Development of a Climate-Data Record of

Development of a Climate-Data
Record of Surface Temperature
of the Greenland Ice Sheet
Dorothy K. Hall
Josefino C. Comiso
Christopher A. Shuman
Waleed Abdalati
Cryospheric Sciences Branch, NASA/GSFC
and
UMBC/GEST
LST Workshop
National Climatic Data Center
Asheville, NC
April 7, 2008
Collaborators
Jason E. Box / OSU
Kimberly A. Casey / Adnet
Simon J. Hook / JPL
Konrad Steffen / Univ. Colo.
LST Workshop
National Climatic Data Center
Asheville, NC
April 7, 2008
Development of a Climate-Data Record
(CDR) of surface temperature of the
Greenland Ice Sheet
Outline
•Background – why do we care?
•Validation of satellite-derived LSTs
•Selection of algorithm for the CDR
•Consistency of AVHRR, MODIS and VIIRS LSTs
Background
• The Arctic has been experiencing changes caused by a
warming climate
• Changes have not been uniform across the Arctic
• The Greenland ice sheet has been experiencing
enhanced melting and warming in recent decades
• CDR will be useful for studying decade-scale LST and
melt trends of the ice sheet
AVHRR data show a trend toward increasing LST over
Greenland: 1982 - 2008
•6.25-km resolution
•Monthly averages
•0.07 to 0.08°C increase per
year
•Rate of increase has increased
Joey Comiso / GSFC
Mean “clear-sky” surface temperature from MODIS LST
MOD11A1 product*
Active-melt season
Annual**
*MOD11A1 LST product developed by Wan et al. (2002)
**Year 2000 not available
Figure from Hall et al., 2008
Melt-Season
Timing and
Duration Trends
in Individual
Drainage Basins
Start of melt
End of melt
Basins 4 & 5:
longer melt
seasons;
earlier start by
up to ~15 days,
and earlier end
(B4) by up to
~9 days
1
2
6
3
*Melt-season start and end is
defined as 2 consecutive days of
melt
5
4
Updated from Hall et al. (2008)
Surface Melt triggers Mass Loss; Cessation of Melt allows Mass Gain
Below 2000 m
GRACEderived
mascon
J
F
M
MODISderived
melt
A
M
J
J
A
S
O
N
D
GRACE data from S. Luthcke / NASA / GSFC
How accurate are satellitederived LST data?
Comparison of AWS-derived and MODIS LSTs
AWS data provided by J. Box
From:
Hall, D.K., J.E. Box, K.A. Casey, S.J. Hook, C.A. Shuman and K. Steffen,
in revision: Comparison of satellite-derived ice and snow surface
temperatures over Greenland with in-situ observations, RSE.
Are “point measurements”
useful for determining the
accuracy of the LST data?
Satellite-derived LSTs are consistent over
snow and ice on the Greenland Ice Sheet
From:
Hall, D.K., J.E. Box, K.A. Casey, S.J. Hook, C.A. Shuman and K. Steffen,
in revision: Comparison of satellite-derived ice and snow surface
temperatures over Greenland with in-situ observations, RSE.
CDR of Greenland Ice Sheet
surface temperature
•AVHRR data from 1981, and MODIS data from 2000 to
the present
•Various spatial and temporal resolutions
•Errors will vary for different parts of the CDR
•Ensure consistency with VIIRS data
Photograph by Peter Hollinger
http://www.pbase.com/plbh/greenlan
d_2003
Which algorithm should we
use to develop the LST CDR
of the Greenland Ice Sheet?
MODIS LST-IST difference
maps
MODIS LST-IST difference
maps
How will we determine which
algorithm is best?
Future work
•Study AVHRR high-resolution 1.1-km resolution
data to compare with MODIS
•Determine best LST algorithm to use with both
AVHRR and MODIS to develop the CDR
•Work on AVHRR long-term dataset consistency
issues
•Study Terra MODIS and Aqua MODIS consistency
issues
•Study compatibility issues with VIIRS
Conclusions
•Greenland surface temperature has been
increasing
•Melt extent, and duration of the melt season at least
in southern Greenland has been increasing
•High confidence in satellite-derived LSTs over snow
and ice
•CDR will be useful for studying decade-scale LST
and melt trends