Cirrus (stylized as cirrus) is a worldwide ATM network. Aerosols affect the formation of clouds, especially cirrus clouds. Consequently, both the Cirrus and Sebring convertible were sold in Europe as the Stratus. Snow was observed to fall from cirrus clouds. Radar units give information on the altitudes and thicknesses of cirrus clouds. Visual observations from aircraft or the ground provide additional information about cirrus clouds. They are sometimes seen with cirrus, cirrocumulus, altocumulus, and stratocumulus. This mechanism is similar to the formation of cirrus uncinus clouds. The ice crystals in cirrus clouds have different shapes in addition to different sizes. The LX was the base Chrysler Cirrus trim level. The Chrysler LeBaron was replaced by the "Cloud Car" Chrysler Cirrus. The Chrysler Cirrus and Mitsubishi-built Dodge Avenger were dropped. The other clouds in this level are cirrus and cirrostratus. This led to a global increase in sulfuric acid (HSO) concentration in high-level cirrus clouds. Thunderstorms can form dense cirrus at their tops.