Earth’s Atmosphere: Climate, Weather, and Natural Phenomena
Lecture 1: Earth’s Atmosphere
Earth’s Spheres and the Earth System
Global change occurs in various places on Earth, including water, land, sky, and underground, within interconnected “spheres” that interact to form the Earth system.
Earth’s Spheres:
- Atmosphere: Wind, weather, climate
- Cryosphere: Polar and mountain ice
- Lithosphere: Rocks, minerals, volcanoes, plate tectonics
- Biosphere: Life, organic matter
- Hydrosphere: Lakes, rivers, oceans, seas
Biogeochemical Cycles:
Repetitive processes that move chemicals between Earth’s living and nonliving spheres, contributing to a planet conducive to life. Examples include:
- Hydrologic Cycle: Evaporation, condensation, precipitation, transpiration
- Carbon Cycle: Regulates climate through processes like the greenhouse effect, where CO2 gases trap heat energy, warming the lower atmosphere.
Climate and Weather
Climate refers to long-term patterns of temperature and precipitation in a region, while weather describes short-term aspects of temperature and precipitation.
Climate Zones:
- Tropics: Between 30 degrees north and 30 degrees south latitude.
- Temperate Regions: 30-60 degrees latitude in both hemispheres.
- Polar Regions: 60-90 degrees latitude.
Atmospheric Circulation (Convection Cells):
Climate zones are associated with six convection cells driven by temperature differences and air density:
- Hadley Cells (H Cells): Tropics
- Ferrel Cells (F Cells): Temperate regions
- Polar Cells (P Cells): Polar regions
Boundaries between these cells create air currents and jet streams, such as the Polar Jetstream and Subtropical Jetstream.
Seasonality:
Predictable changes in precipitation and temperature throughout the year, varying across climate zones.
Deserts
Deserts, defined by less than 250mm of annual rainfall, have a predictable distribution on Earth, often located around 30 degrees latitude in both hemispheres.
Types of Deserts:
- Polar Deserts: Cold, dry regions with little air moisture.
- Subtropical Deserts: Formed by descending dry air masses from Hadley Cells.
- Inland Deserts: Located far from oceans and moisture sources.
- Coastal Deserts: Influenced by cool, dry air from ocean currents.
- Rocky Deserts: Characterized by rocky terrain and sparse vegetation.
Oceans
Oceans play a crucial role in Earth’s climate system, storing vast amounts of heat and influencing weather patterns.
Marine Geology and Oceanography:
- Marine Geology: Study of rocks and minerals associated with oceans and seas.
- Oceanography: Study of the ocean floor’s shape and depth.
- Bathymetry: Subdiscipline of oceanography focusing on the ocean floor’s topography.
Bathymetric Zones:
- Continental Shelf: Shallow, 0-500 meters depth.
- Continental Slope: 500m to 4km depth.
- Continental Rise: 4-4.5km depth, transitional slope.
- Abyssal Plain: Deeper than 4.5 km and flat.
Ocean Currents
Ocean currents are driven by wind, water temperature, and salinity, influencing weather and climate.
Thermo-Haline Circulation:
Global circulation pattern driven by water density, temperature, and salinity, affecting weather, climate, and ocean currents.
Rivers
Rivers, formed by precipitation and gravity, flow from high to low elevations, shaping landscapes and transporting sediments.
River Features:
- Channel: Contains the flowing water (stream).
- Overbank: Area beyond the channel’s capacity, prone to flooding.
- Flood Plain: Area adjacent to the channel that experiences flooding.
River Patterns:
- Meandering Stream: Single channel with an S-shaped geometry.
- Braided Stream: Multiple interconnected channels.
El Nino
El Nino is a climate pattern characterized by warming of surface waters in the tropical Pacific Ocean, impacting weather patterns globally.
Global Impacts of El Nino and La Nina:
- El Nino: Can cause droughts in South Asia and increased hurricane activity in the Atlantic.
- La Nina: Can lead to flooding in Southeast Asia and colder winters in the northern hemisphere.
Hurricanes
Hurricanes are tropical storms with strong winds and heavy rainfall, originating in the tropics.
Hurricane Formation:
Hurricanes form over warm ocean waters and go through a three-step evolution process:
- Tropical Depression: Cyclonic air mass with maximum winds of 38 mph or less.
- Tropical Storm: Cyclonic air mass with maximum winds of 39-73 mph.
- Hurricane: Cyclonic air mass with maximum winds of 74 mph or higher.
Hurricane Sandy:
A powerful hurricane that impacted the East Coast of the United States in 2012, causing significant damage due to storm surge and flooding.
Fronts
Boundaries between air masses with different temperatures and pressures, influencing weather patterns.
Note: This document has been edited for clarity, grammar, and SEO optimization. Headings have been adjusted for better structure and readability.