Ice Cloud Cartographer | EUMITSAT

Head for the heights

Multispectral observations from ground-based networks and meteorological satellites are the primary means of obtaining global-scale ice cloud data for use in cloud products such as cloud quantity and cloud type, which support climate monitoring and weather forecasting.

“To support these products, data sets are integrated into radiative transfer models, computer simulations of how clouds absorb and scatter radiation, which feed into calculations of the balance between incoming and outgoing radiation,” Parlakas explains.

An artist’s impression of the Metop-SGA satellites (foreground) and the Metop-SGB satellites in orbit.

“However, despite great efforts, and because of the great variation in size, shape, and orientation of ice crystals, ice clouds still represent some of the largest unknowns in numerical weather prediction and climate models.”

Capturing these diverse optical properties relies on observations in the visible, near-infrared, infrared and microwave channels, many of which are provided by EUMETSAT’s geostationary Meteosat satellite and the polar-orbiting Metop satellites.

“Advancements in simulation software have enabled microwave data to increasingly contribute to the full picture of the properties and structures of ice clouds at the global scale,” Parlakas says.

“However, existing microwave channels are unable to detect smaller ice crystals, because the frequencies at which they operate are not sensitive enough to measure objects in the sub-millimeter range, which includes smaller ice crystals.”

This is set to change, however, when the Metop Second Generation (Metop-SG) series satellites are launched later this decade as part of the EPS-SG programme, thanks to instruments such as the new Ice Cloud Imager – a cone scanning radiometer that will help… To fill gaps in microwave observations and enrich global observations of ice clouds.

“What is particularly exciting about the Ice Cloud Imager is that it will operate at both millimeter and sub-millimeter frequencies and will therefore be sensitive to both large and small ice crystals,” Barlakas explains. “This will enable specialists to gain a more comprehensive understanding of ice clouds and their properties.

“There will be opportunities to create improved cloud products such as those that detail the amount of ice measured vertically in the atmosphere – known as the water ice track – and even make predictions about the average ice crystal diameter and average ice mass height.

“These products will play an important role in validating and representing ice clouds in climate and weather models.”

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