Climate and Weather Flashcards
Climate
refers to characteristic atmospheric conditions over a long period of time (years or decades)
Weather
refers to atmospheric conditions over short periods of time (days or weeks)
Koppen Climate Classification
Temperature and precipitation to classify climate zones
along with atmospheric pressure, moisture, wind
Climate can be affected
by processes and changes that maintain the climate system:
- ocean currents
- mountain ranges
- plateaus
Earths climate includes interactions of?
atmosphere hydrosphere geosphere biosphere cryosphere - Exchanges energy and moisture between these spheres
Climate imposes major influence on natural processes
- flooding dependent on rainfall amount and intensity
- landslides common in area with rainy climates
- wildfires more likely in dry area
Earths climate system
Natural processes:
- knowing the climate can indicate things about the hazard to expect
- climate classification supplies information about the relationship between climate and vegetation
Permanent gases
Gases whose proportions stay constant
- nitrogen and oxygen
have little effect atmospherically
Variable gases
gases whose proportions vary with time and space
play important roles in atmospheric dynamics
- CO2, water vapour, methane
Aerosols
particles whose proportions vary with time and space
Posotive feedback loops
enhances initial change
- vanishing arctic ice
Negative feedback loops
counteract initial change
- evaporation = cloud formation = cooling = reflectance
Proxy data
indirect evidence using natural recorders of climate variability
- sea floor sediment
- coral deposits
- glacial ice rings
- tree rings
- pollen
Milankovitch theory
- eccentricity of earths orbit (shape)
- obliquity of earths axis (wobble)
- precession of earths axis (angle)
Green Sahara
11,000-5000 years BP (African Humid Period)
controlled position of monsoon rainfall
- increased lake levels
- nike river runoff increased
- period ended when precession shifted and ITCZ migrated back south (removal of moisture)
- return to desert conditions
Solar activity (shorter term controls)
sunspots/solar flares
10’s of years
little ice age/Maunder minimum
medieval warm period
Thermohaline circulation changes
- 100’s to 1000’s of years
Volcanic activity
particulate material in atmosphere
- <10’s or years
Natural Causes of Climate Change
- solar energy changes
- small contribution to overall change
- but make short term hazardous event more likely
- contributor to little ice age initiation
Tipping point
a critical threshold where small change can have significant, long term impact to earths climate
- human or naturally induced
- gradually increasing CO2
Ocean climate patterns
- open oceans climate regions are parallel to latitude lines
- these regions may be modified by surface ocean currents
Ocean’s Climate Zones: Equatorial
- rising air
- weak winds
- doldrums
Ocean’s Climate Zones: Tropical
- north to south equatorial zone
- extend to tropics of Cancer and Capricorn
- strong winds, little precipitation, rough seas
Ocean’s Climate Zones: Subtropical
- high pressure, descending air
- weak winds
- sluggish currents
Ocean’s Climate Zones: Temperate
- strong westerly winds
- sever storms common
Ocean’s Climate Zones: Sub Polar
- extensive precipitation
- summer sea ice
Ocean’s Climate Zones: Polar
- high pressure
- sea ice most of year
Thermohaline circulation change
ocean conveyor belt
- circulation of ocean water in oceans
- can cause abrupt changes in climate
Thermohaline circulation change: Atlantic ocean
• Strong northward movement of near-surface waters are cooled
when they arrive near Greenland
• The water cools, becomes saltier and denser, and it sinks to the bottom
• Current then flows southward around Africa
• Huge amounts of warm water keep Europe warmer than it would be
otherwise
Volcanic eruptions: causes of climate change
- volcanic eruptions
- volcanic ejecta may block sunlight
- need many eruptions in short time period
- minimal impact on climate
Laki fissure eruption
- Sulphur emissions
- fluorine killed 80% Iceland sheep, 50% cows and horses
- impact on population
below average temps
Atmospheric Circulation Systems
range of cells drive the movement of air and moisture across sectors of the globe
- regulating where the different climate zones are located
- Hadley cells show most regular pattern of air movement
(wet weather at equator, aridity on deserts)
Extra-Tropical Cyclones formation
Horizontal and vertical differences in temp and pressure drive formation
Extra-Tropical Cyclones
tracks of the 200 most intense winter cyclone tracks with maximum intensity
Impacts of extratropical cyclones
Hurricane Ophilia downgraded when it hit UK
- high winds
- loss of life
- infrastructure damage
Atmospheric-ocean connections in the pacific ocean
walker circulation cell (normal conditions)
- air pressure across equatorial pacific is high in eastern pacific
- strong southwest trade winds
pacific warm pool on western side of ocean
- thermocline deeper on western side
- upwelling off the coast of peru
El Nino - southern oscillation (ENSO)
- higher pressure in eastern pacific weakens
- weaker trade winds
- warm pool migrates eastward
- thermocline deeper in eastern pacific
- downwelling
- lower biological productivity (Peruvian fishing suffers)
La Nina (ENSO cool phase)
- increased pressure difference across equatorial pacific
- stronger trade winds
- stronger upwelling in eastern pacific
- shallower thermocline
- cooler than normal seawater
- higher biological productivity
- result in increased drought activity
Occurance of ENSO events
- warm phase about every 2-10 years
- high irregular
- phases usually last 12-18 months
- 10,000 year sediment record of events
- may be part of Pacific Decadal Oscillation
- long term natural climate change, lasts 20-30 years
Notable ENSO Events nad hazards
1982-1983 & 1997-1998
- flooding
- drought
- erosion
- fires
- tropical storms
- harmful effects on marine life
Predicting EL Nino events
Tropical Ocean Global Atmosphere (TOGA) program
- 1985
- monitors equatorial south pacific
- 70 buoy system
Tropical Atmosphere and Ocean (TOA) project
- continues monitoring
- ocean and meteorological data
still not fully understood
