The Lower Stratosphere Passage (LSP) is an area of air between the lower and upper stratospheres. This air is highly compressed and is forced to move downward. This action leads to compressional warming. This in turn creates vast areas of subtropical high pressure, centred over the oceans. This region is associated with strong thermodynamic stability and sparse precipitation with technolookup.com
Convective environment
Convection is an important transport process in the stratosphere. It can enhance stratospheric water vapor, but also deplete it. It can transport significant amounts of water ice and carbon monoxide. The presence of these gases in stratospheric air mass could be caused by the formation of deep convection. This deep convection transports air from the troposphere to the stratosphere, where it enhances stratospheric water vapor.
Gravitational waves propagate through the stratosphere when convection occurs. These waves have low-frequency components and a short horizontal wavelength. They propagate horizontally and reach 40 km in one to two hours.
Ozone content
Ozone content in the lower stratosphere varies throughout the year. In the winter months, the concentration of ozone is at its lowest, and then increases over the course of the spring and summer. The ozone content of the stratosphere is also affected by large-scale atmospheric motion.
Scientists use Dobson Units to measure ozone content. A unit of ozone is 0.01% of the thickness of the atmosphere. At the STP, that’s equivalent to about three millimeters thick. These units are the most basic unit of measurement used in atmospheric ozone research. They are named for the scientist G.M.B. Dobson, who was one of the first to study atmospheric ozone. To measure the concentration of ozone, scientists use a Dobson spectrometer, a standard instrument for measuring ozone from the ground. A Dobson spectrometer measures the intensity of ultraviolet-radiation at four wavelengths, and it is a standard instrument for measuring ozone.
In addition to volcanic activity, anthropogenic chemicals can deplete ozone. Volcanic chlorine has been shown to enhance catalytic destruction of ozone. Two examples of volcanic effects are the Pinatubo eruption in 1991 and El Chichon eruption in 1982. In the former case, rainout of soluble HCl from the eruption cloud may have scrubbed out a large amount of ozone-depleting chlorine. This effect is likely related to sulfur dioxide conversion to sulfate aerosol. Sulfate aerosol provides a catalytic surface for chlorine and nitrogen to degrade ozone.
Time scale for ozone loss
The time scale for ozone loss in the Lower stratosphere is long, and can be over a year. This is because the upper and middle stratospheres shield ozone from the solar radiation. The amount of ozone in the lower stratosphere depends on the source of the air and the amount of ozone already present. Unlike the upper stratosphere, where ozone concentrations are more stable, the lower stratosphere has a larger degree of variability.
While the time scale for ozone loss in the Lower stratosphere Passage is long, the rate of ozone destruction has been decreasing over the last several decades. The rate of ozone destruction in the lower stratosphere has decreased by as much as 50% since the 1980s. Although there is no one single factor responsible for the ozone loss, complicated mechanisms are implicated in this process.
Influence of subtropical high pressure system on ozone content
The influence of subtropical high pressure systems on ozone content in the Lower Stratosphere Passage has been studied using mesoscale numerical simulations. These simulations suggest that the axis of a deep trough, corresponding to the W and D cases, is west of the subtropical Andes, thereby transporting ozone-rich air into the lower stratosphere.
The ozone content in the Lower Stratospheric passage can be determined by measuring the ozone mixing ratio, which is calculated from observations over the lower stratosphere. This index is also known as the omega vertical velocity.
Although the ozone hole has largely disappeared from the lower stratosphere, scientists have questioned how far this recovery has gone. The researchers from the Canadian Centre for Climate Modelling and Analysis in Victoria, British Columbia, used two state-of-the-art climate models to determine the atmospheric changes caused by the ozone hole, and compared these changes with the observed changes over the past few decades. Their analysis suggests that the ozone hole effect may be responsible for the observed changes in the Southern Hemisphere.
Effect of gravity waves on ozone content
Gravity waves (GW) are waves of energy in the upper atmosphere, which are generated by deep convection. While these waves are largely absent in the tropics, they still play an important role in exchange processes. They can transport water vapor and ozone.
Gravitational waves have been known to affect the upper and lower stratosphere. However, until the 1960s, they were considered a mystery. This changed when atmospheric researcher Colin Hines began to notice the irregular wave-like patterns in meteor trails. Hines suspected that the patterns were caused by gravity waves crashing like ocean waves at the shore of the upper atmosphere. He developed the first widely accepted theory of gravity waves.
Ozone molecules are constantly being produced in the stratosphere. They are normally destroyed by UV radiation, but certain chemicals react with the radiation and release chlorine or bromine atoms into the stratosphere. These gases affect the ozone layer because they are 60 times more destructive to ozone molecules than chlorine atoms.
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