Combined Enhanced Resolution Passive Microwave and ...

Combined Enhanced Resolution Passive Microwave and Scatterometer Sea Ice Fields Walt Meier and Julienne Stroeve AGU Fall Meeting, 10 December 2007

Enhanced Resolution Scatterometer Fields • NASA SeaWinds QuikScat (QS) Ku-band Two modes: ‘eggs’ and ‘slices’

• Scatterometer Image Reconstruction with Filter (SIRF) algorithm for resolution Developed at Brigham Young Univ. (BYU): Long et al., 1993; Remund and Long, 1999

‘Eggs’ – gridded resolution, 4.45 km ‘Slices’ – gridded resolution, 2.225 km Effective resolution, ~8-10 km 36-hour composite Arctic coverage, poleward of 60°N Using ice mask product

• Archived at BYU http://www.scp.byu.edu/

• Mirror site at NSIDC http://nsidc.org/data/scatterometry/ Meier and Stroeve, AGU Fall 2007 Meeting

Comparison with Standard Passive Microwave Products • NASA Team (NT) Algorithm Sea ice concentration 25 km gridded resolution Developed at NASA Goddard (Cavalieri et al.) SMMR-SSM/I, 1979Present Archived at NSIDC

• Comparison and evaluation with AVHRR: Meier and Stroeve, Ann. Glaciol., vol. 48, in press.

Meier and Stroeve, AGU Fall 2007 Meeting

Comparison with Standard Passive Microwave Products • Winter QS extent inside of NT

• Summer QS extent near NT QS does not capture open water areas within ice cover

QuikScat Extent NT Extent

1 Mar 2000 Meier and Stroeve, AGU Fall 2007 Meeting

1 Sep 2000

Comparison with Standard Passive Microwave Products • QS extent generally lower than NT, except: Antarctic spring & summer Sometimes during Arctic summer

• QS extent is noisier Plot uses 5-day running mean smoothing

• QS matches more closely with NT 30% concentration contour in winter, 15% contour in summer • Slice extent larger than egg Meier and Stroeve, AGU Fall 2007 Meeting

Evaluation of QS and PM ice edge with AVHRR • AVHRR vis/IR imagery 2.5 km gridded resolution From Danish Meteorol. Inst. Barents, Baffin, East Greenland regions Clear-sky scenes Manually-interpreted ice edge From Meier, 2005

• NT ice edge from 15% concentration contour • QS ice edge from QS ice edge product


Evaluation of QS and PM ice edge with AVHRR

Winter

Summer

Baffin

Barents

Greenland

Baffin

Barents

Greenland

Date

17 Dec

28 Feb

19 Mar

15 Jun

16 Jun

27 Jun

Edge

Diffuse

Compact

Diffuse

Compact

Compact

Diffuse

285

292

424

251

232

461

# pixels

Svalbard 28 Feb 2002

QS, NT ice edge errors (relative to AVHRR) strongly dependent on local conditions (e.g., diffuse vs. compact ice edge)

AV QS NT

NT15%

14.0

32.4

16.1

13.7

16.1

25.0

NT30%

19.9

30.0

14.3

20.4

12.0

18.6

Eggs

15.9

27.7

24.6

7.9

10.4

32.0

Slices

14.2

31.5

20.5

13.0

11.4

29.4

Standard Deviation of Difference (km) NT15%

6.8

25.0

10.3

6.0

7.0

16.0

NT30%

9.1

17.8

7.8

8.5

5.4

9.8

Eggs

8.3

25.6

16.7

6.6

5.0

27.5

Slices

9.7

26.9

16.0

6.6

5.2

27.6

16 Jun 2002

Mean Absolute Difference (km)


Combined High-Resolution Fields • Enhanced resolution SSM/I brightness temperatures (Tb)

Research-level product, needs to be validated o

o

Issues with noise in Tb signatures (resolution enhancement on different sensor footprints for different channels) Use “AVE” version to reduce impact of diurnal surface changes – 8.9 km resolution

Not publicly available, but researchers interested in testing are encouraged o

contact: [email protected]

19, 22, 37, 85 GHz, dual polarization

• NASA Team (NT) and Bootstrap (BT) algorithms run on Tbs to retrieve sea ice concentration Weather filters and ocean mask applied Meier and Stroeve, AGU Fall 2007 Meeting

37H GHz 15 Sep 2004

Combined High-Resolution Fields BT, NT, QS BT, NT BT, QS NT, QS BT NT QS

15 Mar 2004 Meier and Stroeve, AGU Fall 2007 Meeting

Combined High-Resolution Fields BT, NT, QS BT, NT BT, QS NT, QS BT NT QS

15 Sep 2004 Meier and Stroeve, AGU Fall 2007 Meeting

Confidence Level of Sea Ice Presence 2004 Extent NExent of 60˚N 2004 Total Ice Definite Ice (3 of 3) Possible Ice (2 of 3) Doubtful Ice (1 of 3)

12 11

Extent (106 km2)

How many of the 3 algorithms indicate sea ice provides a simple level of confidence on the presence or absence of ice.

13

10 9 8 7 6 5 4 1/1

1/31

3/1

3/31

4/30

5/30

6/29

Date


7/29

8/28

9/27 10/27 11/26 12/26

Conclusion • Enhanced resolution fields potentially yield improved ice edge estimates Tradeoff between spatial vs. temporal resolution Tradeoff between resolution and noise Effectiveness depends to some extent on conditions – e.g., stable vs. dynamic ice edge

• Combination of PM and scatterometer can provide levels of confidence on existence of sea ice • Previous research has shown utility of combined PM/QS imagery for sea ice area and motion retrieval (e.g., Haarpaintner and Spreen, 2007; Meier and Vermeychuk, 2003) Meier and Stroeve, AGU Fall 2007 Meeting

Thanks! • Research funded by NASA Grant #NNG04GG72A • Enhanced resolution QuikScat and SSM/I data provided by David Long and NASA-funded BYU Scatterometer Climate Record Pathfinder • AVHRR data provided by the Danish Meteorological Institute; thanks to Søren Andersen • Thanks to Jeff Smith and Terry Haran, NSIDC

[email protected] Meier and Stroeve, AGU Fall 2007 Meeting

References •

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Haarpaintner, J., and G. Spreen, 2007. Use of enhanced-resolution QuikScat/SeaWinds data for operational ice services and climate research: Sea ice edge, type, concentration, and drift, IEEE Trans. Geosci. Rem. Sens., 45(10), 3131-3137. Long, D.G., P.J. Hardin, and P.T. Whiting, 1993. Resolution enhancement of spaceborne scatterometer data, IEEE Trans. Geosci. Rem. Sens., 31(3), 700-715. Long, D.G., and D.L. Dunn, 1998. Spatial resolution enhancement of SSM/I data, IEEE Trans. Geosci. Rem. Sens., 36(2), 407-417. Meier, W.N., and T. Vermeychuk, 2003. Sea ice motions from microwave imagery, Amer. Meteorol. Soc. 7th Conf. on Polar Meteorol. and Oceanogr., Hyannis, MA, 12-16 May. Meier, W.N., 2005. Comparison of passive microwave concentration algorithm retrievals with AVHRR imagery in Arctic peripheral seas, IEEE Trans. Geosci. Rem. Sens., 43(6), 1324-1337. Remund, Q.P., and D.G. Long, 1999. Sea ice extent mapping using Ku band scatterometer data, J. Geophys. Res., 104(C5), 11,515-11,527.
