Book Description

Satellite imagery and other remote sensing products often provide the only observational data of tropical cyclones. This is especially true in the western Pacific where aircraft reconnaissance missions stopped in 1987. Manual estimate procedures using satellite imagery (Dvorak, 1984) provide valuable assistance in determining tropical cyclone intensity. An objective Dvorak technique (Velden, et al., 1998) is currently being studied to enhance the manual method. In an effort to take advantage of the unique characteristics (Hawkins, et al., 1998) of Special Sensor Microwave/Imager (SSM/I) data, one Naval Research Laboratory effort (outside the scope of this paper) involves the computation of empirical orthogonal functions of SSM/I tropical cyclone data and presenting those values as inputs to a neural network to estimate the tropical cyclone intensity at a given imagery time (May, et al., 1997). The algorithm applied in the research described here also uses SSM/l data, specifically the 85 GHz (H-pol) channel and a derived rain rate product. The 512x512 pixel imagery is cyclone-centered and image characteristics (computer vision features) are computed from the imagery data. A subset of these -features is presented to a pattern recognition algorithm (k-nearest neighbor) and an intensity estimate is provided as output. A description of the imagery characteristics (including available data and computer vision features) and feature selection methodology is provided in section two. Section three is a discussion of the algorithm used to automate the tropical cyclone intensity estimate and the current evaluation results.