Cirrus clouds
Cirrus clouds are semi-transparent, wispy, and thin, which makes them difficult to see with the naked eye. Made up of numerous ice crystals, they form at temperatures below approximately -38°C, where liquid water cannot exist under Earth's atmospheric conditions. In mid-latitudes, cirrus clouds can be found at altitudes between 7 and 12 km, while in the tropics, they can extend higher up (until about 18 km).
In the satellite image on the right, the shape of the Nile Delta is clearly visible under a layer of cirrus clouds. However, since they form at high altitudes and at cold temperatures, they emit very little energy back into space. At the same time, they trap longwave radiation, preventing it from escaping into space. Therefore, cirrus clouds have a greenhouse effect similar to that of carbon dioxide. This means that, on average, they contribute to global warming, unlike other cloud types.
Terra satellite, NASA
Not all cirrus clouds are the same. Some are formed at warmer temperatures and then transported to cirrus levels (for example clouds spreading from tops of thunderstorms), while others are formed with the help of small aerosol particles. The third type is formed from small liquid solution droplets.
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In my research I address the following questions:
Which type of cirrus clouds prevail and why does this matter?
Can we reasonably simulate such clouds in climate models?
What are the microphysical differences between cirrus formed by the three cloud formation mechanisms?
For more details please refer to:
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Cirrus cloud properties as seen by the CALIPSO satellite and ECHAM-HAM global climate model (Gasparini et al., 2018, JClim)
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Opinion: Tropical cirrus — From micro-scale processes to climate-scale impacts (Gasparini et al., 2023, ACP)
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Cirrus clouds and their geoengineering potential (Blaž Gasparini ETH Diss., 2017)
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Why cirrus clouds cannot substantially cool the planet? (Gasparini and Lohmann, 2016, JGR)