GEOB 402

key points from Hemispheric transfer reading

under current conditions, local and regional emission changes have the greatest impact on surface air quality For fine particles, the impact of intercontinental transport on surface air quality is primarily episodic a 20 per cent decrease in anthropogenic emissions of nitrogen oxides in any three of these regions together would achieve a 30 to 70 per cent reduction in annual mean O3 concentrations

impacts of air pollutant deposition on ecosystems

water and soil acidification, lake eutrophication, and both fertilization and damage to agro- and forest ecosystems

the entrainment zone

Air bubbles rise through convection into the PBL causing spikes in thermal energy

"arrowhead" diagram

Predicted annual maximum converging with minimum as averaging time increases

primary vs. secondary pollutants

Primary: substances emitted directly from sources (e.g. methane, sulphur dioxide) Secondary: pollutants that arise from chemical reactions with primary pollutants often acting as precursors

dust impacts on climate change and weather

Radiative forcings/aerosol relationship -- absorb radiation and directly warm atmosphere Act as CCN for precipitation

synoptic meteorolgy

a two-stage process involving determination of a relatively small set of atmospheric circulation types (maps) and the assessment of weather elements in relation to these types -Modulates transport and dispersion on timescale of days and greater -Dictates the extent to which ventilation and deposition processes occur -Affects boundary layer depth -Temperature and radiation conditions that promote chemistry -Can affect emissions -Dictates the lengths of 'episodes', seasonal differences

mesoscale

fronts, hurricanes, squall lines, slope flows, land/sea breezes, thunderstorms -When the earth's rotation doesn't impact events

dry deposition

gases and particles are transported by turbulent mixing to surfaces

importance of mesoscale

-A high proportion of the world's population live in coastal zones and/or where the terrain is complex -essential to the assessment and modelling of air pollution dispersion in such regions -Often the phenomena concerned are diurnally repeatable and geographically fixed* -creates hope for successful modelling

McKendry article on synoptic climatology and ozone concentrations in LFV

-Summertime daily maximum ozone concentrations appear to be strongly modulated by the synoptic-scale atmospheric circulation -Synoptic scale conditions that produce clear skies, warm air, light winds reduce the mixing depth and promote reduced air quality

ways of managing air pollution (Oke et al)

-targeting the emission processes, e.g. by requiring proper technological measures, such as emission control systems -fuel switches -efficient use of resources -enforcing a temporary or indefinite ban of vehicles and motors

Chernobyl

1986 90X Hiroshima Nuclear plant explosion in Russia Radionucleides deposited in Lower Fraser valley midlatitudes /Jet Stream carried these around the planet several times

Fukushima

2011 Travelled into Pacifica, looped to Hong Kong and circled back across Asia Rapidly transported to West Coast of North America about 6-8 days later Significant effects on groundwater

Canada-wide standard for PM2.5

30 micrograms/m3 24-hour averaging time

Canada-wide Standard for ozone

63 ppb 8-hour averaging time

Gaussian plume model

A plume emerges from an elevated point source (a stack) that is continuously emitting pollutants at a constant rate As the pollutants enter the urban atmosphere, they form a plume that is advected by the mean wind and mixed by turbulence, which regulates its spread mean pollutant concentration is greatest in the central core and diminishes toward the edges → bell-shaped distribution

diffusion vs. dispersion

Diffusion: the process in which a constituent moves through a concentration gradient (molecular diffusion) Dispersion: the mixing due to physical process (often gets called "diffusion")

mechanically-forced circulation

Driven purely by the terrain itself (not its heating/cooling)

tragedy of the commons

Global atmospheric commons Injection of air pollutants in quantities such that the global atmosphere is changing with negative impacts on humans

dust impacts on biomass productivity

Iron fertilization for plant growth Reaches ocean by long-range dust transport Simulative productivity -- dust Unknown consequences

planetary boundary layer

Layer of the troposphere that is directly influenced by the presence of the Earth's surface -Responds to surface forcings with a timescale of >1 hour -0-3 km deep

scales of air pollution

Local: 5km Urban: 50km Regional: 50-500km -- downwind urban problems, slow reacting primary pollutants (e.g. acid rain), visibility Continental: 500-1000s km -- transboundary issues Global: intercontinental transport, CFCs, radionucleides

diurnal variation in the PBL

Lots of convection in the afternoon (summertime) Stable nocturnal boundary layer due to cooling of the surface

thermally-forced circulation

Sea-breeze -Uplift at boundary -Cools down quickly at night Mountains/valleys Urban effects

Froude number

The ratio of the natural wavelength of the air to the wavelength of the mountain barrier Fr = V/ Nx N= Brunt-Vaisala frequency (stability factor) x= width of mountain V= wind speed

AOT40

accumulated excess of hourly ozone concentrations above 40 ppb during a relevant growing season

averaging time

averaging out the dispersion of instantaneous particles over a certain amount of time

SUM06

comprised of the 90-day maximum sum of the 0800 through 1959 hourly concentrations of ozone > 60 ppb

ventilation coefficient

depth/height [at which it can mix] + wind speed Combo of depth and wind speed How much potential there is for dilution

Siberian fire plume

intense wildfire plume from Siberia that affected the air quality across the Pacific Northwest on July 6-10, 2012 Stable atmospheric conditions along the coast limited the initial entrainment of the plume and caused local anthropogenic emissions to build up Overall, the smoke plume contributed significantly to the exceedances in O3 and PM2.5 air quality standards and objectives that occurred at several communities in the region during the event

plant effects from ozone

leaf stippling, pinish hue, spotting, premature senescence, when the stomata are open and taking in pollutants

chemical weather

local, regional and global distributions of important trace gases and aerosols and their variabilities on time scales of minutes, to hours, to days On a day to day basis, we see variations in chemistry like we do in humidity, temperature, etc

plume shapes

looping coning fanning lofting fumigation

transport

movement by wind (concentration may not change)

macroscale

standing waves, tidal waves, baroclinic waves

baseline concentration

the concentration of a given species in a pristine air mass in which anthropogenic impurities of a relatively short lifetime are not present

combustion

the sum of chemical reactions between hydrocarbons and atmospheric oxygen (O2) that produce heat and light, and release carbon dioxide (CO2) and water vapour into the atmosphere

fugitive emissions

the unintended 'escape' of gases held in pressurised containers

urban canopy layer

the zone of human occupation and the quality of the air at this level is critical for assessing the public health consequences of air pollution

microscale

tornadoes, dust devils, thermals, plumes, turbulence