To celebrate fall, we’ve added a touch of color to our global satellite layer! The color-enhanced infrared (IR) satellite image is designed to visually highlight the coldest cloud tops. Cold cloud tops are often indicative of active thunderstorms that can produce severe or extreme convective turbulence. The animated satellite layer updates every thirty minutes and is accessed in the map mode menu in the Maps view.
How IR Satellite Imagery Works
Any object that has a temperature warmer than absolute zero will emit radiation at many different wavelengths. Radiation produced by the earth and its atmosphere is emitted spaceward from land masses, oceans, lakes and the top of most clouds. Satellite sensors are used to measure this radiation that includes both visible light and those wavelengths that are invisible to the naked eye. The radiation emitted in the infrared part of the electromagnetic spectrum is the source of data used to build our IR satellite layer.
To create this layer, five geostationary satellites look at the entire earth (with the exception of polar regions) and measure the amount of infrared energy being emitted. The infrared satellite sensor measures the amount of energy and calibrates it to temperature using a very simple physical relationship known as Planck’s Law.
High clouds are very cold and emit less infrared radiation than warmer clouds near Earth’s surface. Furthermore, land masses are usually warmer than most clouds. Since the satellite can’t directly distinguish between the earth’s surface and clouds, we employ a software algorithm that determines where it is cloudy and where the sky is clear. While this works well most of the time, snow cover, fog and even the oceans can sometimes fool the algorithm. We recommend using the Sky Coverage and the Satellite layers together to get the most accurate picture.
How To Interpret IR Satellite Imagery
Data measured by the satellites is calibrated and colorized according to the temperature. Warmer objects emit more infrared energy and colder objects less. Shades of gray are used to represent the lowest-topped clouds; the darker the shade of gray, the lower the cloud tops. For higher-topped clouds, color is added. Just above the lightest shades of gray you may see blue and green colors introduced representing still colder and higher tops. Above this, shades of red, orange and yellow represent the coldest and highest cloud tops.
As the temperature of the atmosphere generally decreases with height, a pilot can get a pretty good idea which clouds are high-level and which are low-level based on the color or shades of gray depicted.
The IR Satellite layer allows you to quickly locate the most dangerous weather anywhere in the world. Ground-based radar provides a multitude of information on the location and movement of convective weather, however it is limited to US and Canada. The IR Satellite layer gives you a global, at a glance view of significant weather. This is especially important if you are planning a flight over large bodies of water.
In this image over central Africa, you can quickly see where the most significant weather is located, especially in regions that have a cellular appearance depicted in deep red, orange and yellow colors.
One thing to note is that thick cirrus clouds at very high altitudes will also show up as very cold clouds even though they may not be associated with deep, moist convection. Most of the time these high cirrus clouds do not have the same cellular appearance as convective clouds and thus have very little variation in color.