Atmospheric Properties

what are some atmospheric hazard?

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