An Objective Tropical Cyclone Intensity Estimation Model Based on Digital IR Satellite Images

Abstract

ABSTRACT An objective tropical cyclone (TC) intensity estimation model is proposed based on the statistical relationship between TC intensity and its inner-core convection, plus the persistence of TC intensity. In the model, the inner-core convection is described by several parameters retrieved from digital infrared (IR) satellite images, including the number of convective cores (Num), their distance to the TC center, and their blackbody temperature (TBB), among others. The persistence of TC intensity is embodied by the TC intensity six hours previous (V6h). The model was set up by the stepwise regression technique using a five-year dataset (2006-2010) and was tested using an independent dataset covering 2011-2012, with V6h from the best-track dataset. Selected factors of the model included V6h, Num, Lat (TC center latitude), Lon (TC center longitude), DISmin (minimum distance between convective cores and TC center), and TBBdif (difference between the maximum and minimum TBB value of convective cores). Results showed that, for independent samples during 2011-2012, the MAE (mean absolute error) and RMSE (root-mean-square error) of Vmax estimation were 1.8 m s− 1 and 2.4 m s− 1, respectively. In order to make the model totally independent from the best-track dataset, the model estimation from six hours previous was used as the V6h for a second independent test covering 2011-2012. The results showed that the model had an MAE and RMSE of 5.4 m s− 1 and 7.3 m s− 1, respectively. Large errors were found for strong TCs (Severe Typhoon or Super Typhoon). The error statistics of the proposed model are comparable to published statistics on the widely used Dvorak technique or its objective versions, implying its potential to be used as an alternative tool for TC intensity estimation in either real-time operation or post-season best-track analyses.