kvmdays.blogg.se

They appear to help cause the formation of the infamous holes in the ozone layer by "encouraging" certain chemical reactions that destroy ozone.ĭue to the lack of vertical convection in the stratosphere, materials that get into the stratosphere can stay there for long times. Made of ice, they are found at altitudes of 15 to 25 km (9.3 to 15.5 miles) and form only when temperatures at those heights dip below -78° C. PSCs (also called nacreous clouds) appear in the lower stratosphere near the poles in winter. Polar stratospheric clouds (PSCs) are the exception. Because of this, few clouds are found in this layer. The stratosphere is very dry air, containing little water vapor. Air is roughly a thousand times thinner at the top of the stratosphere than it is at sea level. Commercial jet aircraft fly in the lower stratosphere to avoid turbulence and increased atmospheric drag, which are common in the troposphere below. Because of this temperature stratification, there is little convection and mixing in the stratosphere, so the layers of air there are quite stable. This is exactly the opposite of the behavior in the troposphere in which we live, where temperatures drop with increasing altitude. Temperatures rise as one moves upward through the stratosphere. Ozone, a type of oxygen molecule that is relatively abundant in the stratosphere, heats this layer as it absorbs energy from incoming ultraviolet radiation from the Sun. The lower boundary of the stratosphere is called the tropopause the upper boundary is called the stratopause.

The lower boundary of the stratosphere can be as high as 20 km (12 miles or 65,000 feet) near the equator and as low as 7 km (4 miles or 23,000 feet) at the poles in winter. The height of the bottom of the stratosphere varies with latitude and with the seasons. The top of the stratosphere occurs at an altitude of 50 km (31 miles). The bottom of the stratosphere is around 10 km (6.2 miles or about 33,000 feet) above the ground at middle latitudes. This diagram shows some of the features of the stratosphere. The next higher layer above the stratosphere is the mesosphere. The troposphere, the lowest layer, is right below the stratosphere. It is the second layer of the atmosphere as you go upward. The stratosphere is a layer of Earth's atmosphere.