# Correction of Field-Measured Wind Speed Affected by Deterministic Interference Factors
## 2 Site Overviews and Wind Conditions  
NLDI is an isolated island located in the Pearl River estuary area, which is in the southwest of Shenzhen, with the highest elevation of approximately 300 m. The location of the station is the south end of the island (113.8\({}^{\circ}\) E, 22.42\({}^{\circ}\) N) and the surrounding landform is an open Pearl River water and low island vegetation. Hong Kong Tuen Mun District is 9 km to the east of the station, Hong Kong Airport (HKIA) is 13 km away to the southeast, and Shenzhen Nanshan District is 9 km away to the northeast (Figure 1). Theoretically, the interference of the surrounding environment on the measured wind speed is relatively minimal. However, as the wind mast is located at the end of the island and only 65 m above sea level, the measured wind speed may be affected by the island itself.  
PAFC is located in Futian district with the height of 592.5 m, and an 8 m high hollow-layer is found at the height of 576.0 m (Figure 2). The hollow-layer plane is an inclined four degree slope one with various instruments or equipment of different heights symmetrically installed. An anemometer is fixed in the northeast of the hollow-layer; it is 81 cm over the top of the largest equipment box, and 182 cm over the inclined plane in the model. However, the influence on the measured wind speed resulting from the two pillars symmetrically along the axis of 45\({}^{\circ}\) at the corners and the equipment installed on the hollow-out floor must be considered. The height of the anemometer at the hollow-layer is close to the gradient wind height, and the measured wind speed is slightly affected by the roughness of the surface roughness. However, the influence of the building, especially the symmetrical giant pillars along the 45 \({}^{\circ}\) axis and a large number of instrument boxes installed in the hollow-layer plane, and the measured wind speed must be considered.  
Figure 1: Landscape around NLDI.  
Super Typhoon Mangkhut (No. 1822) is one of the most disastrous tropical cyclones that landed on the coastal areas of South China in the recent 10 years, with the maximum wind level of 17 at the center during landfall [18; 19]. The NLDI and PAFC sites completely recorded the wind speed from 0:00 to 24:00 (UTC + 8) on September 16, 2018 during the passage. Figure 3 shows the 10 min mean wind speed and wind direction curve. The NLDI station recorded the maximum mean wind speed of 40.7 m/s with the wind direction of 52\({}^{\circ}\) at 12:43, and the second maximum mean wind speed was 39.1 m/s with the wind direction of 84\({}^{\circ}\) at 14:47, indicating a slight difference between the results. Meanwhile, the maximum mean wind speed of 33.7 m/s at the PFAC site was recorded at 14:48 under the wind direction of 93\({}^{\circ}\). Compared with tropical cyclones of super typhoon level, the wind speed record at an altitude of nearly 600 m was extremely small. This finding indicated the strong interference around the measured PAFC site. The dominant direction of strong wind in Shenzhen is east wind and its vicinity; thus, the wind directions of 84\({}^{\circ}\) for NLDI and 93\({}^{\circ}\) for PAFC are considered the maximum mean wind speeds when determining the reference wind pressure.  
Figure 2: Information of PAFC: (**a**) building elevations; (**b**) position of anemometer and corner pillars; (**c**) details of the hollow-layer plane.