and GRACE, the GNSS results revealed obvious semi-annual periodic changes, consistent seasonality among different stations, and 93 and 269 as the DOYs of the two peaks of the mean seasonal curves, respectively, with an interval of approximately 0.50 years. The GNSS phases, appearing at the end of March or April, occurred before the GRACE phases, which were concentrated in May.