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Meteorology notesTopic 1 AtmosphereMeteorology​ is the study of the behavior and the composition of the atmosphere.Atmospheric conditions ​include: Temperature and pressure of the given volume of gas, the composition of that volume, whether volume is saturated or dry, and the temperature, pressure, ...

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Meteorology notes Topic 1 Atmosphere Meteorology is the study of the behavior and the composition of the atmosphere. Atmospheric conditions include: Temperature and pressure of the given volume of gas, the composition of that volume, whether volume is saturated or dry, and the temperature, pressure, composition and saturation of the volume compared to atmosphere around it as a whole. Atmosphere is defined as heterogeneous stratified (layered) solution of gas molecules, liquid water and suspended solids. Vertical Structure of the atmosphere Explain the effects on temperature within atmosphere due to ozone? Ozone acts to absorb large amount of UV radiation from the sun increasing temperature within the Stratospheric layer creating inversion which it is defined by. Troposphere: Lowest layer of the atmosphere defined by decrease in temperature with altitude within that layer, and the constant vertical and horizontal motion of the atmosphere within the layer due to conduction, convection and mechanical uplift. Warm by terrestrial radiation. Contains 75% of atmospheric mass. Dimensions vary due to surface temperature and pressure and latitude. Tropopause: The isothermal layer that acts as a transition zone between the Troposphere and the Stratosphere. Height is varied by latitude, angles of insolation, and seasons. Explain how the following changes within the Tropospheric column affect the height of the Tropopause (a) surface pressure (b) temperature: Tropopause marks the upper limit of the Troposphere and its vertical distance from the earth’s surface moves in relation to changes in surface pressure and/or temperature. Tropopause height is directly proportional to temperature i.e. an increase in surface temperature will increase the height of the Troposphere and inversely proportional to pressure i.e. an increase in surface pressure will lead to a decrease in the height of the Tropopause. State the average Tropopause heights and Tropopause temperatures at (a) the equator (b) the poles and (c) the mid-latitudes: (a) equator 55,000ft/ -75C/ 91hPa. (b) poles 24,000ft/-48C/376hPa. (c) 38,000ft/-58C/200 hPa. With respect to the Tropopause (a) describe the idealised global tropopause detailing approximate altitudes and positions of jet streams (b) explain why the height of the tropopause varies with latitude and seasons: (a) look at the recorded lectures at 1 hour mark and figures on pg. 18 & 19.

(b) Variations in latitude are due to variations in rates of insolation and average temperatures with latitude i.e. higher latitudes experience generally lower temperatures and therefore a lower tropopause. Seasonal variations are due to the earth’s axial tilt which will adjust the position of the sun relative to given latitudes and hemispheres. This in turn adjusts average surface temperatures – where temperatures increase i.e. during summer periods tropopause heights also increase and where temperatures decrease i.e. during winter periods tropopause heights decrease Stratosphere: The 2nd  layer of the atmosphere immediately above the Tropopause characterised by a strong inversion layer or increase in temperature with altitude caused by the presence of large amounts of Ozone within a concentrated belt known as the Ozone Layer. An atmospheric layer notable for the largest concentration of Ozone (15ppm) within the atmospheric and characterised by a permanent inversion layer, absence of atmospheric mixing and weather. Warm by solar radiation from above. Explain why the Stratosphere is generally devoid of cloud and turbulence: Due to absence of water vapour and aerosols within the layer and the layers natural temperature inversion.

Aerosols 2 types; Primary and Secondary

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Secondary: Form through coagulation or the physical transformation of other substances. These secondary aerosols tend to prefer moist area eg. the tropics. Explain (a) the sources of aerosols within the atmosphere (b) the effects of aerosols within the atmosphere (c) the importance of aerosols within the atmosphere: (a) sources of aerosols in atmosphere are Natural fires, Volcanic Eruptions, Ejection of salt crystals by breaking waves, Soil erosion, Entrainment of pollen by wind, Human activity. (b) aerosols can affect atmosphere by scattering light (why we see different color skies) but most importantly they act as nuclei for water vapour to condensate. (c) The importance of aerosols: 1) Act as nuclei for condensation and cloud formation, 2) Play a critical role in creation of precipitation, 3) Act to absorb/ reflect radiation in various forms regulating global temperatures, and 4) Affect visibility and have health effects. In general terms, describe the effect of increasing height and/or latitude on aerosol content within the Atmosphere: Changes in concentration: higher in summer over land surfaces. Lower at high altitudes. Over sea areas, greater concentration of salt based aerosols. Land surfaces dominated by smaller aerosols especially in Northern Hemisphere.

Ozone: created when the kind of oxygen we breathe—O2—is split apart by sunlight into single oxygen atoms. Single oxygen atoms can re-join to make O2, or they can join with O2 molecules to make ozone (O3). Ozone is destroyed when it reacts with molecules containing nitrogen, hydrogen, chlorine, or bromine. Explain the effects on temperature within the atmosphere due to (c) ozone: Ozone responsible for absorption of UV component of solar radiation increasing temperatures in the lower stratosphere and creating a permanent atmospheric inversion.

Ozone details: - 90% of Ozone found in Stratosphere between 10-50km. Total mass of Ozone approx. 3 billion metric tons or 0.00006% of the atmosphere with peak concentrations found at 32km at 15ppm (0.0015%). Layer isn’t a layer but a region where concentrations of Ozone are greater Dobson Units 1 DU = the number of molecules of Ozone required to form a layer of pure Ozone 0.01mm thick at a temperature of 0 degrees Celsius at sea-level pressure Global average thickness of ozone layer is 300 DU (approx. 15ppm) with concentrations below 220DU considered to be a sign of a weak or failing layer. Bad Ozone: Direct contact with Ozone is harmful to plant and animal life including people. Near the surface it forms when Nitrogen Oxide gases from vehicle and industrial emissions react with organic compounds (esp. chemical based ones). Natural concentration near surface is 10 parts per billion (0.000001%) – but exposure to levels above 70 parts per billion for 8 hours or longer is unhealthy. These can occur around cities when the air is warm and stable. Harmful effects include throat and lung irritation, asthma or emphysema. Carbon Dioxide: compound of carbon and 2 oxygen molecules. -

Average global concentrations are now 408ppm up from 368ppm when I first started teaching this course.

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0.041% of total atmospheric mass).

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Biggest absorber are the oceans; these also produce majority of our Oxygen

Explain the effects on temperature within the atmosphere due to Carbon Dioxide: Carbon Dioxide is an important greenhouse gas whose main contribution to global temperatures is its ability to trap terrestrial radiation within the earth’s atmosphere increasing global temperatures. Water Vapour: 0.25% of atmosphere is water. Amount in atmosphere varies due latitude and atmospheric temperature. In general terms describe the effect of increasing height and/or latitude on water vapour content in the atmosphere: Increase in latitude ฀ decrease in water vapour content average concentration tropical latitudes 1-5%, in polar latitudes significantly less 10ppm. Increase in altitude ฀ 50% WV concentrated below 1.5km, less than 5% above 5km, and less than 1% above 12km (approx. 36,000ft) to 3ppm in Stratosphere. Explain the effects on temperature within the atmosphere due to (a) water vapour: Water in the atmosphere is a significant contributor to the greenhouse effect acting, in all 3 states, to absorb incoming solar radiation as well as trap outgoing terrestrial radiation with a follow on impact on atmospheric temperatures. On a local scale water phase changes are responsible for significant changes in temperatures due to the release or absorption of latent heat. Latent Heat: Latent heat or hidden energy is the energy given off or absorbed by a substance when it undergoes a change in state or shift from one molecular phase to another. Explain the sources of water vapour in the atmosphere: Hydrologic Cycle is how water is recycled through the Earth’s Climate. First, water from land sources and ocean evaporate, is absorbed by atmosphere. Once in atmosphere, water condenses, forming clouds. When atmosphere become

sufficiently saturated excess moisture returned to earth in form of precipitation. The cycle takes 7-10 days. Topic 2 Temperature and energy exchanges The Sun Sun’s energy is derived from molecular motion (fusion). That energy is emitted as radiation. All objects molecules are in constant motion except for objects at 0 kelvin or so called as Absolute Zero. The molecular motion produces kinetic energy which is emitted by all objects as radiation. Molecular Structure affects on temperature: Solids molecular motion is restricted, amount of kinetic energy produced is low. Radiation is still emitted but a small amount. Hence, temperature of solids in its natural state without additional energy is low. Liquid molecular motion allows some movement, but molecules are still bound. However, compared to solid object with equal volume and density, the liquid object should produce greater amount of kinetic energy, and have a higher temperature. Gas molecular motion. Molecules of gases are largely in complete freedom of movement within that objects volume. This result in a larger amount of kinetic energy and higher temperatures. The radiation emitted is emitted at all wavelengths, but some wavelengths better than others. The emitted wavelengths’ quantity and type are determined by the object’s temperature. Where that radiative energy is transferred to another object it is called heat. What is Temperature? Temperature is the measure of the average kinetic energy and/or molecular activity within an object. Describe the temperature reference points of the centigrade scale used in New Zealand aviation: Celsius is measured along two reference points the freezing and boiling point of pure water. Describe the following units of temperature (a) Celsius (b) Fahrenheit (c) Absolute (Kelvin): Both Centigrade and Fahrenheit are reference scales that measure temperature relative to two common reference points: freezing and boiling point. At sea level, Celsius runs from 0-100, relating to pure water. Fahrenheit runs from 32-212 and relates to saltwater or brine. Kelvin is an absolute scale, starting at an absolute zero. Unlike Celsius and Fahrenheit, where temperature can be below zero, it is impossible to go below zero on Kelvin. Absolute Zero is theoretically argued as the point where all molecular activity ceases and no kinetic energy is produced. Convert between Celsius, Fahrenheit and absolute temperature

Fundamental Laws Stefan Boltzmann: Intensity of energy radiated by a Black Body (assumption that the body emits perfectly 100%) increases according to the fourth power of its absolute temperature.

Wein’s: For any radiating body the wavelength of peak emissions (the most emitted wavelength) is inversely proportional to its temperature. Inverse Square: Amount of energy received by a body diminishes by the distance travelled by that energy squared. Components of Solar Radiation

State the wavelength of solar radiation and terrestrial radiation: Terrestrial radiation Long-wave, low frequency band infrared radiation between 4µm 80µm. Global Energy Budget, Climate and weather are driven by amount of solar energy earth retains and receives, and the terrestrial radiation earth emits. Explain the warming or cooling of the atmosphere with reference to solar and terrestrial radiation: Solar Radiation or Insolation warms the upper layers of the atmosphere and the earth’s surface. Terrestrial radiation emitted by the Earth warms the troposphere. The balance between these two energy sources incoming solar and outgoing terrestrial radiation determines global temperatures and weather conditions. Locations that receive surplus of solar radiation have higher surface temperature and warm weather. Explain what is meant by the terms solar radiation and terrestrial radiation: Solar Radiation describes the visible and non-visible emitted by the sun. Terrestrial radiation emitted by the Earth warms the Troposphere. Sun emits 64 million Wm^2. Earth only receives average of 1,367 Wm^2. This total is called the Total Solar Irradiance. Factors affecting the Total Solar Irradiance: Earth’s orbit round the sun Perihelion(closest) and Aphelion (furthest), Solar Activity, Axial Tilt (Precession). Once energy enters atmosphere, it is vary by: length of day, distance that energy has to travel, surface features, and atmospheric conditions. Explain the factors that influence the amount of solar radiation received at the Earth’s surface:

Length of day, longer day means more sunlight, more solar radiation. Distance energy travel, inverse square law, ‘a given quantity or intensity of energy is inversely proportional to the square of the distance from the source of that energy.’. Surface features, albedo white snow reflects light better, while darker color can absorb light more. Atmospheric conditions, more clouds aerosols can absorb or scatter the radiation. Describe the effect of the following on the amount of solar radiation received at the surface of the earth (a) sun angle (b) length of the day (c) season

If the Earth did not tilt on its axis, there would be no seasons at all, and most places, except the poles, would have 12 hours daylight each day throughout the year. Every year the polar areas have at least one complete 24-hour period of darkness and one of daylight. In theory, the poles themselves should have six months of daylight followed by six months of darkness. In reality, this is not the case because some light from the Sun is bent towards the Earth making nights slightly shorter than they otherwise would be. The equatorial regions do not really have seasons as we know them, as the relative position of the overhead Sun does not change significantly enough throughout the year. At high latitudes the Sun's rays reach the Earth's surface more obliquely, so that the energy is spread over a greater surface area. In addition, more radiation is lost to scattering and absorption as the path through the atmosphere is longer. In the winter at high latitudes, days are short with continuous darkness in polar regions at mid-winter. Here there is a net loss of outgoing long-wave radiation into space with no incoming short-wave radiation to compensate. Nearer the equator, where the sun is near the vertical, at midday the sun's rays strike with greater intensity, as shown in Figure 4. Radiation in atmosphere are either scattered, absorbed or transmitted. Transmission is when radiation passes through atmosphere unimpeded. Absorption and Scattering occurs when radiation encounters solid, liquid or gas object in atmosphere. Process occur depends on: the radiation’s wavelengths, objects that radiation encounters and the relationship between the 2 factors. Scattering Rayleigh, scattering by smaller agent than the radiation. For example, gases which responsible for the blue sky. Mie, scattering by larger agents such as aerosols resulting in little energy being lost back to space. Responsible for greying of the sky, and intensifying of red sunsets and rises. Non Selective scattering, scatter radiation no matter the wavelength. Eg, in clouds and is basis of rainbows. 2 processes occur after scattering: Diffuse, radiation encounters an object, scatter with some loss of energy/intensity. Specular, scatter without loss of energy. With absorption the retention of energy by the encountered object causes that object to increase its own temperature and according to Stefan-Boltzmann and Wein’s Laws the radiation that object

produces will also change. Within the atmosphere this is a critical process as it sees both TR and SR absorbed largely by water vapour and clouds and then remitted in small quantities helping the climate retain the average temperatures we are familiar with.

Approximate figures Reflection by clouds – 19% Absorption by atmosphere – 25% Absorption by surface – 45% Scattering by atmosphere – 6% Reflection by ground – 5%

Explain the factors that influence the amount of solar radiation received at the Earth’s: Snow reflects 80% of insolation, Thick Cloud 50%, Grassland 20-25%, Thick Forest 5%. Amount of absorption varies by cloud type. Clouds also act to prevent terrestrial radiation escaping minimising variations in temperature, e.g., COLD cloudless nights and WARM cloudy nights. UV – almost totally absorbed by Ozone layer / Visible radiation – minimal absorption / Infrared – absorbed mainly by water vapour & CO2. Explain the warming or cooling of the atmosphere with reference to solar and terrestrial radiation: Regional imbalances are compensated by net transfer of sensible and latent heat energy between latitudes by earth’s climate systems. WIND Transfers sensible heat Responsible for about 75% of all heat transference OCEANS Transfers remaining 25% of heat energy Good example is Gulf stream CLOUD COVER Will result in larger diurnal variations in temperature throughout the day, as well certain types of surface, topographical features and vegetation. Define the terms (a) Solstice (b) Equinox. State  the significance of (a) Solstice (b) Equinox. Equinox, Two times of the year when the suns noon rays are vertical at equator and day and night time hours are equal at all latitudes; March & September. This is the time at which earth’s

precession neither points towards nor away from sun. This results in nearly equal amounts of daylight and darkness at all latitudes. Solstice, Two points of year when suns noon rays are vertical at tropics at approximately 23 degrees N/S latitude in June and December. When earth’s tilt is at its maxiomum. Significant in that, the length of day will be either be longer or shorter, affecting the insolation, resulting in colder or hotter weather in the mid latitude. Topic 3 Atmospheric Pressure Atmospheric pressure is the weight of a column of air above a horizontal area from the upper boundary of the atmosphere to the surface, or force exerted by a given volume of air outward on its surroundings. State the meteorological units of pressure used in (a) Australia (b) USA Australia = hPa. United States = Hg (inches of mercury) and PSI Barometers Mercury. Mercury moves up inward tube, responding to pressure changes. The measurement is adjusted for effect of temperature and gravity. Aneroid. Works similarly to altimeter. Aneroid capsule contracts as pressure increases, and expands as pressure decreases. O Density calculation = 0⋅3484x PT

Temperature in Kelvin

Temperature determines the size of a volume of air. While pressure determines mass of air within that volume. Explain the effect of changes in the following elements on air density (a) pressure (b) temperature (c) altitude (d) moisture content of air Where temperature is constant, decrease pressure = decrease in density, and increase in pressure = increase in density. Increase in temperature = decrease in density. Decrease in temperature = increase in density. Density of atmosphere decreases exponentially with altitude. Less than 1% of atmospheric mass is found above the stratosphere. Increase moisture content = decrease density, decrease moisture content = increase in density (changes are meteorologically insignificant). Gas Laws Explain what is meant by the Partial Pressure of Gas: Pressure of a volume of air = sum of the individual contributions of each component gas within that volume. Those component contributions are called a gases partial pressure. For example, 78% of the atmosphere is nitrogen, this mean that in a ty...