🌈Earth Systems Science Unit 9 – Weather Systems and Climate Patterns

Key Concepts and Terminology

• Atmosphere consists of layers (troposphere, stratosphere, mesosphere, thermosphere, exosphere) with varying temperatures and pressures
• Weather refers to short-term atmospheric conditions (temperature, humidity, precipitation, wind) in a specific area
• Climate describes long-term average weather patterns and conditions over a larger region
• Greenhouse gases (carbon dioxide, methane, water vapor) trap heat in the atmosphere contributing to the greenhouse effect
• Albedo measures the reflectivity of a surface (snow, ice, water, land) affecting the amount of solar radiation absorbed or reflected
• Coriolis effect deflects moving objects (wind, ocean currents) to the right in the Northern Hemisphere and left in the Southern Hemisphere due to Earth's rotation
• Jet streams are narrow, fast-moving air currents in the upper atmosphere that influence weather patterns and air mass movement
• Atmospheric pressure decreases with altitude and is measured using barometers (mercury, aneroid)

Atmospheric Composition and Structure

• Atmosphere is a mixture of gases (nitrogen 78%, oxygen 21%, argon 0.93%, carbon dioxide 0.04%) surrounding Earth
• Troposphere is the lowest layer of the atmosphere extending from Earth's surface to ~12 km
  • Contains 75% of atmospheric mass and almost all water vapor
  • Temperature decreases with altitude at a rate of ~6.5°C/km (lapse rate)
• Stratosphere extends from the tropopause to ~50 km and contains the ozone layer
  • Temperature increases with altitude due to ozone absorbing ultraviolet radiation
• Mesosphere extends from the stratopause to ~85 km with temperatures decreasing with altitude
• Thermosphere extends from the mesopause to ~600 km with temperatures increasing due to absorption of solar radiation
• Exosphere is the outermost layer of the atmosphere extending from the thermopause to ~10,000 km
• Ionosphere is a region within the thermosphere containing electrically charged particles (ions) that reflect radio waves

Global Circulation Patterns

• Global atmospheric circulation redistributes heat from the equator to the poles
• Hadley cells are large-scale atmospheric circulation patterns in the tropics
  • Rising motion near the equator, poleward flow aloft, descending motion in the subtropics, and equatorward flow near the surface
  • Responsible for the Intertropical Convergence Zone (ITCZ) and trade winds
• Ferrel cells are mid-latitude circulation patterns characterized by rising motion in the subpolar regions, equatorward flow aloft, descending motion in the subtropics, and poleward flow near the surface
• Polar cells are small-scale circulation patterns in the polar regions with rising motion over the poles, equatorward flow aloft, and descending motion in the subpolar regions
• Walker circulation is an equatorial zonal circulation pattern influenced by the El Niño-Southern Oscillation (ENSO)
  • During normal conditions, easterly trade winds cause upwelling of cold water in the eastern Pacific and warm water in the western Pacific
  • During El Niño, weakened trade winds lead to warmer water in the eastern Pacific, altering global weather patterns
• Monsoons are seasonal wind patterns caused by differential heating between land and ocean, resulting in wet (summer) and dry (winter) seasons

Weather Phenomena and Systems

• Air masses are large volumes of air with uniform temperature and moisture characteristics (maritime tropical, continental polar)
• Fronts are boundaries between air masses with different densities, leading to weather changes
  • Cold fronts occur when cold air displaces warm air, causing thunderstorms and sudden temperature drops
  • Warm fronts occur when warm air replaces cold air, causing steady precipitation and gradual temperature rises
• Cyclones are low-pressure systems characterized by counterclockwise (clockwise) rotation in the Northern (Southern) Hemisphere
  • Tropical cyclones (hurricanes, typhoons) form over warm ocean waters and can cause severe damage
  • Mid-latitude cyclones form along frontal boundaries and bring precipitation and varying weather conditions
• Anticyclones are high-pressure systems characterized by clockwise (counterclockwise) rotation in the Northern (Southern) Hemisphere, often associated with clear skies and stable weather
• Thunderstorms are convective storms that produce lightning, thunder, heavy rain, and sometimes hail or tornadoes
• Tornadoes are violently rotating columns of air extending from a thunderstorm to the ground, causing severe damage along their path

Climate Classification and Zones

• Köppen climate classification system categorizes climates based on temperature and precipitation patterns
  • A: Tropical climates with high temperatures and precipitation year-round (rainforests)
  • B: Dry climates with low precipitation (deserts, steppes)
  • C: Temperate climates with mild temperatures and moderate precipitation (Mediterranean, humid subtropical)
  • D: Continental climates with cold winters and warm summers (humid continental, subarctic)
  • E: Polar climates with extremely cold temperatures year-round (tundra, ice cap)
• Tropical zone extends from the equator to ~23.5° N/S, characterized by high temperatures and precipitation
• Subtropical zones are located between ~23.5° and ~35° N/S, with hot summers and mild winters
• Temperate zones are found between ~35° and ~66.5° N/S, experiencing distinct seasons and moderate temperatures
• Polar zones are located above ~66.5° N/S, with extremely cold temperatures and limited precipitation

Factors Influencing Climate

• Latitude affects the amount of solar radiation received, with higher latitudes receiving less energy per unit area
• Altitude influences temperature and precipitation, with higher elevations generally experiencing cooler temperatures and increased precipitation
• Ocean currents transport heat and moisture, moderating coastal climates (Gulf Stream, Kuroshio Current)
  • Warm currents (from equator to poles) bring warmer temperatures and increased precipitation to adjacent landmasses
  • Cold currents (from poles to equator) bring cooler temperatures and decreased precipitation to nearby coastal areas
• Topography can create microclimates and influence local weather patterns
  • Mountains can block moisture-laden air, causing rain shadows and arid conditions on the leeward side
  • Valleys can trap cold air, leading to temperature inversions and fog formation
• Land-sea interactions affect coastal climates, with land heating and cooling faster than water
  • Sea breezes occur during the day as cooler air from the ocean moves inland
  • Land breezes occur at night as cooler air from the land moves towards the warmer ocean
• Atmospheric and oceanic oscillations (North Atlantic Oscillation, Pacific Decadal Oscillation) can influence regional climate variability on interannual to multidecadal timescales

Climate Change and Its Impacts

• Climate change refers to long-term shifts in temperature, precipitation, and other climate variables
• Anthropogenic factors, such as greenhouse gas emissions (carbon dioxide, methane) from fossil fuel combustion and land-use changes, are the primary drivers of current climate change
• Rising global temperatures lead to increased frequency and intensity of heatwaves, droughts, and wildfires
  • Heatwaves can cause health issues, particularly for vulnerable populations (elderly, children)
  • Droughts can reduce agricultural productivity and strain water resources
• Sea level rise occurs due to thermal expansion of ocean water and melting of land-based ice (glaciers, ice sheets)
  • Coastal flooding and erosion can damage infrastructure and ecosystems
  • Saltwater intrusion can contaminate freshwater aquifers and affect agricultural land
• Changes in precipitation patterns can lead to more frequent and severe flooding or drought conditions
  • Flooding can cause damage to property, infrastructure, and crops
  • Droughts can lead to water scarcity, reduced agricultural yields, and increased wildfire risk
• Shifts in species' ranges and phenology can disrupt ecosystems and affect biodiversity
  • Some species may adapt or migrate to more suitable habitats, while others may face extinction
• Climate change can exacerbate existing social and economic inequalities, disproportionately affecting vulnerable communities and developing nations

Tools and Techniques for Weather and Climate Analysis

• Weather stations measure atmospheric conditions (temperature, humidity, wind speed and direction, precipitation) at a specific location
• Radiosondes are balloon-borne instruments that measure atmospheric properties (temperature, humidity, pressure) at various altitudes
• Radar (radio detection and ranging) uses radio waves to detect and track precipitation, wind, and other atmospheric phenomena
  • Doppler radar measures the motion of objects (precipitation, wind) based on the Doppler effect
• Satellites provide continuous, global observations of Earth's atmosphere, oceans, and land surface
  • Geostationary satellites orbit at ~36,000 km and maintain a fixed position relative to Earth, providing frequent imagery of a specific region
  • Polar-orbiting satellites orbit at lower altitudes (~700-800 km) and provide global coverage, passing over the poles multiple times a day
• Weather models use mathematical equations and numerical methods to simulate and predict atmospheric conditions
  • Global models (GFS, ECMWF) provide long-range forecasts and cover the entire Earth
  • Regional models (WRF, NAM) offer higher-resolution forecasts for specific areas
• Climate models simulate long-term changes in Earth's climate system by incorporating atmospheric, oceanic, and land surface processes
  • General Circulation Models (GCMs) represent physical processes and interactions within the climate system
  • Earth System Models (ESMs) include additional components (carbon cycle, vegetation dynamics) to capture complex feedbacks
• Paleoclimatology uses proxy data (tree rings, ice cores, sediment layers) to reconstruct past climate conditions and understand long-term climate variability