microwave emission signature of snow-covered lake ice
DESCRIPTION
Microwave Emission Signature of Snow-Covered Lake Ice. Martti Hallikainen (1) , Pauli Sievinen (1) , Jaakko Seppänen (1 ) , Matti Vaaja (1) , Annakaisa von Lerber (1) , Erkka Rouhe (1) , Juha Lemmetyinen (2) (1) Aalto University School of Electrical Engineering - PowerPoint PPT PresentationTRANSCRIPT
Microwave Emission Signature of Snow-Covered Lake Ice
Martti Hallikainen(1), Pauli Sievinen(1), Jaakko Seppänen(1), Matti Vaaja(1), Annakaisa von Lerber(1), Erkka Rouhe(1), Juha Lemmetyinen(2)
(1)Aalto University School of Electrical Engineering(2)Finnish Meteorological Institute
International Geoscience and Remote Sensing Symposium 2011
IGARSS 2011
Test site and data collection
Experimental data:
- Brightness temperature (TB) values
- TB differences between selected frequencies
- TB differences between vertical and horizontal polarization
Conclusions
Contents
IGARSS 2011
• Located in the Greater Helsinki area not far from Airport
• Lake Bodom (larger) and Matalajärvi (smaller and shallow; freezes earlier)
• Data over land collected in order to compare results for snow-covered ice vs. snow-covered terrain
• Scale: lower left
Test Site
HUTRAD Non-Scanning Radiometer HUT-2D Interferometer6.8, 10.65, 18.7, 23.8, 36.5 and 94 GHz 1.4 GHz dual-pol 50 deg off nadir, V and H polarization Data averaged over theAntenna beam 3.2 to 5 deg 0 to 5 deg range
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Airborne Radiometers
• Flight altitude: 300 m
and 150 m• 5 overpasses at
each altitude• Accurate localization
of footprint using aircraft attitude and position
• Averaged brightness temperatures used in this presentation
Airborne Data Collection
Data collection
Off Track Error: Mostly Below 20 m
2004: April 72007: January 30, March 20, March 26, April 22011: January 27, February 28, March 31 (am/pm), April 14Data include dry snow conditions and snow/ice melting period
Data collected with HUTRAD radiometer (6.8 to 36.5 / 94 GHz)April 14, 2011 data collected with HUTRAD and HUT-2D (1.4 GHz)
Results from 2011 flights discussed in this presentation
Airborne Data
• Snow temperature profile• Snow density profile• Snow wetness profile• Snow depth• Ice thickness• Presence of water on ice
• These data collected every 100 m (except April 14, 2011)
• Additionally, snow grain size in selected locations
In Situ Data
Example of In Situ Data: Temperature
open/field 9:30
Matalajärvi 11:15
open 12:00
forest 12:15
Bodom 12:35
Bodom 13:10
Bodom 13:30
Bodom 13:50
Bodom 14:08
Bodom 14:26
Bodom 14:40
Bodom 15:02
Bodom 15:20
-18.0
-16.0
-14.0
-12.0
-10.0
-8.0
-6.0
-4.0
-2.0
0.0
2.0
Air
Snow surf
50 cm
40 cm
30 cm
20 cm
10 (5) cm
0 cm
In Situ Data: Snow-Ice Structure
Brightness temperatures at 6.8, 10.65, 18.7 and 36.5 GHz (April 14: also 1.4 GHz) (18.7 GHz: occasional interference) Horizontal polarization (V-pol not shown)
TB differences between 18.7 / 36.5 GHz, and 6.8 / 36.5 GHz
TB differences between vertical and horizontal polarization at each frequency (except 1.4 GHz)
Results from Radiometer Measurements
Lake Bodom: Some slush below snow layer =>TB36 higher than on Lake Matalajärvi
Jan 27, 2011, H-Pol, Alt 300 m
Mostly dry snow / iceOccasional water => TB6 is low
Feb 28, 2011, H-Pol, Alt 300 m
Dry refrozen snow on top of ice => TB36 is low
March 31 AM, 2011, H-Pol, Alt 300 m
Snow top layer getting moist => TB36 higher, but TB6 ~same as AM
March 31 PM, 2011, H-Pol, Alt 300 m
Practically no snow on top of wet slushy ice layer1.4 GHz: TB higher for Lake Matalajärvi (no in situ data available)
April 14, 2011, H-Pol, Alt 300 m
Brightness temperature for Lake Matalajärvi is higher than that for Lake Bodom
HUT-2D Image on April 14, 2011
Jan 27, 2011, TBH:18-36 and 6-36, Alt 300 m
Feb 28, 2011, TBH: 18-36 and 6-36, Alt 300 m m
Dry refrozen snow on top of ice => low TB36 values make TB18–TB36 high
March 31, 2011 AM, TBH: 18-36 and 6-36, Alt 300 m
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March 31, 2011 PM, TBH: 18-36 and 6-36, Alt 300 m
Jan 27, 2011, V-H, Alt 300 m
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Feb 28, 2011, V-H, Alt 300 m
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March 31 AM, 2011, V-H, Alt 300 m
March 31 PM, 2011, V-H, Alt 300 m
April 14, 2011, V-H, Alt 300 m
An extensive range of frequencies was used for lake ice observations
36.5 GHz provides information on dry snow, whereas low frequency penetration provides information on water at snow/ice interface
Observed brightness temperature variation is substantial within Lake Bodom due to occasional presence of water on top of ice
Brightness temperature for adjacent Lake Matalajärvi is different from that for Lake Bodom, obviously due to being shallow
Conclusions
IGARSS 2011