Please note: while above video references Himawari-8, the current satellite in use is Himawari-9. These 2 satellites have the same function and capability.
The Bureau of Meteorology receives satellite observations data from Himawari-9, a geostationary satellite operated by the Japan Meteorological Agency (JMA). The Himawari are situated 35 800 km above the equator at longitude 140.7°E (above the western Pacific, in line with Japan, Papua and central Australia) and so provide excellent coverage of the Australian region.
Himawari satellite data are used extensively within the Bureau to assist in real-time analysis and forecasting, and are also fed into the Bureau's numerical weather prediction (NWP) models.
The following types of imagery are available to the public:
Infrared images
Infrared (IR) images are derived from radiation emitted from the
Earth and its atmosphere at thermal-infrared wavelengths (10-12
µm). These images provide information on the temperature of
the underlying surface or cloud. IR images are available 24 hours
per day because temperatures can always be measured. This is in
contrast to visible images, which are only available during
daylight hours.
Temperatures are represented by a greyscale, where black and white represent the hottest and coldest areas respectively. As clouds tend to be cooler than the ground or sea below (not always the case for low-lying clouds), they appear as light grey to white, making IR images simple to compare with visible images.
To assist in interpreting greyscale IR images, methods can be used
to colour all pixels representing a particular temperature range.
The temperature of clouds is associated with their height, so
highlighting certain temperature ranges is useful for estimating
the height of the observed clouds. These precision of these
temperature measurements are within one or two degrees Celsius.
Images coloured in this way are known as 'false colour' images.
The Bureau also provides false colour infrared images that use
the Zehr colour enhancement, which was developed by
Ray Zehr
from the US National Oceanic and Atmospheric Administration
(NOAA). This enhancement only applies temperature colour ranges to
the cold end of the scale, which highlights very deep convection
that is generally associated with tropical cyclones and
thunderstorms. Hence, this type of image can be useful in tracking
the movement of tropical cyclones.
Visible images
Visible (VIS) images are a record of the visible light scattered
or reflected towards the satellite from the Earth and clouds. They
give meteorologists extra information that may not appear on
infrared images. For example, fog appears in visible images, but
may not show up in infrared images as its temperature is very
close to that of the land below.
Visible images are only available during daytime, as at night there is no reflected sunlight.
Clouds/surface composite
The clouds/surface composites are created by combining information
from two images. The Earth’s surface (land and oceans) is a
static image from NASA's Blue Marble image set. The cloud cover,
which is overlaid on top of this surface image, is derived from a
greyscale infrared image (see Infrared Images), by removing the temperature range associated with the surface.
While a clouds/surface composite gives a good indication of the current cloud cover, it should not be confused with a true visible image.
Daytime visible / night-time infrared blended imagery
Observations from Himawari-8 enable the Bureau to create true
colour visible imagery during the day. To avoid this imagery
fading to black at night, the daytime visible / night-time
infrared blended imagery provides an easy to use product, which
essentially incorporate the best available data for any particular
time of the day.
Image updates and timestamps
Satellite images are timestamped in 'UTC' (Coordinated Universal Time). The timestamp is the start time of the observation of the top of the image from the satellite. It takes approximately ten minutes for Himawari-8 to complete a scan.
Eclipse Mode
As geostationary satellites orbit the Earth, there are certain times during the year when the Earth is directly between the Sun and the satellites. This results in the Earth eclipsing the satellites. Such eclipses occur each year, usually between February to April and between August and October.
In these circumstances, the Sun can shine directly into the optical path of the satellites' instrumentation, overloading the sensors. The observing instrument is shielded to avoid this 'flaring', so a whole image or parts of an image may be missed.
Acknowledgements
The satellite images available via the Bureau web site are obtained from non-Bureau sources. The satellite images may be from geostationary satellites such as: the GMS series; GOES-9; the MTSAT series; and the Feng Yun Series or from the polar orbiting satellites such as the NOAA series and Feng Yun series. Such images are provided with the permission of the Japan Meteorological Agency (JMA), the China Meteorological Administration (CMA) or the United States National Oceanic & Atmospheric Administration (NOAA).
Any use of these images requires the following acknowledgement(s):
Geostationary satellite data
- If the imagery is from the Himawari-9, then the acknowledgement is: Satellite image originally processed by the Bureau of Meteorology from the geostationary satellite Himawari-9 operated by the Japan Meteorological Agency.
- If the image was from GMS-1, GMS-2, GMS-3, GMS-4 or GMS-5 (old imagery), then the acknowledgement is (with the appropriate number replacing the "(n)"): Satellite image originally processed by the Bureau of Meteorology from the geostationary satellite GMS-(n) operated by the Japan Meteorological Agency.
Polar Orbiting satellite data
- If the imagery is from the NOAA series, then the acknowledgement is (with the appropriate number replacing the "(n)"): Satellite image originally processed by the Bureau of Meteorology from the polar orbiting satellite NOAA-(n) operated by the National Oceanographic & Atmospheric Administration (NOAA).