Environmental Science lecture notes - Amazon...
Transcript of Environmental Science lecture notes - Amazon...
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<DALR
Absolutely unstable atmosphere
MALR<DALR<ELR
Conditionally (un)stable atmosphere
MALR<ELR<DALR
QUESTIONS:
What time of the year will unstable conditions be most common over the continental Unites
States and Canada?
--> Spring and Summer, mostly summer (most thunderstorms in summer)
Is the stability of the air more likely to change rapidly near the surface or aloft? At what time
of day are major changes in the ELR most likely?
-->ground
Lecture 8
The ELR increases above 10km because the troposphere has been reached
Cumulonimbus cloud would be expected to see associated to convection under highly
unstable conditions (large difference between MALR and ELR)
Orographic uplift is when a cloud hits a mountain and has to rise up and cools down
The height of where the base of clouds forms is called the lifting condensation level
The air mass starts to warm as it descends the lee side of the mountain at the DALR
Questions:
Why are advection fogs rare over tropical water?
--> 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 (<0 Celsius): ice crystals form & grow
-types of precipitation; rain, freezing rain (glaze), snow, sleet
-raindrops are not tear- shaped
-Bigger than 2mm then its a flattened sphere
-smaller than 2mm then its a sphere
Snow is distributed throughout North America
West: snowfall at higher elevations
East: lower temperatures favour snow over rain
-Lake effect snow is a strong enhancement of snowfall
QUESTIONS:
Why is a warm, tropical cumulus cloud more likely to produce precipitation than a cold,
stratus cloud?
-->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: CF<PGF
Anticyclone: centre of high pressure
Clockwise rotation in northern hemisphere
Supergeostrophic flow: CF>PGF
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