Millions of people watch as meteorologists, anchors, and reporters discuss the formation of tropical depressions during each hurricane season. Some of these systems lose steam and dissipate. Others will continue their intensification, becoming tropical storms or even hurricanes. Maps and animations take center stage as trajectories are calculated, alerts are issued, and people watch one of Earth’s most powerful phenomena barrel towards coastal cities.
Satellites observe from orbit as winds rip in cyclonic motion, bringing lightning, rain, and devastation to communities on the ground. City lights shine through clouds, hinting at the populations below. Developed by scientists at the National Oceanic and Atmospheric Administration (NOAA) and Colorado State University’s Cooperative Institute for Research in the Atmosphere (CSU/CIRA), these maps and animations—known as GeoColor products—are visually impressive. They also highlight a tremendous combination of technologies.
It might surprise you to know the images you see are not exactly what the satellites see. These views are a product of multiple data observations from several sensors, and sometimes even different satellites. To produce these images, multiple types of observations are acquired, stacked into layers, and assembled like a data sandwich. This process ensures that the optimal sensor and analysis method is used for each type of phenomena (e.g., cloud cover, likely precipitation, and lightning). It also builds in reliability and efficiency. Without a need to continuously capture some layers—like the city lights—the animations can make use of the same data in a consistent, standardized way from one hour, or one storm, to the next.

The GeoColor imagery combines different types of cloud data, observed in infrared, with simulated natural color imagery. The Geostationary Operational Environmental Satellites (GOES) observe the electromagnetic spectrum, which is continuous, in smaller discrete chunks, or ‘bands.’ Natural color imagery is created by combining observations for the red, green, and blue bands. GOES does not acquire data for a green band. Instead, a simulated green band is generated from infrared data, and this is used to approximate a natural color image. The infrared and visible data are acquired at five-minute intervals, allowing this portion of the GeoColor imagery to depict near real-time conditions and show weather, fires, and other events as they are occurring. These data are blended with static layers based on the location and brightness of the sun. This allows the simulated natural color imagery to fade away and reveal city lights as day transitions to night.
Since GOES does not observe city lights, GeoColor makes use of a static nighttime lights image acquired years ago that does not change as new data comes in. Satellite observation of nighttime lights is a sophisticated and non-trivial technique. It requires sensors designed specially to collect data on nighttime lights. The data must then be processed to reduce the influence of airglow in the atmosphere, reflections from the Moon and starlight, snow, and other elements of the landscape. This poses a challenge to near real-time operations.
Using a static nighttime lights layer is efficient, but this approach has some drawbacks. Since nighttime lights reflect a single snapshot in time, GeoColor products cannot currently be used to assess power outages or damage levels based on city lights. Observations of nighttime lighting on specific nights from other satellites can be used to assess power outages, and even then, in situ data from customers is required for validation. More accurate assessments of power outages from satellites are typically only possible well after a storm, when clouds have subsided. At present, imagery of nighttime lights is captured once per evening. This is incompatible with GeoColor’s five-minute acquisition interval.
Whether for purposes of defense, weather forecasting, or emergency response, satellite observations are a cornerstone of security and safety. It is no easy feat to launch precision instruments into orbit and keep valuable data returning to Earth. And millions of lives depend on the information they provide.
What begins as a marvel of engineering ends up as intuitive maps, images, and animations. Innovations like this allow scientists, responders, and the public alike to keep watch on our ever-changing planet.
More to Explore
- Read an open-access paper about the GeoColor blending technique.
- View current GeoColor imagery.
- See how GeoColor and similar products can also be used to monitor wildfires and volcanic eruptions.
- Explore similar imagery of the Eastern Hemisphere acquired by the Japanese Himawari-9 satellite.