climate and life study guide 2

Frictional Force

• Force from air rubbing against Earth’s surface

• Strongest at the surface, weak higher up

• Slows wind down and changes its direction (toward low pressure)

Geostrophic Balance

• Balance between:

  • Pressure Gradient Force (PGF) → pushes air from high → low pressure

  • Coriolis Force → deflects motion (right in NH, left in SH)

• Occurs high in the atmosphere (where friction is negligible)

• Wind flows parallel to isobars

Isobar

Line connecting points of equal pressure on a map

Cyclone

• Low pressure

  • Air rises

  • Cloudy, stormy weather

Anticyclone

• Anticyclone = High pressure

  • Air sinks

  • Clear, dry weather

Humidity

Amount of water vapor in air

Global Pattern

• High humidity near equator

• Low in subtropics (deserts)

Global Warming & Precipitation

• Warmer air holds more moisture → heavier rainfall events

Dalton’s Law

• Total pressure = sum of partial pressures of gases

Measuring Humidity

• Vapor pressure

• Relative humidity (RH)

• Dew point

Temperature & Vapor

• Warmer air → higher saturation vapor pressure

Precipitable Water

• Total water vapor in a column of air

• Highest in tropics/oceans

• Increasing since 1979 → more extreme rain

Relative Humidity & Warming

• RH stays roughly constant globally, but moisture increases

Advection

• Horizontal movement of air

Air Parcel

• Small “blob” of air used for analysis

Sounding

• Vertical profile of atmosphere (temp, humidity, etc.)

Condensation

Occurs when air reaches 100% RH

3 ways:

1. Cool the air

2. Add moisture

3. Mix air masses

Condensation Nuclei

• Tiny particles (dust, salt)

• Water condenses onto them → cloud formation

Fog, Dew, Frost

• Fog = cloud at surface

• Dew = liquid water on surface

• Frost = ice (below freezing)

Diabatic vs Adiabatic

• Diabatic: heat added/removed → fog common

• Adiabatic: temp changes due to expansion/compression → clouds/precip

Air Mass

• Large body of air with uniform temp & humidity

4 Lifting Mechanisms

1. Convection (warm air rises)

2. Orographic (mountains)

3. Frontal lifting

4. Convergence

Rainshadow

• Wet windward side, dry leeward side

Stability

• Unstable → air rises → storms

• Stable → air resists rising → clear skies

• Neutral → stays where moved

Lapse Rate

• Rate temp changes with height

Lifting Condensation Level (LCL)

• Height where cloud forms

• After LCL → condensation releases heat → helps further rising

Why clouds don’t always rain

• Droplets too small

Growth Mechanisms

• Collision-Coalescence

  • Warm clouds (tropics)

• Bergeron Process

  • Ice crystals grow at expense of water droplets

  • Common in mid-latitudes

Precipitation Types

• Rain, snow, sleet, freezing rain

• Depends on temperature profile

FOG TYPES

• Radiation fog → cooling at night

• Advection fog → warm air over cold surface

Unequal Heating

More solar energy at equator than poles → drives circulation

Three-Cell Model

1. Hadley Cell

2. Ferrel Cell

3. Polar Cell

ITCZ

• Rising air, storms, heavy rain near equator

Subtropical Highs

• Sinking air → deserts

Wind

• Trade winds (easterlies) → tropics

Westerlies → mid-latitudes

Jet Streams

• Fast winds caused by temperature gradients

Ocean Currents

• Move heat around planet

• Western sides → warm

• Eastern → cold

Density

• Controlled by:

  • Temperature

  • Salinity

• Cold + salty = densest

Thermohaline Circulation

• Deep ocean “conveyor belt”

• Important for climate

• Linked to abrupt climate shifts

AMOC

• Atlantic circulation system

• Weakening with climate change

SST & Rainfall

• Warmer water → more evaporation → more rain

El Niño

• Warm eastern Pacific

• Weak trade winds

• More global weather disruptions

La Niña

• Strong trade winds

• Cold eastern Pacific

Thermocline

• Boundary between warm & cold water

• Flattens (El Niño), steepens (La Niña)

Hurricanes

• Tropical low-pressure systems

• Called:

  • Hurricanes (Atlantic)

  • Typhoons (Pacific)

Hurricane Structure

• Eye → sinking air, calm

• Eyewall → strongest winds & rain

• Rainbands → spirals outward

Hurricane Formation Requirements

• Warm water (>26.5°C)

• Moist air

• Low wind shear

• Coriolis force

➡ Don’t form at equator (no Coriolis)

Hurricane Strengthening

Heat release from condensation

Hurricane Weakening

• Landfall → loses moisture source

• Friction increases

Saffir-Simpson Scale

• Based on wind speed

• Cat 1 < Cat 3 < Cat 5 (most destructive)

Climate Change & Hurricanes

• Stronger storms, more rainfall

• Frequency less clear

Hurricane Steering

Controlled by large-scale winds (trade winds, westerlies)