The Himawari series of geostationary meteorological satellites provides constant and uniform coverage of the earth from around 35,800 km above the equator with an orbit corresponding to the period of the earth’s rotation. This allows them to perform uninterrupted observation of meteorological phenomena such as typhoons, depressions and fronts.
Satellite output includes visible imagery, infrared imagery and water vapor imagery.
Visible imagery captures sunlight reflected by clouds and land. Developed rain clouds reflect sunlight well, and thicker clouds appear whiter in visible imagery. At nighttime, visible imagery is black due to the absence of sunlight. The spatial resolution of visible imagery is 500 m at the sub-satellite point.
Infrared imagery captures infrared radiation emitted from clouds, land and the atmosphere. High-altitude clouds are cold and appear white in infrared imagery, while low-altitude clouds and fog are hardly distinguishable from land. As high-altitude clouds may be either well-developed thunderclouds or clear-day cirrus, areas appearing in white are not necessarily associated with heavy rain. The spatial resolution of infrared imagery is 2 km at the sub-satellite point.
Water vapor imagery captures 6.2-micrometer infrared radiation emitted by water vapor in the atmosphere. As atmospheric water vapor absorbs and emits such radiation, areas containing large amounts of vapor in the upper and middle troposphere appear white in this type of imagery. It shows atmospheric humidity and the atmospheric stream via a series of animated images.
In addition, color-enhanced imagery is derived from the above output. This type of imagery shows cloud-top heights in rainbow-like colors superimposed onto visible imagery (daytime) and infrared imagery (nighttime). Cloud-top heights are estimated from the intensity of infrared radiation emitted from clouds. Red is used to indicate the possible presence of well-developed thunderclouds. Color-enhanced imagery is provided at Satellite Imagery (Rapid Scan).
Observation for full-disk Himawari satellite imagery is performed every 10 minutes, while observation for the Japan area and the target area is performed every 2.5 minutes. For more information, see Observation area and periodicity.
At night during the equinox season, sunlight shines directly against the Himawari satellite’s direction of view. Accordingly, some imagery may be partially missing in order to avoid the direct incidence of sunlight onto the satellite’s imager. Visible imagery is also corrected to prevent the appearance of stray sunlight in imagery.
Satellite Program Division, Japan Meteorological Agency
E-mail: metsat AT met.kishou.go.jp