cryosphere applications of scatterometer data

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Cryosphere Applications of Scatterometer Data David Long Boulder, Co 7 Oct 2013

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Cryosphere Applications of Scatterometer Data. David Long Boulder, Co 7 Oct 2013. Cryosphere Applications. Sea-ice extent Operationally deployed for QuikSCAT, OSCAT, ASCAT Sea-ice age Demonstrated Sea ice motion (tracking) Demonstrated Freeze-thaw state & melt onset Demonstrated - PowerPoint PPT Presentation

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Page 1: Cryosphere Applications of Scatterometer Data

CryosphereApplications

of ScatterometerData

David Long

Boulder, Co7 Oct 2013

Page 2: Cryosphere Applications of Scatterometer Data

Cryosphere Applications Sea-ice extent

Operationally deployed for QuikSCAT, OSCAT, ASCAT Sea-ice age

Demonstrated Sea ice motion (tracking)

Demonstrated Freeze-thaw state & melt onset

Demonstrated C-band operational

Natural hazards: iceberg tracking Operationally deployed for QuikSCAT, OSCAT, ASCAT

Page 3: Cryosphere Applications of Scatterometer Data

Measurement Requirements Sampling

Once per day minimum, twice or more preferred< 10 km resolutionLatitudes 55° to 90°

Sigma-0 precisionLong-term stability: <0.1 dBShort-term stability: <0.2 dB

Incidence angleWide diversity useful for discriminating ice characteristicsCan use high (>50°) incidence effectively)

PolarizationDual-pol

Page 4: Cryosphere Applications of Scatterometer Data

Enhanced Resolution

ASCAT & QuikSCAT Enhanced resolution false color image

using a single day (JD 217, 2008) of data from Ku-band QuikSCAT and C-band ASCAT. Red: QuikSCAT h-pol so at 46º Green: QuikSCAT v-pol so at 45º Blue: ASCAT v-pol so at 40º Open ocean is blue/green. Dark

purple is young first year sea ice. Older first year and multi-year sea ice are yellow/gold. Glacial ice that has melted/refrozen is white, with unmodified firn showing as browns and golds. Icebergs show up a as white.

Dual-frequency offers more discrimination capability than single frequency

Page 5: Cryosphere Applications of Scatterometer Data

Iceberg Tracking

Icebergs in radar images Contrast between ice &

oceanNot affected by

illumination or cloud cover

BYU computer code used at the National Ice Center for iceberg tracking

BYU has world’s largest iceberg tracking database

Page 6: Cryosphere Applications of Scatterometer Data

Icebergs Increasing?

Much of the apparent NIC increase is anartifact of better iceberg tracking technology

Recent calvings of Ross and Ronne Ice shelves are within the range of expected variation

Major icebergcalving events

First radarobservations

National IceCenter count: low OK

1980 1985 1990 1995 2000 2005 2010

Iceb

erg

Cou

nt

Year

Page 7: Cryosphere Applications of Scatterometer Data

ArcticSea Ice

Sea ice mapping vital for shipping & climate studies Higher resolution than

radiometer data Operational use

(NOAA/NIC)year day

Page 8: Cryosphere Applications of Scatterometer Data

Temporal Trends in Multi-Year Sea Ice

MY Ice

FY Ice

QuikSCAT VV (σ0 in dB)

Winter2006-2007

Ku-band backscatter is strongly sensitivity to Has proven useful in mapping sea ice age

Distinction between ice types is related to Ice salinity Porosity Surface roughness Ridge structure

Daily backscatter histogram

A.M. Swan and D.G. Long, “Multi-Year Arctic Sea Ice Classification Using QuikSCAT,” IEEE Transactions on Geoscience and Remote Sensing, Vol. 50, No. 9, pp. 3317-3326, 2012.

MY Ice

FY Ice

Page 9: Cryosphere Applications of Scatterometer Data

Ku-bandMulti-year Sea

Ice Trends Distributions in (a)

are approximately bimodal

There is a shift in the modes of FY and MY ice

Total area of ice in (b) is similar each winter

Conclude that FY ice is replacing MY ice

(a) (b)

First year ice

Multi year ice

Page 10: Cryosphere Applications of Scatterometer Data

Reduction in MY Ice Cover

Page 11: Cryosphere Applications of Scatterometer Data

C-band Sea Ice Age Timeseries

Deficit of old ice in ‘94, ‘95, ‘96. Thin ice originating along Sib. Shelf

causes bimodal pdf in 1996 Gyre reversal compresses newly

grown lead ice into thick FY.

Thin ice from Laptev Sea

+3.96

-3.78 -0.2 +0.72 +1.7 +2.8+3.28 +2.67 +3.03 NAO Index

Page 12: Cryosphere Applications of Scatterometer Data

Dual Frequency Scatterometry Single day (JD 217, 2008) false color

enhanced resolution image of Greenland from QuikSCAT and ASCATRed: QuikSCAT h-polGreen: QuikSCAT v-polBlue: ASCAT v-pol Purple corresponds to land. Summer

melt on the ice sheet periphery is the darker region between the white and purple regions. Refrozen melt-zone is bright white. Unmelted firn in central Greenland is brown and gold

(Texturing in the lower left portion of the melt zone is an artifact of the diurnal melt cycle due to using passes at different times of the day)

Combined, the two scatterometers offer more discrimination capability than either alone

Greenland

Page 13: Cryosphere Applications of Scatterometer Data

Greenland Ice Sheet

Summer melt - dramatic impact

on backscatterof entire ice sheet

Integrative effect:Summer melting Builds more and

more buried ice lenses