An observational study of the inner core structure of Typhoon Meranti (2016) near landfall

Abstract

When passing by Taiwan, Typhoon Meranti (2016) was deflected northwards and shrank on infrared images, while its intensity maintained above 50 m⋅s–1 with the radius of maximum wind (RMW) smaller than 30 km. In this paper, satellite and ground‐based dual‐Doppler data were adopted to document Meranti's inner core evolution after its interaction with Taiwan's topography. It was found that the eyewall of Meranti was highly asymmetric on radar reflectivity with maximum on the down motion left side during its landfalling stage in Taiwan Strait, whereas the environmental vertical shear (about 3 m⋅s–1) was not favorable for asymmetry of this strength. As Meranti was very close to Taiwan's southern tip when passing by, its deep convection distribution, especially part on the down motion right side, was impaired by the topography of Central Mountain Range, thus contributed to this asymmetry. The eyewall at 1645 UTC was examined in detail, and it was found that the primary circulation with weaker azimuth perturbations remained intact at this time, while vertical circulation differed with direction. Besides, there was a low level northeast‐southwest flow through the eye, same as the direction of Taiwan Strait. Perhaps this radial inflow, along with the primary circulation, had contributed to the maintenance of asymmetry in reflectivity, so the eyewall did not recover in the Strait despite the weak wind shear. In addition, stronger storm‐relative wind asymmetry in the mid‐troposphere was observed. This wind asymmetry was in favor of track deflection, so was the diabatic heating associated the rainfall asymmetry. The channel wind, along with downslope wind from Taiwan, may help to maintain the intensity of Meranti and the smaller RMW, which needed further investigation with high resolution numerical models.

Microphysics of Heavy Rain Associated With the Eyewall and Inner Rainbands of Typhoon Meranti (2016)

“…X. Zhang et al. (2020) used this DPR in Xiamen along with retrieved wind data to analyze the inner core structure of Typhoon Meranti, whose data set is also adopted in this study. Finally, the radar data after QC is interpolated onto the Cartesian coordinate with horizontal and vertical resolution respectively of 0.01° and 500 m.…”

“…First, the RMW (∼45 km) is estimated by the retrieved wind field based on two Doppler radars in Xiamen and Quanzhou of Fujian province, whose detail description was introduced in the work of Shanghai Typhoon Institute (X. Zhang et al, 2020). And then, the final-adopted RMW at each radar scanning time was modified according to the structure of annular reflectivity near the RMW (Figure 1b).…”

“…The same DPR data and retrieved wind field as in X. Zhang et al (2020) are used in this study. Figure 5 shows the contoured frequency by altitude diagrams (CFADs; J.…”

“…Figure5. The contoured frequency by altitude diagrams of vertical velocity with a bin of 0.5 m s −1 in the convective area of (a) the eyewall and (b) inner rainbands from 1446 UTC to 1955 UTC 14 September, derived from the same retrieved wind field as in X Zhang et al (2020)…”

Precipitation Characteristics of an Abrupt Heavy Rainfall Event over the Complex Terrain of Southwest China Observed by the FY-4A Satellite and Doppler Weather Radar

“…Radar detection over complex terrain may be influenced by the topography itself [18], but the radar observations cannot be ignored in characterizing the orographic rain structure and its associated spatiotemporal scales [16,19,20]. The Himawari-8 satellite and ground-based dual-Doppler radar data were adopted to document the inner core evolution of Typhoon Meranti (2016) after its interaction with Taiwan's topography [21].…”