A Comparison of Passive Microwave
Derive Melt Extent to Melt Intensity
Estimated from Combined Optical and
Thermal Satellite Signatures Over the
Greenland Ice Sheet from 2001-2005
Unquiea Wade
Mentor: Dr. Derrick Lampkin
The Center for Remote Sensing
of Ice Sheets
The Center for Remote Sensing of Ice Sheets (CReSIS)
is a Science and Technology Center established by the
National Science Foundation (NSF) in 2005
•
• The mission of CReSIS is to develop new technologies
and computer models to measure and predict the
response of sea level change to the mass balance of ice
sheets in Greenland and Antarctica.
• NSF’s Science and Technology Center (STC) program
combines the efforts of scientists and engineers to
respond to problems of global significance, supporting
the intense, sustained, collaborative work that is
required to achieve progress in these areas.
The earth is a system
Which is effected by
processes that occur
Responds to these
processes and
changes
These changes
are then study
and monitored
Data



Special Sensor
Microwave/ Imager
brightness temperature
grids were downloaded
from National Snow
and Ice Data Center.
(NDIDC)
SSMI files were
collected for three
different channels
Satellite
Ascending/Descending:
19H.GHZ,37V .GHZ,
/37V.GHZ
Brightness Temperature
This distinct change is observed in the brightness
temperature (Tb) signal according to the Rayleigh
Jeans approximation:
TB ( )  TP
where Tb refers to the microwave brightness
temperature at a particular wavelength (λ or
frequency υ), ε is the microwave emissivity, and Tp
is the effective physical temperature of the snow
(Zwally, 1977)
Melt Occurrence and Extent
Retrival Techniques

Technique 1:Cross Polarization Gradient Ratio (XPGR
) [Abdalati and Steffen [1995, 1997]
TB (19 H )  TB (37V )
XPGR 
TB (19 H )  TB (37V )

Technique 2: Dirnual Ampltiude Variation (DAV)
[Ramage and Isacks [2002]
DAV  abs(TB (37V )ascending - TB (37V )descending )  B
TB  A
XPGR Derived Melt Occurrence (Day 161 , Year 2000)
Blue: Melt Occurrence
White: No Melt Occurrence
DAV Derived Melt Occurrence (Day 161 , Year 2000)
Blue: Melt Occurrence
White: No Melt Occurrence
Melt Magnitude
Retrieval
Liquid Water
Fraction
Results
2001 Melt Occurrence vs Melt Magnitude for Composite Period 193
XPGR and DAV
AVERAGE EMELT
2002 Melt Occurrence vs Melt Magnitude for Composite Period 193
0.25
0.25
0.2
0.2
0.15
DAV and XPGR
Average EMELT
0.1
XPGR AVG EMELT
DAV AVG EMELT
0.05
0
1
2
3
4
5
6
7
8
9
0.15
0.1
XPGR AVG EMELT
DAV AVG EMELT
0.05
0
1
2
3
4
5
6
7
8
9
XPGR AVG EMELT 0.05 0.13 0.13 0.14 0.14 0.14 0.13 0.13 0.12
XPGR AVG EMELT 0.05 0.08 0.1 0.11 0.11 0.1 0.11 0.14 0.15
DAV AVG EMELT 0.01 0.02 0.02 0.02 0.03 0.05 0.08 0.1 0.11
DAV AVG EMELT 0.02 0.02 0.02 0.02 0.03 0.04 0.07 0.09 0.1
XPGR and DAV DAILY COUNTS
DAV and XPGR Daily Counts
Results Contd..
2003 Melt Occurrence vs Melt Magnitude for Composite Period 193
0.3
0.3
0.25
0.25
0.2
0.2
DAV and XPGR
0.15
AVG EMELT
DAV and XPGR
0.15
EMELT
XPGR AVG EMELT
0.1
DAV AVG EMELT
0.05
0
1
2
3
4
5
6
7
8
9
0 0.01 0.02 0.03 0.03 0.04 0.07 0.1 0.12
DAV and XPGR DAILY COUNT
XPGR AVG EMELT
0.1
DAV AVG EMELT
0.05
0
XPGR AVG EMELT 0.05 0.12 0.13 0.13 0.14 0.14 0.14 0.15 0.15
DAV AVG EMELT
2004 Melt Occurrence vs Melt Magnitude for Composite Period 193
1
2
3
4
5
6
7
8
9
XPGR AVG EMELT 0.08 0.12 0.12 0.13 0.13 0.14 0.14 0.13 0.13
DAV AVG EMELT 0.05 0.07 0.06 0.06 0.07 0.09 0.1 0.12 0.12
DAV and XPGR DAILY COUNTS
Results Contd…
2005 Melt Occurrence vs. Melt Magnitude for Composite Period 193
0.25
0.2
DAV and XPGR
EMELT
0.15
0.1
XPGR AVG EMELT
DAV AVG EMELT
0.05
0
1
2
3
4
5
6
7
8
9
XPGR AVG EMELT 0.05 0.1 0.13 0.13 0.13 0.13 0.14 0.13 0.12
DAV AVG EMELT 0.02 0.02 0.02 0.03 0.03 0.06 0.09 0.1 0.11
DAV and XPGR DAILY COUNTS
Conclusions


Results indicate that DAV show a much more proportional
relationship to melt magnitude than XPGR consistently
during the analysis period. Both techniques show a scaled
increase in melt occurrence with melt magnitude from the
early part of the melt season (Day 145- May 25) than later
in the melt season (Day 193-July 12).
Difference in the comparison of XPGR and DAV to E-melt
may be due to the ability of DAV to track more night time
persistent melt, producing higher occurrences of melt. Emelt values derived from surface reflectance and
temperature may be sensitive the diurnal effects as well
resulting in a stronger relationship to DAV than XPGR.
Further work is necessary to explain these trends.
Questions
Acknowledgements
Center for Remote Sensing of Ice
Sheets
 Center of Excellence in Remote
Sensing Education and Research
 College of Earth and Mineral Sciences
 Peter Burkett
 Dr. Derrick Lampkin
 Dr. Linda Hayden
