Satellite Image BasicsSatellite Image Basics

Visible: Senses reflected solar (lunar) radiation: Senses reflected solar (lunar) radiation– Cloud thickness, texture; not useful at nightCloud thickness, texture; not useful at night

Infrared (IR): Senses IR radiation emitted by earth (IR): Senses IR radiation emitted by earth and atmosphereand atmosphere– Cloud-top temperature and thus heightCloud-top temperature and thus height

Water Vapor: Senses radiation emitted by water : Senses radiation emitted by water vapor (6.7 micron wavelength)vapor (6.7 micron wavelength)– Tracks atmospheric motion even when no cloudsTracks atmospheric motion even when no clouds

Atmospheric AbsorptionAtmospheric Absorption

High-energy (U-V) radiation (U-V) radiation Lower-energy (IR) radiation (IR) radiation

– Greenhouse gasesGreenhouse gases– Keep planet 60F warmer than withoutKeep planet 60F warmer than without– ENHANCED GREENHOUSE EFFECTENHANCED GREENHOUSE EFFECT

Total Atmosphere– Visible radiation poorly absorbedVisible radiation poorly absorbed

Distribution of Solar RadiationDistribution of Solar Radiation

Total entering top of Total entering top of atmosphere 100%atmosphere 100%– < one billionth of the sun’s < one billionth of the sun’s

energyenergy

Reflected = 30% (Albedo Reflected = 30% (Albedo of earth = 0.3)of earth = 0.3)

Absorbed by Absorbed by atmosphere = 19%atmosphere = 19%

Absorbed at earth’s Absorbed at earth’s surface = 51%surface = 51%

THE SUN WARMS THE THE SUN WARMS THE GROUND AND THE GROUND GROUND AND THE GROUND

WARMS THE AIR!!!WARMS THE AIR!!!

ConductionConduction Convection (hot Convection (hot

air rises)air rises) Vertical Vertical

temperature temperature structurestructure

ElevationElevation

Temperature VariationTemperature Variation

Seasonal (tilt of Seasonal (tilt of earth’s axis)earth’s axis)

DiurnalDiurnal Effect of clouds on Effect of clouds on

diurnal cyclediurnal cycle– Decrease daytime Decrease daytime

temperaturetemperature– Increase nighttime Increase nighttime

temperaturetemperature all else being equal!all else being equal!

Seasonal Temperature LagSeasonal Temperature Lag

Delay between maximum (minimum) solar Delay between maximum (minimum) solar input and maximum (min) temperatureinput and maximum (min) temperature– Just like pizza in the ovenJust like pizza in the oven

Heat Capacity of water is 3 times that of Heat Capacity of water is 3 times that of landland– Sunlight penetrates waterSunlight penetrates water– Constant mixing (waves, currents)Constant mixing (waves, currents)– Maritime locations generally have larger lag Maritime locations generally have larger lag

timetime

Key FiguresKey Figures

2.9, 2.10, 2.13, 2.19, 2.20, 3.2, 5.8, 5.14, 2.9, 2.10, 2.13, 2.19, 2.20, 3.2, 5.8, 5.14, 5.205.20