International Workshop on Antarctic Clouds
Columbus, 14-15 July 2010
What we do (don’t) know about
Antarctic clouds
David H. Bromwich1, Julien P. Nicolas1 and
Jennifer E. Kay2
1Polar
Meteorology Group, Byrd Polar Research Center, The Ohio State University,
Columbus, OH
2 National Center for Atmospheric Research, Boulder, CO
Outline
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Introduction
Observation methods
Cloud spatial distribution (horizontal/vertical)
Temporal (seasonal) variability
Physical properties (phase)
Trends/observed changes
Conclusions
Introduction
Why knowledge of Antarctic is important
 Antarctic radiative budget
1. Clouds reflect solar energy
2. Clouds absorb long-wave radiation emitted from the
surface
Over high-albedo surfaces, the short-wave flux
absorbed at the surface is already small:
effect 2 > effect 1
 Impact on Antarctic surface mass balance
 Role of stratospheric clouds in ozone depletion
– Polar stratospheric clouds support chemical reactions
conducive to the destruction of stratospheric ozone
Observing Antarctic clouds
Ground-based measurements
• Dedicated effort to study and measure Antarctic clouds
– South Pole Atmospheric Radiation and Cloud LIDAR
Experiment (SPARCLE) 1999-2001
• Instruments:
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Polar Atmospheric Emitted Radiance Interferometer (PAERI)
Tethered Balloon System
Micropulse Lidar
South Pole Transmissometer
• Results:
– Climatology of clouds (e.g., M. Town)
– Cloud microphysics (e.g., V. P. Valden)
Ground-based measurements
• Visual observations
CLOUD COVER AT SOUTH POLE
(MONTHLY MEANS)
– Provide the longest
observational record of
Antarctic clouds
– Problem in winter
(underestimation of cloud
cover)
• More about groundbased cloud
observations with Erika
Key and Irina
Gorodetskaya
PAERI
pyrgeometer
visual
[Town et al.,2007]
Passive remote sensing
• VIS/IR channels
• But cloud tops have
albedo and temperature
comparable to ice
sheet’s surface
Weak contrast on
satellite imagery over
ice-covered surface
Problematic for
detection of Antarctic
thin clouds
[Image: AMRC/SSEC/UW Madison]
Active remote sensing: Lidar
McM
Morley et al., 1989
SP
• Lidar measurements
onboard an LC-130
flown between McM
and South-Pole, Jan.
1986
• Multilayering of
clouds
• Ice crystals trails from
high-elevated cirrus
observed to “seed”
the mid-level clouds
Active remote sensing: Lidar
• Ex.: Geoscience Laser Altimeter System (GLAS) on ICESat
Backscatter cross-section from GLAS over Antarctica at 15:00 UTC, 1 Oct. 2003
[Spinhirne et al., 2005]
Active vs passive cloud remote sensing
 Cloud frequency over
Antarctica in Oct. 2003
from GLAS, MODIS and
ISCCP [Hart et al., 2006]
Cloud frequency
from GLAS and HIRS
(NOAA-14) from
Oct. 1-Nov. 16 2003
[Wylie et al. 2007] 
More about cloud satellite remote sensing with Dan Lubin
Mean cloud distribution
2007-08 mean seasonal cloud fraction
(from Cloudsat radar/Calipso lidar)
2007
2008
Cloud cover over West Antarctica
• Tongue of higher cloud fraction/frequency over central West
Antarctica seen in Oct. 03 and in the 06-07 annual mean
• Denotes the frequent intrusions of marine air inland associated
with the cyclonic activity over the Ross/Amundsen Seas.
Cloud frequency over Antarctica in Oct. 2003
GLAS Lidar
AMPS
[Spinhirne et al. 2005; Nicolas and Bromwich, 2010]
AMPS cloud fraction
2006-2007
Cloud cover climatology
Coastal areas: McMurdo
• Mean seasonal cloud cover over
McMurdo area in Jun 02-May 03
from AMPS forecasts
[Monaghan et al., 2005]
• Cloud cover primarily influenced by
the presence of open water in the
Ross Sea
• Maximum cloud cover in DJF/MAM ,
minimum in JJA
• Cloudiest region found over the
quasi-permanent polynya (N-E of
McM)
JJA 02
SON 02
DJF 02-03
MAM 03
[Monaghan et al., 2005]
Cloud vertical profile: West Antarctica
(from Cloudsat/Calipso)
2007
2008
Cloud vertical profile: East Antarctica
(from Cloudsat/Calipso)
2007
2008
Polar Stratospheric Clouds (PSCs)
GLAS backscatter ratio for Sept. 29 (top) and 30 (bot.), 2003
(western Dronning Maud Land sector)
Tropopause
PSCs: linkages to troposphere
• Formation of PSC associated with deep tropospheric cloud
systems:
– Cooling of the lower stratosphere through adiabatic and radiative
processes
– Air transport from the lower troposphere up to the upper tropo. /
lower stratosphere
• Figure: Measurements from CloudSat/CALIPSO. Example of a
deep cloud system associated with a PSC system in the
Weddell Sea
West Antarc.
Ross Sea
Height (km)
Weddell Sea
[Wang et al., 2008]
Offshore synoptic system penetrating
over the Antarctic interior
• Some deep synoptic
weather system do
penetrate over the
Antarctic interior
• Figure: Mosaic of
AVHRR images of East
Antarctica on Dec. 29
2001 showing a
blocking-high related
cloud band
[Massom et al., 2004]
Cloud microphysics
Cloud microphysics
• Measurements with the
PAERI allow for the
retrieval of cloud
microphys. properties
• Figure: relative
occurrence of different
cloud types in Feb. 01
at South Pole
Cloud types at South Pole
[Ellison et al., 2006]
Cloud microphysics
• Measurements from tethered balloon at South Pole
on 2 Feb. 2001 [Valden et al., 2005]
 super-cooled water clouds
Pressure (hPa)
Temperature
-30°C
~450m
above sfc
RH wrt. water
Cloud microphysics
• Discrimination cloud phase on a global scale possible
through Space-borne lidar measurements
Ice cloud observations from CALIPSO/CALIOP lidar, Jan. 2007
[Hu et al., 2009]
Cloud microphysics: climatic impact
• Lubin et al. (1998) evaluated the impact of changes
in cloud properties over Antarctica
• 10-μm ice clouds vs (control) 10-μm water clouds:
[Lubin et al., 1998]
Long-term changes in Antarctic
cloud cover?
Trends in Antarctic cloud cover
• Decadal changes in cloud cover based on long-term records of visual
observations at some Antarctic stations allow . But large significant
uncertainty, esp. in winter.
South Pole
Syowa
[Yamanouchi et al., 2007]
[Town et al., 2007]
Trends in Antarctic cloud cover
• Mean monthly anomalies in
cloud fraction 1982-1999 based
on AVHRR observations
[Comiso and Stock, 2001]
• Negative trends in cloud
fraction:
-0.50 ± 0.06% (ice sheet >2000m)
-0.21 ± 0.04% (ice sheet <2000m)
-0.09 ± 0.03% (sea ice area)
-0.06 ± 0.01% (open ocean)
PSCs and tropospheric warming
• Significant mid-tropospheric
warming has been observed in
winter over Antarctica
• The warming may be related to
larger amounts of PSCs induced by
increased tropospheric CO2
concentration and the associated
stratospheric cooling [modeling
studies from Lachlan-Cope et al.,
2009]
Trends in mid-tropospheric temp.
At Ant. Stations
(1971-2003)
At 500-hPa
from ERA-40
(1979-2001)
[Turner et al., 2006]
 600hPa
Conclusions
• Antarctic cloud studies are in a new era with
the spaceborne observations (CloudSat,
CALIPSO)
• Validation is needed in the full range of
Antarctic environments
• The record is short and temporal resolution is
limited
References
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Comiso, J. C and L. V. Stock, 2001: Studies of Antarctic cloud cover variability from 1982 through 1999.
Proc. of the Int. Geosci. and Remote Sensing Symposium, vol. 4, 1782-1785.
Ellison, M. E., et al., 2006: Properties of water-only, mixed-phase, and ice-only clouds over the South Pole.
Proceedings of the 12th conference on cloud physics and 12th conference on atmospheric radiation, 9–14
July 2006, Madison, WI, Amer. Meteor. Soc. (ed), Boston, MA
Hart, W. D., et al., 2006: Global and polar cloud cover from the Geoscience Laser Altimeter System,
observations and implications. Extended abstract of the 12th Conference on Atmospheric Radiation, AMS,
Madison, 2006.
Hatzianastassiou, N., et al., 2001: Polar cloud climatology from ISCCP C2 and D2 datasets. J. Climate, 14,
3851-3862.
Hines, K. M., et al., 2004: Antarctic clouds and radiation within the NCAR climate models. J. Climate, 17,
1198-1212.
Hu, Y., et al., 2009: CALIPSO/CALIOPcloud phase discrimination algorithm. J. Atmo. Ocean. Tech, 26, 22932309.
Lachlan-Cope, T. A., et al., 2009: Antarctic wintertropospheric warming – the potential role of polar
stratospheric clouds, a sensitivity study.Atmos. Sci. Let., 10, 262-266.
Morley, B. M., et al., 1989: Airborne lidar observations of clouds in the Antarctic troposphere. Geophys.
Res. Lett., 16(6), 491-494.
Lubin, D., et al., 1998: The impact of Antarctic cloud radiative properties on a GCM climate simulation. J.
Climate, 11, 447-462.
References (cont.)
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Massom, R.A., et al., 2004: Precipitation over the interior East Antarctic Ice Sheet related to mid-latitude
blocking-high activity. J. Climate, 17(10), 1914–1928.
Nicolas, J. P. and D. H. Bromwich, 2010: Marine signature in West Antarctica. J. Climate, in press.
Palm, S. P., et al., 2005: Observations of Antarctic polar stratospheric clouds by the Geoscience Laser
Altimeter System. Geophys. Res. Lett., 32, L22S04.
Spinhirne, J. D., et al., 2005: Antarctica cloud cover for October 2003 from GLAS satellite lidar profiling. 32,
L22S05.
Town, M. S., et al., 2007: Cloud cover over the South Pole from visual observations, satellite retrievals, and
surface-based infrared radiation measurements. J. Climate, 20, 544-559.
Walden, V. P., et al., 2005: Properties of super-cooled water clouds over South Pole. Preprints, Eighth Conf.
on Polar Meteorology and Oceanography, San Diego, CA, Amer. Meteor. Soc.
Wang, Z., et al., 2008: Association of Antarctic polar stratospheric cloud formation on tropospheric cloud
systems. Geophys. Res. Lett., 35, L13806.
Wylie, D., et al., 2007: A comparison of cloud cover statistics from the GLAS lidar with HIRS. J. Climate, 20,
4968-4981.
Yamanouci, T. and Y. Shudou, 2007: Trends in cloud amount and radiative fluxes at Syowa Station,
Antarctica. Polar Science, 1, 17-23.
Thank you