# Cross-Regional Pavement Temperature Prediction Using Transfer Learning and Random Forest
## 3 Analysis of Meteorological Characteristics  
### Meteorological Characteristics  
To analyze the meteorological characteristics across different regions, the data on air temperature, solar radiation, relative humidity, and wind speed from Site01 to Site04 were statistically summarized. The distribution patterns of each variable were illustrated using histograms and relative frequency distribution curves, as shown in Figure 2. Overall, significant regional variations in these meteorological factors were observed, highlighting the distinct climatic conditions of each site. Table 2 shows the normal distribution fitting results for meteorological data across regions. As shown in Figure 2a, notable differences in air temperature distribution were observed among the regions. At Site01, the air temperature ranges from \(-15\)\({}^{\circ}\)C to \(35\)\({}^{\circ}\)C. A higher relative frequency is observed in the \(0\)\({}^{\circ}\)C to \(20\)\({}^{\circ}\)C interval. This pattern indicates pronounced seasonal variation and considerable temperature fluctuation. Site02 exhibits a broader temperature span, from \(-15\)\({}^{\circ}\)C to \(40\)\({}^{\circ}\)C, suggesting the presence of seasonal variability. In contrast, Site03 shows a more uniform distribution, predominantly between \(5\)\({}^{\circ}\)C and \(25\)\({}^{\circ}\)C, which implies a relatively mild climate with limited diurnal temperature variation. Site04 displays the most concentrated temperature range, primarily between \(25\)\({}^{\circ}\)C and \(30\)\({}^{\circ}\)C. This steep distribution curve reflects high temperature stability, while the distinct peak indicates infrequent occurrences of extreme values. Overall, the most pronounced temperature variability is found at Site01, while Site04 demonstrates the greatest thermal stability. Site02 and Site03 fall between these extremes, each exhibiting different degrees of seasonal transition. \begin{table}
\begin{tabular}{c c c c c c c c c c c c} \hline \hline
**Meteorological** & \multicolumn{3}{c}{**Site01**} & \multicolumn{3}{c}{**Site02**} & \multicolumn{3}{c}{**Site03**} & \multicolumn{3}{c}{**Site04**} \\ \cline{2-13}
**Characteristics** & \(\mu\) & \(\sigma\) & **RMSE** & \(\mu\) & \(\sigma\) & **RMSE** & \(\mu\) & \(\sigma\) & **RMSE** & \(\mu\) & \(\sigma\) & **RMSE** \\ \hline Air temperature & 9.45 & 12.33 & 0.037 & 16.48 & 13.66 & 0.043 & 15.35 & 9.85 & 0.045 & 21.96 & 6.09 & 0.042 \\ Solar radiation & 1.05 & 0.76 & 0.042 & 1.07 & 0.72 & 0.042 & 0.99 & 0.82 & 0.056 & 1.10 & 0.79 & 0.048 \\ Relative humidity & 45.59 & 21.65 & 0.032 & 59.23 & 22.50 & 0.033 & 73.47 & 17.17 & 0.046 & 75.25 & 14.53 & 0.043 \\ Wind speed & 2.69 & 1.94 & 0.036 & 1.52 & 1.38 & 0.059 & 1.73 & 1.15 & 0.026 & 1.69 & 1.03 & 0.026 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Normal distribution fitting results for meteorological data across regions. Figure 2: Meteorological characteristics in different regions. Figure 2b presents the distribution pattern of solar radiation across the regions. A typical single-peak pattern can be observed in all four regions, indicating that the highest frequency occurs near a specific radiation intensity. Despite the overall similarity, differences are evident in the peak positions and curve shapes among the regions. These variations suggest distinct solar radiation characteristics. At Site03, the distribution is the most concentrated, mainly between 0.5 MJ/m\({}^{2}\) and 1.5 MJ/m\({}^{2}\). The steep curve indicates stable radiation intensity with limited fluctuation. The peak positions of Site01, Site02, and Site04 are close to that of Site03; however, the peak heights are lower, suggesting similar typical radiation levels. Compared to Site03, greater daily or seasonal fluctuations are implied, and the radiation stability is relatively reduced. Figure 2c further illustrates the regional characteristics of relative humidity at each site. At Site01, relative humidity is mainly concentrated between 20% and 60%, with a higher frequency observed below 50%.