Augmentation of Early Intensity Forecasting in Tropical Cyclones
ARIZONA UNIV TUCSON OPTICAL SCIENCES CENTER
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The long-term goals of our research team are twofold 1. To develop a suite of objective intensity estimation tools that are based on remote sensing data and multiparameter spatiotemporal analysis tools. 2. To understand the physical mechanisms giving rise to the observable signatures that are used for forecasting. Our principal objective is to develop an objective and automatic intensity estimator of Tropical Cyclones TCs based on satellite infrared IR imagery. The proposed methodology analyzes the TC s structure to estimate their intensity, which will be available every 30 minutes or depending on image acquisition availability for the Atlantic, Eastern North Pacific and Western North Pacific basins. We are investigating the underlying atmospheric dynamics by using mesoscale modeling and comparing the modeled storms to the measured signatures. The deviation-angle variance DAV technique was introduced in Pineros et al. 2008 as a procedure to objectively estimate the intensity of tropical cyclones. The level of axisymmetry of tropical cyclones is quantified by calcualting the gradient of the brightness temperature field in infrared images. The deviation-angle of these gradient vectors with respect to a radial line projected from a center indicates their level of alignment . Fig. 1a shows an example of this calculation for a single gradient vector in a brightness temperature field. In this case the center is located at the eye of the vortex. The calculation is done for every pixel within a chosen radius of the center point, and the variance of the distribution of angles quantifies the axisymmetry of the cyclone Fig. 1b. The deviation-angle variance decreases as the majority of gradient vectors are pointing toward or away from the center.