Detecting Intensity Evolution of the Western North Pacific Super Typhoons in 2016 Using the Deviation Angle Variance Technique with FY Data

This paper analyzes the complete lifecycle of super typhoons in 2016 in the western North Pacific (WNP) using the deviation angle variance technique (DAV-T). Based on the infrared images from Fengyun (FY) satellites, the DAV-T enables quantification of the axisymmetry of tropical cyclones (TCs) by using the DAV values; and thus, it helps improve the capability of TC intensity estimation. Case analyses of Super Typhoons Lionrock and Meranti were performed to explore the distribution characteristics of the DAV values at the various stages of TC evolution. The results show that the minimum DAV values (i.e., map minimum values: MMVs) gradually decreased and their locations constantly approached the circulation center with enhancement of the TC organization; however, when a ring or disk structure was formed around a TC, significant changes in MMV locations were no longer observed. Nonetheless, when large-scale non-closed deep convective cloud clusters appeared at the early stage or the dissipation stage of the typhoon, the axisymmetry of the TC was poor and the MMV locations tended to lie in the most convective region rather than in the TC circulation center. Overall, the MMVs and their locations, respectively, exhibited a strong correlation with the TC intensity and circulation center, and the correlation increased as the TCs became stronger. Combined with the China Meteorological Administration BestTrack dataset (CMA-BestTrack), statistical analysis of all research samples reveals that the correlation coefficient between the MMVs and maximum surface wind speeds (V_max) was –0.80; the root mean square error (RMSE) of relative distance between the MMV locations and TC centers was 140.3 km; and especially, when the samples below the tropical depression (TD) intensity were removed, the RMSE of the relative distance decreased dramatically to 95.0 km. The value and location of the MMVs could be used as important indicators for estimating TC intensity and center.