Meteorology Lecture 1 Weather and Climate Review

What drives our weather? The sun Insolation – solar energy reaching the Earth Remember the sun’s output can vary, which impacts weather on Earth –e.g. The Little Ice Age

Folklore: Sirius – The Dog Star Thought to produce heat at the end of summer Worshipped by numerous civilizations The “Dog Days of Summer” Sirius Sun

What about the Moon? Does it warm the Earth? Why does it glow? Albedo – % of insolation an object reflects High – light surfaces Low – dark surfaces

Solar Radiation and Earth’s Surface

Why do we have seasons?

Sun conditions at the Solstices and Equinoxes

atitudinal change ofsubsolar points  Solar declination: latitudinal change of subsolar points

Energy Pathways Figure 4.1

Heat Transfer Heat – energy produced by the motion of molecules and atoms in a substance 4 ways to transfer heat: 1. Radiation – electromagnetic waves (sunlight) 2. Conduction – energy moved from high to low 3. Convection – vertical movement of energy 4. Advection – horizontal movement of energy

Earth’s Modern Atmosphere The atmosphere is absolutely essential for life on Earth Earth’s atmosphere exists in a series of spheres or layers that grade into one another Layers: Composition, temperature, and function

Protective Atmosphere Figure 3.6

Energy Balance in the Troposphere Greenhouse Effect – where gases (carbon dioxide, water vapor, methane, nitrous oxide, and CFCs) absorb insolation and reradiate it back to Earth in longer wavelengths thereby warming the lower troposphere The Greenhouse Effect and Atmospheric Warming –Atmosphere absorbs heat energy –Atmosphere delays transfer of heat from Earth into space

Local Factors Influencing Air Temperature Urban Effect –Urban Heat Island Darker surfaces – less reflection Less forest cover Less water on surface Heat from human energy use

The Urban Environment Figure 4.21

Urban Heat Island Figure 4.22

Global NET R Surfaces lose heat in one of 3 ways: –Latent heat of evaporation – energy released as water changes state; can’t feel it –Sensible heat – heat you can feel and measure; convection and conduction –Ground heating and cooling – energy stored during warm periods and released during cool periods

Radiation Budgets Figure 4.20 El Mirage, CA Pitt Meadows, BC

Principal Temperature Controls Latitude Altitude Cloud Cover Land-Water Heating Differences

Latitude and Temperature Figure 5.4 Latitude –Affects insolation –Sun angles –Daylength

Altitude Figure 5.5 Altitude –High altitude has greater daily range –High altitude has lower annual average

Cloud Cover

Land–Water Heating Differences Evaporation (= latent heat) Transparency (= penetration of insolation) Specific heat (differs among objects) Movement (= vertical mixing) Ocean currents and sea surface temperatures (= spread of energy spatially) All this leads to this important concept: Marine vs. continental effects

Land–Water Heating Differences Figure 5.7

Global Temperature Ranges Figure 5.17

Atmospheric Pressure Systems High-pressure system -also called anticyclone -circulating body of air -descending air -clockwise circulation in northern hemisphere Low-pressure system -also called cyclone -circulating body of air -rising air -counterclockwise circ. in northern hemisphere

Atmospheric Pressure Map Isobars – lines of equal air pressure on a map

Wind Direction Winds are named according to the direction FROM which they are blowing

Direction of Air Flow Unequal heating of land surfaces Pressure gradient force – air flows from high to low Coriolis force – deflection or change in direction caused by Earth’s rotation Frictional forces – places a drag on that air flow

Pressure Gradient Force Fluctuations in the Pressure Gradient High pressure to low pressure, perpendicular to isobars

Coriolis Force Due to Earth’s rotation Pulls wind to right in northern hemisphere Pulls wind to left in southern hemisphere Strongest at poles None at equator Coriolis Force

Frictional Forces Near surface, friction (f) works against pressure gradient force (pgf), so resulting wind direction is between pressure gradient force and coriolis force (cf) pgf f cf – northern hemisphere WIND

Three Forces Combined

Rossby Waves Figure 6.17

 Strong boundaries often occur between warm and cold air. In the mid-latitudes, the polar front marks this thermal discontinuity at the surface. The Polar Front and Jet Streams

Relative Humidity Relative humidity is the indication of how close the air is to saturation and when condensation will begin Dew-point temperature not really a temperature, but a measure of moisture content When air temperature tries to decrease below the dew point, surplus water vapor is removed from the air by condensation

Relative Humidity Figure 7.8 Cooling Warming Actual water vapor

Hydrologic Cycle