Weather Patterns and El Nino

• Air is forced up by mountains (orographic lifting), causing precipitation on the windward side.
• Precipitation is concentrated on one side of a mountain, resulting in temperature variations.
• Clouds affect temperature differently based on height and thickness; higher, thinner clouds absorb more heat from the Earth.
• Clouds block sunlight, cooling the ground, while cloudless conditions lead to hot days and cool nights.

El Nino

• South American fishermen coined the term "El Nino" due to the unusual rise in water temperature around December.
• El Nino is associated with Christmas and is also known as "The Boy."
• El Nino Southern Oscillation (ENSO) is a broader climate pattern encompassing El Nino.
• Trade winds normally blow west, but during El Nino, they weaken.
• This causes warm water to move eastward, resulting in warm temperatures in the east and cold temperatures in the west.
• Waters flow from west to east, making the west colder and the east warmer during an El Nino phase.
• El Nino typically lasts 9-12 months.
• It leads to dry conditions, causing difficulty in farming and food production in tropical regions that usually receive rain.

La Nina

• La Nina is a phase where trade winds strengthen.

• Warm water is pushed towards Asia.

• It also lasts 9-12 months.

• It causes increased precipitation as warm water accumulates around Asia, increasing water vapor leading to rain.

• Can destroy crops, flooding

• La Nina and El Nino often occur back-to-back.

• These events impact global precipitation patterns.

• Asia, Africa, and America tend to receive the most precipitation.

Weather Patterns and Severe Storms

• Air masses are large bodies of air (approximately 1,600 km across and several km thick) with uniform temperature and humidity.
• The area where an air mass originates determines its characteristics.
• Air masses that stay over a source region longer are more likely to acquire its properties.
• Air masses at the poles are cold, while those at the equator are warm.
• Air mass characteristics change as they move.
• Land air masses are generally warmer than ocean air masses.

Types of Air Masses

• Maritime (m) air masses are moist while Continental (c) air masses are dry.

• Continental Polar (cP) air masses are cold and dry air masses originating from land (Arctic, Antarctica).

• Continental Tropical (cT) air masses are warm and dry originating from land (Philippines, Australia, etc.).

• Maritime Polar (mP) air masses are cold and moist originating from water (North Atlantic/Pacific).

• Maritime Tropical (mT) air masses are warm and moist originating from water (Pacific, Indian Ocean)

• As air masses move, their characteristics can change.

• Air masses can move, interact, and converge.

• Air masses move at different speeds, influenced by the Coriolis effect.

• Fronts are boundaries separating different air masses, with one often being warmer and having higher moisture content.

• Fronts can be identified by temperature changes and motion.

• Warm fronts develop when a fast warm air mass slides over a slower, colder air mass.

• Colliding warm air starts to replace cold air

• These fronts often bring nimbostratus, altostratus, cirrostratus, and cirrus clouds.

• There will be moderate precipitation, with nimbostratus and altostratus clouds leading to precipitation

• The result is a white span of stratus clouds covering larger areas, leading to light or moderate precipitation that lasts for an extended period.

• Leads to warm temperatures, moderate precipitation, and cirrus clouds.

• Fair weather/clear skies

• Cold fronts form when a fast cold air mass displaces a slower, warmer air mass.

• Warm air is forced up, resulting in cumulonimbus clouds and heavy but short rain/thunderstorms.

• Leads to colder weather and heavy precipitation

• Characterized by cold temperatures and heavy but short precipitation

• Stationary fronts occur when cold and warm air masses either don't move or move slowly.

• Warm air masses will be warmer with cold air masses being colder

• The weather changes based on which side you are on (boundaries).

• Occluded fronts occur when a fast cold air mass overtakes a slower warm front ("sandwiched between").

• Warm air is sandwiched by two cold air masses and forced upwards

• This results in heavy rain/thunderstorms as precipitation occurs as the warm air rises.

• It leads to cold temperatures and heavy precipitation

• Triangles/symbols on weather maps indicate the direction the front is moving (N, S, W, E).

• Pressure maps indicate zones of high and low pressure.

• Isobars are lines connecting points of equal air pressure at sea level (4-point increment), such as 1008, 1012, and 1016.

• In a high-pressure zone, wind goes down (descending air).

• In a low-pressure zone, wind goes up (ascending air).

• Wind blows clockwise around high pressure and counterclockwise around low pressure.

• Tight isobars indicate a significant difference in air pressure, resulting in strong winds and high pressure.

• Wide isobars indicate even, light or no wind.

• To locate the direction of a high/low-pressure system in the Northern Hemisphere, stand with your back to the wind; low pressure will be to the left, and high pressure to the right.

• Sailors discovered this to sail to safe spots (avoiding low-pressure systems).

• Temperatures can be located using isotherms.

• Tightly spaced isotherms indicate warmer weather, while widely spaced isobars and isotherms in high pressure are colder.

• Surface dewpoint is the point where air is cold enough to condense into liquid.

• Isodrosotherms are lines connecting points of equal dew point temperature at sea level.

• Locations with high humidity mean high precipitation.

• Low pressure = high temperature = high humidity = high pressure change = wet weather.

• Pressure change helps define air masses and identify fronts based on boundaries.

• Weather stations measure atmospheric characteristics, indicated by wind direction, wind speed

• TL = air temperature, BL = dew point, TR = air pressure, R = pressure change/trend on weather maps

• Minobars greater than 500 start with 9 (e.g., 760 becomes 976.0).

• Minobars lower than 500 start with 10 (e.g., 150 becomes 1015.0).

• Compare temperature and dew point to predict precipitation

• Near 0°C/32°F, snow is likely

• Above 20°C/72°F, rain is likely

Tropical Cyclones

• Warm ocean water warms the air above it.
• Warm air rises, creating an area of low pressure.
• Tropical cyclones are warm-core low-pressure systems with a spiral inflow of mass at the bottom and spiral outflow at the top.
• It develops over tropical and sub-tropical waters at any level with organized circulation.
• General direction of cyclones (latitudes 5-30) = West, then North
• Blown west by Trade Winds (latitudes 10-30)

Conditions for Tropical Cyclone Formation

• Ocean waters must have a minimum temperature of 26-27°C (79-80°F).
• Must be further than 5 degrees from the equator to allow the Coriolis effect to facilitate spinning.
• There must be a low-pressure disturbance.
• Winds at different altitudes should have similar speed and direction.

Stages of Tropical Cyclone Development

• Formative Stage: Develops low-pressure system

• Immature Stage: Speed increases, and pressure begins to drop with an inflow of air at the low-pressure system.

• Mature Stage: Storm reaches its strongest point.

• Decaying Stage: Storm decays over land or cooler areas

• Storms rely on water vapor as an energy source, so lack of warm ocean water leads to weakening.

• Moving north causes a storm to encounter higher pressure and cooler temperatures, also causing weakening.

• Climate Change and Cyclones: Warmer waters feed cyclones, making them stronger.

• The eye is the strongest point with clear conditions.

Categories of Typhoons

• Classified through wind speed; Tropical Depression, Tropical Storm, Severe Tropical Storm, Typhoon, Super Typhoon

Effects of Tropical Cyclones

• Storm surge: Abnormal water rise around coastal and inland areas
• Strong winds: Widespread damage and destruction
• Tornadoes: Localized destruction
• Rainfall and flooding: Heavy rain

World Climates + Global Climate Change

• Climate is the long-term weather pattern in a region.
• Factors affecting climate include temperature, pressure, wind, humidity, precipitation, cloudiness, and irradiance.
• Climate differs from weather only in timescale.
• Precipitation and temperature are most important in climate.
• Altitude, latitude, ocean currents, prevailing winds, albedo, cloud cover, continentality, and topography influence climate.
• Climates vary by region; some regions are more stable, while others fluctuate.
• Koppen Climate Classification categorizes five main climate types: tropical, dry, temperate, continental, and polar.
• Tropical climates have an average temperature above 18°C and average precipitation of 150-400 cm/year.
• Dry climate
• Climate changes naturally through oscillation (El Nino, La Nina)

Milankovitch Cycles

• Milankovitch Cycles affect Earth's climate. These cycles involve changes in eccentricity, obliquity, and precession.

• Eccentricity: Earth's orbit becomes more elliptical every 100,000 years.

• Increased distance from the Sun results in cooler temperatures.

• Obliquity: Changes in Earth's tilt (22.1 -> 24.5 degrees) every 41,000 years.

• More tilt results in uneven temperature distribution.

• Less tilt -> more even distribution -> temperatures go up.

• Precession: Earth wobbles on its axis every 26,000 years.

• Earth's climate has historically swung every ~100,000 years.

• Little Ice Age, followed the Industrial Revolution

• Little Ice Age started by volcanoes

• Global temperatures dropped 2 degrees C (3.6 F) during 1300-1850 (~500 years)

Human-Caused Climate Change

• Relates to the Greenhouse Effect vs. Global Warming:
• Greenhouse Effect is a natural phenomenon where greenhouse gases trap heat near Earth's surface, keeping it warm.
• Three main greenhouse gases are water, carbon dioxide, and methane.
• Carbon dioxide is the most concerning and has steadily risen along with emissions
• Increases in atmospheric CO2 trap more heat, causing the globe to become warmer.
• Global Warming is a consequence of the Greenhouse Effect.
• CO2 levels have fluctuated over the last 800k years seeming to be a natural cycle but never higher than 300 ppm.
• With the Industrial Revolution, factories started using coal/fossil fuels = Replaced with cars, fueled by petroleum/gasoline = Electricity, made by burning fossil fuels
• Starts rising since with more CO2 production