## 4 Case Study
### Basic Data  
To better reflect the dynamic changes in traffic demand and travel time, the study period selected is from 23 February 2023, to 15 April 2023. The model involves primary data, including hourly airport weather data, flight OD, scheduled departure time, actual departure time, scheduled arrival time, and actual arrival time. (1) Hourly Airport Weather Reports  
The collection of airport weather data includes the airport name, observation time, surface wind direction, wind speed, wind direction variation range, visibility, cloud type and altitude, temperature, corrected sea level pressure, and a two-hour weather forecast. After quantifying the collected airport weather report information, one-dimensional vectors are created for each of the K weather elements over R periods in one operational day, forming an R*K two-dimensional vector. Table 1 shows a portion of the weather data for Xi'an Xianyang International Airport. The quantified variables for airport weather reports include the following:  
* VRB represents variable wind direction, indicating that the wind direction changes by more than 180 degrees or the average wind speed is less than 2 m per second. In \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Variables**} & \multicolumn{4}{c}{**Time**} \\ \cline{2-5}  & **2/23/500–600** & **2/23/600–700** &... & **4/15/2200–2300** & **4/15/2300-2400** \\ \hline Wind stability & 0 & 1 &... & 1 & 1 \\ Average wind direction (\({}^{\circ}\)) & 0 & 210 &... & 360 & 360 \\ Average wind speed (m/s) & 1 & 2 &... & 1 & 1 \\ Visibility (m) & 3000 & 3000 &... & 10,001 & 10,001 \\ Cloud width 1 & 0 & 0 &... & 0 & 0 \\ Cloud height 1 (feet) & 0 & 0 &... & 0 & 0 \\ Cloud width 2 (feet) & 0 & 0 &... & 0 & 0 \\ Cloud width 3 & 0 & 0 &... & 0 & 0 \\ Cloud height 3 (feet) & 0 & 0 &... & 0 & 0 \\ TCU & 0 & 0 &... & 0 & 0 \\ CB & 0 & 0 &... & 0 & 0 \\ Temperature (\({}^{\circ}\)) & 10 & 8 &... & 18 & 17 \\ Dew point (\({}^{\circ}\)) & 3 & 4 &... & 6 & 9 \\ Corrected sea level pressure (hPa) & 1023 & 1022 &... & 1004 & 1003 \\ Weather forecast & 0 & 0 &... & 0 & 0 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Weather data per hour (portion). Figure 4: Layout of routes in Xianyang Airport (cyan dots represent the airports). this case, the average wind direction value can be interpolated using the stable wind direction values from before and after the observation. A binary variable is set: 0 for variable wind direction and 1 for stable wind direction. * CAVOK indicates good weather and visibility, with visibility being more significant than 10 km. This is quantified as the minimum value, in this case, 10,001 m.
* For cloud thickness, FEW represents 1/8 to 2/8 cloud cover, SCT represents 3/8 to 4/8 cloud cover, BKN represents 5/8 to 7/8 cloud cover, OVC represents 8/8 cloud cover, SKC indicates clear skies, NSC represents no clouds above 5000 feet, TCU represents towering cumulus clouds, and CB represents cumulonimbus clouds. For quantification, the maximum value of each cloud type's thickness is used, and two binary variables are set for towering cumulus and cumulonimbus clouds: 0 represents the absence of these clouds, and 1 represents their presence. * For the two-hour weather forecast, an ordinal categorical variable is set: TEMPO indicates temporary weather changes, BECMG indicates gradual weather changes, and NOSIG indicates no significant changes in the weather. * Flight OD Data  
Based on the flight's origin-destination (OD), scheduled departure time, actual departure time, scheduled arrival time, and actual arrival time, the operational delay time for each route can be obtained.