PHYC40050-L01-Structure

PHYC40050-L01-Structure - Climate, Climate Change Nuclear...

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Unformatted text preview: Climate, Climate Change Nuclear Power and the Alternatives Climate, Climate Change Nuclear Power and the Alternatives PHYC 40050 Peter Lynch Meteorology & Climate Centre School of Mathematical Sciences University College Dublin Introduction to Meteorology & Climate Introduction to Meteorology & Climate OUR HOME Lecture 1 The Composition and Structure of the Atmosphere Introduction to Meteorology & Climate Introduction to Meteorology & Climate COMPARISON OF HEMISPHERES 70% of the globe covered by water Introduction to Meteorology & Climate Introduction to Meteorology & Climate 1 COMPOSITION OF THE EARTH’S ATMOSPHERE 0.0002% 100% O 2 N2 H2 N2O CH4 PM CO O3 ←SO2, NO2, CFC’s, etc Atmospheric Composition 1% Ar CO2 Inert gases 0.04% Introduction to Meteorology & Climate Introduction to Meteorology & Climate ATMOSPHERIC COMPOSITION Molecular oxygen and nitrogen are major Molecular components – 99% Of the remaining 1% , 96% is the inert Of gas argon Of the remaining 4%, 93% is carbon Of dioxide All remaining gases – about 2 parts in All 100,000 are known as trace species These gases control the chemistry of the These troposphere Introduction to Meteorology & Climate ~78% ~21% ~1% .04% Introduction to Meteorology & Climate THE EARLY ATMOSPHERE 4.6 billion years ago: Earth’s gravity too weak to hold hydrogen Earth’s and helium (unlike Sun, Jupiter, Saturn, Uranus) Earth’s present atmosphere from Earth’s volcanoes (outgassing) (outgassing) Water vapor condensed to form oceans Water CO2 went into oceans and rocks CO N2 Oxygen forms by break-up of water by Oxygen breaksunlight, later from plants … photosynthesis. photosynthesis. ATMOSPHERIC EVOLUTION Earth’s early atmosphere consisted of Earth’s Hydrogen (H), Helium (He), Methane (CH4) and Ammonia (NH3) As the earth cooled volcanic eruptions As occurred emitting water vapour (H2O), carbon dioxide (CO2) and nitrogen (N2). The molecular oxygen (O2) in the The current atmosphere came about as single celled algae developed in the oceans about 3 billion years ago. Introduction to Meteorology & Climate Introduction to Meteorology & Climate 2 ATMOSPHERIC EVOLUTION Oxygen is produced as a by-product of Oxygen byphotosynthesis, the making of sugars from photosynthesis, water vapor and carbon dioxide. This oxygen produces ozone (O3) in the This upper atmosphere which filtered out harmful ultraviolet radiation from the sun. This allowed plants and animals to This develop on land. Introduction to Meteorology & Climate Introduction to Meteorology & Climate Keeling Curve (Charles Keeling) CARBON DIOXIDE CYCLE Sources Plant/animal respiration Plant/animal Plant decay Plant Volcanoes Volcanoes Burning of fossil fuels Burning Deforestation Deforestation Sinks Plant photosynthesis Plant Oceans Oceans Carbonates Carbonates Introduction to Meteorology & Climate Introduction to Meteorology & Climate HYDROLOGICAL CYCLE HYDROLOGICAL CYCLE Water is everywhere on earth Water It is in the oceans, glaciers, rivers, lakes, the It atmosphere, soil, and in living tissue All these ‘reservoirs’ constitute the hydrosphere hydrosphere All The continuous exchange of water between the The ‘reservoirs’ is called the hydrological cycle The hydrological cycle is powered by the Sun The It comprises It Evaporation and transpiration Evaporation Precipitation Precipitation Percolation into ground Percolation Run-off to the sea Run- Introduction to Meteorology & Climate Introduction to Meteorology & Climate 3 Trace Constituents Methane and world population Introduction to Meteorology & Climate Introduction to Meteorology & Climate CFCs: global production Introduction to Meteorology & Climate CFCs: global concentration Introduction to Meteorology & Climate AEROSOLS Particles suspended in the atmosphere Particles Diameters of microns – one millionth of a meter. Diameters Modify the amount of solar energy reaching Modify the surface. Act as condensation nuclei for cloud droplets. Act PRIMARY SOURCES: Sea salt spray Sea Wind erosion Wind Volcanoes Volcanoes Fires Fires Human activity Human Introduction to Meteorology & Climate 1 nm 1| um 1 mm Aerosols: particle sizes Introduction to Meteorology & Climate 4 PRESSURE AND DENSITY Pressure is the force exerted on a given area. Pressure Air pressure results when air molecules Air move and collide with objects. Air pressure is exerted in all directions. Air Density is the concentration of molecules, or Density mass per unit volume. The pressure, density, and temperature of a The gas are all related to each other. Los Alamos Fire, 2000 Introduction to Meteorology & Climate Introduction to Meteorology & Climate PRESSURE AND ALTITUDE Pressure is measured in terms of inches of Pressure mercury, or in millibars or hectopascals. hectopascals. Average sea-level pressure is 29.92 inches Average seaof mercury or 1013.25 millibars (hPa). hPa). Atmospheric pressure always decreases Atmospheric with increasing altitude. The air pressure measured on top of the The Sugar Loaf is always less than the pressure in Kilmacanogue. Kilmacanogue. To subtract the effect of station elevation, To air pressure is corrected to report what it would be at sea level (sea level pressure) (sea pressure) Introduction to Meteorology & Climate Introduction to Meteorology & Climate Blaise Pascal Density decreases exponentially with height Introduction to Meteorology & Climate Introduction to Meteorology & Climate 5 ATMOSPHERIC PRESSURE Pressure at a point is the weight of air above Pressure that point. A column of air of cross-section 1 square column crossmetre weighs about 10 tonnes ! In still air, two factors determine the pressure In – temperature and density Ideal gas law: Ideal Pressure = Constant X Density X Temperature Pressure decreases with altitude. Pressure ATMOSPHERIC DENSITY The concentration of molecules in measured The in terms of density, or mass per unit volume. density, Density at sea level for temperature of 15ºC Density 15ºC is about 1.2 kilograms per cubic metre. metre. Density decreases with altitude. Density Introduction to Meteorology & Climate Introduction to Meteorology & Climate IDEAL GAS LAW The relationship between pressure, The temperature, and volume is given by the ideal gas law: p = RρT where p = pressure R = the gas constant ρ = (Greek letter rho) density rho) T = temperature Introduction to Meteorology & Climate IDEAL GAS LAW Knowing the Ideal Gas Law, you should be Knowing able to say what happens to one variable if a change in one of the others occurs (while the third remains constant). E.g., what happens to pressure if density E.g., increases (temperature constant)? Introduction to Meteorology & Climate ATMOSPHERIC LAYERS STRATIFICATION OF THE ATMOSPHERE The atmosphere can be divided up The according to pressure (500 mb layer is about halfway up in the atmosphere). The atmosphere can also be divided up The according to temperature (which does not follow a simple relationship with height). Averaging out temperature values in the Averaging atmosphere, we identify four layers. layers. Introduction to Meteorology & Climate Introduction to Meteorology & Climate 6 ATMOSPHERIC LAYERS Troposphere – Troposphere temperature decreases with height Stratosphere – Stratosphere temperature increases with height Mesosphere – Mesosphere temperature decreases with height Thermosphere – Thermosphere temperature increases with height Introduction to Meteorology & Climate Introduction to Meteorology & Climate TROPOSPHERE From the surface up to about 12km From (varies with latitude and season – higher in Summer, and in the tropics). Temperature decreases with height Temperature because the troposphere is heated by the surface and not directly by sunlight. Almost all of what we call “weather” Almost occurs in the troposphere. Contains 80% of the atmosphere’s mass Contains Introduction to Meteorology & Climate STRATOSPHERE Between about 12km and 50km. Between Temperature increases with height because Temperature the ozone layer absorbs ultraviolet light and warms up as a result. Lack of mixing and turbulence. Lack Very little exchange occurs between the Very stratosphere and troposphere (but it is important where it does). 99.9% of the atmospheric mass below the 99.9% stratopause. stratopause. Introduction to Meteorology & Climate MESOSPHERE & THERMOSPHERE Mesosphere between 50km and 85km. Mesosphere Thermosphere goes up and up and up: there Thermosphere is no clear separation between the thermosphere and interplanetary space. The highest temperatures in the atmosphere The are found in the thermosphere due to high energy radiation being absorbed by gases. Ionosphere (charged gas atoms) that Ionosphere reflects radio waves, and aurora are here. Introduction to Meteorology & Climate Introduction to Meteorology & Climate 7 1. Troposphere- literally means region where air “turns over” -temperature usually decreases (on average ~6.5°C/km) with altitude Tropopause 2. Stratosphere- layer above the tropopause, little mixing occurs in the stratosphere, unlike the troposphere, where “turbulent mixing” is common Stratopause 3. Mesosphere- defined as the region where temperature again decreases with height. Mesopause 4. Thermosphere- region with very little of the atmosphere’s mass. High energy radiation received by the thermosphere: high temperatures. Very low density (not much “heat” felt). Introduction to Meteorology & Climate Introduction to Meteorology & Climate In meteorology we often refer to altitude as a certain pressure value rather than height. The atmosphere moves mainly on constant pressure surfaces (isobaric surfaces) 850 mb ≈ 1500 700 mb ≈ 3000 500 mb ≈ 5500 300 mb ≈ 9000 m m m m (5000 ft) (10,000 ft) (18000) (30,000) Introduction to Weather Maps Introduction to Meteorology & Climate Introduction to Meteorology & Climate ATMOSPHERIC FRONTS Front – a boundary between two regions of Front air that have different meteorological properties, e.g. temperature or humidity. Cold front – a region where cold air is Cold replacing warmer air. Warm front – a region where warm air is Warm replacing colder air. Stationary front – a front that is not moving. Stationary Occluded front – a front where warm air is Occluded forced aloft. Introduction to Meteorology & Climate Introduction to Meteorology & Climate 8 WARM FRONT COLD FRONT Introduction to Meteorology & Climate Introduction to Meteorology & Climate WEATHER PLOTTING SYMBOLS SYNOPTIC WEATHER CHART Introduction to Meteorology & Climate Introduction to Meteorology & Climate METEOROLOGICAL TIME All weather reports are labelled using All Coordinated Universal Time (UTC), also called Greenwich Mean Time (GMT), and also denoted Zulu (Z). Zulu is the time along the 0º longitude Zulu 0º line, which runs through Greenwich. Meteorology uses the 24 hour clock Meteorology which omits the use of a.m. and p.m. (0900 = 9 a.m., 2100 = 9 p.m.) Introduction to Meteorology & Climate Introduction to Meteorology & Climate 9 Revision: Layers of the Atmosphere Hot top: oxygen Hot absorbs sunlight Warm middle: ozone Warm absorbs ultraviolet (UV) End of Lecture 1 Warm surface: land and Warm ocean absorb sunlight Introduction to Meteorology & Climate Introduction to Meteorology & Climate 10 ...
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This note was uploaded on 01/31/2011 for the course PHYC 40050 taught by Professor Staff during the Summer '08 term at UC Davis.

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