Calculating Tropical Cyclone Critical Wind Radii and Storm Size Using NSCAT Winds

摘要

Subjective and objective analyses of satellite scatterometer near-surface windsare utilized to estimate tropical cyclone (TC) critical wind radii and size over a region of the western North Pacific. An outer wind profile assuming a linear slope dependent on the TC latitude is used to determine the radial extent of cyclonic winds beyond a set radius. Inside the set radius, a partial conservation of angular momentum is assumed into the TC maximum wind radius and the 35, 50, and 100-kt radii are calculated. Nine TCs were investigated during the operating period of the NASA scatterometer (NSCAT). Critical wind radii values in four quadrants (front, right, rear, and left) of the TCs are found to be comparable to the Joint Typhoon Warning Center (JTWC) critical wind radii values issued in warnings. The radial extent of cyclonic winds are also comparable to the radius of zero winds estimated by determining where the cyclonic flow turned to anticyclonic flow in the NSCAT sea-surface wind swaths.