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