## 1 Measurement and Analysis of Local Humidity
### Results and Analysis  
Similar to the reporting method previously described in reference [23], humidity data of the 15 measurement points was acquired throughout the day on 31 July 2013, which was taken as an example for this analysis. The data of each bay type (open, semi-open, or closed) was plotted, as shown in Figure 2. To show the relationship between the humidity of each bay and the ambient humidity, the acquired humidity from within the thermometer shelter is also illustrated on the graphs presented in Figure 2. On that day, the ambient humidity varied significantly within the range of 38.6 to 90.76% RH, and a light to moderate rain shower took place between 16:25 and 16:50, causing dramatic variations in humidity.  
Figure 1: Measurement of local temperature and humidity inside aircraft. 1: Inlet; 2: Cockpit; 3: Front tank; 4: Engine inspect bay; 5: Tail bottom; 6: Landing gear bay; 7: Exhaust nozzle; 8: Main tank; 9: Gun well; 10: Wing middle part; 11: Wing root; 12: Fuselage bottom; 13: Wingtip; 14: Fuselage posterior; 15: Thermometer shelter.  
Figure 2: \(Cont.\)  
From the humidity curves, it can be observed that from 9:00 to 22:00, differences in humidity between measurement points existed, as suggested by the relatively large variation in the 15 humidity curves. The maximum difference in humidity can be observed at 14:50 when the highest humidity was measured at measurement point 12 as 28% RH higher than the lowest humidity measured at measurement point 13. Differences in humidity are relatively small during the nighttime, with a maximum difference of approximately 10% RH. The humidity measured inside the thermometer shelter was in the medium-to-high range among the other measurement points.  
Large humidity differences can occur between different measurement points within the bays of the same open/closed state, as seen in the cases of the pair of measurement points 6 and 7 and pair of points 12 and 13. Humidity differences that occur between bays of the same open/closed state do not necessarily imply that the bay type has no influence on local humidity. This can be owing to three reasons. First, the vapor transmission process can be affected by the open/closed state of the bay. Second, the difference in local temperature as a result of differences in bay type can affect local humidity. Third, water can accumulate in a bay, which directly affects local humidity. A comparison with the previous study reveals that the difference in local humidity between bays of the same type is smaller compared to differences in local temperature [23]. In other words, humidity is more closely related to bay type.  
All bays underwent humidity changes due to the rain shower from 16:25 to 16:50, as indicated by the peaks on the curves during this period. However, the extent and length of the response varied from bay to bay. The rain shower caused the atmospheric humidity to increase by 7.7% RH. The largest increase in local humidity (13%) occurred at measurement point 14 (fuselage posterior), and the least change (2%) was observed at measurement point 3 (front tank). While the humidity changed almost immediately at most of the measurement points in response to the changes in atmospheric humidity  
Figure 2: Humidity variation curves on 31 July 2013.  
after the rain shower started and reached a maximum when the rain stopped, the humidity response at measurement point 2 (cockpit) was approximately one hour later.