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Cloud-cover symbols used on weather teleprinters and aviation reports in the US [6] In the early 20th century, it was common for weather maps to be hand drawn. The symbols for cloud cover on these maps, like the modern symbols, were drawn inside the circle marking the position of the weather station making the measurements.
Clouds of the genus nimbostratus tend to bring constant precipitation and low visibility. This cloud type normally forms above 2 kilometres (6,600 ft) [10] from altostratus cloud but tends to thicken into the lower levels during the occurrence of precipitation. The top of a nimbostratus deck is usually in the middle level of the troposphere.
Meteorology is a branch of the atmospheric sciences (which include atmospheric chemistry and physics) with a major focus on weather forecasting.The study of meteorology dates back millennia, though significant progress in meteorology did not begin until the 18th century.
The luminance or brightness of a cloud is determined by how light is reflected, scattered, and transmitted by the cloud's particles. Its brightness may also be affected by the presence of haze or photometeors such as halos and rainbows. [114] In the troposphere, dense, deep clouds exhibit a high reflectance (70–95%) throughout the visible ...
The yellow color is due to the presence of pollutants in the smoke. Yellowish clouds caused by the presence of nitrogen dioxide are sometimes seen in urban areas with high air pollution levels. [22] Red, orange and pink clouds occur almost entirely at sunrise and sunset and are the result of the scattering of sunlight by the atmosphere.
Snow crystals form when tiny supercooled cloud droplets (about 10 μm in diameter) freeze. These droplets are able to remain liquid at temperatures lower than −18 °C (0 °F), because to freeze, a few molecules in the droplet need to get together by chance to form an arrangement similar to that in an ice lattice.
The discovery of 90377 Sedna in 2003, together with a few other objects discovered around that time such as (148209) 2000 CR 105 and (612911) 2004 XR 190, has motivated discussion of a category of distant objects that may also be inner Oort cloud objects or (more likely) transitional objects between the scattered disc and the inner Oort cloud. [2]
Polar stratospheric clouds over Western Norway. The stratosphere is very dry; unlike the troposphere, it rarely allows clouds to form.In the extreme cold of the polar winter, however, stratospheric clouds of different types may form, which are classified according to their physical state (super-cooled liquid or ice) and chemical composition.