Environmental Science lecture notes
Environmental Science lecture notes
Environmental science first lecture: -water vapor is at the center of the atmosphere -dark grey areas on water vapor scale means its relatively dry compared to lighter areas -higher co2 ppm per million molecules in the atmosphere… rapid increase since industrial revolution atmospheric aerosols influence air temperature, play a role in cloud formation, are generated by human activities and natural processes, include sea salt crystals We find Ozone at ground level cause of cars' fumes.. Found in smog. It is bad on the ground. QUESTIONS: 1. The thermosphere has extremely high temperature, but a person exposed to it would rapidly freeze. Explain this apparent contradiction. -not enough molecules close to each other to transmit the heat to your body plus the pressure is so low. 2. What climate-change processes might you expect to witness during your time? Which ones do you think take too long for you to experience? -Seasons. Global warming/ice age Environmental Science lecture 2 -air is denser near the Earth's surface atmospheric pressure is force exerted by air molecules per unit area Ideal Gas Law states: --> slide 3 p=pRT temperature=constant X pressure -air pressure decreases with altitude
-air at a higher altitude less dense -> less oxygen -altitudes above 3000 meters can cause mountain sickness Questions: Pressurized cans of shaving cream say not to expose to excessive heat. What might happen if it is and will this potential problem last throughout the product life. A standard pressure of 1,013.2 hPa is also known as one atmosphere (1 ATM). Look at the next figure and determine at approximately what levels you would record a pressure of 0.5 ATM and 0.1 ATM.
Lecture slides 4: Solar luminosity was much less 4.6 billion years ago when Earth formed. The Earth was colder than now. To find the intensity of the radiation: Stefan-Boltzman equation: E=oT^4 A blackbody is a body that is perfectly efficient at emitting radiation For graybodies, Stefan-Boltzmann equation becomes I=eoT^4 Wein's Law: A=2897/T The impact on Earth's temperature if scattering in the atmosphere increase would depend on which type of scattering. But usually colder. If cloud cover increased, the Earth's temperature would be
Net Radiation= incoming radiation-outgoing radiation
Poleward heat transport: Surplus energy moves toward poles (deficit regions) Poleward heat transport is a driving force of climate Warming is occurring due to the presence of greenhouse gases. Incoming solar energy is equaled to the outgoing IR energy. Greenhouse effect keeps the Earth warm. Without it the Earth's temperature would be ~ -15 degrees celsius Energy absorbed by Earth - Energy absorbed at the surface = Energy recycled within the Earth's system
Questions: Would you expect both the Northern and Southern hemisphere to have same average albedo/ What factors might cause the two hemispheres to reflect different percentages of insolation back to space? -->No they won't have the same average altitude because southern him sphere has more water than land mass, and northern hemisphere has more land so more snow will increase average albedo.
Which would have the greatest effect on the Earth's greenhouse effect: Removing all of the CO2 from the atmosphere or removing all of the water vapour? Explain why you chose your answer. -->
Environmental Science Lecture 3 Lecture 5 Sub-solar point - at noon, the sun will be directly over it
-summer in the southern hemisphere is associated with the sub solar point at 23.5 degrees South. -an average rate of 55W/m^2 in insolation can be observed at 90 degrees South, at the December Solstice. -an average rate of 440W/m^2 in insolation can be observed at 0 Degrees, at the March Equinox -the maximum temperature occurs in mid-late afternoon even though the the amount of time it takes to reradiate the solar radiation -temperature is more inconsistent the further from the equator -equatorial zone is associated with rain forests -grasslands are associated with the midlatitude zone -If the Earth was not tilted, the Earth's radiation budget would have a greater loss of energy at high latitudes -coastal locations have lower temperature ranges than locations inland because it takes a lot more energy to heat up a body of water than land -wind mixes the warm water with the cold water -greater loss of latent heat with a body of water Continentality-effect of an inland location that favours greater temperature extremes -What factors influence local temperatures--> surface type, latitude, elevation -The surface type contributes the most to maintaining temperatures at a given location higher than nearby areas (asphalt holds heat more than vegetation, farmers fields etc.)
-there will be a higher range of temperature year round the further the area is from water/the higher the latitude -the Wind-Chill index is the "feel" of temperature under cold conditions
QUESTIONS: An orchard farmers hears a weather forecast for overnight low temperatures to hover just above freezing point of 0 Degress Celsius, but with wind chill temperatures expected to drop significantly lower. Will the wind chill increase the possibility of frost damage? Why or why not? ANSWER: Suppose that the Earth's axis were tilted at 40 degrees to the plane of the ecliptic, instead of 23.5 degrees. How would the seasons change in Hamilton? what would be the global effect of the change? ANSWER: The summer would be hotter, winter would be colder. The seasons would be even more extreme. Lecture 6 -Humidity is the amount of water vapour in the air. -Specific Humidity (SH) is the actual quantity of water vapour in air -SH=mass of water vapour (g)/mass of total air (kg)
-Saturation Specific Humidity is the maximum amount of H2Ov (i.e. SH) that an air parcel can contain at any given time based on its temperature -Saturation is achieved when the density of gas cannot be increased above a certain level change of phase once limit is reached -Dew Point - Temperature at which air, when cooled, becomes saturated -If two air parcels have the same specific humidity, but different temperatures, they will still have the same dew point
-Relative Humidity (RH) = 100 X (SH/saturation SH)
-If there temperature rises, and the specific humidity stays the same, the relative humidity will fall QUESTIONS: How can frozen clothes "dry" outside in subfreezing weather? What is taking place? A crowded classroom is filled with students. In what way the presence of the students affect the dew point and relative humidity in the room? Answer: 2. Dew point will be increasing because of more moisture and the more people makes it hotter too. The relative humidity decreases. If the increase in the temperature is far larger than the increase in the dew point, the relative humidity will decrease. Environmental Science Lecture 4 -Pressure (mb) is the same as hPa -Rate of temperature decrease with altitude for a parcel of dry or unsaturated air as it rises: 10 degrees celsius/1,000m -rate of temperature decrease with altitude for a parcel of air saturated with water vapour as it rises: 4-9 Celsius/1,000m -lifting condensation level (LCL): height at which saturation occurs Slide 7 Diagram from bottom to top -Air cools at DALR - Unsaturated -Air becomes saturated - saturated -Air cools at SALR - SALR=MALR -Level of free convection LFC Latent heat released compensates for decrease in temperature
Atmospheric stability - no vertical movement occurs -Stability: Air parcel resists upward displacement -Instability: air parcel keeps rising Absolutely stable atmosphere is ELR<MALR it is not the best temperature for advection fogs to form In many regions, the orographic effect causes precipitation to increase with elevation. Can you think of any reason why this might not be true all the way up to the top of Mt Everest? -->By the time the water vapour has been forced to lift along the mountain slope, it has already condensed and formed into clouds and precipitation
Environmental science lecture 5 Lecture slide 9 -Precipitation is any form of water that falls from a cloud and reaches the ground - In warm clouds (>0 Celsius): water droplets condense - Constant speed achieved when air resistance = gravity: terminal velocity - In cold clouds (there is more moisture that can be held with the cold stratus cloud Both the arctic and the Canadian Prairies have relatively low snow cover. Is the cause for this the same in both regions? --> Lecture slides 10 -Water in all its forms: ~1.4 billion km^3 -Overland and interflow are affected by human development -a water balance represents Hydrological cycle at the local scale Water balance equation: P= (PE-D) + S + or - AST D= PE - AE P= precipitation PE= potential evapotranspiration -moisture demand D= deficit -Moisture shortage S= surplus -oversupply AST: soil moisture storage change -moisture savings AE= actual evapotranspiration -if all demand is satisfied, AE=PE -Deficit occurs when PE cannot be satisfied through; P, soil moisture Under ideal conditions; AE and PE are close -Surplus: When PE is satisfied, and ST is full
ACCWL: accumulated potential water loss -water taken from ST when: P< or equal to PE -october to mid december; recharge QUESTIONS: 1. What effect does a large ST have on a location as compared with another location that has the same P and PE totals but a lower ST? 2. How do impervious surfaces such as parking lots impact the water balance terms? --> the actual evaporation is going to be lower, and higher deficits in the summer months; Soil storage. ^ON FINAL EXAM
Environmental Science lecture 6 Lecture slides 11 -Wind is air that is moving horizontally relative to Earth's surface. It is caused by unequal heating of the Earth's atmosphere -Winds are generated by differences in pressure drive wide. -Pressure gradient force: difference in pressure between regions -Pressure is mapped by constant height: plot variations in air pressure on a constant elevation On maps: isobars connect points of equal pressure -pressure drops 10 hPa/100 metres in standard atmospheric conditions -lines of isobars: bend & turnaround areas of High (H) & Low (L) pressure -Constant height charts can be used to:
-Constant pressure maps: show variations in altitude for a constant pressure -also known as isobaric charts and upper level charts Constant pressure maps -High heights correspond to high temperatures -Low heights correspond to low temperatures Ridges an troughs on maps -Contour lines or isobars tend to decrease in value from equator to the poles Winds and temperature on pressure maps -H: high pressure; anticyclones -L: low pressure; mid-latitudes cyclones -Pressure gradient force: difference in pressure over distance -Pressure gradient crosses isobars: -Closely packed height lines indicate: large pressure gradient -pressure gradients are created through unequal heating of the atmosphere South Asia is known for a seasonal shift in the thermal circulation between land and ocean QUESTIONS Pilots often use the expression "high to low, look out below" In terms of upper-level temperature and pressure, explain what this can mean? --> if the temperature was lower, the pressure would be lower and push the plane down. The pilot of a small plane wants to fly at constant height above ground Can the pilot fly at a constant pressure level (e.g. 500 hPa) to achieve this? Why or why not? --> no, the pressure changes with temperature. if it is a very short distance, possible he might be able to achieve this. Long distance, not a chance. Lecture slides 12 Coriolis force
-Strongest near the poles, non along equator relates to the Coriolis force -Relation to latitudes: Strongest near poles, non along equator Geostrophic wind -Parallel to isobars -PGF=CF -Spacing of isobars indicates speed (Vg) Gradient flow -winds that flow parallel to curved isobars -constantly changes direction Upper-level cyclones & anti cyclones -are rotating air parcels -Generated by Centripetal force: imbalance between PGF and CF -Force is at: right angle to the winds -Winds flows in upper-level cyclones counterclockwise rotation in Northern hemisphere -->low pressure -Subgeostrophic flow: CFPGF Surface winds -wind direction influenced by: frictional force (FF) -3 forces combine: PGF,CF,FF Buys-Ballot's Law In the NH, with winds at your back: L to the left, H to the right Convergence - created by air spinning into a cyclone -convergence at surface --> divergence above
Divergence - created by air spiralling out from an anticyclone -divergence at surface --> convergence above QUESTIONS: Why are surface winds that blow over the ocean closer to being geostrophic than those that blow over land? --> Why is that, on the equator, winds may blow either counterclockwise or clockwise with respect to an area of low pressure?
Environmental Science lecture 7 Slides 13 - Atmospheric circulation -General circulation of the atmosphere refers to the average air flow -the basic cause of the general circulation is The one-cell model is uniform water surface -the Earth does not rotate It is impossible on Earth for a Hadley Cell to extend from the equator to the poles because of the coriolis force The three-cell model allows Earth to spin -implies no land surfaces HIgher pressure=denser air= colder air Hadley Cell - air going to be warming, rising, and eventually lowering.. Low pressure. Sun is usually right above most of year. There is little variation in the position of the pressure centres in the Southern Hemisphere , between January and July because o the presence of Antarctica
From low to high latitudes, wind flow and pressure patterns aloft are created by: temperature and pressure gradients Coriolis force also contributes to jet streams Polar front: where warm air meets cold air Pilots prefer to fly in the core of a jet stream rather than just above or below it because the fastest winds are found in the jet stream core and clear air turbulence is found above and below the jet stream core QUESTIONS: Which of the belts depicted in the three-cell model is likely to exhibit greatest temperature …?
Slides 14 What drives oceanic circulation? -oceanic temperature structure -differences in salinity at the surface: - wind action Oceanic temperature structure Mixed layer: mixed by waves and wind Mixing can only occur near the poles Ocean currents are a persistent and horizontal movements of ocean water At surface: driving by friction from prevailing winds -Ekman spiral speed and direction not uniform with depth -Gyres are large-scale circular currents bounded by continents -upwelling is warm surface waters replaced by colder waters, from below
-coastal algal blooms are triggered by upwelling Earth's major currents are Western boundary currents (e.g. gulf stream) and Eastern boundary currents (upwelling) The water surface temperature along the coast of the northern California is warmer in the winter than the summer because upwelling is strongest in the summer and because in the summer, the region is more under the influence of a subtropical high Melting of the Greenland ice sheet could decrease the strength of the Gulf Stream The migration of plastic ducks has been used to understand the direction of the oceanic currents Thermohaline circulation is a slow circuit of deeps currents, from 1 km to the ocean bottom The global circulation achieves the transfer of heat from low to high latitudes as well as the transfer of moisture from low to high latitudes The importance of the thermohaline circulation is that it reduces the concentration of atmospheric CO2 QUESTIONS Why do ocean surface temperature patterns change slowly when compared to atmospheric patters? The coriolis force deflects moving water to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. Why then does upwelling tend to occur along the western margins of continents in both hemispheres? Environmental science Lecture 9 Lecture slide 16
3 types of travelling cyclones -Multilatitude cyclone, tropical cyclone, tornado stage 1: Cyclogeneses is the formation of a multilatitude cyclone Stage 2: -Frontal wave: disturbance in polar front generates wavelike movement along front Stage 3: -Distinct cold and warm fronts: warm sector in between Stage 4: -cold front overtakes & squeezes warm front Stage 5: -Mature cyclone: advanced occlusion Stage 6: Dissipation: cut-off cyclone Middle of the cyclone would be uplift by convergence cause there is also lower pressure Consistent paths taken by a cyclone is called storm tracks Succession of cyclones alone a path is called a cyclone family
Environmental Science lecture 10 Lecture slides 17 -Storms with vertical motion sufficient to cause lightning & thunder are considered thunder storms -Thunderstorms are cumulonimbus clouds There are three stages: (see slides for more info) Cumulus stage: condensation leads to continued updraft within cloud Mature stage: organized convection then latent heat release at altitude Dissipating stage: and release of latent heat -The bottom half of a dissipating storm usually "disappears" before the top because at the top, there is less air sinking and evaporation -Severe thunderstorms are capable of producing tornados
-Sinking air warms, yet the downdrafts in a thunderstorm are usually cold due to sinking air warming along the MALR Mesoscale convective systems are made up of multiple, organized thunderstorm cells Two sections of it; the Squall line and the mesoscale convective complex A squall line is a line of thunderstorms of differing strengths Mesoscale convective complex forms: starts as a group of air-mass thunderstorms during the day, then individual storms combine into one system -Lightning is an electrical discharge producing light from cloud to ground, or cloud to cloud -Thunder is the sound of rapid expansion & cooling of superheated air, around a lightning bolt -Sheet lightning is 80% of all lightning is within clouds Ground to ground lightning is only 20% of all lightning Positive electrons are always at the top of the cloud while negative charges are near the bottom -A lightning flash often consists of a series of very rapid strokes -A tornado is a rapidly rotating column of air, from the base of the thunderstorm touching the ground -extreme low pressure in centre of circulation A tornado is a cyclone QUESTIONS: Why is the incidence of thunderstorms much lower near the Pacific coast than at the Atlantic coast? Lecture slides 18
-The structure of a hurricane is driven by extremely low pressure/strong PGF -A hurricane needs to form at least 5 degrees away from the equator, has to have a high ELR, and weak but uniform steering winds -hurricanes don't cross the equator because of the low ELR -A high ELR is required for hurricanes to develop because conditions are unstable as a result -There are more hurricanes and storms in September because that's when the ocean water is warmest -Each region has it's own lists of names for hurricanes Environmental Science lecture 11 Lecutre slides 19 At which timescales does climate change? -Climate change is the norm -processes involved are interconnected -Timescales involved vary Proxy data provides indirect record of climate (i.e. the rings that you look at on a tree stump, the more, the older the tree) -When the tilt of the Earth is at a minimum, it increases the likelihood of an ice age happening in the Northern hemisphere due to less sun reaching the northern hemisphere causing snow to not melt as much during the summer -the impact of recent eruptions has caused a drop in global temperatures from 0.2-0.30C -sulfur dioxide with water sulfuric acid -sulfate particles contribute to lower surface temperatures because they reflect sunrays El Nino -is a time of unusually warm water off the coast of Peru -occurs every 3-8 years
-linked to changes in atmospheric circulation off the coast of Australia called southern oscillation: ENSO What happens during ENSO? -Normal conditions -En Nino conditions El Nino years on the temperatures around the great lakes are on average warmer El Nino’s global impacts: Teleconnections: changes in one region impact climates of other, distant regions What are climate feedbacks? -Feedbacks can amplify effect of changes: -positive feedback -climate forcing makes initial change in climate
Lecture slides 20 What is anthropogenic climate forcing? -change in climate resulting from human activities at local to global scale How have CHC concentrations changed? CH4 change due to: Agriculture (60%) Burning of fossil fuel (20%) N20 similar pattern What are future emissions and concentrations scenarios? -developed to estimate future CO2 concentrations Global climate models (GCM’s) GCMs combine atmospheric, ocean & land surface models GCMs reveal that they can only replicate current conditions: w/past human increases in Greenhouse Gasses (GHG) What changes are predicted to happen?
-faster rate of change in temperature than over the past 10,000 years -60C temperature change during glaciation What will be the regional variations? -Observed values & GCMs show greatest temperature rise: at high latitudes What is the impact of urbanization? -Urban heat island: city much warmer than surrounding countryside Which factors contribute to Urban Heat Islands? -Little evapotranspiration from urban asphalt & concrete
Environmental science first lecture: -water vapor is at the center of the atmosphere -dark grey areas on water vapor scale means its relatively dry compared to lighter areas -higher co2 ppm per million molecules in the atmosphere… rapid increase since industrial revolution atmospheric aerosols influence air temperature, play a role in cloud formation, are generated by human activities and natural processes, include sea salt crystals We find Ozone at ground level cause of cars' fumes.. Found in smog. It is bad on the ground. QUESTIONS: 1. The thermosphere has extremely high temperature, but a person exposed to it would rapidly freeze. Explain this apparent contradiction. -not enough molecules close to each other to transmit the heat to your body plus the pressure is so low. 2. What climate-change processes might you expect to witness during your time? Which ones do you think take too long for you to experience? -Seasons. Global warming/ice age Environmental Science lecture 2 -air is denser near the Earth's surface atmospheric pressure is force exerted by air molecules per unit area Ideal Gas Law states: --> slide 3 p=pRT temperature=constant X pressure -air pressure decreases with altitude
-air at a higher altitude less dense -> less oxygen -altitudes above 3000 meters can cause mountain sickness Questions: Pressurized cans of shaving cream say not to expose to excessive heat. What might happen if it is and will this potential problem last throughout the product life. A standard pressure of 1,013.2 hPa is also known as one atmosphere (1 ATM). Look at the next figure and determine at approximately what levels you would record a pressure of 0.5 ATM and 0.1 ATM.
Lecture slides 4: Solar luminosity was much less 4.6 billion years ago when Earth formed. The Earth was colder than now. To find the intensity of the radiation: Stefan-Boltzman equation: E=oT^4 A blackbody is a body that is perfectly efficient at emitting radiation For graybodies, Stefan-Boltzmann equation becomes I=eoT^4 Wein's Law: A=2897/T The impact on Earth's temperature if scattering in the atmosphere increase would depend on which type of scattering. But usually colder. If cloud cover increased, the Earth's temperature would be
Net Radiation= incoming radiation-outgoing radiation
Poleward heat transport: Surplus energy moves toward poles (deficit regions) Poleward heat transport is a driving force of climate Warming is occurring due to the presence of greenhouse gases. Incoming solar energy is equaled to the outgoing IR energy. Greenhouse effect keeps the Earth warm. Without it the Earth's temperature would be ~ -15 degrees celsius Energy absorbed by Earth - Energy absorbed at the surface = Energy recycled within the Earth's system
Questions: Would you expect both the Northern and Southern hemisphere to have same average albedo/ What factors might cause the two hemispheres to reflect different percentages of insolation back to space? -->No they won't have the same average altitude because southern him sphere has more water than land mass, and northern hemisphere has more land so more snow will increase average albedo.
Which would have the greatest effect on the Earth's greenhouse effect: Removing all of the CO2 from the atmosphere or removing all of the water vapour? Explain why you chose your answer. -->
Environmental Science Lecture 3 Lecture 5 Sub-solar point - at noon, the sun will be directly over it
-summer in the southern hemisphere is associated with the sub solar point at 23.5 degrees South. -an average rate of 55W/m^2 in insolation can be observed at 90 degrees South, at the December Solstice. -an average rate of 440W/m^2 in insolation can be observed at 0 Degrees, at the March Equinox -the maximum temperature occurs in mid-late afternoon even though the the amount of time it takes to reradiate the solar radiation -temperature is more inconsistent the further from the equator -equatorial zone is associated with rain forests -grasslands are associated with the midlatitude zone -If the Earth was not tilted, the Earth's radiation budget would have a greater loss of energy at high latitudes -coastal locations have lower temperature ranges than locations inland because it takes a lot more energy to heat up a body of water than land -wind mixes the warm water with the cold water -greater loss of latent heat with a body of water Continentality-effect of an inland location that favours greater temperature extremes -What factors influence local temperatures--> surface type, latitude, elevation -The surface type contributes the most to maintaining temperatures at a given location higher than nearby areas (asphalt holds heat more than vegetation, farmers fields etc.)
-there will be a higher range of temperature year round the further the area is from water/the higher the latitude -the Wind-Chill index is the "feel" of temperature under cold conditions
QUESTIONS: An orchard farmers hears a weather forecast for overnight low temperatures to hover just above freezing point of 0 Degress Celsius, but with wind chill temperatures expected to drop significantly lower. Will the wind chill increase the possibility of frost damage? Why or why not? ANSWER: Suppose that the Earth's axis were tilted at 40 degrees to the plane of the ecliptic, instead of 23.5 degrees. How would the seasons change in Hamilton? what would be the global effect of the change? ANSWER: The summer would be hotter, winter would be colder. The seasons would be even more extreme. Lecture 6 -Humidity is the amount of water vapour in the air. -Specific Humidity (SH) is the actual quantity of water vapour in air -SH=mass of water vapour (g)/mass of total air (kg)
-Saturation Specific Humidity is the maximum amount of H2Ov (i.e. SH) that an air parcel can contain at any given time based on its temperature -Saturation is achieved when the density of gas cannot be increased above a certain level change of phase once limit is reached -Dew Point - Temperature at which air, when cooled, becomes saturated -If two air parcels have the same specific humidity, but different temperatures, they will still have the same dew point
-Relative Humidity (RH) = 100 X (SH/saturation SH)
-If there temperature rises, and the specific humidity stays the same, the relative humidity will fall QUESTIONS: How can frozen clothes "dry" outside in subfreezing weather? What is taking place? A crowded classroom is filled with students. In what way the presence of the students affect the dew point and relative humidity in the room? Answer: 2. Dew point will be increasing because of more moisture and the more people makes it hotter too. The relative humidity decreases. If the increase in the temperature is far larger than the increase in the dew point, the relative humidity will decrease. Environmental Science Lecture 4 -Pressure (mb) is the same as hPa -Rate of temperature decrease with altitude for a parcel of dry or unsaturated air as it rises: 10 degrees celsius/1,000m -rate of temperature decrease with altitude for a parcel of air saturated with water vapour as it rises: 4-9 Celsius/1,000m -lifting condensation level (LCL): height at which saturation occurs Slide 7 Diagram from bottom to top -Air cools at DALR - Unsaturated -Air becomes saturated - saturated -Air cools at SALR - SALR=MALR -Level of free convection LFC Latent heat released compensates for decrease in temperature
Atmospheric stability - no vertical movement occurs -Stability: Air parcel resists upward displacement -Instability: air parcel keeps rising Absolutely stable atmosphere is ELR<MALR it is not the best temperature for advection fogs to form In many regions, the orographic effect causes precipitation to increase with elevation. Can you think of any reason why this might not be true all the way up to the top of Mt Everest? -->By the time the water vapour has been forced to lift along the mountain slope, it has already condensed and formed into clouds and precipitation
Environmental science lecture 5 Lecture slide 9 -Precipitation is any form of water that falls from a cloud and reaches the ground - In warm clouds (>0 Celsius): water droplets condense - Constant speed achieved when air resistance = gravity: terminal velocity - In cold clouds (there is more moisture that can be held with the cold stratus cloud Both the arctic and the Canadian Prairies have relatively low snow cover. Is the cause for this the same in both regions? --> Lecture slides 10 -Water in all its forms: ~1.4 billion km^3 -Overland and interflow are affected by human development -a water balance represents Hydrological cycle at the local scale Water balance equation: P= (PE-D) + S + or - AST D= PE - AE P= precipitation PE= potential evapotranspiration -moisture demand D= deficit -Moisture shortage S= surplus -oversupply AST: soil moisture storage change -moisture savings AE= actual evapotranspiration -if all demand is satisfied, AE=PE -Deficit occurs when PE cannot be satisfied through; P, soil moisture Under ideal conditions; AE and PE are close -Surplus: When PE is satisfied, and ST is full
ACCWL: accumulated potential water loss -water taken from ST when: P< or equal to PE -october to mid december; recharge QUESTIONS: 1. What effect does a large ST have on a location as compared with another location that has the same P and PE totals but a lower ST? 2. How do impervious surfaces such as parking lots impact the water balance terms? --> the actual evaporation is going to be lower, and higher deficits in the summer months; Soil storage. ^ON FINAL EXAM
Environmental Science lecture 6 Lecture slides 11 -Wind is air that is moving horizontally relative to Earth's surface. It is caused by unequal heating of the Earth's atmosphere -Winds are generated by differences in pressure drive wide. -Pressure gradient force: difference in pressure between regions -Pressure is mapped by constant height: plot variations in air pressure on a constant elevation On maps: isobars connect points of equal pressure -pressure drops 10 hPa/100 metres in standard atmospheric conditions -lines of isobars: bend & turnaround areas of High (H) & Low (L) pressure -Constant height charts can be used to:
-Constant pressure maps: show variations in altitude for a constant pressure -also known as isobaric charts and upper level charts Constant pressure maps -High heights correspond to high temperatures -Low heights correspond to low temperatures Ridges an troughs on maps -Contour lines or isobars tend to decrease in value from equator to the poles Winds and temperature on pressure maps -H: high pressure; anticyclones -L: low pressure; mid-latitudes cyclones -Pressure gradient force: difference in pressure over distance -Pressure gradient crosses isobars: -Closely packed height lines indicate: large pressure gradient -pressure gradients are created through unequal heating of the atmosphere South Asia is known for a seasonal shift in the thermal circulation between land and ocean QUESTIONS Pilots often use the expression "high to low, look out below" In terms of upper-level temperature and pressure, explain what this can mean? --> if the temperature was lower, the pressure would be lower and push the plane down. The pilot of a small plane wants to fly at constant height above ground Can the pilot fly at a constant pressure level (e.g. 500 hPa) to achieve this? Why or why not? --> no, the pressure changes with temperature. if it is a very short distance, possible he might be able to achieve this. Long distance, not a chance. Lecture slides 12 Coriolis force
-Strongest near the poles, non along equator relates to the Coriolis force -Relation to latitudes: Strongest near poles, non along equator Geostrophic wind -Parallel to isobars -PGF=CF -Spacing of isobars indicates speed (Vg) Gradient flow -winds that flow parallel to curved isobars -constantly changes direction Upper-level cyclones & anti cyclones -are rotating air parcels -Generated by Centripetal force: imbalance between PGF and CF -Force is at: right angle to the winds -Winds flows in upper-level cyclones counterclockwise rotation in Northern hemisphere -->low pressure -Subgeostrophic flow: CFPGF Surface winds -wind direction influenced by: frictional force (FF) -3 forces combine: PGF,CF,FF Buys-Ballot's Law In the NH, with winds at your back: L to the left, H to the right Convergence - created by air spinning into a cyclone -convergence at surface --> divergence above
Divergence - created by air spiralling out from an anticyclone -divergence at surface --> convergence above QUESTIONS: Why are surface winds that blow over the ocean closer to being geostrophic than those that blow over land? --> Why is that, on the equator, winds may blow either counterclockwise or clockwise with respect to an area of low pressure?
Environmental Science lecture 7 Slides 13 - Atmospheric circulation -General circulation of the atmosphere refers to the average air flow -the basic cause of the general circulation is The one-cell model is uniform water surface -the Earth does not rotate It is impossible on Earth for a Hadley Cell to extend from the equator to the poles because of the coriolis force The three-cell model allows Earth to spin -implies no land surfaces HIgher pressure=denser air= colder air Hadley Cell - air going to be warming, rising, and eventually lowering.. Low pressure. Sun is usually right above most of year. There is little variation in the position of the pressure centres in the Southern Hemisphere , between January and July because o the presence of Antarctica
From low to high latitudes, wind flow and pressure patterns aloft are created by: temperature and pressure gradients Coriolis force also contributes to jet streams Polar front: where warm air meets cold air Pilots prefer to fly in the core of a jet stream rather than just above or below it because the fastest winds are found in the jet stream core and clear air turbulence is found above and below the jet stream core QUESTIONS: Which of the belts depicted in the three-cell model is likely to exhibit greatest temperature …?
Slides 14 What drives oceanic circulation? -oceanic temperature structure -differences in salinity at the surface: - wind action Oceanic temperature structure Mixed layer: mixed by waves and wind Mixing can only occur near the poles Ocean currents are a persistent and horizontal movements of ocean water At surface: driving by friction from prevailing winds -Ekman spiral speed and direction not uniform with depth -Gyres are large-scale circular currents bounded by continents -upwelling is warm surface waters replaced by colder waters, from below
-coastal algal blooms are triggered by upwelling Earth's major currents are Western boundary currents (e.g. gulf stream) and Eastern boundary currents (upwelling) The water surface temperature along the coast of the northern California is warmer in the winter than the summer because upwelling is strongest in the summer and because in the summer, the region is more under the influence of a subtropical high Melting of the Greenland ice sheet could decrease the strength of the Gulf Stream The migration of plastic ducks has been used to understand the direction of the oceanic currents Thermohaline circulation is a slow circuit of deeps currents, from 1 km to the ocean bottom The global circulation achieves the transfer of heat from low to high latitudes as well as the transfer of moisture from low to high latitudes The importance of the thermohaline circulation is that it reduces the concentration of atmospheric CO2 QUESTIONS Why do ocean surface temperature patterns change slowly when compared to atmospheric patters? The coriolis force deflects moving water to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. Why then does upwelling tend to occur along the western margins of continents in both hemispheres? Environmental science Lecture 9 Lecture slide 16
3 types of travelling cyclones -Multilatitude cyclone, tropical cyclone, tornado stage 1: Cyclogeneses is the formation of a multilatitude cyclone Stage 2: -Frontal wave: disturbance in polar front generates wavelike movement along front Stage 3: -Distinct cold and warm fronts: warm sector in between Stage 4: -cold front overtakes & squeezes warm front Stage 5: -Mature cyclone: advanced occlusion Stage 6: Dissipation: cut-off cyclone Middle of the cyclone would be uplift by convergence cause there is also lower pressure Consistent paths taken by a cyclone is called storm tracks Succession of cyclones alone a path is called a cyclone family
Environmental Science lecture 10 Lecture slides 17 -Storms with vertical motion sufficient to cause lightning & thunder are considered thunder storms -Thunderstorms are cumulonimbus clouds There are three stages: (see slides for more info) Cumulus stage: condensation leads to continued updraft within cloud Mature stage: organized convection then latent heat release at altitude Dissipating stage: and release of latent heat -The bottom half of a dissipating storm usually "disappears" before the top because at the top, there is less air sinking and evaporation -Severe thunderstorms are capable of producing tornados
-Sinking air warms, yet the downdrafts in a thunderstorm are usually cold due to sinking air warming along the MALR Mesoscale convective systems are made up of multiple, organized thunderstorm cells Two sections of it; the Squall line and the mesoscale convective complex A squall line is a line of thunderstorms of differing strengths Mesoscale convective complex forms: starts as a group of air-mass thunderstorms during the day, then individual storms combine into one system -Lightning is an electrical discharge producing light from cloud to ground, or cloud to cloud -Thunder is the sound of rapid expansion & cooling of superheated air, around a lightning bolt -Sheet lightning is 80% of all lightning is within clouds Ground to ground lightning is only 20% of all lightning Positive electrons are always at the top of the cloud while negative charges are near the bottom -A lightning flash often consists of a series of very rapid strokes -A tornado is a rapidly rotating column of air, from the base of the thunderstorm touching the ground -extreme low pressure in centre of circulation A tornado is a cyclone QUESTIONS: Why is the incidence of thunderstorms much lower near the Pacific coast than at the Atlantic coast? Lecture slides 18
-The structure of a hurricane is driven by extremely low pressure/strong PGF -A hurricane needs to form at least 5 degrees away from the equator, has to have a high ELR, and weak but uniform steering winds -hurricanes don't cross the equator because of the low ELR -A high ELR is required for hurricanes to develop because conditions are unstable as a result -There are more hurricanes and storms in September because that's when the ocean water is warmest -Each region has it's own lists of names for hurricanes Environmental Science lecture 11 Lecutre slides 19 At which timescales does climate change? -Climate change is the norm -processes involved are interconnected -Timescales involved vary Proxy data provides indirect record of climate (i.e. the rings that you look at on a tree stump, the more, the older the tree) -When the tilt of the Earth is at a minimum, it increases the likelihood of an ice age happening in the Northern hemisphere due to less sun reaching the northern hemisphere causing snow to not melt as much during the summer -the impact of recent eruptions has caused a drop in global temperatures from 0.2-0.30C -sulfur dioxide with water sulfuric acid -sulfate particles contribute to lower surface temperatures because they reflect sunrays El Nino -is a time of unusually warm water off the coast of Peru -occurs every 3-8 years
-linked to changes in atmospheric circulation off the coast of Australia called southern oscillation: ENSO What happens during ENSO? -Normal conditions -En Nino conditions El Nino years on the temperatures around the great lakes are on average warmer El Nino’s global impacts: Teleconnections: changes in one region impact climates of other, distant regions What are climate feedbacks? -Feedbacks can amplify effect of changes: -positive feedback -climate forcing makes initial change in climate
Lecture slides 20 What is anthropogenic climate forcing? -change in climate resulting from human activities at local to global scale How have CHC concentrations changed? CH4 change due to: Agriculture (60%) Burning of fossil fuel (20%) N20 similar pattern What are future emissions and concentrations scenarios? -developed to estimate future CO2 concentrations Global climate models (GCM’s) GCMs combine atmospheric, ocean & land surface models GCMs reveal that they can only replicate current conditions: w/past human increases in Greenhouse Gasses (GHG) What changes are predicted to happen?
-faster rate of change in temperature than over the past 10,000 years -60C temperature change during glaciation What will be the regional variations? -Observed values & GCMs show greatest temperature rise: at high latitudes What is the impact of urbanization? -Urban heat island: city much warmer than surrounding countryside Which factors contribute to Urban Heat Islands? -Little evapotranspiration from urban asphalt & concrete
