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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.
Although clouds can exist within a wide range of altitudes, typical cloud cover has a base at approximately 4,000m and extends up to an altitude of about 5,000m. [9] Clouds height can vary depending on latitude; with cloud cover in polar latitudes being slightly lower and in tropical regions the cloud cover may extend up to 8,000m.
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 origin of the term "cloud" can be found in the Old English words clud or clod, meaning a hill or a mass of stone. Around the beginning of the 13th century, the word came to be used as a metaphor for rain clouds, because of the similarity in appearance between a mass of rock and cumulus heap cloud.
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]
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.
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.