Atmospheric Properties

what are some atmospheric hazard?

* blizzard
* hurricane
* flood

what is atmospheric composition?

* dry air:
* Mostly 78% nitrogen (N2)
* 21% oxygen (O2)
* water:
* percent varies depending on time and place
* constantly changes phase to liquid and solid
* aerosols:
* liquid or solid particles
* dust, soil, salt, ash, pollen, bacteria, mold
* create haze when present with water vapor

water in atmosphere?

* invisible water vapour
* clouds consisting of liquid water droplets
* clouds consisting of ice crystals

aerosols in the atmos

* volcanic ash
* pollen
* sea salt
* soot
* Aerosols that capture water molecules can produce haze

what is weather?

* refers to the day-to-day changes in atmos conditions: temperature, precipitation

what is climate?

* is long-term statistical avg of weather conditions
* assessed using at least 30-yrs of data

what is temperature?

* air molec’s avg speed
* faster molecs results in higher temperature
* measured in ºF and ºC

pressure refers to?

* the force applied by air on a specified surface area
* the weight of a column of air
* molecules move apart in hot air:
* hotter air is less dense → lower p
* molecs mover closer tgt in cool air
* cool air is more dense → higher p
* air p varies daily n seasonally

atmospheric p

* air p and density decreases as altitude increases
* \~99.9% of atmos lies below 50 km

layers of the atmosphere

* tropopause is layer focused

what is enviro lapse rate?

* the change of temperature w/ altitude \~6.5ºC/km
* troposphere temperature decreases w/ increasing altitude

adiabatic cooling

* air that is lifted experiences a drop in pressure, allowing it to expand
* expansion of air uses energy, so the air mass becomes cooler
* initially, it is warm
* as the air mass cools, water vapour condenses, the air mass becomes supersaturated n clouds form
* as becomes warm again, goes down

when does adiabatic cooling occur?

* when rising air cools

what is dry adiabatic lapse rate?

* rate of cooling of a parcel of dry air (\~ 10ºC/km)

what is saturated (moist) adiabatic lapse rate?

* rate of cooling of a parcel of saturated air (\~6ºC/km)

what are clouds?

* visible water droplets and/or ice crystals w

when do clouds form?

* when saturated air becomes supersaturated
* water condenses on aerosol condensation nuclei

cloud formation

* warm air is less dense that cold air → warm air rises
* clouds form when saturated warm air rises, cools and condenses; and becomes supersaturated
* air rises when it undergoes lifting

what are the 3 types of cloud formation relating to lifting?

1. warm + cool air come tgt → front
2. has to go over → forced to rise, thus forming cloud
3. localized heating

what is the temperature of warm clouds?

* they have consistent temperature > 0ºC
* liquid state

if water droplets consolidate to ________ mm diameter, they will fall

>0.5

how do raindrops grow?

* as they fall by colliding w/ other droplets
* can grow to \~4 mm diameter.

cold clouds temperature?

* consistent temperatures < 0ºC.

what are the 2 ways ice crystals may grow?

1. snowflakes: when liquid water gradually freezes to ice nuclei
2. rime: when supercooled droplets instantly freeze to ice nuclei
* when don’t have aerosols, latch onto other crystals

how do graupel and hail dev?

* when rime ice crystals keep growing

how do low pressure systems work?

* as air at Earth’s surface expands and rises w/ local heating it pushes air up above it
* air then starts to flow outward in the upper atmos
* the total vol of air decreases, low p devs

how do high pressure systems work?

* as air at Earth’s surface cools and contracts, air in the upper atmos flows inward
* the total vol of air increases, high p devs

what is a pressure gradient?

* pressure change divided by distance
* air always moves from higher to lower p; represented on maps w/ isobars; lines of equal pressure
* this air is wind
* high p gradient → faster wind

what is the Coriolis effect?

* air’s apparent deflection relative to the spinning Earth
* air veers right in N hemis, left in S hemis
* Coriolis Effect increases as air speed increases
* axis rotation speed at Earth’s equator = 1,670 km/ hr


* Axis rotation speed at Earth’s poles = 0 km/hr

winds in the northern hemis

* northern hemis low p
* wind spirals from higher p into a low p, counterclockwise

when do hurricanes form?

* between 5 -30º latitude

what is the Ferrel cell?

* region where cold polar air and warm tropical air converge
* steep p gradient creates polar jet stream
* can produce parge storms called mid-latitude cyclones

what is a polar front?

* the boundary between warm, tropical and cold, polar air

what do steep pressure gradient generate?

* polar front jet stream

what is a polar-front jet stream?

* very fast wind, 10km high, flowing over the polar front

polar front and jet stream flow in __________ undulations

wave-like

how does jet stream air flow?

* uneven manner
* speed is not the same → more air can flow out of a region than into it