A Study of Typhoon Rainbands with Quantitized Radar Data

Abstract

Conventional PPI radar echoes which were associated with Typhoon 7617 in September 1976 are quantitized in the form of an echo coverage within a 10 km square grid over the area of 400×400km. A mean state of radar rainbands (MRB) which lies from sea to land and variability in the time series of echo coverage are discussed in connection with the rainfall amounts obtained by raingauges. The area of significant rainfall is in average concentrated into a few narrow bands which run almost parallel to the prevailing wind of the typhoon circulation. A main rainband runs perpendicularly to land, Shikoku with increasing its intensity and west-east width.
A uniform magnitude of the variance with time and a predominant period with the order of one hour are obtained for the rain activity in the MRB. The two-dimensional (timespace) spectral analysis shows that the MRB consists of organized convective rain complexes with the predominant period of one hour. The complexes travel with the speed of about 20 m/sec and are separated longitudinally by about 50-100km in the MRB.