## 3 Results and Discussion
### Analysis of the Communication under Evaporation Ducts  
#### 3.2.1 Propagation Effect  
Based on the evaporation duct characteristics at the analyzed position (23.4\({}^{\circ}\) N, 120.0\({}^{\circ}\) E) in Figure 3, we investigated the communication effects across the Taiwan Strait under the evaporation duct, focusing on quality and accessibility. With a view to providing favorable support for maritime applications across the Taiwan Strait, a communication radius of 300 km was considered, which could basically cover the northeast to southwest area. The propagation effect at the receiving position 300 km away using the evaporation duct is shown in Figure 7; monthly and hourly statistical results of path loss and serviceability ratio with 8 m antenna height at 10 GHz are described. Considering the analysis results in Section 2.3, a path loss budget of 250 dB was set, in which the receiver could demodulate the signal at 1 Hz.  
Figure 6: Distribution of the EDH in the Taiwan Strait in different periods and seasons during 2020: (**a**) statistical results from 9 to 14 0\({}^{\circ}\)clock; (**b**) statistical results in other periods.  
Figure 7: Propagation effects under the evaporation duct channel at the analyzed position (23.4\({}^{\circ}\) N, 120.0\({}^{\circ}\) E) for a 300 km range during 2020: (**a**) serviceability ratio at 1 Hz at different times of the day; (**b**) path loss distribution at different times of the day; (**c**) path loss spatial distribution of transmission link in the Taiwan Strait; (**d**) statistical results of path loss in different months; (**e**) serviceability ratio at 1 Hz in different months.  
Most periods are depicted in blue, representing lower path losses, in the contour map of Figure 7c. A wide contour area with a path loss below 160.0 dB from 9 to 14 o'clock emerged, which may supply efficient support for constructing a communication system using evaporation ducts. The red covered area, representing maximal losses, mainly occurred at right-time (from 19 to 4 o'clock), which may lead to serious signal interruptions.  
The annual serviceability ratio reached 93.50%, in Figure 7a, with the path loss budget fixed at 250 dB, while the highest available period, from 12 to 13 o'clock, reached 100.00%. The available ratio fell to a minimum of 86.88% at 4 o'clock.  
Affected by the transition between stable and unstable conditions, in Figure 7b, the hourly median path loss, as depicted by the red line, increased rapidly from 0 o'clock to the maximum median loss of 202.41 dB at 7 o'clock. The minimum median path loss was 150.05 dB, which exceeded the preset path loss budget by 99.95 dB. The propagation loss changed rapidly during the periods of sunrise (from 5 to 9 o'clock) and sunset (from 15 to 18 o'clock), resulting in the deep fading of received signals.  
The monthly median path losses, presented as the black line in the colorful boxes in Figure 7d, were around 150 dB. The serviceability ratio fluctuated wildly, in Figure 7e, varying from a minimum of 45.83%, to a maximum of 100.00%. A noticeable proportion of path losses exceeded the preset budget from January to April, and signal interruptions may, in the future, occur from time to time during this period. In contrast, the overall path loss was significantly reduced in summer and autumn, and the serviceability ratio continuously exceeded 80%.