Reading Satellite Colors

In short: six satellite views are false color. Each paints three satellite channels, or differences between channels, as red, green and blue, so a pixel’s color is three measurements at once and there is no scale to read it against. Each product has a short list of named colors instead. This guide gives that list for all six, what each is for, and where the colors mislead. For the single-channel views with a temperature scale (visible, infrared and water vapor), see Visible, Infrared & Water Vapor.

Which view, when.

• Daytime storms: Day Cloud Phase to watch cumulus freeze, Day Convection for the first strong updraft.
• Fog before dawn: Night Microphysics.
• Fire: Day Land Cloud Fire for smoke and burn scars, Fire Temperature for the cores, day or night.
• Snow on the ground versus cloud: Day Cloud Phase or Day Land Cloud Fire; snow holds still between frames.
• Upper air, fronts, a deepening low: Airmass.

The GOES imager records sixteen pictures at once at different wavelengths: one good at cloud-top temperature, one at ice versus liquid water, one at water vapor high up, one at the heat of a fire. An RGB composite picks three, stretches each over a fixed range, and paints them red, green and blue. All three high is white, all three low is black, and each kind of cloud, air or ground lands in its own patch of color between. So there is no number behind a color (the Inspect tool reads nothing off these views), and the colors are typical, not fixed: every recipe leans on sunlight or surface temperature somewhere, and every quick guide warns that the colors shift with time of day, season and latitude. Each product below lists its named colors as MesoRadar’s color bar shows them, measured at midday through the app’s own recipes; how the bar and its pill work is covered after the six products.

Airmass

What it is for. The air several miles up: where cold and warm air masses meet, and where very dry air sinks out of the stratosphere beside the jet stream. Built from two water vapor channels, the ozone channel and the infrared window, so it works day and night; blue stands for cold or moist upper air.

The bands. Cold air, a cold air mass. Warm air, a warm air mass. Warm, drier air, warm air with less moisture aloft. Dry air aloft, dry air high up, often along the jet. Mid cloud, cloud in the middle levels with warmer tops than storms. Thick high cloud, deep, cold cloud tops: storms or a frontal cloud shield.

How to read it. Look for the boundaries: a sharp line between green and purple is an upper-level front, and a rust tongue curling into the back of a comma-shaped cloud shield is a low strengthening. Low cloud has no band: it takes the color of the air around it.

Where it misleads. In summer the rust also appears over hot deserts, where it means only dry upper air. Toward the edge of the satellite’s view the long-wavelength channels look through more atmosphere and read colder; the Air Mass guide’s limitation box calls this limb cooling and says the whole limb turns blue and violet, so warm tropical air can look cold there. In MesoRadar’s frame this shows toward the corners farthest from the satellite: on GOES-East the Pacific Northwest and western Canada, on GOES-West the Northeast, and far out to sea on both.

Day Cloud Phase

What it is for. Telling water cloud from ice cloud in daylight, which is how you watch cumulus turn into storms. It also shows snow on the ground. One channel is cloud-top temperature, two are reflected sunlight. The quick guide credits the recipe to the Japan Meteorological Agency, which built it for Himawari-8.

The bands. Water, open water, no cloud. Land, bare ground, no cloud. Water cloud, low cloud made of water droplets. Ice cloud or snow, cloud turning to ice, or snow on the ground. Thick ice cloud, thick, high cloud with ice: storm tops. Thin ice cloud, thin, high ice cloud. Cold mid cloud, mid cloud of very cold droplets, often mixed with ice.

How to read it. Cyan tops that turn green are freezing; green that turns yellow is a storm top. Thin ice cloud at the top of an older storm, or cirrus blowing off it, reads red-orange: cold enough to light the red channel, too thin to reflect much in the green and blue. The bar is in that growth order, not weaker to stronger.

Where it misleads. Snow and freezing cloud share a green; snow does not move between frames. Near sunrise and sunset, and all day in northern winter, the two reflective channels fall off while cold winter ground drives the temperature channel on its own, so the whole scene goes reddish, clear cold land included, and the water-versus-ice contrast weakens. The quick guide notes that the thin magenta it labels as mid-level water cloud is sometimes thin high ice cloud. Treat the thin bands as the least certain.

Day Convection

What it is for. Finding new, strong updrafts in daylight. A strong updraft freezes droplets into very small ice, and small ice reflects strongly in the 3.9 micrometer channel, the one that turns a top yellow.

The bands. Two groups with a gap. Left, the sky that is not a storm: Clear sky or low cloud, clear ground or low water cloud, both purple here; Thin high cloud, thin high ice cloud or mid cloud, not a storm top. Right, the storm tops: Large ice, high up, a weak or fading storm or a thick high cloud layer, the same color for both; Moderate updraft, a cold, tall storm top with small ice; Strong updraft, the coldest, tallest storm tops, with small ice.

How to read it. The right group runs by updraft strength, yellow the strongest. A yellow top is one of the coldest, tallest tops on the map. An orange top can be just as severe; the radar says which.

Where it misleads. Its most striking color is also the least reliable.

• Purple is often clear ground. The textbook reading is thin cirrus, but over bare land the 1.6 micrometer channel is brighter than the visible, so clear ground comes out the same purple. On a GOES-19 frame from 2026-11-03, measured by MesoRadar through its own recipe, about two thirds of the purple on that one frame was clear ground. Low water cloud lands in purple too, so the band says “Clear sky or low cloud”.
• Yellow has other causes. The quick guide lists three. Sunlight mirrored off water and smooth cloud lights the 3.9 micrometer channel near the part of the Earth that reflects the sun straight back at the satellite. Very cold tops with only moderate 3.9 reflectivity look yellow though the updraft is average. Mountain wave clouds and dusty or polluted air turn yellow; dust carried aloft keeps small ice alive for a long time. MesoRadar computes the glint zone from the frame time and the satellite’s position: it reaches only the map’s southern edge (the Gulf and Mexico), from about May to July, mostly afternoons, and a dashed line marks it while you hold the yellow band. A yellow top with no radar echo under it is a reason to doubt the yellow.
• Red has three meanings. A fading storm, a thick high deck and thin icy cloud over warm ground all land in the red band. The pill says so.
• It fades at dusk. Two of its three channels lean on sunlight (the 3.9 micrometer reflection and 1.6 minus 0.64 micrometers), so it is a daytime product; after dark the Storms view switches to Infrared.

Day Land Cloud Fire

What it is for. A near-natural look at the ground in daylight with fire hot spots forced to red: smoke, burn scars, snow cover, flooding and the fires on one picture. The recipe starts from EUMETSAT’s Natural Color RGB and puts the 2.2 micrometer channel in the red slot instead of 1.6. Fires are bright at 2.2, so they turn red; ice absorbs at 2.2, so most cloud loses its red and comes out cyan.

The bands. Water, water or flooded ground. Bare land, bare land or dormant plants. Vegetation, growing plants. Smoke, darker and flatter than low cloud. Low cloud, low or mid cloud. Ice cloud or snow, high ice cloud or snow on the ground, brighter than low cloud. Hot fire, a fire hot spot.

How to read it. Smoke is a dark, soft cyan smear trailing downwind from a red dot. Snow and high ice cloud are the same bright cyan; the snow is still there next frame.

Where it misleads. Only hot fires turn red. A satellite pixel here is about 2 km across, larger toward the north; a small or smoldering fire does not fill enough of it to show. Airborne dust and bare land share a color, and on the frames MesoRadar measured, dark or dormant ground sat close to the smoke band. Most cloud is cyan and small-droplet water cloud such as fog comes out gray to dull white, so leave cloud phase to Day Cloud Phase. It needs daylight.

Fire Temperature

What it is for. Ranking fires by heat. Everything that is not burning stays dark, and the fires run red, orange, near white as they get hotter. Red is the 3.9 micrometer channel, the first to respond to a hot spot; green and blue (2.2 and 1.6 micrometers) light up only once a fire is hot enough to emit at their shorter wavelengths, so a cool fire is red alone and the hottest saturate toward white.

The bands. Water, snow or night, water or snow by day and everything but fire at night. Clear land, warmer ground looks pinker. Water cloud. Ice cloud. Burn scar, ground that burned recently. Fire, the coolest of the three fire colors. Hotter fire. Hottest fire, a very hot or large fire. Three rungs in MesoRadar; the quick guide shows four.

How to read it. Find the red dots and look at their centers: a core gone orange or white is burning far hotter than one red throughout. This is not a daytime-only product: at night the clouds and the land go black, because the two shorter channels have no sunlight to reflect, and the fires stay.

Where it misleads. Cloud hides fire completely. Red is not always fire: the NASA SPoRT quick guide warns that hot, bare desert ground can glow in the 3.9 micrometer channel on its own, and a fresh burn scar sits close to the red of a cool fire. The ladder tracks the heat reaching the satellite from the pixel: how hot the fire is times how much of the pixel burns. A small, very hot fire and a large, cooler one can share a rung.

Night Microphysics

What it is for. Fog and low cloud at night, which plain infrared cannot separate from ground at nearly the same temperature. It also sorts the other cloud types, and it is the night partner to Day Cloud Phase. All three inputs are heat channels, so it needs no sunlight; the blue channel is surface temperature.

The bands. Clear, clear ground, warmer ground looks bluer. Fog or very low cloud, fog or cloud near the ground. Low cloud, low cloud in cool air; fog in cold air looks like this too. Mid cloud, thick cloud in the middle levels, often ahead of a front. High thick cloud, high, thick cloud. Thin cirrus, very thin, high ice cloud.

How to read it. Fog is the dull, washed-out version of low cloud, thin enough that the ground leaks into the pixel. The two low-cloud bands are one kind of cloud at two temperatures: the blue channel is surface temperature, so a cold night takes the blue out of aqua and leaves yellow-green.

Where it misleads. Fog and low cloud have no sharp line between them; the pill says to check surface reports. No satellite view shows a cloud base, so how high the fog or stratus sits is a question for the ground. Clear ground has no one color here. The NASA SPoRT quick guide lists three things that move it: how warm the ground is, what kind of surface it is, and how much water vapor sits above it. The quick guide also notes speckled yellow noise on very cold cloud tops, below about minus 30 Celsius. Once the sun is up, reflected sunlight spoils the 3.9 micrometer channel and the bar no longer applies.

Six things that are true of all of them

• The bar is not a scale. Only Day Convection’s storm group and Fire Temperature’s fire ladder run weak to strong.
• Colors drift with the season and the sun. Winter Day Cloud Phase scenes redden; summer deserts on Airmass turn rust; cooling ground on Night Microphysics slides from pink to blue.
• The three Day products fade at dusk. Day Cloud Phase, Day Convection and Day Land Cloud Fire lean on reflected sunlight; the pill says so when the sun is low. Fire Temperature keeps its fires at night.
• The edge of the view lies. Toward the limb the atmosphere reads colder than it is, and on Airmass everything goes blue and purple.
• One color, two meanings. Snow and ice cloud, fog and low cloud, a fading storm and a thick deck: the pill names both. The loop and the radar settle it.
• Satellite sees tops, radar sees inside. None of these products shows what a storm is doing under its anvil. The next tap is the radar.

A working order. Storm day: midday Day Cloud Phase on the cumulus field, the first yellow on Day Convection, then radar. Fire day: Day Land Cloud Fire for the smoke, Fire Temperature for the cores. Fog morning: Night Microphysics before dawn, then surface reports.

How the bar in MesoRadar works

The bar sits where the radar scale normally is, one band per named kind of thing, in the order that fits the product. Where two neighbors really run into each other the bar blends between them; between unrelated things the edge is hard. Drag or hold: a pill names the band and its meaning, with a second line where something else can look the same, and the map dims every other color and rings every spot of that one. If none is on screen, the pill says so. The bands above use the app’s names and colors. Where to find it.

The recipes

Each input is stretched over a fixed range before it is painted (the quick guides list the ranges). Airmass, Convection and Night Microphysics are EUMETSAT designs carried to GOES by NASA SPoRT; Day Cloud Phase is the Japan Meteorological Agency’s.

On Day Convection’s green: MesoRadar squares the 3.9 minus 10.3 difference, which is EUMETSAT’s standard gamma of 0.5 for this RGB (CIRA’s rendering does the same). The quick guide’s table shows the plain difference, so compared with it fewer storm tops are painted yellow here: only the smallest ice saturates the green.