Surface Pressure Features of Landfalling Typhoon Rainbands and Their Possible Causes

Abstract

This study uses temporally high-resolution surface observations, Doppler radar, and micro rain radar to document the finescale features of the two landfalling rainbands associated with Typhoon Longwang (2005) as they passed over northern Taiwan. The present case allows a unique opportunity to investigate well-defined, convectively active tropical cyclone rainbands over land. In particular, the surface pressure fluctuations observed during the passage of the two rainbands and their possible causes are explored. The rainbands were predominantly convective in nature, with embedded stratiform precipitation outside their inner/outer edge. Analyses of surface observations show similar surface pressure fluctuations during the rainband?s passage. Low (high) pressure with relatively strong (weak) cross-band flow and warmer (colder) temperature was located inside the outer (inner) edge. Maximum (minimum) pressure perturbations were observed to be ?1.5 (??1) mb, with smaller magnitudes (<?0.4 mb) outside the outer/inner edge. In particular, the studied rainbands possess some wavelike characteristics such as outward propagation, undulations of surface pressure perturbations, and opposite phase relation between the surface pressure perturbations and the cross-band flow. Detailed analyses indicate that the combined effects of pressure perturbations produced by moist convection and those associated with wave activities initiated within the typhoon could explain the observed surface features. The present study provides observational evidence to support the importance of wave dynamics and their interactions with moist convection for the generation of surface pressure perturbations associated with the observed tropical cyclone rainbands.