Lecture - Chapter 2: Climate Flashcards
The physical environment
Ultimately determines where organisms can live and the resources that are available. Understanding this environment is key to understanding all ecological phenomena.
Weather
current conditions - temperature, precipitation, humidity, cloud cover
Climate
Long-term description of weather, based on averages and variation measured over decades.The most fundamental component of the physical environment. Determines the geographic distribution of organisms. Characterized by average conditions and full scope of variation
Climate change
increases the variance of temperature and rainfall, which may lead to large-scale die-offs of vegetation
Principles governing climate
Energy balance. Heat, water and land.
Variation in Climate
Spatial variation - latitudinal, altitudinal.
Temporal variation - daily, seasonal, supra-annual
The sun
The ultimate source of energy that drives the global climate system
Energy gains from solar radiation must be ____
offset by energy losses if Earth’s temperature is to remain the same. Solar radiant energy absorbed by the planet is ultimately lost and radiated back out to space as heat.
Greenhouse gasses
Gasses contained in the atmosphere that absorb and reradiate the infrared radiation emitted by Earth. Include Water Vapor (H2O), carbon dioxide (CO2), methane (CH4), nitroous oxide (N2O)
Climate change - Global warming
without greenhouse gases, Earth’s climate would be about 33 Celsius cooler. Current climate change is due to increased CO2 and other gases in the atmosphere due to human activities
What generates weather and climate
Differences in solar radiation across Earth’s surface result in: movement of energy, variation in temperature and precipitation –> winds and ocean currents. Imbalance of incoming radiation drives global atmospheric circulation
Spatial variation in climate - Latitude
Net energy balance is positive at low latitudes, negative at high latitudes. There is a net movement of heat from low to high latitudes within atmosphere
Temperature decreases with altitude due to physical properties of air
Warm air is lighter than cold air.
Atmospheric pressure affects temperature and density - adiabatic cooling
Temperature affects the ability of air to hold water
Density of warm air
Solar radiation heats Earth’s surface, which emits infrared radiation to the atmosphere, warmign the air above it.
Warm air rises, expands and cools.
Cool air holds less water, leads to condensation and cloud formation
Density of moist air
Since water has a lower molecular weight than N2, moist air is lighter than dry air
Adiabatic cooling
Air at the bottom of the atmosphere experiences more pressure than does air at the top.
As air rises, pressure declines, volume increases and temperature decreases.
Decrease in air temperature through expansion is adiabatic cooling.
Temperature and water content of air
Ability of air to hold water increases exponentially with temperature
Vapor pressure
Pressure due to water vapor or given water content of air
Saturation Vapor Pressure / Water Capacity of Air
Pressure of water content of air at saturation
The maximum amount of water for a given volume f air and temperature
(evaporation rate = condensation rate)
Absolute Humidity
Amount of water in a given volume of air
Relative Humidity
Amount of water in air as a % of SVP
Dew point temperature
for a given amount of water content of an air parcel, the temperature where SVP is reached
The tilt of Earth’s axis causes seasonal changes in climate
In addition to circling around the sun, the earth rotates about an axis. This tilt causes seasonal variation of temperature and day length
Atmospheric circulation
Air moves due to rising and sinking air and the Earth’s rotation around its axis. Tropical regions receive the most solar radiation and the most precipitation
When air masses reach the troposphere - stratosphere boundary, air flows towards the poles
Subsidence
The air descends when it cools and forms a high pressure zone
prevailing winds
areas of high and low pressure result in air movements called prevailing winds
coriolis effect
the winds appear to be deflected due to the rotation of the earth
air masses in the northern hemisphere deflect to the
right
air masses in the souther hemisphere deflect to the
left
Inter tropical convergence zone
Near the equator where the north and south easterly trade winds meet
A zone of convection and cloud formation
Near but not on the equator
Engine of much of earths weather
Warm moist air here rises
Subtropical fronts
Sinking cool air compresses and warms
Results in low relative humidity and arid condiitons
Polar fronts
Unstable boundary
instability forces moist air upward
causes rain
Atmospheric and oceanic circulation
Major ocean surface currents are driven by surface winds so patterns are similar
Ocean currents affect climate by transferring heat from the tropics to the poles
El Nino Southern Oscillation (ENSO)
Longer scale climate variations that occur every 3 to 8 years and last about 18 months
Macroclimates
Large-scale and long term shaped by sun tilting of earth wind, ocean currents etc
Microclimates
Climatic variation on smaller scales measured over short time spans
shaped by
altitude
vegetation
topography
