Cirrus clouds
Cirrus clouds are semi-transparent, wispy, and thin, making them often difficult to see with the naked eye. They are made up of numerous ice crystals and form at temperatures below approximately -38°C, where liquid water cannot exist under Earth's atmospheric conditions. In mid-latitudes, they can be found at elevations between 7 and 12 km, while in the tropics, they can extend to higher elevations (up to 18 km).
Cirrus clouds reflect only a portion of solar (visible) radiation. On the satellite picture, we can still clearly see the shape of the Nile delta under a layer of cirrus clouds. However, since they form at high altitudes and cold temperatures, they emit very little energy back into space. At the same time, they also trap longwave radiation, preventing it from escaping to space. Therefore, they have a greenhouse effect similar to that of carbon dioxide. This means that, on average, they contribute to warming the climate 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)