Answer · confidence: partial
How do ground stations and satellites tell apart a sky dimmed by smoke from one dimmed by thin cloud?
The records show that smoke and clouds are hard to tell apart in satellite imagery because they share similar spectral characteristics 1. One method, the Fisher smoke and cloud recognition index, is reported to achieve high accuracy in separating smoke from clouds over vegetation, soil, and water 2. Lidar depolarization ratio is described as a useful tool for classifying aerosol types and estimating how much each type contributes to elevated layers 5. The records do not describe how ground stations specifically separate smoke from thin cloud, and the newest related fact, on smoke aerosols, dates from 2026 34.
Checked 2026-10-18. Only documented and supported facts are used.
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[1] documented
Smoke and clouds are difficult to distinguish because they exhibit similar spectral characteristics in satellite imagery.
"In remote sensing monitoring of forest fires, smoke and clouds exhibit similar spectral characteristics in satellite imagery, which can easily lead to clouds being misjudged as smoke."Research on Forest Fire Smoke and Cloud Separation Method Based on Fisher Discriminant Analysis (2025)
[2] documented
The Fisher smoke and cloud recognition index (FSCRI) models achieve high accuracy in distinguishing smoke from clouds over vegetation, soil, and water.
"Their recognition accuracy rates for smoke and clouds in the underlying surfaces of vegetation, soil and water reached 95.5%, 93.5% and 99%, respectively."Research on Forest Fire Smoke and Cloud Separation Method Based on Fisher Discriminant Analysis (2025)
[3] documented
Smoke aerosols are distinct from stratospheric sulfate aerosols in their chemical, optical, and microphysical properties.
"Smoke aerosols are distinct in their chemical, optical, and microphysical properties from stratospheric sulfate aerosols."Retrieval of bimodal aerosol size distributions for stratospheric sulfate and smoke aerosols using multi–wavelength satellite measurements (2026)
[4] documented
Pyrocumulonimbus events inject smoke plumes containing aerosols and trace gases into the upper troposphere and lower stratosphere, driving stratospheric aerosol variability.
"Pyrocumulonimbus events (pyroCb) are a natural driver of stratospheric aerosol variability by injecting smoke plumes containing aerosols and trace gases into the upper troposphere and lower stratosphere."Retrieval of bimodal aerosol size distributions for stratospheric sulfate and smoke aerosols using multi–wavelength satellite measurements (2026)
[5] supported
Lidar depolarization ratio is a useful tool for classifying aerosol types and quantifying how much each aerosol type contributes to elevated layers.
"Depolarization ratio is highly valuable in lidar-based aerosol classification and can be used to quantify the contributions of different aerosol types to elevated layers [1]."Comparing Halo Doppler lidar depolarization ratio with PollyXT (2020)
[6] documented
Lidar measurements of cirrus clouds use the depolarization ratio, which the study reports varies with height and is smaller than 0.3 above 16 km, as one property used to characterize these clouds.
"The depolarization ratio is found to increase with a height at 11–15 km and smaller than 0.3 above 16 km."Lidar ratio and depolarization ratio for cirrus clouds (2002)