Part 2. Air Flashcards
What is Meteorology?
Meteorologists study the physical and chemical properties of the atmosphere, large-scale circulations within it, and the ways in which it interacts with the Earth’s land and ocean surfaces. Both climate and weather are manifestations of the properties and behaviour of the atmosphere, so meteorology is also concerned with short-range weather forecasting and the study of long-term changes in climate.
Imagine that you have a quantity of water in a sealed container, but not enough to fill it. Briefly describe, in everyday terms, how the water molecules (regard each H2O molecule as an individual particle) will behave when the water is in solid?
In solid form, as ice, the water molecules maintain a fixed position relative to each other. A lump of ice would retain its shape without the need for the container.
Imagine that you have a quantity of water in a sealed container, but not enough to fill it. Briefly describe, in everyday terms, how the water molecules (regard each H2O molecule as an individual particle) will behave when the water is liquid?
As liquid water, the molecules can move relative to each other. However, they will remain close together, so the liquid water would flow and settle at the bottom of the container.
Imagine that you have a quantity of water in a sealed container, but not enough to fill it. Briefly describe, in everyday terms, how the water molecules (regard each H2O molecule as an individual particle) will behave when the water is gas?
In the gas phase, the water molecules would move freely. They would fill the container, however big it was.
What are the main constituents of dry air?
Nitrogen. Oxygen. Argon, Carbon Dioxide and Ozone
What is a trace gas?
A trace gas is one that makes up only a small proportion of a sample.
What are the trace gases in air?
Argon, Carbon Dioxide and Ozone
What is a mixing ratio?
The mixing ratio is the number of molecules (or atoms of monatomic species, such as argon) of the gas divided by the total number of molecules of all gases present. For trace gases these are given as either parts per million by volume (ppmv, where 1 ppmv is a mixing ratio of 10−6) or parts per billion by volume (ppbv, where 1 ppbv is a mixing ratio of 10−9).
What is the mixing ratio of Nitrogen in air?
0.781
What is the mixing ratio of Oxygen in air?
0.209
What is the mixing ratio of Argon in air?
0.0093
What is the mixing ratio of Carbon dioxide in air?
400 ppmv
What is the mixing ratio of Ozone in air?
0–200 ppbv (troposphere)
0.1–8 ppmv (stratosphere)
What does the atmosphere do?
The atmosphere transports heat, water and gases around the Earth. It shapes the solid surface and drives ocean currents. Both the ocean and the land are affected mechanically through winds, by evaporation and the removal of fresh water from some regions and by the precipitation of water as rain and snow in other regions.
The atmosphere also protects the Earth’s surface from shortwave, ultraviolet radiation from the Sun, which would otherwise damage living cells. This tenuous layer of gas surrounding the Earth is essential to all complex forms of life for these reasons as well as for the supply of gases for respiration and photosynthesis. In turn, the Earth’s atmosphere has been modified over the planet’s history by the presence of life. One result is the supply of oxygen to the present-day atmosphere by the development of photosynthesis, without which humans would not be here.
How does the atmosphere affect the temperature of the planet and what would happen if it wasn’t there?
The atmosphere is, in turn, supplied with gases and small particles (known as aerosols when suspended in a gas) from the interior of the planet by volcanic eruptions, which modify the climate and so the surface temperature of the Earth. A natural ‘greenhouse effect’, trapping thermal radiation emitted by the Earth, keeps the planet’s surface about 35 °C warmer than it would otherwise be.
What is the troposphere?
the lowest 10–15 km of the atmosphere, where most weather phenomena occur and about three-quarters of the mass of the atmosphere is located
What is the coldest part of the atmosphere?
The tropopause
What is a lapse rate?
This change of temperature with height is known as the lapse rate
What is the typical lapse rate for the lower troposphere?
A typical lapse rate for the lower troposphere is about 6 °C km−1 but this value varies with location and the time of yea
In what layer of the atmosphere does the weather mainly occur?
The troposphere
In what layer of the atmosphere does the temperature stop decreasing?
The temperature stops decreasing at the tropopause and then begins to increase in the stratosphere
Why does the temperature increase in the stratosphere?
Largely, this change is caused by internal heating of the stratosphere where a layer of ozone absorbs incoming solar ultraviolet radiation. The stratosphere is so named because it is a very stable, or stratified, region with little convection.
What parts of the atmosphere are known as the lower, middle and upper atmosphere?
The troposphere is known as the lower atmosphere and the stratosphere and mesosphere can be referred to together as the middle atmosphere. The expanse above the mesopause is called the upper atmosphere.
What happens to the temperature at the stratopause?
the temperature again reverses at the stratopause, decreasing with height again throughout the mesosphere.
What is latitude?
Latitude is the angle that measures a place’s location with respect to the poles and the Equator
What is the latitude of the equator, north pole and south pole?
The Equator has a latitude of 0°, the North Pole is 90° N and the South Pole is 90° S.
How does the location on Earth affect the amount of solar radiation and why?
Locations on Earth that are closer to either of the poles generally receive less solar radiation than those closer to the Equator. The explanation for this is based on the angle between the direction of the solar radiation and the Earth’s surface, or, in everyday language, the height of the Sun above the horizon. In equatorial regions, the Sun is almost directly above an observer around noon. However, in polar regions the Sun is never high in the sky, even in summer, although it can remain above the horizon (i.e. there is continual daylight) for up to six months of the year. In winter, the Sun can be below the horizon for up to six months.
How will a low lying high latitude sun affect the solar radiation that reaches the Earth?
A low-lying, high-latitude Sun means that the incident (incoming) radiation is spread over a greater surface area than in equatorial latitudes, as shown in Figure 2.1.5. This ‘dilution’ of radiation per unit area is so important that it outweighs the effect of the almost continuous day in the polar summer, meaning that the poles do not become warmer than low latitudes. Also, as you can see in Figure 2.1.5, solar radiation has to traverse a greater depth of the atmosphere before arriving at locations that are further from the Equator. This means that atmospheric absorption of the solar radiation is increased, and less energy reaches the surface.
What causes the Earth to have seasons?
The tilt of the Earths axis
What is a hemisphere?
each half of the Earth, either north or south of the Equator
How can energy present itself in our atmosphere?
Energy is present in the atmosphere in a variety of forms. It can present as thermal energy of warm air, from the slightest breeze to the most violent thunderstorm, as kinetic energy in the weather as well as in radiation.
Where does almost all of the Earths energy come from? and in what form?
Almost all of this energy is ultimately supplied from our local star – the Sun – in the form of solar radiation.
Where does thermal energy that originates from within the Earth come from?
Through various cycles, some energy does enter the atmosphere from thermal energy within the Earth. This energy originates mainly from radioactive decay and some residual energy from the Earth’s formation (e.g. volcanoes, hot springs and geysers), but it represents an insignificant contribution to the atmosphere’s total energy compared with the energy from the Sun.
What is the SI unit of power?
The watt is the SI unit of power
What is the total energy output per second from the sun?
The total energy output per second from the Sun, or radiative power, amounts to a colossal 3.85 × 10^26 watts, where 1 watt (W) equals one joule per second (J s−1)
What is a commonly used term for solar radiation that reaches the Earth.
A commonly used term when considering the solar radiation that reaches Earth is insolation. This is the energy arriving per unit area of the planet’s surface.
What is electromagnetic radiation?
You can think of electromagnetic radiation as waves travelling through space, carrying energy in the form of oscillating electric and magnetic fields
describe the term wavelength?
The distance from one crest in each field to the next is the wavelength.
What you see electromagnetic fields?
You cannot see these fields themselves, but your eyes are designed to detect the waves at one specific range of wavelengths (known as the visible part of the spectrum or, in everyday language, ‘light’) and relay the information to the brain. Different wavelengths in the visible range are interpreted as colours, and white light is a mixture of all visible wavelengths.
How does a radio detect radio waves?
A radio performs a similar function to the eye in a different part of the electromagnetic spectrum, detecting radio waves and relaying them to a speaker to make sound.
Electromagnetic waves with wavelengths shorter than 4 × 10−7 m are described as ultraviolet radiation; this continues down to about 1 × 10−8 m, at which point they start to become known as X-rays. Electromagnetic waves with wavelengths longer than 7 × 10−7 m are described as infrared radiation; this continues up to about 1 × 10−3 m, at which point they start to become known as microwaves. Ultraviolet, visible and infrared radiation are the most important regions to be aware of for understanding the atmospheric energy balance.
Order ultraviolet, visible and infrared radiation by increasing frequency?
Infrared radiation has the lowest frequency, then visible radiation, and ultraviolet radiation has the highest frequency.
What is a black body in regards to electromagnetic waves?
A black body is an ideal, theoretical object which both emits and absorbs radiation perfectly at all wavelengths.
State how the peak wavelength of an object’s spectrum depends on temperature, and whether higher or lower wavelength radiation would be emitted by a hotter object. λT = 2.9 × 10−3 m K
So, peak wavelength is inversely proportional to temperature. A hotter object would emit lower wavelength radiation.
λ= (2.9 × 10−3 m K)/T
What is back scattering?
Scattering in which the path of radiation is changed by more than 90°, so that the radiation which was moving downwards is now moving upwards and vice versa, is known as back-scattering. Back-scattering is sometimes referred to as reflection (more accurately ‘diffuse reflection’). However, that term will be reserved for mirror-like reflection from a surface, where all the light is bent through the same angle, rather than the process here, where light is bent through a varied range of angles by particles or rough surfaces.
Why is the sky blue?
In fact, the reason the sky is blue is because incoming light radiation with a short wavelength (i.e. blue) is scattered through much larger angles than longer wavelengths (i.e. red) when both interact with particles (atoms and molecules, in this case) that are very much smaller than the wavelength of the incoming radiation. This phenomenon is called Rayleigh scattering after the British physicist Lord Rayleigh (1842–1919). When an observer is looking away from the Sun, a light ray from it would have to divert through a large angle to reach the person’s eye and only blue light (and shorter wavelengths) is scattered to such an extent. Hence, most of the sky appears blue.
What components of the atmosphere help to keep the Earth cool by limiting the amount of solar radiation?
Light is also scattered by particles that are larger than its wavelength. A good example is scattering by clouds, which appear white or various shades of grey. Clouds scatter solar radiation in all directions, including back into space (back-scattering). For this reason, clouds have a significant effect on the Earth’s atmosphere.
In addition to back-scattering by clouds, the surface of the Earth can also scatter light by different amounts. For example, snow and ice back-scatter much more light than forests or grassland. All of these factors contribute to how much of the incoming solar radiation is absorbed by the Earth. Clouds also scatter the outgoing terrestrial radiation, which can ‘close’ the atmospheric infrared window and keep the surface warmer; their net effect is complex, and is a subject of much ongoing research.
What is steady state?
The atmosphere is dynamic and constantly changing. However, if conditions in the atmosphere were averaged over long enough time periods (which might be many weeks to allow for weather variations, and possibly one or more years to allow for seasonal effects), you might expect to see a broadly steady picture in which the amount of energy in different forms was constant. This is known as a steady state
What is a dry adiabatic lapse rate?
In the troposphere, if a parcel of dry air is lifted rapidly (perhaps through being heated slightly more than its surroundings, or pushed up by a front or by wind passing over a mountain), it expands and is cooled by about 10 °C per 1 km of height gained. In a similar way, a lowered parcel of dry air is compressed and is warmed by about 10 °C per 1 km of height lost. This is the dry adiabatic lapse rate; ‘adiabatic’ means without energy or mass exchange with its surroundings, which is why the parcel was said to be lifted rapidly.
Is the dry adiabatic lapse rate the same as the observed background lapse rate?
The dry adiabatic lapse rate is not the same as the observed background lapse rate, which is generally around 6 °C km−1 in the lower troposphere. This background rate exists because of a combination of air movement, mixing and heating in the atmosphere (i.e. non-adiabatic processes as well as adiabatic lifting).
Imagine that an air parcel from Figure 2.1.17 at 5 km altitude is rapidly lifted up to 7 km. How would its temperature change? (Assume that the parcel remains unsaturated and use the dry adiabatic lapse rate for it.) What would be its final temperature?
The air parcel’s temperature would fall by 20 °C, since it has risen by 2 km (using the dry adiabatic lapse rate of 10 °C per 1 km). Its initial temperature was about −20 °C (reading the blue line) so, at 7 km, it would have a temperature of −40 °C.
