Relevant information about this
satellite page
|
The current generation of weather satellites are developed and supported by funding from
the National Oceanic and Atmospheric Administration (NOAA). This generation of
Geostationary Operational Environmental Satellites (GOES), known as the GOES-R Series, are
the most advanced fleet of geostationary weather satellites ever to be deployed. These
geostationary satellites circle the Earth in geosynchronous orbit, meaning they orbit the
Earth’s equatorial plane at a speed that matches the Earth’s rotation. This allows them to
stay in a fixed position with respect to a point on the Earth’s surface. Two GOES satellites are
always in operation at any given time; one is situated over the Pacific providing views of
Hawaii and the western United States, and one is situated over the Atlantic, providing views
of the eastern United States and the Atlantic Ocean. GOES satellites are designated with a
letter prior to launch and renamed with a number once they reach orbit. GOES-R and GOES-
S, the current satellites in orbit, are now referred to as GOES-16 (over the Atlantic Ocean)
and GOES-18 (over the Pacific Ocean) respectively. More information can be found on the
GOES-R series webpage: https://www.goes-r.gov/mission/mission.html
|
The GOES-R generation of weather satellites measure 16 different channels, or ABI
(Advanced Baseline Imager) bands. They are in the following portions of the electromagnetic
spectrum:
Band 1: Visible – Blue Band (0.47 microns)
Band 2: Visible – Red Band (0.64 microns)
Band 3: Near-Infrared – Veggie Band (0.86 microns)
Band 4: Near-Infrared – Cirrus Band (1.37 microns)
Band 5: Near-Infrared – Snow/Ice Band (1.6 microns)
Band 6: Near-Infrared – Cloud Particle Size Band (2.24 microns)
Band 7: Infrared – Shortwave Window Band (3.9 microns)
Band 8: Upper Troposphere Water Vapor (6.2 microns)
Band 9: Mid-Level Troposphere Water Vapor (6.9 microns)
Band 10: Low-Level Troposphere Water Vapor (7.3 microns)
Band 11: Cloud Top Phase (8.4 microns)
Band 12: Ozone (9.6 microns)
Band 13: Clean IR Longwave (10.3 microns)
Band 14: IR Longwave (11.2 microns)
Band 15: Dirty IR Longwave (12.3 microns)
Band 16: CO2 Longwave IR (13.3 microns)
|
|
The Satellite page on this site provides real-time satellite images from many of the bands
listed above. These images update on a 5-minute basis and include close-up, high
resolution images. The resolution capability of these satellites is approximately 0.5-1 km for
the visible imagery and 1 km for the other bands. The images available here are remapped to a
Lambert Conformal projection.
|
Visible
The visible (color) imagery is a combination of bands 1, 2, and 3 and gives a "true color"
perspective. The visible (grayscale) imagery shows band 2 only. The visible images display
the earth very similarly to how humans see it with their eyes or how typical cameras view it.
Clouds and snow appear bright white (high albedo/reflectance) but oceans and trees are much
darker.
|
Infrared
The infrared imagery shows band 14. This band is calibrated to temperature and expressed in
degrees Celsius. Where clouds exist, the temperature is that of the tops of clouds. Where
clouds do not exist, the temperature is that of the ground or the water. This information is very
valuable to aviators since clouds with cloud top temperatures below 0°C may indicate that an
aircraft icing hazard exists. Generally speaking, the warmer an object, the more infrared
energy it emits. The satellite sensor measures this energy and calibrates it to temperature using
a very simple physical relationship (Planck's Law). In the real world, clouds that are very high
in the atmosphere are generally quite cold (perhaps -50°C) whereas clouds that are very near
the earth's surface can be quite warm (perhaps +5°C). Likewise, the land may be even warmer
than the lower clouds (perhaps +20°C) in the summer. Those colder clouds emit much less
infrared energy than the warmer clouds and the land emits more than those warm clouds. The
data measured by the satellite are calibrated and colorized according to the temperature with
red shades representing higher (warmer) temperatures and blue shades representing lower
(cooler) temperatures. If the temperature of the atmosphere decreases with height (which is
typical), a user can get an idea of which clouds are high-level and which are low-level based
on the cloud top temperature.
|
Water Vapor
The low/mid/high water vapor imagery shows imagery from bands 10, 9, and 8 respectively.
The water vapor bands are also calibrated to temperature in degrees Celsius but are typically
interpreted more by their colors. Warm colors (oranges and reds) indicate very dry regions and
areas that are likely to have few to no clouds whereas cool colors (purples, blues, and greens)
indicate regions with higher moister contents and may indicate areas of cloudiness. Gray
colors fall in between. The most useful tidbit to be gained from the water vapor images is the
locations of storm systems and the jet stream.
|
Day Cloud Phase
The GOES-based RGB product assigns each of three distinct channels or channel combinations to the red, green, and blue components of a color image. The Day Cloud Phase processor maps GOES-R infrared channel 13 (10.3 micron) brightness temperatures from 7.5 °C to -53.5 °C to red image component values, where cold clouds and surfaces will appear redder than relatively warm clouds and surfaces. GOES-R visible channel 2 (0.64 micron) reflectance values from 0 to 78% are mapped to green image component values, such that highly reflective surfaces like clouds, snow, and white sand will appear greener than surfaces of lower reflectance like water, vegetation, and land. Finally, GOES-R near-infrared channel 5 (1.6 micron) reflectance values from 1 to 59% are mapped to blue image component values, to take advantage of the relatively low response from cloud ice when compared to cloud water, so that water clouds will appear bluer than ice clouds. The colors in the image generated from these three channels can be interpreted as clouds of various phases (liquid, ice, or a mixture), land, water, or snow-covered land. For example, water clouds usually appear either cyan or lavender (depending on how cold they are) while snow covered land usually appears as bright green against the blue background of open land. Since channels 2 and 5 rely on reflectance of solar radiation, the Day Cloud Phase RGB is only valid during the day. Additionally, given the dependence on channel 13, colors may vary based on season and latitude. For additional information, see the NOAA Day Cloud Phase Quick Guide
|
Nighttime Microphysics
The Nighttime Microphysics RGB is designed to provide insight into cloud top phase and temperature in the absence of reflected solar radiation. The Nighttime Microphysics processor maps the GOES-R channel 15 (12.4 micron) minus channel 13 (10.4 micron) brightness temperature differences, also called the Split Window Difference, from -6.7 °C to 2.6 °C to red image component values. This difference is used as a proxy for cloud thickness, with thicker clouds appearing redder than thinner clouds. The GOES-R channel 13 (10.4 micron) minus channel 7 (3.9 micron) brightness temperature differences, known as the legacy “fog” product, from -3.1 °C to 5.2 °C, are mapped to green image component values. This channel difference indicates the presence of water clouds such that they appear as shades of green. Finally, GOES-R infrared channel 13 (10.3 micron) brightness temperatures from -29.6 °C to 19.5 °C are mapped to blue image component values, resulting in warm clouds and surfaces that appear bluer than cold clouds and surfaces. The RGB combination of these components can be interpreted as a variety of cloud types at various altitudes. For example, low-level liquid clouds usually appear as aqua or light green, while high, cold, glaciated cloud tops usually appear as dark red or dark red mottled with yellow pixels. Since channel 7 becomes contaminated by reflected solar radiation during the day, the Nighttime Microphysics RGB is only valid during the night. Additionally, given the dependence on channel 13, colors may vary based on season and latitude. For additional information, see the NOAA Nighttime Microphysics Quick Guide
|
|
|
