CReSIS PolarGrid CI-TEAM for Remote Sensing of Ice Sheets Research Experience for Undergraduates
Sea ice remote sensing from space
description
Transcript of Sea ice remote sensing from space
![Page 1: Sea ice remote sensing from space](https://reader036.fdocuments.in/reader036/viewer/2022062519/56814f95550346895dbd5330/html5/thumbnails/1.jpg)
Sea ice remote sensing from space
Remote Sensing I
Lecture 10
Summer 2006
![Page 2: Sea ice remote sensing from space](https://reader036.fdocuments.in/reader036/viewer/2022062519/56814f95550346895dbd5330/html5/thumbnails/2.jpg)
Sea ice remote sensing from space
• Optical (e.g. MODIS)– High resolution (about 100 meters)– Can‘t „see“ through clouds; difficult to distinguish
clouds and sea ice• Passive Microwave
– Can differentiate between open water, first year and multiyear ice
– Can „see“ through clouds– Low spatial resolution (several km)
• Radar– Can look through clouds– High spatial resolution (< 1km)– Images difficult to interprete
![Page 3: Sea ice remote sensing from space](https://reader036.fdocuments.in/reader036/viewer/2022062519/56814f95550346895dbd5330/html5/thumbnails/3.jpg)
MODIS - Antarctica 21 March 2005
![Page 4: Sea ice remote sensing from space](https://reader036.fdocuments.in/reader036/viewer/2022062519/56814f95550346895dbd5330/html5/thumbnails/4.jpg)
Radar Image
ENVISAT ASAR
15 April 2005
![Page 5: Sea ice remote sensing from space](https://reader036.fdocuments.in/reader036/viewer/2022062519/56814f95550346895dbd5330/html5/thumbnails/5.jpg)
Sea ice concentration fromAMSR-E 89 GHz
09 July 2006
courtesy of Lars Kaleschke
www.seaice.de
![Page 6: Sea ice remote sensing from space](https://reader036.fdocuments.in/reader036/viewer/2022062519/56814f95550346895dbd5330/html5/thumbnails/6.jpg)
Sea ice concentration fromAMSR-E 89 GHz
23 April 2006
courtesy of Lars Kaleschke
![Page 7: Sea ice remote sensing from space](https://reader036.fdocuments.in/reader036/viewer/2022062519/56814f95550346895dbd5330/html5/thumbnails/7.jpg)
1. RADAR
![Page 8: Sea ice remote sensing from space](https://reader036.fdocuments.in/reader036/viewer/2022062519/56814f95550346895dbd5330/html5/thumbnails/8.jpg)
Real Aperture Radar
h
S
Opening angle β
Xa
Xr
Viewing angle θ
![Page 9: Sea ice remote sensing from space](https://reader036.fdocuments.in/reader036/viewer/2022062519/56814f95550346895dbd5330/html5/thumbnails/9.jpg)
Antenna beamwidth
D
The opening angle β (beamwidth) of an antenna with aperture Dat a wavelength of λ is given by:
The azimuth resolution for a real aperture radar is then
coscos D
hhX a
![Page 10: Sea ice remote sensing from space](https://reader036.fdocuments.in/reader036/viewer/2022062519/56814f95550346895dbd5330/html5/thumbnails/10.jpg)
Azimuth resolution fro real aperture radar
coscos D
hhX a
Example: h=800km, λ=23cm, D=12m then Xa=16km
This is a coarse resolution!
![Page 11: Sea ice remote sensing from space](https://reader036.fdocuments.in/reader036/viewer/2022062519/56814f95550346895dbd5330/html5/thumbnails/11.jpg)
Synthetic aperture radar: Schematic
L
L D
hL
2
Ground
Radar flight direction
![Page 12: Sea ice remote sensing from space](https://reader036.fdocuments.in/reader036/viewer/2022062519/56814f95550346895dbd5330/html5/thumbnails/12.jpg)
Synthetic aperture radar
D
hL
2
h
D
L 2SAR
2SARSAR,
DhX a
Ground „footprint“ L given by:
Individual measurements can be combined, corresponding to aMeasurement with a virtual or synthetic aperture of size L.
The resolution for such a synthetica aperture radar (SAR) is thengiven by:
![Page 13: Sea ice remote sensing from space](https://reader036.fdocuments.in/reader036/viewer/2022062519/56814f95550346895dbd5330/html5/thumbnails/13.jpg)
2. Passive Microwave Sensors
![Page 14: Sea ice remote sensing from space](https://reader036.fdocuments.in/reader036/viewer/2022062519/56814f95550346895dbd5330/html5/thumbnails/14.jpg)
Passive microwave remote sensing
![Page 15: Sea ice remote sensing from space](https://reader036.fdocuments.in/reader036/viewer/2022062519/56814f95550346895dbd5330/html5/thumbnails/15.jpg)
Emissivity of Sea Ice vs. Frequency
Frequency [GHz]
Em
issi
vity
Water
Multiyear Ice
First year Ice
Summer
![Page 16: Sea ice remote sensing from space](https://reader036.fdocuments.in/reader036/viewer/2022062519/56814f95550346895dbd5330/html5/thumbnails/16.jpg)
Polarization Ratio (PR) and Spectral Gradient (GR)
HTVT
HTVTPR
BB
BB
1919
1919
VTVT
VTVTGR
BB
BB
1937
1937
Clouds
![Page 17: Sea ice remote sensing from space](https://reader036.fdocuments.in/reader036/viewer/2022062519/56814f95550346895dbd5330/html5/thumbnails/17.jpg)
Sea ice concentration
1iceyear Multiiceyear First Open Water CCC
The sea ice surface concentration C can then be calculated from thecontributions of the three base points for open water, first year ice,and multi year ice.
The sum of the three concentrations must sum to unit:
![Page 18: Sea ice remote sensing from space](https://reader036.fdocuments.in/reader036/viewer/2022062519/56814f95550346895dbd5330/html5/thumbnails/18.jpg)
MODIS
645, 555, 469 nm
AMSR-E
89 GHz
courtesy of Lars Kaleschke
![Page 19: Sea ice remote sensing from space](https://reader036.fdocuments.in/reader036/viewer/2022062519/56814f95550346895dbd5330/html5/thumbnails/19.jpg)
Optical tick clouds are still transparent at 89 GHz
courtesy of Lars Kaleschke
![Page 20: Sea ice remote sensing from space](https://reader036.fdocuments.in/reader036/viewer/2022062519/56814f95550346895dbd5330/html5/thumbnails/20.jpg)
courtesy of Lars Kaleschke