Some characteristics of typhoons as revealed by the recent SSM/I microwave radiometry

Tropical cyclones are notorious for their destruction. Because they occur mostly over oceans their structures are revealed only through aerial reconnaissance, radar or through satellites. The recently launched DMSP satellite (F8) has provided polarized microwave Brightness Temperatures, TB's. Using certain algorithms, rainrates and wind speeds were derived for a few typhoons.The 85 GHz TB's available at nearly 15 km intervals, disclosed that low values such as 230 K are registered within 2° of the advancing side of the center. These low TB's moved centerward as the typhoon developed further. They propagated rearwards as the storm weakened.Convective rainrates, defined as those equalling or exceeding 3 mm h^–1, within the core, seem to set trends for the intensification. On the other hand convective rain outside the core had a negative effect on the storm. Similarly convective rainrates within the core of developing storms were significantly different from those of the weakening typhoons while the corresponding stratiform rainrates were not markedly different between intensifying and deintensifying ones. Some typhoons developed strong winds exceeding 30 m s^–1 even as far from the center as 440 km. The derived speeds decreased in accuracy in rain situations.These preliminary results are to be interpreted with caution in view of the recency of the algorithms and the smallness of the sample. However, the hazards scientist would find the SSM/I data to be valuable in forewarning the public and in using these data for purposes such as surge forecasting.