| CEOS EO HANDBOOK – MEASUREMENTS
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Measurements > Atmosphere >
Cloud type, amount and cloud top temperature
  | The study of clouds, their location and characteristics, plays a key role in the understanding of climate change. Low, thick clouds primarily reflect solar radiation and cool the surface of the Earth. High, thin clouds primarily transmit incoming solar radiation, but at the same time they trap some of the outgoing infrared radiation emitted by the Earth and radiate it back downward, thereby warming the surface. Parameters include temperature and moisture profiles, fractional cloud cover, cloud top height, cloud top pressure, surface temperature and surface emissivity. | |
| Detailed Measurement | Description* | Instruments | Timeline |
Cloud cover
Link:   | 3D field of fraction of sky filled by clouds - Physical unit [ % ], Accuracy unit [ % ] | 40 instruments | |
| Cloud imagery | Intended for observation of features like cloud occurrence, pattern, frontal bands, cyclones, volcanic ash plumes. | 42 instruments | |
| Cloud mask | Binary product (cloud or cloud-free) derived from Cloud imagery - Accuracy expressed as Hit Rate [ HR ] and False Alarm Rate [ FAR ]. | 10 instruments | |
| Cloud top height | Height of the upper surface of the cloud - Physical unit: [ km ] - Accuracy unit: [ km ]. | 37 instruments | |
Cloud top pressure
Link: | Pressure at the top of the cloud - Measuring Units hPa, Uncertainty Units hPa | 3 instruments | |
Cloud top temperature
Link: | Temperature of the top of the cloud (highest cloud in case of multi-layer clouds) - Physical unit [ K ], Accuracy unit [ K ] | 18 instruments | |
| Cloud type | Result of cloud type classification - Accuracy expressed as number of classes. Actually [ classes-1 ] is used, so that smaller figure corresponds to better performance, as usual. | 33 instruments | |
| Freezing level height | Height of the atmospheric layer in cloud where liquid-solid states transform into each other - Physical unit: [ km ] - Accuracy unit: [ km ]. | 0 instruments | |
| Melting layer depth in clouds | Depth of the atmospheric layer in cloud where liquid-solid states transform into each other - Physical unit: [ km ] - Accuracy unit: [ km ]. | 0 instruments | |
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* Description adapted from WMO.
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