The following highlights summarize research papers in Geophysical Research Letters (GL). The papers related to these
Highlights are printed in the next paper issue of the journal
following their electronic publication.

1. Buoy measurements confirm satellite rainfall estimates
2. Estimating the age of Martian ice crater formations
3. Global views of space weather "plasma bubbles"
4. Cause of increased lightning flashes over cities
5. NAO-snow level link could provide earlier winter storm warnings
6. Sea-salt aerosols effect on global climate overlooked
7. Study confirms human influence on regional climate
8. Coupled ocean model can improve El Nino prediction
9. Satellite data provides global coverage of stratospheric ozone
10. Iron fertilization not a sure route to sequester carbon

A report comparing the results from rain-collecting buoys in the
tropical Pacific to satellite measurements can help improve rainfall
estimates and allow researchers to better estimate global
atmospheric circulation patterns. Bowman et al. verified the
algorithms used in two sensors to interpret precipitation data
aboard the Tropical Rainfall Measuring Mission satellite. The
researchers found that the satellite's microwave imager provided a
highly accurate measure of rainfall over the tropical oceans,
although it has a limited swath of coverage. However, they found
that the precipitation radar estimations were nearly 30 percent
lower than the amount of water found in the gauges. The authors
propose that the buoys present a more realistic measure of oceanic
rainfall than gauges located on land, which often get more rain
because of surface heating and topographic influences.

Title: Comparison of TRMM rainfall retrievals with rain gauge
data from the TAO/TRITON buoy array

Authors:
Kenneth P. Bowman, Amy B. Phillips, Gerald R. North, Texas
A&M University, College Station, Texas.

Source: Geophysical Research Letters (GRL) paper
10.1029/2003GL017552, 2003

The growth rate of distinct "Swiss cheese" formations on the
Martian ice cap may help researchers better understand the
properties of the planet's frozen southern pole. Byrne and Ingersoll
created a model simulating the expansion rate of deep, flat-floored
circular pits observed by the Mars Orbiter Camera and interpreted
the age of the polar formations by their size. The authors propose
that the common size shared by many of the crater-like depressions
indicates that the majority of the features likely formed around the
same time and that environmental changes were responsible for
starting the growth up to several centuries ago. Their analysis also
suggests the possibility for additional Swiss-cheese features on the
polar cap that may have formed different shapes as environmental
changes affected the growth and shape of the depressions.

Title: Martian climatic events on timescales of centuries: Evidence
from feature morphology in the residual south polar ice cap

Authors:
Shane Byrne, Andrew Ingersoll, California Institute of Technology,
Pasadena, California.

Source: Geophysical Research Letters (GRL) paper
10.1029/2003GL017597, 2003

New observations from a recently launched satellite will likely
allow a global view of ionospheric anomalies and may allow
researchers to better understand storms at the Earth-space interface.
Kelley et al. report that the TIMED satellite's ultraviolet imager can
observe fast-moving, bubble-shaped plumes of plasma that can
stretch from the Earth's magnetic equatorial ionosphere to
mid-latitudes and adversely affect space-based communications
and navigational systems. The authors found that combining
ground-based and satellite measurements of plasma emissions from
the unstable ionospheric region provides an explanation for oddly
shaped features seen during convective ionospheric storms. They
conclude that their data taken near the equator is consistent with
existing ground-based radar and, combined with other methods to
monitor the upper atmosphere, can provide a new tool for
monitoring space weather.

Title: The first coordinated ground- and space-based optical
observations of equatorial plasma bubbles

Authors:
Michael C. Kelley, Cornell University, Ithaca, New York;
Jonathan J. Makela, Naval Research Laboratory, Washington,
D.C.;
Larry J. Paxton, Hyosub Kil, Johns Hopkins University Applied
Physics Laboratory, Laurel, Maryland;
Farzad Kamalabadi, Joseph M. Comberiate, University of Illinois
at Urbana-Champaign, Urbana, Illinois.

Source: Geophysical Research Letters (GRL) paper
10.1029/2003GL017301, 2003

The combination of increased aerosol pollution and higher
atmospheric temperatures likely contributes to increased
cloud-to-ground lightning observed above large cities. Naccarato et
al. analyzed two years of cloud-to-ground lightning flashes over
three large metropolitan areas in Brazil and found up to a 100
percent increase in flash density in the urban areas compared to the
surrounding regions. Their observations confirm a previously
reported link seen in cities worldwide between increased lightning
and elevated airborne particulate matter levels and raised
temperatures from manmade urban " heat islands". The authors
suggest that neither pollution nor heat alone can explain the
enhanced lightning characteristics; they propose that the two
factors combine to cause the lightning increases.

Title: Evidence of thermal and aerosol effects on the
cloud-to-ground lightning density and polarity over large urban
areas of Southeastern Brazil

Authors:
K. P. Naccarato, O. Pinto, Jr., I. R. C. A. Pinto, National Institute
for Space Physics, Sao Jose dos Campos, Brazil.

Source: Geophysical Research Letters (GRL) paper
10.1029/2003GL017496, 2003

A moderate statistical correlation between summertime snow
levels in the Northern Hemisphere and the following winter's North
Atlantic Oscillation (NAO) may help researchers better predict
wintertime storminess over the North Atlantic Ocean. Qian and
Saunders studied the available 30-year snow record for the
Northern Hemisphere and found that years with high summer snow
cover typically correspond to winters with low North Atlantic
storminess. They also found that low summertime snow cover
could help predict high storminess later in the year. The authors'
analysis found a statistically significant correlation between strong
wintertime winds associated with the NAO and prior snow levels.
They suggest that such information could help reduce the risk and
uncertainty associated with the year-to-year variability in
storminess levels.

Title: Seasonal predictability of wintertime storminess over the
North Atlantic

Authors:
Budong Qian, Mark A. Saunders, University College London,
Holmbury St. Mary, Dorking, Surrey, United Kingdom.

Source: Geophysical Research Letters (GRL) paper
10.1029/2003GL017401, 2003

Oceanic winds have a significant and overlooked effect on Earth's
heat balance by increasing sea-salt aerosols, according to a report
that suggests high sea surface winds can cause large errors in
climate models. Satheesh and Lubin propose that high winds
enhance sea-salt aerosols, which has the net effect of offsetting
sea-surface solar heating and lead to incorrect predictions of
atmospheric conditions and the global climate. The authors'
experiments over the tropical Indian Ocean suggest that sea-salt
aerosols generated by moderate winds reduce solar heating by
nearly half, whereas high winds increase the radiation levels
coming from the Earth. The researchers conclude that sea-salt
aerosols have a significant effect on atmospheric conditions and
should be included in models of global climate and temperature
studies.

Title: Short wave versus long wave radiative forcing by Indian
Ocean aerosols: Role of sea-surface winds

Authors:
S. K. Satheesh, Indian Institute of Science, Bangalore, India;
D. Lubin, Scripps Institute of Oceanography, University of
California-San Diego, La Jolla, California.

Source: Geophysical Research Letters (GRL) paper
10.1029/2003GL017499, 2003

An analysis of temperature change in six continental-scale areas
confirms that the climate is changing regionally as a result of
human activities. Peter A. Stott carried out a series of statistical
examinations of warming in Africa, Asia, Australia, Europe, North
America, and South America and found significantly elevated
temperatures from increasing manmade greenhouse gas
concentrations in all of the regions during the 20th century. He also
proposes that manmade sulfate aerosols likely absorbed some solar
radiation at high altitude and helped to counteract some of the
surface warming in the latter half of the century. The report is one
of the first studies to detect regional changes in climate and is the
first to show that natural factors like solar variability and volcanic
aerosols cannot explain warming observed in Europe, North
America and the other continental regions.

Title: Attribution of regional-scale temperature changes to
anthropogenic and natural causes

Author: Peter A. Stott, Hadley Centre for Climate Prediction and
Research, Bracknell, Berkshire, United Kingdom.

Source: Geophysical Research Letters (GRL) paper
10.1029/2003GL017324, 2003

Including the results from subsurface oceanic temperature analyses
can improve the accuracy and lengthen the lead time for predicting
future El Nino circulation patterns. Tang et al. show that El Nino
predictions that included data from the National Centers for
Environmental Prediction improved estimates for sea surface
temperature anomalies caused by the El Nino circulation pattern,
well in advance of current methods. The authors suggest that their
coupled model may allow researchers to predict an El Nino up to a
year before it occurs and accurately estimate the oscillation's
effects approximately 4-6 months in advance. They propose that
including the additional information in their oceanic global
circulation model can produce findings similar to those from direct
ocean temperature observations. Such observations are rarely
collected now, making the new technique an effective and
convenient method to predict El Nino weather patterns.

Title: The use of ocean reanalysis products to initialize ENSO
predictions

Authors:
Youmin Tang, Richard Kleeman, New York University, New
York, New York;
Andrew M. Moore, University of Colorado, Boulder, Colorado;
Anthony Weaver, European Center for Research and Advanced
Training in Scientific Computation (CERFACS), Toulouse Cedex,
France;
Jerome Vialard, Laboratory for Dynamic Ocean and Climatological
Studies (LODYC), Paris, France.

Source: Geophysical Research Letters (GRL) paper
10.1029/2003GL017664, 2003

An analysis of data from a recently launched satellite will likely
allow scientists to study the global coverage of ozone levels at
various altitudes on a daily basis. Von Savigny et al. report the
findings from the Swedish Odin satellite, which was launched in
2001 with an optical spectrograph and infrared imaging system
capable of measuring stratospheric ozone levels from the sunlight
scattered in the atmospheric. The satellite uses a recently devised
technique called limb scatter that has been confirmed by other
instruments to accurately estimate the ozone density in the
stratosphere. The authors suggest that the limb-scatter method can
provide stratospheric ozone profiles with a much larger coverage
area than most existing satellite instruments.

Title: Stratospheric ozone profiles retrieved from limb scattered
sunlight radiance spectra measured by the OSIRIS instrument on
the Odin satellite

Authors:
C. von Savigny, C. S. Haley, C. E. Sioris, I. C. McDade, E.
Griffioen, J. C., McConnell, B. Solheim, Center for Research in
Earth and Space Science (CRESS), York University, Toronto,
Ontario, Canada;
E. J. Llewellyn, D. Degenstein, R. L. Gattinger, N. D. Lloyd,
University of Saskatchewan, Saskatoon, Saskatchewan, Canada;
W. F. J. Evans, Trent University, Peterborough, Ontario, Canada;
E. Kyrola, Finnish Meteorological Institute, Helsinki, Finland;
C. A. McLinden, Meteorological Services of Canada, Toronto,
Ontario, Canada;
G. Megie, Pierre Simon Institute of Environmental
Science-Aeronomy Division, National Center for Scientific
Research, Paris, France;
D. P. Murtagh, Chalmers University of Technology, Goteborg,
Sweden;
K. Strong, University of Toronto, Toronto, Ontario, Canada.

Source: Geophysical Research Letters (GRL) paper
10.1029/2003GL016401, 2003

Iron-induced patches of algae at the ocean surface will only sink to
the ocean floor after forming large clusters of a certain size, a
finding that complicates the theory that adding iron to parts of the
sea can effectively reduce global atmospheric carbon levels and
help mitigate the greenhouse effect. Waite and Johnson found that
artificially created phytoplankton blooms do not routinely descend
until the algal clumps eclipse a threshold size that depends on its
surrounding conditions. The authors suggest that the amount of
carbon that sinks depends on the balance between algal growth and
the dispersive effect from ocean mixing. They also propose a
model that may be able to predict the conditions necessary for
carbon sequestration. Their findings clarify the effects from iron
seeding that is intended to sequester surplus carbon in sediment on
the ocean floor.

Title: Critical space spaces for aggregation-mediated carbon export
from ocean fertilization

Authors:
Anya M. Waite, David Johnson, Center for Water Research,
University of Western Australia, Crawley, Western Australia,
Australia.

Source: Geophysical Research Letters (GRL) paper
10.1029/2003GL016997, 2003

*****
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