Meteorolojik Uzaktan Algılamaya Giriş

Erdem ErdiUzaktan Algılama Şube Müdürlüğü

7-8 Mayıs 2012, İzmir

Outline

Visible: RGB, Radiance and Reflectance

Near Infrared: Absorption

Infrared: Radiance and Brightness Temperature

Sensor Geometry

Sensor

Optics

Electronics

Terminology of radiant energy

Energy from the Earth Atmosphere

Flux

over time is

which strikes the detector area

Irradiance

at a given wavelength interval

MonochromaticIrradiance

over a solid angle on the Earth

Radiance observed by satellite radiometer

is described by

can be inverted to

The Planck function

Brightness temperature

Definitions of Radiation__________________________________________________________________

QUANTITY SYMBOL UNITS__________________________________________________________________

Energy dQ Joules

Flux dQ/dt Joules/sec = Watts

Irradiance dQ/dt/dA Watts/meter2

Monochromatic dQ/dt/dA/d W/m2/micron Irradiance

or

dQ/dt/dA/d W/m2/cm-1

Radiance dQ/dt/dA/d/d W/m2/micron/ster

or

dQ/dt/dA/d/d W/m2/cm-1/ster__________________________________________________________________

All MSG channels• Channel 01: VIS 0.6 • Channel 02: VIS 0.8 • Channel 03: NIR 1.6 Channel 04: MIR 3.9 Channel 05 WV 6.2 Channel 06: WV 7.3 Channel 07: IR 8.7 Channel 08: IR 9.7 („Ozon“) Channel 09: IR 10.8 Channel 10: IR 12.0 Channel 11: IR 13.4 („CO2“) Chanell 12: HRV (High Resolution Visible)

Visible(Reflective Bands)

Infrared(Emissive Bands)

Visible: Reflective Bands

Used to observe solar energy reflected by the Earth system in the:

• Visible between .4 and .7 µm • NIR between .7 and 3 µm

About 99% of the energy observed between 0 and 4 µm is solar reflected energy

Only 1% is observed above 4 µm

Sun radiation Earth radiation

Ch01: 0.6 Ch02: 0.8 Ch03: 1.6

Wavelength (micron)

Ozone

Watervapour

Carbondioxid

Watt/m2 andmicron

Comparison of radiation sources sun - earth

For wave length < 5 m solar radiation is dominant For wave length > 5 m radiation of earth is dominant

only VIS

VIS +IR

only IR

• Ch01, 02, 03, 12: only sun radiation • Ch04: both: radiation from sun and earth • Ch 05, 06, 07, 08, 09, 10, 11: only thermal earth radiation

Sun radiation Earth radiation

Watt/m2

andmicron

Reflectance To properly compare different reflective channels we need

to convert observed radiance into a target physical property

In the visible and near infrared this is done through the ratio of the observed radiance divided by the incoming energy at the top of the atmosphere

The physical quantity is the Reflectance i.e. the fraction of solar energy reflected by the observed target

Soil

Vegetation

Snow

Ocean

VIS 0.6 and VIS 0.8: land surface In VIS 08 better recognition of

surface structures because of higher reflectance of soil and leafs

0.6 0.8

Ch01: 0.6

Ch02: 0.8

NIR 1.6: cloud Different appearance of ice - and waterclouds because of

stronger absorption in the icephase Waterclouds: white Iceclouds: black

icecloud

watercloud

0.6 0.8 1.6

Snow/Ice: low reflectivity

Cloud: high reflectivity

After source: EUMETSAT

Different Reflectivity of Ice/snow and Watercloud in 1.6

0.6 0.8 1.6

Big difference between snow/ice and water clouds

No difference between snow/ice and water clouds

After source: EUMETSAT

Different Reflectivity of Ice/snow versus Watercloud in 0,6, 0,8 and 1.6

?? ??

??

??

cloud

snow

earth

0.6

?? ??

??

??

cloud

snow

earth

0.8

cloud

snow

earth

1.6

Ch01:0.6

Only signals fromreflected solar radiation

Different greyshades:different reflectivity;earth: dark

Ch02:0.8

Only signals fromreflected solar radiation

Different greyshades:different reflectivity;earth: grey;higher reflectance ofearth surface than in 0.6

Transparent clouds:

Band 201.38 micron

Channel 12

HRV

Solar energy spectrum

27

Land Surface Channel 01 (VIS0.6) Clouds High reflectanceHigh reflectance

Very thick clouds

Very thin clouds over land

Very thin clouds over ocean

Low reflectanceLow reflectance

Sun GlintSnow

Desert

Bare Soil

Forest

Ocean, Sea

31 October 2003, 11:30 UTC

28

Land Surface Channel 02 (VIS0.8) Clouds

Sun GlintSnow

Desert

Gras, Rice fields

Forest

Bare Soil

Ocean, Sea

31 October 2003, 11:30 UTC

High reflectanceHigh reflectance

Very thick clouds

Very thin clouds over land

Very thin clouds over ocean

Low reflectanceLow reflectance

29

Land Surface Channel 03 (NIR1.6) Clouds High reflectanceHigh reflectance

Water clouds with small droplets

Water clouds with large droplets

Ice clouds with small particles

Ice clouds with large particles

Low reflectanceLow reflectance

Sun Glint Sand Desert

Gras, Rice fields

Forest

Bare Soil

SnowOcean, Sea

31 October 2003, 11:30 UTC

30

Land Surface Channel 12 (HRVIS) Clouds

31 October 2003, 11:30 UTC

Sun GlintSnow

Desert

Bare Soil

Forest

Ocean, Sea

High reflectanceHigh reflectance

Very thick clouds

Very thin clouds over land

Very thin clouds over ocean

Low reflectanceLow reflectance

Cb clouds over Nigeria as seen in the high-res. visible channelMSG-1, 24 April 2003, 08:00 UTC

Visible 0.6 m High-res. Visible

Cirrus clouds over the Algerian desert as seen in the high-res. visible channelMSG-1, 9 May 2003, 14:00 UTC

Visible 0.6 m High-res. Visible

Von Karman Vortex Streets as seen in the high-res. visible channelMSG-1, 6 June 2003, 09:00 UTC

Visible 0.8 m High-res. Visible

MSG-18 September 200315:00 UTCRGB CompositeR = HRVG = HRVB = IR10.8i

Thin CirrusCirrus Outflow

Overshooting Top

Low-Level CloudsMonitoring of

Fine-Scale Structures with the

HRV Channel

Niger

MSG-15 June 200314:45 UTCRGB CompositeR = HRVG = HRVB = IR10.8i

Monitoring of Fine-Scale

Structures with the HRV ChannelThick Cb Cloud

Thin Cirrus Anvil

Visible(Reflective Bands)

Infrared(Emissive Bands)

Emissive Bands

Used to observe terrestrial energy emitted by the Earth system in the IR between 4 and 15 µm

• About 99% of the energy observed in this range is emitted by the Earth

• Only 1% is observed below 4 µm• At 4 µm the solar reflected energy can significantly affect

the observations of the Earth emitted energy

Spectral Characteristics of Energy Sources and Sensing Systems

IR

4 µm11 µm

Brightness Temperature To properly compare different emissive channels

we need to convert observed radiance into a target physical property

In the Infrared this is done through the Planck function

The physical quantity is the Brightness Temperature i.e. the Temperature of a black body emitting the observed radiance

All MSG channels Channel 01: VIS 0.6 Channel 02: VIS 0.8 Channel 03: NIR 1.6 Channel 04: MIR 3.9 Channel 05 WV 6.2 Channel 06: WV 7.3 • Channel 07: IR 8.7 Channel 08: IR 9.7 („Ozon“)• Channel 09: IR 10.8 • Channel 10: IR 12.0 Channel 11: IR 13.4 („CO2“) Chanell 12: HRV (High Resolution Visible)

42

Land Surface Channel 04 (IR3.9) Clouds Daytime

High reflectance / High reflectance / WarmWarm

Low-level Water Clouds (land)

Low-level Water Clouds (sea)

Cold Ice Clouds (small particles)

Cold Ice Clouds (large particles)

Low Reflectance / Low Reflectance / ColdCold

Sun Glint Fires

Hot Sand Desert

Warm Tropical Areas

Cold Land

Ocean, Sea

Cold Snow

31 October 2003, 11:30 UTC

43

Land Surface Channel 04 (IR3.9) Clouds Nighttime

WarmWarm

Low-level Clouds

Mid-level Clouds

High-level Clouds

ColdCold

Fires

Warm Surfaces (tropical oceans,

seas, lakes)

Cold Surfaces (arctic ice areas)

29 October 2003, 02:00 UTC

44

Water Vapour Channel 05 (WV6.2) Clouds WarmWarm

High-level Clouds

ColdCold

Low UTH

High UTH

31 October 2003, 11:30 UTC

45

Water Vapour Channel 06 (WV7.3) Clouds WarmWarm

Mid-level Clouds

High-level Clouds

ColdCold

Low MTH

High MTH

(High-level warm surfaces)

31 October 2003, 11:30 UTC

46

Land Surface Channel 07 (IR8.7) Clouds WarmWarm

Low-level Clouds

Mid-level Clouds

High-level Clouds

ColdCold31 October 2003, 11:30 UTC

Hot Land Surf.

Warm Sea Surf. (tropical oceans,

seas, lakes)

Cold Land Surf. (arctic ice areas)

47

Land Surface Channel 08 (IR9.7) Clouds WarmWarm

Low-level Clouds

Mid-level Clouds

High-level Clouds

ColdCold31 October 2003, 11:30 UTC

Hot Land Surf.

Warm Sea Surf. (tropical oceans,

seas, lakes)

(Areas of high IPV)

Cold Land Surf. (arctic ice areas)

48

Land Surface Channel 09 (IR10.8) Clouds WarmWarm

Low-level Clouds

Mid-level Clouds

High-level Clouds

ColdCold31 October 2003, 11:30 UTC

Hot Land Surf.

Warm Sea Surf. (tropical oceans,

seas, lakes)

Cold Land Surf. (arctic ice areas)

49

Land Surface Channel 10 (IR12.0) Clouds WarmWarm

Low-level Clouds

Mid-level Clouds

High-level Clouds

ColdCold31 October 2003, 11:30 UTC

Hot Land Surf.

Warm Sea Surf. (tropical oceans,

seas, lakes)

Cold Land Surf. (arctic ice areas)

50

Land Surface Channel 11 (IR13.4) Clouds WarmWarm

Low-level Clouds

Mid-level Clouds

High-level Clouds

ColdCold31 October 2003, 11:30 UTC

Hot Land Surf.

Warm Sea Surf. (tropical oceans,

seas, lakes)

Cold Land Surf. (arctic ice areas)

Conclusions• Radiance is the Energy Flux (emitted and/or reflected by

the Earth) which strikes the Detector Area at a given Spectral Wavelength (wavenumber) over a Solid Angle on the Earth;

• Reflectance is the fraction of solar energy reflected to space by the target;

Given an observed radiance, the Brightness Temperature is the temperature, in Kelvin, of a blackbody that emits the observed radiance;

Knowing the spectral reflective (Vis) and emissive (IR) properties (spectral signatures) of different targets it is possible to detect: clouds, cloud properties, vegetation, fires, ice and snow, ocean color, land and ocean surface temperature ……