Topic 2 Flashcards
What are the formulas for pressure and force?
Pressure = Force/Area
Force = mass * acceleration
What is the formula of atmospheric pressure p0?
p0 = Atmospheric mass * gravitational acceleration const / 4pi * surface area of the globe.=
When are relative concentrations used to quantify concentration of gas molecules?
For bulk compents (such as N2 / O2), they are expressed as a percentage of a whole amount whereas trace gases are expressed in ppm/ppb/ppt etc
What is the absolute concentration term used to quanitfy conc of gas molecules?
Molecules per unit volume is is the absolute concentration term used to quanitfy conc of gas molecules. The standard unit is molecules cm-3.
What is the formula relating number of moles to number of particles?
no. of moles = no. of particles / Avagadro’s
Formula for partial pressure to molecules cm-3?
[X] molecules cm-3 = Avagadros * partial pressure / 10^6 RT
Formula for parts per to molecules cm-3?
[X] molecules cm-3 = a * Avagadros * atmospheric pressure / 10^6 * b * RT
Where a and b are a parts per b.
What is atmospheric pressure?
Atmospheric pressure is 101 325 Pa.
What are the four layers of the atmosphere?
The four layers of the atmosphere are the troposphere, the stratosphere, the mesophere, and the thermospere.
What is the radiative cooling effect and how does it happen?
Radiative cooling is the cooling of the planet as we move away from the surface. This ie because there are less molecules to absorb IR.
What is adiabatic cooling?
Adiabatic cooling the process of reducing heat through a change in air pressure caused by volume expansion.
What is temperature inversion?
Temperature inversion means temperature increases with altitude.
How does adiabatic expansion occur on a gas particle in the troposphere?
A gas particle from an emitor (likely to be a combustion process) will have a relatively high temperature so the gases move up in the atmosphere. The pressure gets lower very rapidly so the particle increases in size (as there are less air particles to fight against the increase in enthalpy). Therefore the volume of the particle increases and there is a cooling effect on the particle.
What forces are acting on a gas particle in the troposphere?
Internally to a particle there is adiabatic expansion/cooling and externally there is radiative cooling.
Explain the temperature up to 11km and the inversion around 11km (troposphere)?
Up to 11km the particle temperature is greater than the ambient atmospheric temperature but around 11 km there is inversion and the ambient atmoshere is warmer than the air particle meaning the particle settles down and there is a convection effect.
What are the start and end heights of the stratosphere?
The strasophere starts and 20km and ends at 50km. It is where the most ozone is present.
Why is there an increase in the temperature of the strasophere?
The ozone photochemistry in the stratosphere releases lots of heat increase the T. It is also futher from the Earth’s surface meaning solar radition becomes more potent (there is less filtration meaning UV increases and eventually leads to presence of ionising radiation).
Is there any convection in the stratosphere?
There is very little convection in the stratosphere as gases can’t go up in T.
How does the lack of ozone in the mesophere affect the temperature?
The lack of ozone in the mesophere means there is little photochemistry so radiative cooling takes over. The only T source is whatever heat comes from lower surfaces and how many gases are there to hold heat.
How does the low pressure of the mesophere affect it’s cooling effects?
As pressure is low in the mesosphere there is not much pressure change therefore there is no adiabtic cooling - only radiative cooling.
