Relationships between Tropical Cyclone Intensity and Eyewall Structure as Determined by Radial Profiles of Inner-Core Infrared Brightness Temperature

Abstract

Radial profiles of infrared brightness temperature for 2405 different satellite observations from 14 western North Pacific tropical cyclones (TCs) from the 2012 season were analyzed and compared to intensity and changes in intensity. Four critical points along the inner core of each infrared (IR) brightness temperature (BT) profile were identified: coldest cloud top (CCT), first overshooting top (FOT), and lower (L45) and upper (U45) extent of the inner eyewall. Radial movement of the mean CCT point outward with increasing TC intensity, combined with subsequent warming of the mean L45 point with intensity, highlighted structure changes that are consistent with eye and eyewall development. When stratified by latitude and vertical wind shear, the CCT point moved radially outward for all cases, notably at higher intensities for lower-latitude TCs and at lower intensities for higher-latitude TCs. The majority of the warming of the L45 point with increasing intensity occurred for low-latitude and low-shear cases. Slopes of IR BT between the four critical points were statistically significantly negatively correlated with intensity, indicating that stronger (weaker) TCs had more (less) negative slopes of IR BT and more (less) vertical eyewall profiles. Furthermore, except in high-shear cases, the most negative correlations were found in the inner eyewall, consistent with results from recent studies based on radar reconnaissance data. Finally, 12-h changes in slope were found to lead 12-h changes in intensity most often at higher latitudes, providing evidence that changes in the secondary TC circulation may lead changes in the primary TC circulation for both strengthening and weakening TCs.

A Multiple Linear Regression Model for Tropical Cyclone Intensity Estimation from Satellite Infrared Images

“…All these predicators are probably relevant to TC intensity, while the significance of each one is not determined. Note that in Table 2, all terms of the eyewall follow previous studies [39,41]. Table 2.…”

“…The third and fourth critical points are selected to define a lower and upper extent (hereinafter denoted as L45 and U45) of the inner eyewall, respectively. The L45 in this paper is identified as the first 45° downturn inflection point, which is the location at which the orientation of the IR profile changes from vertical to the horizontal, and vice versa the U45,because According to Sanabia (2014) [39], IR profiles in the TC inner core could be represented by four critical points which locate mainly within 100 km from the TC center. The first critical point is the radial location of the coldest cloud top (CCT) within 200 km from the TC center.…”

“…In Figure 2, the solid curve represents the mean of the 16,126 IRBT profiles. According to Sanabia (2014) [39], IR profiles in the TC inner core could be represented by four critical points which locate mainly within 100 km from the TC center. The first critical point is the radial location of the coldest cloud top (CCT) within 200 km from the TC center.…”

“…The third and fourth critical points are selected to define a lower and upper extent (hereinafter denoted as L45 and U45) of the inner eyewall, respectively. The L45 in this paper is identified as the first 45˝downturn inflection point, which is the location at which the orientation of the IR profile changes from vertical to the horizontal, and vice versa the U45, because we adopted normal cartesian coordinate system without inverting the y axis as did in Sanabia (2014). The mean location of the four critical points are plotted in Figure 2.…”

A Systematic Classification Investigation of Rapid Intensification of Atlantic Tropical Cyclones with the SHIPS Database

“…In addition to case studies, composite analysis is another major methodology for identifying common factors affecting TC intensity changes and for understanding the underlying physics (e.g., Hanley et al 2001;Knaff et al 2004Knaff et al , 2008Zehr and Knaff 2007;Camargo et al 2007;Ventham and Wang 2007;Hendricks, et al 2010;Sanabia et al 2014). Ventham and Wang (2007) also suggested that composite analysis may help to derive new predictors for RI.…”