Meteorology Lec 2b - Energy in the Atmosphere

Reasons for Seasons

Determined by sunlight angle and daylight duration at Earth's surface

Sunlight Angle

Affects solar energy intensity; more direct rays

more concentrated energy

Daylight Duration

Longer daylight hours

more solar energy absorption

Summer Solstice

June 21; longest day in Northern Hemisphere; sun at highest point

Winter Solstice

December 21; shortest day in Northern Hemisphere; sun at lowest point

Equinoxes

March 20 & September 22; equal day/night globally (except poles)

Arctic Circle

66.5°N latitude; experiences 24-hour daylight in summer

Midnight Sun

Continuous daylight in polar regions during summer months

Geometric Sunrise/Sunset

When sun's center is at 0° elevation angle

Apparent Sunrise/Sunset

When sun's top appears at horizon due to atmospheric refraction

Twilight

Period of scattered light before sunrise/after sunset

Daytime Warming

Ground heats first, then transfers heat to air via conduction

Thermals

Rising pockets of warm air that distribute heat vertically

Temperature Lag

Peak temperature occurs 3-5PM due to energy balance delay

Nighttime Cooling

Radiational cooling of ground and adjacent air layers

Radiation Inversion

Temperature increases with height at night due to surface cooling

Daily Temperature Range

Difference between max/min daily temperatures

Cloud Effect

Reduces daily temperature range by trapping infrared radiation

Urban Heat Island

Cities have smaller temp ranges due to heat retention by structures

Controls of Temperature

Latitude, land/water distribution, ocean currents, elevation

Isotherms

Lines connecting points of equal temperature on maps

Mean Daily Temperature

Average of highest/lowest temps in 24 hours

Normal Temperature

30-year average for a specific date

Annual Temperature Range

Difference between warmest/coldest monthly averages

Wind-Chill Index

Measures how cold wind makes the body feel

Liquid-in-Glass Thermometer

Uses mercury/alcohol expansion to measure temperature

Maximum Thermometer

Records highest daily temp via constriction in glass tube

Minimum Thermometer

Records lowest daily temp using alcohol and index marker

Thermistor

Ceramic sensor whose resistance changes with temperature

Thermocouple

Measures temperature via electrical current between two metals

Bimetallic Thermometer

Uses brass/iron strip bending to indicate temperature

Radiometer

Measures radiant energy intensity/wavelengths remotel