Atmosphere of Planet V

This article is about the atmosphere of planet v.

See also: Climate of Vallhyn 

The atmosphere of Planet V is a layer of gases surrounding Planet V that is retained by Planet V's gravity. The atmosphere protects life on Planet V by absorbing ultraviolet solar radiation, warming the surface through heat retention (greenhouse effect), and reducing temperature extremes between day and night (the diurnal temperature variation).

The common name given to the atmospheric gases used in breathing and photosynthesis is air. By volume, dry air contains 73% nitrogen, 26% oxygen, 0.9% argon, 0.05% carbon dioxide, and small amounts of other gases. Air also contains a variable amount of water vapor, on average around 1% at sea level, and 0.4% over the entire atmosphere. Although air content and atmospheric pressure vary at different layers, air suitable for the survival of terrestrial plants and terrestrial animals currently is only known to be found in Planet V's troposphere and artificial atmospheres.

The atmosphere has a mass of about 5.15×1018 kg, three quarters of which is within about 11 km (6.8 mi; 36,000 ft) of the surface. The atmosphere becomes thinner and thinner with increasing altitude, with no definite boundary between the atmosphere and outer space. The Kármán line, at 100 km (62 mi), or 1.57% of Earth's radius, is often used as the border between the atmosphere and outer space. Atmospheric effects become noticeable during atmospheric reentry at an altitude of around 120 km (75 mi). Several layers can be distinguished in the atmosphere, based on characteristics such as temperature and composition.

Composition
Air is mainly composed of nitrogen, oxygen, and argon, which together constitute the major gases of the atmosphere. Water vapor accounts for roughly 0.25% of the atmosphere by mass. The concentration of water vapor (a greenhouse gas) varies significantly from around 10 ppmv in the coldest portions of the atmosphere to as much as 5% by volume in hot, humid air masses, and concentrations of other atmospheric gases are typically provided for dry air without any water vapor. The remaining gases are often referred to as trace gases, among which are the greenhouse gases such as carbon dioxide, methane, nitrous oxide, and ozone. Filtered air includes trace amounts of many other chemical compounds. Many substances of natural origin may be present in locally and seasonally variable small amounts as aerosols in an unfiltered air sample, including dust of mineral and organic composition, pollen and spores, sea spray, and volcanic ash. If compared to Earth, there is a strong difference in amount of nitrogen (78% for Earth's atmosphere) and oxygen (21% for Earth's atmosphere). The high percentage of oxygen allows for the existence for larger creatures, such as insects. Similarly, because oxygen levels are over 25%, fires are significantly easier to light, with even wet material being capable of catching flame. Luckily, it is still below 30%, at which point wildfires would be catastrophic and almost impossible to put out.

The percentage of carbon dioxide is also higher than Earth's (0.03%), allowing for larger plant growth. Crop yields are also larger on Planet V, as plants can take more nutrition from the air and less from the soil. This allows for more mineral-rich land. That said, the amount of protein within crops decreases and creatures must eat more meat to make up the loss. This makes practices like veganism much more difficult.

Structure
In general, air pressure and density decrease with altitude in the atmosphere. However, temperature has a more complicated profile with altitude, and may remain relatively constant or even increase with altitude in some regions. Because the general pattern of the temperature/altitude profile is constant, the temperature behavior provides a useful metric to distinguish between atmospheric layers. In this way, Planet V's atmosphere can be divided (called atmospheric stratification) into five main layers. Excluding the exosphere, Planet V has four primary layers, which are the troposphere, stratosphere, mesosphere, and thermosphere. From highest to lowest, the five main layers are:


 * Exosphere: 700 to 10,000 km (440 to 6,200 miles)
 * Thermosphere: 80 to 700 km (50 to 440 miles)
 * Mesosphere: 50 to 80 km (31 to 50 miles)
 * Stratosphere: 12 to 50 km (7 to 31 miles)
 * Troposphere: 0 to 12 km (0 to 7 miles)

Climate and Weather
A majority of the planet's weather occurs strictly within the troposphere, sometimes extending up into the lower reaches of the stratosphere.

Temperature
As per the Stefan-Boltzmann equation, the effective temperature of the planet if around 281.228 K. Thanks to the planet's low albedo (0.287) and the greenhouse gases within the atmosphere, the planet's average global temperature is actually higher at 292.328 K.

On average, temperature within the troposphere falls by 6.5 degrees K with every rise of 1 km. This is known as the environmental lapse rate.

Temperature also decreases with increase latitude degrees. In general, temperature remains close to constant between the equator and 10 N/S. Between 10 N/S and 20 N/S, the change is light, only amount to about 2 degrees. After that, however, temperatures drop around .63 degrees per degree latitude. As such, while the average temperature at the equator is around 34 degrees C, the poles are, on average, around -20 degrees C.