Weather and climate shape our daily lives and long-term environmental conditions. Weather is the day-to-day state of the atmosphere, while climate represents long-term patterns over decades or more.

Understanding these concepts is crucial for predicting short-term events and long-term trends. Factors like temperature, humidity, and air pressure influence weather, while global patterns and geographical features shape climate zones worldwide.

Weather vs Climate

Defining Weather and Climate

• Weather refers to the day-to-day atmospheric conditions in a specific location
  • Includes temperature, humidity, precipitation, and wind
  • Can change rapidly over short periods (hours or days)
  • Examples: a sunny day, a thunderstorm, a cold front passing through an area
• Climate describes the long-term average weather patterns and conditions in a region
  • Typically measured over a period of 30 years or more
  • Represents the expected weather conditions for a given location and time of year
  • Examples: hot and humid conditions in tropical rainforests, dry and arid conditions in deserts, cold and snowy conditions in polar regions

Comparing and Contrasting Weather and Climate

• Weather is short-term and highly variable, while climate is long-term and more stable
• Weather conditions can be influenced by local factors (topography, urban heat islands), while climate is determined by global factors (latitude, ocean currents, atmospheric circulation patterns)
• Weather forecasts predict conditions for the near future (days to weeks), while climate projections estimate long-term trends and changes (decades to centuries)
• Understanding both weather and climate is crucial for various sectors, such as agriculture, transportation, and energy production

Factors Influencing Weather

Temperature, Humidity, and Air Pressure

• Temperature measures the average kinetic energy of molecules in the atmosphere
  • Influenced by latitude (solar radiation intensity), altitude (air density), and proximity to large bodies of water (heat capacity)
  • Affects air density, pressure, and the formation of convection currents
• Humidity is the amount of water vapor present in the atmosphere
  • Influences the formation of clouds, precipitation, and the perceived temperature (heat index)
  • Can be measured as absolute humidity (g/m³), relative humidity (%), or dew point temperature
• Air pressure is the force exerted by the weight of the atmosphere on a given surface area
  • Influenced by temperature (warm air rises, creating low pressure), altitude (pressure decreases with height), and the presence of high or low-pressure systems
  • Affects wind patterns, as air moves from high to low pressure areas

Wind and Atmospheric Circulation

• Wind is the horizontal movement of air from areas of high pressure to areas of low pressure
• Influenced by the Coriolis effect (deflection due to Earth's rotation), friction (surface roughness), and temperature differences
• Global wind patterns, such as trade winds and westerlies, are driven by unequal heating of the Earth's surface and the resulting atmospheric circulation cells (Hadley, Ferrel, and Polar cells)
• Local wind patterns, such as sea breezes and mountain-valley breezes, are caused by temperature differences between land and water or between mountain slopes and valleys

Air Mass Formation and Characteristics

Types and Source Regions of Air Masses

• Air masses are large bodies of air with relatively uniform temperature and humidity characteristics
• Originate in specific regions known as source regions, where air remains stationary long enough to acquire the properties of the underlying surface
• Four main types of air masses:
  • Continental Polar (cP): cold and dry, originates over high-latitude land masses (Canada, Siberia)
  • Continental Tropical (cT): hot and dry, originates over arid regions (Sahara, Australian Outback)
  • Maritime Polar (mP): cold and moist, originates over high-latitude oceans (North Atlantic, North Pacific)
  • Maritime Tropical (mT): warm and moist, originates over subtropical oceans (Gulf of Mexico, Caribbean Sea)

Air Mass Modification and Interaction

• Air masses can be modified as they move across different surfaces
  • Continental air masses become more humid as they move over water bodies
  • Maritime air masses become drier as they move over land
• Interaction between different air masses along frontal boundaries leads to weather phenomena
  • Cold fronts: cold air mass displaces warm air mass, causing lifting and condensation (thunderstorms, heavy precipitation)
  • Warm fronts: warm air mass overtakes cold air mass, causing gradual lifting and condensation (steady precipitation, stratus clouds)
  • Stationary fronts: air masses meet but neither advances, causing prolonged precipitation and cloudiness
  • Occluded fronts: cold air mass catches up to a warm front, lifting the warm air off the ground (complex weather patterns, mixed precipitation)

Climate Zones and Weather Patterns

Major Climate Zones

• Earth's surface is divided into three main climate zones based on latitude
  • Tropical zone: between the Tropic of Cancer and the Tropic of Capricorn (23.5°N to 23.5°S)
    • High temperatures, high humidity, and abundant rainfall throughout the year
    • Examples: Amazon rainforest, Congo Basin, Indonesian archipelago
  • Temperate zones: between the tropics and the polar regions in both hemispheres (23.5° to 66.5°)
    • Distinct seasonal changes in temperature and precipitation
    • Examples: Eastern United States, Western Europe, Eastern China
  • Polar zones: near the North and South Poles (66.5° to 90°)
    • Extremely cold temperatures, low humidity, and limited precipitation (mostly snow)
    • Examples: Arctic tundra, Antarctic ice sheet, Greenland ice cap

Köppen Climate Classification System

• Sub-classifications within each climate zone based on temperature, precipitation, and seasonality
• Five main climate groups: tropical (A), arid (B), temperate (C), continental (D), and polar (E)
• Each group is further divided into sub-categories based on precipitation patterns and temperature ranges
  • Examples: Af (tropical rainforest), BWh (hot desert), Cfb (marine west coast), Dfc (subarctic), ET (tundra)
• Provides a standardized way to describe and compare climates across different regions

Factors Influencing Climate Patterns

• Atmospheric circulation patterns: Hadley, Ferrel, and Polar cells redistribute heat and moisture globally
• Ocean currents: transfer heat and moisture between regions, affecting coastal climates (Gulf Stream, Kuroshio Current)
• Distribution of land and water masses: land heats up and cools down faster than water, creating temperature gradients and influencing precipitation patterns
• Topography: mountains can block moisture-laden air, creating rain shadows and affecting local climates (Andes, Himalayas)
• Latitude: determines the amount of solar radiation received, affecting temperature and seasonality