Abstract
This study used the spectral features of the geostationary satellite infrared window channel and the water vapor channel data to calculate a new parameter, normalized difference convection index (NDCI), to help determine the overshooting areas in typhoon cloud systems and the centers and intensity of typhoons. The results showed that the two-dimensional NDCI analysis helped to identify typhoon convective cloud systems and the positions of overshooting areas. In addition, because the NDCI values near a typhoon eye were rather significant, if a typhoon eye was formed, the NDCI cross-section analysis could help to confirm its position. When the center of a typhoon was covered by the high anvils and cirrus layers, it could still be qualitatively found through two-dimensional analysis. As for determining the intensity of typhoons, this study also tried to perform correlation analyses with NDCI and maximum sustained wind speed. The result showed that in the ranges within circles of 200 to 250 km radii with a typhoon eye as the center, the correlation between the area with the NDCI values <0 and the maximum sustained wind speed is high with a coefficient 0.7. Thus, the NDCI value could be a referential index to determine the intensity of a typhoon.
Highlights
Tropical cyclones are one of the nature’s most destructive weather systems
This study discussed the distributions of the convective cloud system of the typhoon based on the normalized difference convection index (NDCI) cross-section analysis and the two-dimensional analysis with the NDCI values
The result showed that, according to the two-dimensional NDCI distribution, the areas with the NDCI value
Summary
Identifying and forecasting tropical cyclone intensity changes have been a challenge for forecasters As most of these powerful storms initially develop over an ocean, direct in situ measurements are scarce.[1,2,3] Given the high spatial and temporal resolutions of satellites, satellite remote sensing has become a tool that heavily relies on tropical cyclone monitoring to provide pertinent vital data. Some of the techniques estimate intensity using microwave data from the advanced microwave sounding unit,[4,5,6] the special sensor microwave imager,[7,8] and tropical rainfall measuring mission/microwave imager (TRMM/TMI).[9] Yet, as most microwave instruments are placed on board polar-orbiting satellites, it is difficult to obtain hourly data regarding tropical cyclone intensity changes, even though the global precipitation measurement mission could provide frequent observations (every 2 to 3 h) of Earth’s precipitation. In contrast to the microwave data, the optical observations from geostationary meteorological satellites are Journal of Applied Remote Sensing
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