Weather and Climate PDF

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Lecture #1: January 25, 2018 Class Overview - Lectures: clicker and key concepts and facts - Discussion: review of class material, in-class exercise (pre-session reading), exercise discussion in groups of five, summarize discussion and submit to TA - Midterm and final: online via ELMS facility - Tak...

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Lecture #1: January 25, 2018 Class Overview - Lectures: clicker and key concepts and facts - Discussion: review of class material, in-class exercise (pre-session reading), exercise discussion in groups of five, summarize discussion and submit to TA - Midterm and final: online via ELMS facility - Take within a time window - Open book/notes/internet - Quizzes in class (1 quiz between now and midterm, 1 between midterm and final) - FINAL: Thursday May 12-18 (will be given a time window) - Cumulative but more on the second half - Other grading events: - Clicker based interactions: in class - Discussion exercises: at discussion - 2 quizzes: 15% each - Midterm 25% - Final 25% - Classroom response participation: 5% (if answer 80% then okay) - Discussion worksheets 15% (best 80%) Introduction to Topic - Atmosphere and its role in heating of the Earth - What is forcing the climate? - The sun - It affects multiple terrains differently - Ocean absorbs energy before reflecting back - Dark so absorbs more than grass or snow - Mountain reflects off the light - Albedo averages (% reflected) - Earth’s albedo average (31%) - Grass 25-30% - Fresh snow 80-95% - Forests 10-20% - Crops, grasslands 10-25% - Asphalt 5-10% - Concrete 1727% - Brick, stone 20-40% - Light roof 35-50% - Dark roof 8-18% - Water bodies 10-60% - The atmosphere is the thin blue region along the edge of the earth - Very shallow layer - The Atmosphere-Ocean Climate System - The Climate System (very complicated)

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Clouds, volcanic ash, particles (aerosols) all interfere with how much of the energy we can get The Atmosphere is characterized by - Vertical structure - Temperature change from surface all the way up - Wind speed - Air pressure - Constituents - Atmospheric composition - Atmospheric moisture - Variable gas - Water vapor - Gas laws - Laws that govern the behavior of gas The role of atmosphere in heating of the earth - Atmospheric layers - Atmouspheric omposition - Important atmospheric greenhouse gases - Effect of atmospheric composition on Earth’s temperature Main layer of the atmosphere - Troposphere, stratosphere, mesosphere, thermosphere - Tropopause, stratopause, mesopause

- Why does the graph change its mind, increase, decrease - Important to know this chart (one from textbook) Atmosphere - Thin film  of gaseous mixtures - In the vertical, more than 99% of mass found below 30km - Horizontal dimensions may be represented by distance between poles (20,000 km); if proportion preserved, thickness of atmosphere on an office globe- a coat of paint - Yet-atmosphere-central component of climate system - Shallow, but very important for climate Main layers of atmosphere - Troposphere, stratosphere, mesosphere, thermosphere - Separated by conceptual partitions-called pauses - Uniform composition

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- Up to mesopause uniform with respect to: nitrogen, oxygen, inert gas Variable components - Water vapor, ozone - CO2 mixed below mesopause Complication Liquid and solid water, dust particles, sulfate aerosols, volcanic ash

Other - Because the atmosphere is shallow, its motion is primarily horizontal - Horizontal wind speeds are significantly greater than vertical wind speeds - Yet, the small vertical displacements of air have an important impact on the state of the atmosphere Atmospheric structure and role of each layer

Average decrease in temperature as a function of height in the troposphere - Lapse rate - 3.5 degrees/1000’

Lecture 2: January 30 ● About 50% of the globe is covered by clouds Overview ● The vertical structure of the atmosphere ● What is in the “natural” atmosphere ● Sources of energy responsible for our climate ● The effect of atmospheric constituents on the state of the Earth/Atmosphere system ● How can it change by adding man-made materials Main layers of the Atmosphere ● Troposphere ○ The weather is happening in troposphere ○ Temp declines with altitude ● Stratosphere ○ Temp rises, ozone absorbs the UV ○ Less vertical component mixing ● Mesosphere ● Thermosphere Measure Temperature ● Temperature reported to public is measure at about 2m level in a protected and ventilated screen ● Temperature as a function of height ● Shelter to measure temperature ● Temperature change because of surroundings or climate change Temperature Scales ● Measured in K, °C, °F ● Boiling point: 373, 100, 212 ● Zero level: 273, 0, 32 (no motion) ● C: 5/9 (F-32) Absolute zero temperature ● The absolute zero temperature is the temperature at which the molecules do not move at all ● This temperature occurs at -273°C ● The Kelvin scale is a new temperature scale that has its zero value Measuring air temperature ● Liquid-in-glass thermometers ● Max and min thermometers ● Bimetallic thermometers ○ Bimetallic strip bends because the two metals expand differently. The extent of the bending depends on temperature. Bending can be calibrated to ambient temperature. The levers amplify the deformation and allow the arm to record changes in temperature ○ Used in the shelter temp measurer ● Where measured: instrument shelters ● Temperatures can also be measured remotely using infrared sensors (radiometers)

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Radiosonde ○ Measures temperature, humidity and wind above the earth’s surface ○ Can go up to about 30-40 km (if goes higher it will pop because of air pressure) ■ Pressure from inside is greater than outside and will explode ○ Doesn’t go straight up due to wind pressure, drift because of air circulation ○ Only about 20% of the approx 75,000 radiosondes each year are found ○ Radiosonde data plotted on a chart, red line shows temperature, green line shows the dew-point (measure of moisture) ■ Temp as function of height ■ Humidity as a function of height ■ Not exactly vertical because of the drift

Layers ● The ionosphere is a part of the upper atmosphere comprising portions of the mesosphere, thermosphere and exosphere, distinguished because it is ionized by solar radiation. It pays an important part in atmospheric energy. It has practical importance because among other functions, if inclurend radio propagation to distance places on earth ●

F, E, D layer → each ionized at a different intensity ○

Communication can be disrupted by solar activity ■ Solar flares ■ So now we use satellites for communication Communication ● Radio propagation is affected by the daily changes of water vapor in the troposphere and ionization in the upper atmosphere due to the Sun ● Since radio propagation is not fully predictable such services as emergency locator transmitters, in flight communication with ocean crossing aicrag and some television broadcasting have been moved to communication satellites. A satellite link can offer highly predictable and stable line of sigh coverage of a given area Composition of the Atmosphere Gas

Percentage by Volume

Nitrogen (N2)

78.08

Oxygen (O2)

20.95

Argon (Ar)

0.93

Trace Gases Carbon Dioxide

.038

methane

.00017

ozone

.000004

chlorofluorocarbons

.00000002

Water vapor ●

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Highly variable (0-4%)

Water vapor ○ Atmosphere is capable of holding only a minute fraction of the mass of water vapor ○ Water can exist in 3 different phases ■ Gas, liquid, solid ■ Important for life on Earth and distribution of heat in the atmosphere ○ Resides mostly in the troposphere Ozone ○ A pungent blue gas, detected in small amounts, discovered in a lab in the mid 1800s: in green ozein-to smell ○ Average concentration is 3 parts per million by volume ○ Highest concentration around 25 km Stratospheric “good ozone” ○ Protects the biosphere from potentially damaging doses of ultraviolet radiation ○ Documented that Ground level “bad ozone” ○ Forms when nitrogen oxide gases from vehicle and industrial emissions react with volatile organic compounds Ozone hole watch web ○ Gives latest states of the ozone layer over the south pole ○ Satellite instruments that monitor the ozone layer ■ OMI, TOMS, GOME, NOAA SBUV/2, MLS Carbon Dioxide ○ Emitted naturally and through human activities like the burning of fossil fuels ○ Removed by oceans and growing pants, also known as “sinks” and emitted back into the atmosphere through natural processes also known as “sources” ■ When in balance the carbon dioxide emissions and removals are roughly equal ○ Since the industrial revolution in the 1700s human activities had lead to a constant increase ○ The Keeling Curve ○

Mauna Loa → where CO2 measurements are made ■ ■ ■

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First well documents eruption in 1843 Erupted 33 times since then, most recent eruption was in 1984 High above surface and in middle of ocean, far away from industrial sources Data is reported as a dry air mole fraction defined as the number of molecules of CO2 and divide by the number of all molecules in air, including Co2 itself, after water vapor has been removed Mole fraction is expressed as parts per million (ppm) Increase from 2013-2018

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Highest number 410 ppm Hasn’t reached this height for many millions of years, it is at an all-time high Sources of Natural Variable Gases and Materials ● Volcanoes: sulfur, oxide, particulates (aerosols) ● Forest fires: carbon monoxide and dioxide, nitrogen oxides, aerosols ●

Lecture 3: February 1, 2018 Pre-lecture notes ● Shelters protect from sun and openings provide ventilation. At 1.5m level, chance influences from the surface are small ● As evident, large changes in temperature at the surface between day and night by less at higher elevation. ● Weather maps show the temperature forecast for the high temperature for the day ○ Low temperature forecast for the night ● Jet stream ○ Goes around the globe like a wave ○ When it dips low it allows the cool arctic air to come down ○ Sharp jet stream dip ushers in cooler air Anthropogenic Pollution ● Human impacts ○ Industrialization, deforestation, and other land-use changes all have impacts ● Anthropogenic=man made What drives the functioning of the atmosphere? ● Sun is the source of energy ○ Hits the surface The Sun elevation law ● When sun high in the sky, perpendicular to earth, energy distribution over smaller area ● If sun low in the sky, same energy distribution over larger area ● The perihelion and aphelion are the nearest and farthest points of a body’s direct orbit around its sun The heating of the earth ● Factors that determine amount of energy received on Earth-Sun Earth Distance The Inverse Square Law ● The further you go, same energy spread over larger area (inversely proportional to distance squared) or E is about 1/r^2 ● The further you get from the sun, the less energy ● Sun is closer to earth in winter (december) yet more energy is received in summer ○ Exposure to the sun during winter is different than in summer ■ In winter less is illuminated than in the summer ● The earth is closest to the sun at its perihelion aout 2 weeks after the december solstice and farthest from the sun at its aphelion about 2 weeks after the june solstice ● Earth is farther from the sun on its orbit when it is summer in the northern hempisphere ● Shortest distance to the sun changes every year Changing Elliptical Orbit ● Earth orbits the sun in an elliptical path, which means that there is 1 point of the path when the sun is at its closest to earth and 1 point when it is furthest away ● Orbit changes shape ○ The shape of this path varies due to gravitational influences of other planetary objects particularly the moon

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Approx. every 100,000 years earth's orbital path changes from being nearly circular to elliptical. The difference of the earth’s orbital from from a person Because of the axial tilt of the earth in its orbit, the maximal intensity of sun’ rays hit the earth 23.4 degrees north of the equator at the June solstice (at the tropic of cancer) and 23.4 degrees south of the equator at the december solstice (tropic of Capricorn)

History ● It was not until the 16th century that a geometric mathematical model of a heliocentric system was presented, by the Renaissance mathematician, astronomer Copernicus leading to the Copernican Revolution ● Kepler elaborated upon and expanded this model to include elliptical orbits ● Galileo Galilei presented supporting observations made using a telescope Seasons ● The orientation of the Earth towards the sun also determines how much energy is received at the surface clicker ● Earth is closest to the sun in january ● Orientation of the earth towards the sun affects how much energy is received at the surface How does the energy from the sun get to the earth ● 1 micrometer=10^-6 m ● 1 micometers=1000 nm ● Radiation from the sun is an electromagnetic wave ● Wavelength: solid curve-position of the wave at time t; dashed curve-the wave at a later time ● time=t + (change in time) ● In the atmosphere all the wavelengths behave the same way. However when they encounter dense obstacles (water, glass) each wavelength is refracted differently and will emerge as a different color Principle of rainbow formation ● When the white light from the sun hits a raindrop, each wavelength is refracted differently. When it hits the inside of the drop it is reflected like from a mirror and when it exits it is again refracted Sun radiation ● Not all radiation from the sun is received by the surface, some goes back ● About 30% of the sun is reflected back (albedo=reflection) ● 20% is absorbed ● About half of the energy sent reaches us Reference Unit of Energy from the sun ● Solar constant-S0 is the irradiance of solar energy received on a surface exposed normal to sun rays (Ion) at the mean Earth-Sun distance and in absence of atmosphere ● S0=1372 W/m^2 (watts per square meter) ● Earth’s albedo about 31% ● If more land surface is made into streets (asphalt) the albedo would decrease ○ Asphalt absorbs light because it is dark

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Earth’s surface is heated by radiation-temperature will increase ○ Temperature measures of its average speed Fundamental law of radiation theory ● All objects with a temperature above absolute zero (0 on the K scale and -271.15 on the celsius) emit radiation ● Stefan-boltzmann law states that the amount of energy per square meter per second that is emitted by an object is related to the fourth power of its kelvin temperature (E is proportional T^4) ● Therefore a warmer object emits significantly more radiation than a cooler object, the sun emits more energy than the earth Basic Climate Model ● What comes in also goes out ● This model yields an average earth temperature of -18°C ● Solar incident energy is absorbed from the sun, solar reflected energy is emitted, earth emitted energy ● Each object that is not at absolute zero then it radiates energy ○ Amount of radiation depends on the temperature ○ Warmer admits more ○ Simple climate model

Quiz: chapters 1,2,3,6 Review ● The geostrophic wind ○ Wind that is the response between the PGF and the CF Forces that influence winds ● Coriolis force ○ Apparent deflection due to rotation of the earth ○ Right in northern hemisphere and left in southern hemisphere ○ Stronger wind=greater deflection ○ No coriolis effect at the equator ● Circulation around center of low pressure is called cyclonic, circulations around center of high pressure is called anti-cyclonic (irrespective of hemisphere) ● Upper air data is taken from balloons which measure upper air conditions over a particular location. This includes plots of data on the standard mandatory and height levels, contours of various upper air parameters and a set of sounding plots for most US sites. These data updates once every 12 hours around 9:45 EST ● Surface of constant pressure ○ Cross section in height (3,000m) of the atmosphere if the temperature is not the same across the surface then the pressure will differ Northern hemisphere ● Low pressure goes in, high pressure goes out Southern hemisphere ● Low goes in, high goes out General circulation of the atmosphere ● Early attempts to understand the general features of atmospheric circulations were based on the concept of single cell model ○ Assume ■ Uniform water surface ■ Sun always directly overhead the equator ■ Earth does not rotate ■ Result: ● The actual patterns of surface winds include the coriolis effect ● The wind direction includes the deflection due to the coriolis effect General circulation of the atmosphere ● Global wind patterns ○ The above pattern applies to a globe covered by water only but allowing the earth to rotate namely being under the influence of the coriolis force ○ Three cell model only applies to a globe covered by water ○ Intertropical conversion zone Horse latitudes Implications of the general circulation ● Vegetation is where you have the clouds and the rain ● Location of the deserts

The warm and dry conditions of the horse latitudes contribute to the existence of deserts such as sahara deserts, southern western US and northern mexico, parts of the middle east ● Precipitation patterns ○ Rain where air rises (low pressure) ○ Less rain where air sinks (high pressure) ● The different biomes are closely related to the general atmospheric circulation model ● Jet streams ○ Polar and subtropical jet ○ Flow in upper atmosphere ○ The westerly winds in upper atmosphere strongest where greatest contrast in the temperature of the air mass ○ Average position of the polar jet stream and the subtropical jet stream with respect to a model of the general circulation in winter. Both jet streams are flowing from west to east ○ 100-200 kt winds at 10-15 km, thousands of kn long, several 100 km wide and few km think (polar and subtropical) ○ Observations: dishpan experiment ■ Illustrates waves with trough and ridge, develops in a rotating pan with heat on the exterior and cold at the center Actual global warming distribution ● The described pattern of wind distribution is for an idealized sphere that has only water ● Once land is introduced, many of these patterns break ● The next two figures illustrate what the actual pattern look like Effect of land on wind patterns ● The lands heats differently than the oceans so the belt of high pressure is disrupted ● Less so in southern hemisphere where there is less land and more water General circulation of the atmosphere ● Aberga surface wind and pressure in the real world ○ Semi-permanent high and lows ○ Northern vs. hemisphere ○ feature shift seasonally with the sun ■ North in july ■ South in december Clicker ● Intertropical convergence zone (ITCZ) is found around the equator ● Most deserts can be found around 30° latitude and at descending branch of the Hadley cell ○

Lecture 11: Moisture in the Atmosphere Overview ● Absolute humidity ● Specific humidity ● Vapor pressure ● Saturation vapor pressure ● Wet bulb temperature/psychomotors ● Relative humidity Circulation of water in the atmosphere ● Clouds are circulation of water in the atmosphere ● Evaporation, condensation, precipitation ● The water vapor content (humidity) inside this air parcel can be expressed in a number of ways

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Absolute humidity=mass of water vapor/volume of air ■ With the same amount of water vapor in a parcel of air, an increase in volume decreases absolute humidity Specific humidity=mass of water vapor/total mass of air ■ The specific humidity does not change as air rises and descends ■ The average specific humidity for each latitude, the highest average values are observed in the tropics and the lowest values in polar regions

● More measures of humidity ○ Vapor pressure (e) ○ Saturation vapor pressure (es)

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The process of evaporation in a closed contained will proceed until there are as many molecules returned to the liquid as there are escaping At this point the vapor is said t...