High-resolution Atmospheric Motion Vector Fields of Typhoon Revealed by GF-4 Images

Atmospheric motion vector (AMV) fields are very useful for numerical weather prediction, especially over ocean areas where other wind observations are very sparse. In this paper, high-resolution AMV fields of Typhoon Megi (2016) have been revealed by GF-4 Images. It is the first time, to our knowledge, that such high resolution and nearly continuous AMV data of a typhoon system have been produced. GF-4 (GaoFen-4) is the first high-resolution geostationary satellite in China, launched on December 29, 2015. Its VNIR (Visible and Near InfraRed) optical sensors are capable of imaging the Earth at 50 m resolution, covering a 500 km × 500 km area with a minimum imaging interval of 20 seconds. More than 300 GF-4 images, taken in four sequences with imaging rates of 36 and 69 seconds per scene, captured the development of Typhoon Megi (2016) - from its peak in the afternoon of September 26, 2016 to its dispersion two days later in the morning of September 28. These consecutive images recorded the motion field of the typhoon’s top clouds nearly continuously. By using advanced image matching technology - the phase correlation technique, the motion has been estimated at every pixel, at subpixel accuracy from image pairs with 179 and 206 second intervals. The process has generated time series of AMV fields at 50 m spatial resolution for the whole imaged area. The data provide accurate measurements of the typhoon top cloud motion speed and direction, and reveal quantitative details of the motion field in terms of spatial patterns and temporal evolution of this cyclone system.