Weather Phenomena Notes

Science

Atmosphere's Role in Weather Phenomena

What is Weather?

  • Refers to the specific atmospheric conditions at a particular place and time.
  • Includes temperature, precipitation, cloud cover, humidity, air pressure, and wind.
  • Refers to the short-term, day-to-day conditions of the atmosphere.
  • Examples: a sunny day, a rainy afternoon, a cold night.

Climate

  • Refers to the average weather conditions over a long period, typically 30 years or more.
  • Examples: a region's average temperature in summer, the typical amount of rainfall in a year, or the likelihood of droughts or heatwaves.

Insolation

  • Exposure to the sun’s rays.
  • The amount of incoming solar energy that makes contact with the surface of the Earth.

Angle of Insolation

  • The angle at which the sun's rays strike a particular location on Earth.
  • Vertical rays:
    • Strike the Earth directly at a 90∘90^\circ angle.
    • Also known as direct rays.
    • Concentrated in small areas, bringing in more heat.
  • Oblique rays:
    • Strike the Earth at an angle less than 90∘90^\circ.
    • Also known as slanting rays.
    • Concentrated on broader areas, so there is less heat in the area.

Atmospheric Factors and Weather Formation

  • Temperature
  • Humidity
  • Air Pressure
  • Cloudiness
  • Wind

Temperature

  • Temperature differences lead to air movement (wind) and convection currents.
  • Warm air rises, while cold air sinks, creating pressure differences that influence weather.

Wind

  • Wind is the movement of air within the atmosphere, driven by temperature and pressure differences.
  • Wind patterns can transport moisture, temperature, and pollutants across large distances, influencing weather in different regions.

Coriolis Effect

  • Because the Earth rotates on its axis, circulating air is deflected toward the right in the Northern Hemisphere and toward the left in the Southern Hemisphere.

Air Pressure

  • Atmospheric pressure differences drive weather patterns, with air moving from high-pressure areas to low-pressure areas, creating winds and influencing temperature, humidity, and cloud formation.
  • In high-pressure areas, air descends, which warms and dries the air, leading to clear skies and calm winds.
  • These systems are often associated with fair, settled weather.
  • In low-pressure areas (also known as “depression”), air rises, cools, and condenses, forming clouds and potentially precipitation.
  • Low-pressure systems are often associated with unsettled weather, including storms.

Humidity

  • Warm air can hold more water vapor than cold air, leading to condensation and cloud formation when air cools.
  • Humidity levels influence the type and intensity of precipitation (rain, snow, etc.).

Clouds

  • Clouds can reflect sunlight back into space, leading to cooler temperatures.
  • Different types of clouds are associated with different weather conditions, such as rain, snow, or thunderstorms.

Types of Clouds

  • Three levels: Low-Level, Middle-Level, High-Level
Low-Level Clouds
  • Appear below 6,500 feet.
  • Primarily composed of water droplets.
  • Types:
    • Stratus
    • Cumulus
    • Stratocumulus
    • Nimbostratus
    • Cumulonimbus
Cumulus
  • Puffy, white clouds with flat bases and dome-shaped tops, often seen on sunny days.
Stratus
  • Gray, featureless, sheet-like clouds that often cover the entire sky and can produce drizzle or light rain.
Stratocumulus
  • Appear as patchy, layered sheets or rolls, often with a slightly puffy appearance.
  • A layer of globular masses of dark clouds which may produce brief rain showers.
Nimbostratus
  • Dark, grey, and thick clouds that produce continuous, widespread precipitation, like rain or snow.
  • Known to be heavy rain bearers.
Cumulonimbus
  • Large, towering clouds that can extend through all three levels, often associated with thunderstorms and heavy precipitation.
Middle-Level Clouds
  • Appear between 6,500 to 20,000 feet.
  • Can be composed of water droplets or ice crystals, with the higher portions of these clouds tending to be ice crystals.
  • Types:
    • Altocumulus
    • Altostratus
Altocumulus
  • Composed of puffy or sheet-like formations, often appearing as rounded masses or rolls.
Altostratus
  • Gray or bluish-gray, sheet-like clouds that can cover the entire sky, sometimes allowing the sun to be dimly visible through them.
High-Level Clouds
  • Appear above 20,000 feet.
  • Composed of ice crystals due to the cold tropospheric temperature.
  • Types:
    • Cirrus
    • Cirrocumulus
    • Cirrostratus
Cirrus
  • Thin, wispy clouds made of ice crystals, often appearing as feathery streaks or patches.
  • Before sunrise and sunset, cirrus is often colored brightly yellow and red.
Cirrocumulus
  • Small, white, puffy clouds that appear in sheets or patches, often resembling ripples or waves.
  • A cloud that looks like fish scales.
Cirrostratus
  • Thin, sheet-like clouds that can cover the entire sky, sometimes creating a halo effect around the sun or moon.

Precipitation

  • Water that falls from the clouds towards the ground, especially as rain or snow.
Types of Precipitation
  • Drizzle
  • Sleet
  • Hail
  • Rain
Drizzle
  • Consists of very small water droplets, typically less than 0.50.5 millimeters in diameter.
Sleet
  • Forms when raindrops freeze as they fall through a layer of freezing air, resulting in small, transparent or translucent pellets of ice.
Hail
  • Precipitation in the form of hard, rounded pellets of ice, often larger than sleet.
Rain
  • Large, far-apart droplets of water larger than 0.50.5 mm in diameter.

Weather Systems in the Philippines

Tropical Cyclones
  • Generally known as "Bagyo."
  • Classified according to wind velocity: depression, storm, and typhoon.
Breeze
  • A light to moderate wind, weaker than a gale, and is a type of wind that blows from high to low-pressure zones.
Sea Breeze
  • Blows from the sea to the land.
  • During the day, land heats up faster than water, creating a temperature difference.
  • The warmer air above the land rises, and cooler air from over the sea moves in to replace it, resulting in a sea breeze.
Land Breeze
  • Blows from the land to the sea.
  • At night, land cools down faster than water, creating a temperature difference.
  • The cooler air above the land becomes denser and sinks, while warmer air over the sea rises, leading to a land breeze.
Monsoon
  • A seasonal change in the direction of the prevailing, or strongest, winds of a region.
  • Monsoons cause wet and dry seasons throughout much of the tropics.
Intertropical Convergence Zone (ITCZ)
  • A low-pressure area near the equator where the trade winds of the Northern and Southern Hemispheres converge, leading to rising air, abundant cloud cover, and heavy rainfall.
  • The ITCZ can affect weather patterns in the Philippines, particularly during the summer months, as it can bring heavy rainfall and thunderstorms to Southern Luzon, Visayas, and Mindanao.

Tropical Cyclone Classification

  • Tropical Depression (TD): Wind speed of 6161 km/h or less.
  • Tropical Storm (TS): Wind speed of 62−8862-88 km/h.
  • Severe Tropical Storm (STS): Wind speed of 89−11789-117 km/h.
  • Typhoon (TY): Wind speed of 118−184118-184 km/h.
  • Super Typhoon (STY): Wind speed of 185185 km/h or higher.