Microwave Radiation Characteristics of Glacial Ice Observed by AMSR-E

Hyangsun Han and Hoonyol Lee

Kangwon National University, KOREA

Contents

Introduction

Study Area and Data

Method

Radiation Characteristics of Glacial Ice

Conclusion

Introduction

Glacial IceOriginated from fresh water (snow)Glaciers, Icebergs, Ice sheets, and Ice shelvesAir bubbles are small enough to cause Rayleigh scatteringCrystal size is very large because of slow recrystallizationThe GLACIAL ICE has different radiation characteristics from SEA ICE frozen from salty water

Importance of glacial ice studyGlacial ice changes coastal landform and environment of sea ice formation

Introduction

Passive Microwave Sensorwidely used to study the polar ice

- sea ice concentration, snow depth, ice extent, …high temporal resolution, low spatial resolutionAMSR-E is a typical passive microwave sensor

Objective of studyEvaluation of accuracy of glacial ice on AMSR-E sea ice concentration in George V Coast, Southern AntarcticaAnalysis of microwave radiation characteristics of glacial ice

Study Area

Radarsat-1 mosaic image of the Antarctic

George V CoastSouthern Antarctica

ASAR Data and AMSR-E NT2 SIC Data

SIC

100%

50%

Ice sheet masked in AMSR-E NT2

SIC

Two ENVISAT ASAR Images

Wide Swath SLC/HH polarization2006/04/20, 2006/04/26

AMSR-E L1 data products

Brightness temperature, sea ice concentration 2006/04/20, 2006/04/26

ENVISAT ASAR image of the study area (2006/04/26, 100 km×100 km)

AMSR-E sea ice concentration of the study area (2006/04/26, 100 km×100 km)

Ice sheet

Identification of Ice Type in ASAR

Most sea surface was covered with ice

Several icebergs

A ice tongue

Distinction between sea ice and ice shelf is difficult by only ASAR data

Ice sheet

Icebergs

Ice tongue

Sea ice Sea ice (new ice)

ENVISAT ASAR image of the study area (2006/04/26, 100 km×100 km)

2006/04/29 2006/02/19 2005/12/17

2005/02/02 2004/03/08 2003/02/23

MODIS Imagery

MODIS time-series images

- A region of ice shelf is confirmed

Comparing ASAR SIC with AMSR-E SIC

SIC

100%

50%

Ice sheet masked in AMSR-E NT2

SIC

Ice shelf

IcebergsSea ice

Sea ice

Ice shelf

IcebergsSea ice

Sea ice

Ice sheet

ASAR Ice Concentration

Masking inland in ASAR images using land mask product of AMSR-E

Classifying ice type into sea ice, icebergs, and ice shelf by supervised classification and digitizing

Overall accuracy: 97.4% and 94.4% in each ASAR image

Calculating ice concentration of sea ice, icebergs, and ice shelf

Comparing with AMSR-E sea ice concentration

AMSR-E Sea Ice Algorithm

AMSR-E6.9, 10.7, 18.7, 23.8, 36.5, and 89.0 GHz dual polarized channels Daily sea ice concentration with 12.5 km spatial resolution by using NASA Team2 Algorithm

NASA Team2 AlgorithmBetter spatial resolution and accuracy of sea ice concentration than NASA Team Algorithm Identifies Ice type A, B, C, and open water by data plotting in PR and GR domain

, ,

, ,B B

B B

T V T HPR

T V T H

1 21 2

1 2

, ,

, ,B B

B B

T p T pGR p p

T p T p

(Cavalieri et al., 1997)

Comparing ASAR SIC with AMSR-E SIC

Difference between ASAR and AMSR-E SICSea ice: very small difference (RMSE 1.4%)Icebergs: AMSR-E NT2 SIC was underestimated (RMSE 29.5%)Ice shelf: AMSR-E NT2 SIC was underestimated (RMSE 23.3%) → analysis of microwave radiation characteristics of the glacial ice in PR and GR domain is needed

PR(18)-GR(37V18V) Scattergram

Sea ice Icebergs Ice shelf

PR(18) 0.047 0.086 0.064

GR(37V18V) 0.006 0.024 0.027

GR(89H18H)-GR(89V18V) Scattergram

Sea ice Icebergs Ice shelf

GR(89H18H) 0.048 0.117 0.124

GR(89V18V) 0.021 0.067 0.083

Ice type A-B line

100% Ice type A

100% Ice type B

Open water

100% Ice type C

Conclusions

We evaluated AMSR-E NASA Team2 sea ice concentration in Antarctic glacial ice region

AMSR-E NT2 algorithm is very accurate in sea ice region

We found that AMSR-E NASA Team2 algorithm underestimates ice concentration in icebergs and ice shelf

Glacial ice has higher PR(18), GR(37V18V), GR(89V18V), and GR(89H18H) than those of sea ice

Microwave radiation characteristics of glacial ice are quite different from that of sea ice and open water

Ongoing Study

Analysis of radiation characteristics of microwave from glacial ice in various seasons and regions

Improvement of the accuracy of AMSR-E NASA Team2 sea ice concentration by adding glacial ice concentration (GIC)

GIC can be used for- Improvement of land mask product from AMSR-E NASA Team2

algorithm- Icebergs tracking- Monitoring of coastal landform change by movement of glacial ice