cryosphere applications of scatterometer data
DESCRIPTION
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 PresentationTRANSCRIPT
CryosphereApplications
of ScatterometerData
David Long
Boulder, Co7 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 C-band operational
Natural hazards: iceberg tracking Operationally deployed for QuikSCAT, OSCAT, ASCAT
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
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
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
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
ArcticSea Ice
Sea ice mapping vital for shipping & climate studies Higher resolution than
radiometer data Operational use
(NOAA/NIC)year day
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
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
Reduction in MY Ice Cover
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
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
Greenland Ice Sheet
Summer melt - dramatic impact
on backscatterof entire ice sheet
Integrative effect:Summer melting Builds more and
more buried ice lenses