In-depth Weather Notes

Understanding Weather

  • Weather is defined as the state of the atmosphere at a specific point in time.
  • Parameters to describe weather include:
    • Temperature
    • Precipitation
    • Humidity
    • Wind speed
    • Cloudiness
    • Sunlight intensity

Convection

  • Convection: Heat transfer due to bulk movement of molecules within fluids (gases, liquids).
    • Emerges from fluids warmed from below.
    • Rising parcels of fluid cool at higher elevations.
    • An efficient way to transfer heat.
    • Essential for storm formation, ocean circulation, and plate tectonics.

Thunderstorms

  • Thunderstorms develop from atmospheric convection:
    • Warm, moist air rises, cools, and condenses releasing heat.
    • Further cooling can lead to freezing, releasing additional heat.
    • Storms organize into intense circulation; precipitation occurs as condensed water rains out.
    • Can persist as long as warm, moist air is available.

Tropical Weather

  • Characterized by two main seasons:
    • Wet Season: Dominated by convection and thunderstorms.
    • Dry Season
  • Key weather systems include:
    • Inter-Tropical Convergence Zone (ITCZ)
    • Monsoons
    • Tropical Cyclones

Inter-Tropical Convergence Zone (ITCZ)

  • A band of thunderstorms encircling the Earth, forming where the sun is overhead.
  • Position influences local rainfall patterns:
    • Shifts north and south with seasons (farthest north during Northern Hemisphere summer, and vice versa).
    • Affects mid-tropics with two rainy seasons; surrounding regions receive one.

Monsoons

  • Caused by land-sea temperature differences:
    • Heating of land creates a low-pressure zone, drawing in moist ocean air.
    • Enhanced by geographical features (e.g., mountain ranges).
    • Cycle reverses in winter, leading to dry conditions.

Tropical Cyclones

  • Form from clusters of thunderstorms in warm sea conditions (>26°C).
  • Requires:
    • Warm ocean water
    • Low shear winds
    • Ability to organize into a low-pressure system.
  • Naming conventions vary by region:
    • Hurricanes: Atlantic, Eastern Pacific
    • Typhoons: Western Pacific
    • Cyclones: Indian Ocean

Extra-Tropical Weather

  • Dominated by high and low-pressure systems:
    • High pressure from descending winds; low pressure from rising air.
    • Air movement creates pressure gradients influencing weather patterns.
  • High pressure typically leads to clear, sunny weather; low pressure results in cloudiness and storms.

Front Formation

  • Fronts are boundaries between air masses:
    • Warm Fronts: Warm air rises over cooler air, leading to gradual temperature increases and light rain.
    • Cold Fronts: Cold air forces warm air upwards, resulting in heavy precipitation and strong winds.
    • Occluded Fronts: Form when a cold front overtakes a warm front, lifting warm air to create intense precipitation.

Extreme Weather

  • Defined as unexpected, unpredictable, severe, or unseasonal weather.
    • Includes storms (tropical cyclones, tornadoes) and extreme temperature events (heat waves, cold waves).

Tornado Formation

  • Developed through:
    1. Shear winds creating horizontally rotating air.
    2. Updrafts catching spinning air and bending it vertical.
    3. Formation of a super-cell thunderstorm capable of producing tornadoes.
  • Tornadoes are short-lived yet can be extremely intense; capable of causing localized severe damage.

Local Weather Effects

  • Local geographical features also influence weather:
    • Orographic Precipitation: Moist air rises over mountains, cools, and precipitates, leaving a dry rain shadow on the leeward side.
    • Sea Breezes: Generated by temperature contrasts between land and ocean, moving air from ocean to land.
    • Katabatic Winds: Cold, dense air flowing downhill from high elevations; strongest in valleys and over glaciers. These winds can reach over 300 ext{ km/h}.