## 3 Results and Discussion
### Comparison Results of TL Calculations
Specifically, when SD = 100 m, the RMSE in winter was less than that in summer (the difference of unsmoothed results was about 1 dB); When SD = 300 m, the unsmoothed results of the two seasons were equivalent; when SD = 500 m, the RMSE in winter was less than that in summer (the difference of unsmoothed results was still about 1 dB). Analyzing the reasons for the difference of the RMSE of TL under different sound source depths in the two seasons, we believed that in terms of the frontal zone position and \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Date**} & \multirow{2}{*}{**SD**} & \multirow{2}{*}{**Frequency**} & \multicolumn{2}{c}{**Unsmoothed Results**} & \multicolumn{2}{c}{**Smoothed Results**} \\ \cline{3-6}  & & & **RMSE (dB)** & \
\begin{tabular}{c} **\% Over 10 dB** \\ **Difference** \\ \end{tabular} & **RMSE (dB)** &
\begin{tabular}{c} **\% Over 10 dB** \\ **Difference** \\ \end{tabular} \\ \hline \multirow{6}{*}{0101} & \multirow{2}{*}{100 m} & 50 Hz & 4.0979 & 4.51 & 4.0635 & 3.09 \\  & & 400 Hz & 3.5768 & 3.56 & 2.2081 & 1.43 \\ \cline{2-6}  & & 50 Hz & 6.0864 & 7.84 & 5.0327 & 6.41 \\  & & 400 Hz & 5.3627 & 7.13 & 4.0636 & 4.51 \\ \cline{2-6}  & & 50 Hz & 6.7936 & 13.06 & 5.9864 & 10.21 \\  & & 400 Hz & 7.2301 & 16.63 & 6.0486 & 11.88 \\ \hline \multirow{6}{*}{0201} & \multirow{2}{*}{100 m} & 50 Hz & 3.6767 & 3.33 & 2.7750 & 2.14 \\  & & 400 Hz & 4.5213 & 4.75 & 4.3992 & 4.04 \\ \cline{2-6}  & & 50 Hz & 5.3600 & 9.74 & 4.7712 & 7.84 \\  & & 400 Hz & 5.8099 & 12.11 & 4.8880 & 10.93 \\ \cline{2-6}  & & 50 Hz & 5.2164 & 5.70 & 4.0808 & 1.90 \\  & & 400 Hz & 5.3095 & 6.65 & 3.8610 & 2.61 \\ \hline \multirow{6}{*}{0701} & \multirow{2}{*}{100 m} & 50 Hz & 6.4535 & 11.96 & 5.9976 & 10.53 \\  & & 400 Hz & 4.6909 & 5.26 & 4.2114 & 3.59 \\ \cline{2-6}  & & 50 Hz & 5.2250 & 6.46 & 4.4719 & 3.83 \\ \cline{2-6}  & & 400 Hz & 5.4706 & 8.37 & 3.9669 & 5.02 \\ \cline{2-6}  & & 50 Hz & 5.8910 & 13.64 & 5.2886 & 11.72 \\  & & 400 Hz & 5.7010 & 8.61 & 4.8033 & 5.02 \\ \hline \multirow{6}{*}{0801} & \multirow{2}{*}{100 m} & 50 Hz & 4.2503 & 5.50 & 3.8117 & 4.55 \\  & & 400 Hz & 4.9431 & 7.18 & 4.7813 & 6.46 \\ \cline{1-1} \cline{2-6}  & & 50 Hz & 5.8038 & 9.81 & 4.9057 & 7.18 \\ \cline{1-1}  & & 400 Hz & 5.4635 & 9.81 & 3.7415 & 6.46 \\ \cline{1-1} \cline{2-6}  & & 50 Hz & 4.4016 & 1.91 & 3.8120 & 1.20 \\ \cline{1-1}  & & 400 Hz & 4.8585 & 3.83 & 3.8297 & 1.20 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Comparison between the TL calculated through the model and the actual situation at different times, different sound source depths, and different frequencies. influence depth, the sound speed distribution obtained by the model in winter was more similar to the actual KEF distribution than that in summer (Figure 8). Therefore, when the sound source and reception depth were shallow, the RMSE of TL obtained in winter was smaller; at deeper depths, the phenomenon of convergence area is no longer obvious compared with that of shallow sound source depth (Figure 9c,f and Figure 12c,f), the RMSE may be greater in winter than in summer (this level was only less than 1 dB, which was acceptable, but we can not deny that the effectiveness of the model in winter was better).