Extended Abstract (64K)5A.1
Temporal and spatial variations of precipitation of landfall typhoons in the Taiwan area
Ben Jong-Dao Jou, National Taiwan University, Taipei, Taiwan
This study examines the temporal and spatial variations of precipitation structure of landfalling typhoons by using reflectivity data observed by the Doppler radars in Taiwan. Typhoons landed Taiwan during the period of 1996-2003 with different tracks and intensities were analyzed. The azimuthally averaged reflectivity data were used to show the mean characteristics of precipitation. Strong and narrow rainband concentrated near center was shown in Toraji (2001), wide spread with medium strength in Nari (2001), bi-modal peak distribution in Herb (1996), and concentric eyewall feature in Dujuan (2003). These distributions provide a crude estimation of the total amount and spatial variations of rainfall along the track of the storm. It is further analyzed to divide the reflectivity data into four quadrants in terms of the direction of movement to show the evolution of the eyewalls, the rainbands in the annular area outside the eyewall, and areas extended to 300 km from the center of the storm. More than 60 hours radar data with time interval of 6 or 8 minutes are analyzed in this study. The contraction of the eyewall during landfall period, the concentric eyewall evolution, the outward and/or inward propagating spiral rainbands, and the organized convective precipitation areas possibly related to the island topography are identified. The asymmetric characteristic of the precipitation structure is documented, the signature of vortex Rossby waves is examined, and the effect of vertical wind shear and the topography of Taiwan on the nature of these precipitation features are also described.
Session 5A, Tropical cyclone Rainfall I
Tuesday, 4 May 2004, 8:00 AM-9:45 AM, Le Jardin Room
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