## 4 Results  
### TC Center Positioning Results  
We compare scatterometer-based and AHI-based center positioning results with the IBTrACS best track for Doksuri, Khanun, and Haikui. The best track was determined by integrating different types of data. For example, the Automated Rotational Center Hurricane Eye Retrieval (ARCHER) is an automated TC center-fixing algorithm to determine a TC center position based on the structure and organization of cloud features in visible and infrared imagery from geostationary meteorological satellites and other data sources (e.g., radar data, aerial reconnaissance data, land observations, and ship reports, etc.) [45], and later adding microwave observations from imagers onboard polar-orbiting meteorological satellites [46]. The IBTrACS is one of the most reliable best track datasets that is currently available. Figure 3 shows the scatterometer-based tracks vs. IBTrACS for each typhoon. The track deviations are usually smaller for stronger typhoons. For Doksuri, 25 scatterometer passes exist (3.65 per day). For Khanun, 67 passes (5.15 per day). For Haikui, 28 passes (4 per day). The joint observations of typhoons by multiple satellites effectively avoid the problem of a single satellite observing a typhoon no more than two times a day. When a typhoon approaches land or islands, the wind field observed by satellite scatterometers cannot cover the center of the typhoon and is excluded from this study. Vortex initialization for TCs located near-shore regions could rely on high-resolution GOES imagers [45; 47], as well as radar and aircraft reconnaissance data [8; 48]. A systematic northeast deviation of the scatterometer-based track from the best track was noticed during the early period of the lifetime of Typhoon Haikui (Figure 3c). This could result from a displacement of the near-surface circulation center from the upper-level cloud center within Typhoon Haikui during these times. In order to confirm this, we overlap the spatial distribution of scatterometer observations with that of AHI channel-13 infrared observations within and around Typhoon Haikui at 1450 UTC on 29 (Figure 4a, HY-2D) and 1930 UTC 30 on August 2023 (Figure 4b, HY-2C). The typhoon center position (cross symbol) from HY-2C/D scatterometer wind vectors (black arrow) is located to the northeast of the center (black circle symbol) determined from AHI observations of brightness temperature (color shading) at both times. The reasons for the inconsistency of the two data types will be discussed later. Figure 5 compares all three tracks (best, scatterometer, and AHI). For Doksuri/Khanun (both reached category 3+), the scatterometer and AHI tracks closely match the best track. For Haikui, during the early period, the scatterometer-based centers are northeast of the best track, whereas the AHI-based centers are southwest (Figure 4). Since the determination of the best track was based on multiple sources of satellite observations, radar data, and  
sounding balloon or dropsonde observations, it is understandable that the best track is located in between the scatterometer-determined and AHI-determined tracks. Figure 4: The 10-m sea surface wind vector (black arrow) from scatterometer observations and brightness temperature observations at AHI channel 13 (color shading) within and around Typhoon Haikui at **(a)** 1450 UTC 29 (HY-2D) and **(b)** 1930 UTC 30 August 2023 (HY-2C), as well as the typhoon center positioning results from scatterometer wind observations (black cross symbol) and AHI observations of brightness temperature (black circle symbol). Figure 3: The best track from IBTACS (black symbol) and the track determined based on scatterometer sea surface wind observations from different satellites (color symbol) of typhoons. **(a)** Doksuri from 1800 UTC 21 to 0600 UTC 28 July 2023; **(b)** Khanun from 0000 UTC 28 July to 1200 UTC 10 August 2023; and **(c)** Haikui from 1200 UTC 28 August to 1200 UTC 4 September 2023.