Weather and Climate Introduction

Introduction to Weather and Climate

• Weather refers to short-term atmospheric conditions at a specific place, which can change daily
• Climate refers to long-term atmospheric conditions, usually over 30-35 years, and remains largely unchanging
• Six key elements of weather: temperature, pressure, winds, relative humidity, clouds, and precipitation (rainfall)

Structure of the Atmosphere

• The atmosphere is a layer of air surrounding Earth, containing gases, water vapor, and dust
• The atmosphere is divided into four layers based on temperature
• The troposphere is the lowest layer, holding 80% of the atmosphere's mass, and where all weather occurs
• Temperature in the troposphere decreases with altitude by about 6.5°C per kilometer
• The stratosphere lies beyond the troposphere, containing roughly 19.9% of the atmosphere's mass
• The mesosphere and thermosphere exist beyond the stratosphere
• The thermosphere has no defined upper limit
• The stratosphere contains ozone and protects from ultraviolet radiation

Earth's Energy Budget

• The Earth's energy budget is the balance between incoming solar radiation (insolation/shortwave radiation) and outgoing terrestrial radiation (longwave radiation/"heat")
• This system is constantly working to maintain balance
• Imbalances caused by natural phenomena or human activities adjust the Earth's temperature to restore a balance
• Approximately 30% of insolation is reflected by clouds, atmospheric molecules, and the Earth's surface (albedo)
• Around 19% of insolation is absorbed by the atmosphere and clouds
• Only about 51% of solar radiation gets absorbed by Earth's surface
• Solar radiation absorbed is converted and released as longwave outgoing terrestrial radiation (heat), influencing the temperature
• In a typical year, radiation received equals radiation lost around 38° N and S latitudes
• Polar latitudes lose more radiation than they gain, while tropical latitudes gain more than they lose
• The Earth's total energy budget balances, keeping the Earth in thermal equilibrium

Temperature Factors: Latitude

• Temperature indicates hotness or coldness, with highs above 20°C and lows below 10°C

• Small diurnal temperature range: below 10°C

• Large diurnal temperature range: above 15°C

• Spatial variation in mean annual temperature due to differences in insolation received at different locations

• On a global scale, latitude significantly impacts insolation and absorption due to differences in the angle of incidence

• Angle of incidence accounts for different amounts of insolation received

• At the topics, insolation strikes at a higher angle, leading to less beam spreading

• Higher concentration of insolation leads to higher tempatures for a higher angle of incidence

• Increasing latitude decreases the angle, causing less solar radiation due to curvature

• Lower angle of incidence at the poles causes more beam spreading

• More distribution of insolation decreases radiation per unit area and temperature

• Varying latitudinal atmosphere penetration affect insolation

• More atmopshere to pass through near poles due to ow angle of incidence causes less insolation at the surface

• More radiation is absorbed, scattered, or reflected by atmosphere, resulting in less insolation received at the poles

Factors: Temporal Tempature Variation, Altitude

• Seasonal shifts can cause high and low temperatures with annual ranges between 15-30°C

• Earth's 23.5° tilt and revolution are responsible for these occurances

• Earth's axis is tilted 23.5° towards the sun on June 21 or 22

• Subsolar point, where sunlight strikes the surface at a right angle, reaches 23.5°N at the Tropic of Cancer marking June Solstice

• Only Tropic of Cancer locations experience a 90° angle of incidence due to Earth's shape

• The north experiences summer for June Solstice, while south is in the winter

• Subsolar point migrates to 23.5°S at Tropic of Capricorn on December 21 or 22 for the December Solstice

• In this configuration, the north will experience winter while southern hemisphere will enter the summer

• Equinoxes occur between solstices

• Subsolar point reaches the equator 0 degree latitude

Altitude

• Altitude has a negative correlation to temperature with troposphere drop of 6.5°C per kilometer
• As temperature increases, altitude mainly because the atmosphere absorbs sun radiation from Earth
• Reflection, scattering, and absorption of insolation by means only half is absorbed by Earth's sphere
• Ground absorbs insolation, warms, and emits longwave radiation, which heats the atmosphere
• Low troposphere is warmed as it is closer to Earth
• Temperature decreases with less atmospheric density, at high altitudes
• Terrestrial Earth radiation is absorbed by water vapor and carbon dioxide
• As shown in Figure 7, less dense are at smaller concentration of gases and vapor and cant retain heat as effectively

Distance from the Sea

• Specific heat capacity is the heat to raise 1kg of substance to 1C, water is much higher than land
• This means that the ocean effect on summer and winter tempatures means that water gains heat more slowly than land
• Maritime and continiental effect
• Maritime where coastal near seas experience smaller tempature range from cooler summers and warmer winters, sea gets less heated or cooled due to position
• The sea affect is more observable in temperate
• Continental effect in inland areas is more extreme in contrast
• Areas are not effected by the sea so extreme tempatures

Cloud Cover and Albedo effects

• Cloud cover is the extent of the sky covered by clouds

• Cloud cover density varies globally according to latitude as shown in Figure 9

• Where cloud density is higher tempature range is smaller

• Rainforest areas may be lower then 10C because amount of insolation decreases

• As the effect with cloud as blanked and absorbs heat toward, the ground heat increase over night

• The absense of clouds with high insolation in ground level at maximum day time. Desert can show up high 40C day time while tempature decrease at freezing level at night

• Albedo is the reffectivity of a surface. Some radiation reflected will be considered high and dark will be considered low Albedo

• Brighter will contain higher Albedo and less energy

• Dark objects will contain lower Albedo for high road effect

Factors: Air Pressure and Winds, Moving Air

• Pressure gradient force and coriolois affect air movement