热带气旋复杂程度的分形维数表征

Fractal dimension characterization of tropical cyclone complex degree

应用2006—2010年69个热带气旋1295个时次的红外云图等资料,提取了1295个TC的外缘线,用圆规法计算了这些外缘线的分形维数。将这1295个分形维数自小到大排列,按等频数规则,将1295个数分为5类,分别记为A、B、C、D、E类。A、B、C、D、E类分形维数的均值分别为1.21、1.26、1.29、1.33、1.40。然后寻找与这5个均值最接近的样本。这5个样本的红外云图和TBB等值线分布图显示:随着分形维数的加大,边缘线的非光滑程度逐渐加大,图形与准圆形的偏离程度逐渐加大,TC空间结构的复杂程度也逐渐加大。说明外缘线的分形维数可以在一定程度上定量表征TC的复杂程度。

This paper extracts 1 295 TC edges from 1 295 IR images of 69 TCs during 2006--2010,and calculates the fractal dimension of the edges using the compasses method. The 1 295 TC edge fractal dimension are sorted in descending order and classified into five categories, denoted by A, B, C, D and E, which are in the same frequencies. The fractal dimension mean value of the five categories are 1.21, 1.26,1.29,1.33 and I. 40, respectively. Then we find five samples nearest to the five averages. The IR images and TBB contour map of the five samples show that the edges of TCs are more rough and noncircular, and the structures of TCs are more complicated, as the increase of the fractal dimension. All above indicate that the fractal dimension of TC edges can quantitatively describe the complex degree of TC to some extent.