Final Flashcards
Can air pollution transport around the globe?
Yes
What is the pollutant behavior at the local scale
- Path is given by wind speed and direction.
- Pollutants are dispersed by turbulence
What is the mixing layer
is the unstable atmospheric layer that extends from the surface up to the base of stable layer (inversion).
Mixing depth
is the vertical extent of the mixing layer.
How does the mixing layer form?
From the surface upward
- Surface based inversion
- Sunrise causes the surface of ground to heat.
- Mid a.m. causes more surface heating
- Afternoon vertical mixing
Explain how surface based inversion effects mixing layer formation
early in the morning inversion starts at ground surface
Explain how Sunrise effects mixing layer formation
surface heating, shallow unstable layer erodes inversion from the ground upwards (mixing in a shallow layer)
Explain how Mid a.m. effects mixing layer formation
more surface heating, unstable layer grows thicker as inversion is eroded from the ground up (mixing in a deeper layer)
Explain how afternoon effects mixing layer formation
vertical mixing virtually unlimited: ground based inversion completely eroded from below.
What factors control air pollution
- wind
- stability
- topography
What do high wind speeds affect?
Transport and dispersion
how fast and how far the pollutants move downwind
What would faster winds imply with regards to the transport and dispersion of pollutants
Concentrations will be lower because:
- Increased spreading pollutants along transport direction farther.
- Increased dispersion due to turbulent mixing caused by more interaction with surface features.
how far up vertically is considered near surface
<1000m
What does near surface stability depend on
Change in temp with height (ELR)
When is the ELR stable
Night/early morning when the sky is clear
What does a stable ELR mean
Vertical motion is suppressed (no or little mixing)
When is the ELR unstabe
Hot afternoons
What does an unstable ELR mean?
Strong vertical motions (intense mixing)
What is the plume behavior when: Inversion layer > Hstack
Little up and down motion (Fanning Plume)
-This happens in early morning when there is strong surface inversion.
What is the plume behavior when: Inversion layer above Hstack
Pollutants mix downward (Fumigation Plume)
This happens in late morning due to surface inversion destabilizing
What is the plume behavior when:Mixing height increases very high above stack
Enhanced vertical dispersion. Rising and sinking air make wavy path (Looping plume)
This happens in afternoon due to the inversion disappearing
Describe what a fanning plume looks like
Flat line of smoke just below temperature inversion
Describe what a fumigation plume looks like
Smoke fans out from top of the temperature inversion to the ground
Describe fanning as a plume behavior
- Caused by stable (inversion) with light winds, no or little vertical movement,
- plume spread only horizontal (from the top it looks like a fan).
Little or now smoke near the ground (unless there is a hill)
Describe fumigation as a plume behavior
-Caused by mixing layer grows upwards with continued surface heating, reaches elevated fanning plume, rapidly mixes concentrated plume to surface.
-Ground level concentrations:
near zero, followed by high “burst” for short-period, then concentrations drop (as mixed layer continues to grow higher)
Describe looping as a plume behavior
- Caused by Unstable conditions, strong vertical mixing (updrafts and downdrafts).
- Plume has up and down wavy shape.
-Ground level concentrations:
high at a localized spot near stack. Farther away, low
What are some factors that affect dispersion of pollutants from chimneys
- Temp
- exit velocity
- wind speed/direction,
- chimney height
Why do pollutants get trapped downhill at night?
Cold air drains downhill at night which strengthens existing surface inversion and traps pollutants.
This carries pollutants from surrounding hillsides and traps them in the valley
What is the urban heat effect
Urban infrastructures release heat during night, warm the city’s air
This Temperature gradient causes a country breeze, and bring rural pollution: plumes, pollen, rural dust etc… into the city.
What would an episode of major air pollution due to?
combination of:
- Many sources of air pollution
- High pressure system with light winds and poor vertical mixing causing atmospheric stagnation
- Light wind
- A shallow mixing layer
- Geographical features (e.g. valley)
- Local condition
What are some local conditions that could cause severe pollution at night
- clear skies: ground-based inversion with stable conditions, no mixing of pollutants emitted near ground
- valleys/basins, pollutants accumulate at bottom due to drainage flows
- if urban area large enough, heat island effect can pull pollutants from rural areas into core and re-circulate
What are some local conditions that could cause severe pollution in the day
-clear skies, surface heating may not completely erode inversion (cooler seasons), thus trapping pollutants in mixing layer
Why is weather forecasting important
- Saves lives
- Saves property from being damaged
- Informs general public
What does diurnal mean?
Happening during the day instead of at night
What is involved in weather forecasting>
- Establishing current state
- Data centers
- Analysis products
- Remote sensing
- numerical weather prediction (NWP) Models
- Local conditions
- Forecaster
What does establishing current state mean in regards to weather forecasting?
Observations
World Meteorological Organization (procedures for observation):
- surface (temp, dew point, winds, pressure, clouds, precipitation, visibility) every hour at observation stations
- upper level (upper level balloons, Doppler radar)
- Satellite (visible, IR, water vapour)
What does data centers mean in regards to weather forecasting?
collect and distribute observations:
NCEP (National Centers for Environmental Prediction) USA
What does Analysis Products mean in regards to weather forecasting?
(00, 06, 12, 18 hour intervals)
- Weather charts: surface maps, upper air isobaric maps and soundings
- Canada: Canadian Meteorological Centre produces analysis products
What does Remote Sensing mean in regards to weather forecasting?
Satellite, Doppler Radar
What does Numerical Weather Prediction (NWP) models mean in regards to weather forecasting?
Canada: Canadian Meteorological Centre
-Mathematical equations describing how the atmosphere/atmospheric processes changes over time (complex and solved by supercomputers using current data to predict future events/ state of atmosphere) Produces prognostic charts (charts to predict things)
What does Local Conditions: mean in regards to weather forecasting?
consideration of unique local characteristics
What does Forecaster mean in regards to weather forecasting?
synthesis of all information – forecasts disseminated by web and media
What are some other examples of Numerical weather prediction (NWP) models?
- General Circulation model (GCM) -> Coast resolution/global coverage and predicts deviation from average conditions
- Regional (limited area) model -> Fine resolution and forecasts precise weather conditions
- Model ensemble ->Combination of multiple models or one model with different initial conditions
How do models work?
Equations are translated into complex software using programming language (ex. FORTRAN)
- Surface and upper air observations are fed into equations
- Equations are solved for small time increments (e.g. 5 min) covering large geographical areas and vertical levels
- supercomputers solve it and produce outputs for post processing and visualization
What are some uncertainties with forecasting?
- Flaws in models
- Resolution
- Model sensitivity
- Inaccurate initial condition
- Representation of physical processes
- Local effects
What are some simple forecasting methods?
- Persistence Forecasting
- Steady state or trend forecasting
- Analogue Method
- Climatological Method
Explain persistence forecasting?
future weather will be same as present weather. If snowing today, then snow tomorrow as well.
Explain steady state/ trend forecasting?
moving weather systems or fronts continue to move at constant speed and same direction.
Explain Analogue method
forecast weather associated with recurring weather patterns on a weather chart (pattern recognition)
Explain climatological method
forecast based on past climatic conditions
What are some local influences on forecast for Vancouver island?
- Elevation (Rain here but snow at higher elevations)
- Rain shadow (Sooke hills get more rain then oak bay)
- Coastal effects (i.e. sea breeze winds different then inland, Cooler/less variation in daytime temp compared to inland)
- Vallleys, mountains, land use (Forest vs. Open) and urban heat
What are the different time ranges for forecasts?
- Now cast
- Short-Range forecast
- Medium-Range forecast
- Long-range forecast
- Seasonal outlook
Explain now cast
Very short range (Less then 6 hours)
Explain short - range forecast
up to 3 days
Explain medium range forecast
about 3 - 8 days
Explain long range forecast
past 8 days
Explain seasonal outlook
forecast covering 3 months, gross features (probability of warmer or cooler, or wetter or drier than normal)
What is the role of forecasting?
Analysis products, remote sensing, NWP and local knowledge are synthesized by forecaster and disseminated by wed and media
Define the ocean
the vast body of saline water that occupies the depressions of Earth’s surface.
What are the 5 major oceans
- Southern
- Atlantic
- Pacific
- Indian
- Arctic
How much of earths surface is covered by oceans
71%
How much of earths water is in the ocean?
97% (2.5% is land ice, groundwater, lakes and rivers)
What are the 3 largest oceans?
- Pacific (~46% ocean area)
- Atlantic (~23%)
- Indian (~20%)
Is the average ocean depth more then the height of mount everest?
No, Average ocean depth is 3,682 m whereas mt everest is 8,848
The deepest part of the ocean is about 11,000 m (Marianas trench)
Define Salinity
The concentration of dissolved salt solids in seawater
What is the average seawater salinity
3.5% (35g/kg)
Is warm slightly salty water or cold more salty water more dense?
Cold
Is seawater or fresh water more salty?
seawater is 2% to 3% heavier due to dissolved salt
Can two water samples have the same density with different combinations of temp and salinity?
Yes
What is the ocean organized by?
Density (the ocean is stratified by density)
What does seawater’s density increases with?
- increasing salinity
- increasing pressure
- decreasing temperature
What is the principal of constant proportions
Salinity may vary with location, but the ratio of dissolved solids (% of salts) in seawater remains constant
True or False: The ocean is at chemical equilibrium
True (What goes in must go out)
Should you measure salinity in the ocean by heating up water and measuring residual salts
No, not accurate
In certain type of salts, water molecules do not evaporate completely and some of the salts evaporate
How is Salinity calculated?
by conductivity
you can use a salinometer
Does the equator or the poles have high salinity?
Equator
What are the three zones of density in the ocean
- surface/mixed layer
- Pycnocline layer
- Deep layer
Explain the surface zone/mixed layer
- Well mixed layer
- Temp. and salinity constant due to waves and currents
- Least dense water
- Depth varies from 150 m – 1000 m
Explain Pycnocline layer
means strong slope
- Temperature decreases rapidly with depth ->thermocline -> major factor to form the pycnoline layer
- Polar water receive less radiation = much colder, no stratification -> no thermocline layer (forms in mid-low latitude)
- Density increases with depth due to decrease in water temperature
- Low salinity
Explain deep zone
-Below 1,000 m in mid-latitude
- Very cold water (-1°C – 3°C)
- Very little change in density
- Contains about 80% of ocean water
What are Colligative Properties and what do they depend on?
Properties of a solution, they depend on the concentration
What are some examples of Colligative Properties?
- Heat capacity (Decreases with increasing salinity)
- Freezing point (Decreases with increasing salinity)
- Evaporation (decreases with increasing salinity)
- Osmotic pressure (increases with increasing salinity)
What is osmotic pressure
Pressure exerted on a biological membrane
Can cold or hot water hold more gas?
Cold
Why are dissolved gases importan
MArine plants and animals need them to survive
Can marine animals break down water
no
Can marine plants manufacture CO2
no
what percentage of the ocean is nitrogen
Whats its purpose
48%
organisms require N to build proteins but cannot use them directly from atmosphere of ocean (they need nitrifying bacteria)
what percentage of the ocean is oxygen
36%
what percentage of the ocean is CO2
15%
-Dissolves quickly but is hard to get out of the ocean.
present in the form of H2CO3, H+, HCO3,-, and CO3^2-
Carbonate then forms calcium carbonate (limestone) this is used by marine organims to form shells
Do gas concentrations vary with depth
Yes
Does O2 increase or decrease with depth?
Decrease due to respiration
does co2 increase or decrease with depth
increases due to respiration
What is the pH of seawater?
8
is water acidic or basic at surface
basic
is water acidic or basic at the deep layer?
acidic
What is ocean circulation driven by?
winds and differences in water density
How is tropical heat distributed worldwide?
by winds and ocean currents
What are surface currents
wind driven movements of water at or near the oceans surface
what are thermohaline currents
the slow, deep currents that affect the seawater circulation
-Depend on density differences by T and salinity
How do surface currents move
In circular path around the peripheries of major ocean basins called gyre
Do El Nino and La nina affect the ocean and atmosphere?
yes
What is mass flow (currents) driven by?
Wind and gravity
What are the main currents in the ocean
- Surface
- Thermolhaline
How much of the water in the ocean is influenced by surface currents
10%
What is the primary force driving surface currents
wind
What direction does water move in Northern hemisphere
Clockwise
What direction does water move in southern hemisphere
Counter-clockwise
Can gyres be subdivided into distinct currents?
Yes, There are four interconnected currents in the north atlantic gyre which all have different flow characteristics and temperatures
How many major gyres are there
6
What is Ekman Transport
When the movements of all the individual layers of water in the spiral are added, the net direction of transport within the water column is at a right angle (90°) to the wind direction.
Why does water move in a circular pattern
Ekman spiraling and the coriolis effect
What are geostrophic gyres
Gyres in balance between pressure gradient and corriolis effect
what is the only major gyres that is not geostrophic
antarctic circumpolar current
what are western boundary current
- narrow, deep, fast, move warm water
- at western bounaries of oceans
- well defined boundaries
- can move long distances
How many western boundary currents are there
5
What are eastern boundary gyres
- Flow in eastern edge of ocean basin
- cold, shallow, broad currents
- boundaries not well defined
How is heat distributed from equator to poles
ocean surface currents
What is up welling
The upward motion of water. This brings cold nutrient rich water to the surface.
(occurs where flow of surface water is away from sea)
Happens where there is divergence at the surface and deeper water moves to replace it
What is downwelling
Downward motion of water. It supplies the deeper ocean with dissolved gasses (occurs where there is convergence)
`Explain El nino
An extensive ocean warming that extends westward from the coast of Peru and Ecuador across eastern tropical Pacific Ocean, typically every 2-7 years
Explain La nina
A condition where the surface temperature of the central and eastern tropical pacific ocean turn cooler than normal.
Explain an el nino year
- Air and surface water flow westward
- Upwelling of nutrient rich water along the coast of south amarica = high pressure area
- trade winds drag huge ammount of warm water over pacific =low pressure
- causes rainfall across Australia and Asia
Explain an La nina year
- Trade winds weakens or reverse
- warm water across eastern pacific = more evaporation/ sea levels rise
- flooding across eastern pacific and drought across australia and asia
Explain thermohaline circulation
- Movement of deeo ocean water due to density differences
- water masses (Water masses often dont mix easily)
What are the five types of water masses
- Surface water (200m)
- central water (to bottom of main thermocline)
- Intermediate water (to 1500m)
- Deep water (below intermediate water to 4000m)
- Bottom water (in contact with seafloor)
What does the circulation of deep water resemble
a conveyor belt that carries surface water to the depths and back again
How do ocean water circulate
in currents
How much of the ocean do surface currents affect
uppermost 10%
What is thermohaline circulation driven by
Density
What shapes global circulation patterns
The coriolis effect
