Types of PSC
PSCs are classified into three types Ia, Ib and II according to their chemical composition.
- Type I clouds contain nitric acid and water.
- Type Ia clouds consist of crystals formed from nitric acid dihydrate (NAD) or trihydrate (NAT) and water.
- Type Ib clouds droplets additionally contain sulfuric acid and are present in the form of supercooled ternary solution.
- Type Ic clouds consist of metastable water-rich Nitric acid in a solid phase.
- Type II clouds consist of water ice only.
Only Type II clouds are necessarily nacreous whereas Type I clouds can be iridescent under certain conditions, just as any other cloud.
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A type II (water) PSC showing iridescence
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A veil of type I PSC, easily confused with cirrostratus clouds or tropospheric haze
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A type I PSC (white cloud above the orange tropospheric clouds), showing fine horizontal structures in the veil.
Read more about this topic: Polar Stratospheric Cloud
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