1. New method finds strong global electric fields near Earth
2. Geoengineering not an antidote to greenhouse warming
3. Oceanic carbon may help track hurricanes
4. Simulated gravity waves may yield better forecasts
5. Dust devils dumping dirt on Mars
6. Southwest droughts may trigger Midwest flooding
7. Aircraft exhaust effect on climate change
8. "Whistler" waves effect on Van Allen radiation belt 
9. Arabian Sea pollution caused by natural sources
10. Predicting winter storms from oceanic temperatures
11. Possible cause of multiple seismic zones

A new technique to measure global plasma has produced observations that indicate the presence of strong and irregular electrical fields in Earth's inner magnetosphere. The findings by C:son Brandt et al. may change the currently accepted understanding of the planet's near-space charged plasma layer,
known as the ring current. The new technique allowed the researchers to detect energetic neutral atoms by analyzing the reaction between charged ions in the plasma surrounding the Earth and neutral gas in space. Those images, which were recorded during several geomagnetic storms, allowed the authors to infer the
existence of strong electrical fields in the near-Earth space environment. Their evidence, confirmed by measurement and model results, suggests that electrical fields produced during geomagnetic storms affect the ring current and the upper layer of the planetary atmosphere.

Title: Global ENA observations of the storm mainphase ring current: Implications for skewed electric fields in the inner magnetosphere

Authors:
Pontus C:son Brandt, S. Ohtani, D. G. Mitchell, E. C. Roelof, R. Demajistre, Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland;
M.-C. Fok, NASA Goddard Space Flight Center, Greenbelt, Maryland.

Source: Geophysical Research Letters (GL) paper: 10.1029/2002GL015160, 2002

Planetary-scale engineering projects to mitigate the effects from global warming will likely do little to prevent the effects of increased greenhouse gases on the terrestrial biosphere, according to Govindasamy et al. The authors modeled the impact on Earth's biosphere from various schemes that would reduce solar radiation reaching the planet's surface, which would compensate for the radiative effects from a buildup of greenhouse gases in the atmosphere. They suggest that trapping outgoing radiation with carbon dioxide would be negated by reduced solar input, also pointing out that effects on the Earth's surface from increased carbon dioxide would be largely unaffected by geoengineering plans. Among the effects of increased atmospheric carbon dioxide concentrations, many of which are unknown, are that photosynthesis of plants would be accelerated, changing the growth and distribution of plant and animal life.

Title: Impact of geoengineering schemes on the terrestrial biosphere

Authors:
Balasubramanian Govindasamy, S. Thompson, P. B. Duffy, K. Caldeira, Lawrence Livermore National Laboratory, Livermore, California;
C. Delire, Institute for Environmental Studies, University of Wisconsin-Madison, Madison, Wisconsin.

Source: Geophysical Research Letters (GL) paper: 10.1029/2002GL015911, 2002

Satellite measurements of dissolved organic carbon in the wake of oceanic hurricanes and typhoons provide a new way to estimate the atmosphere-ocean interaction during the major storms. Hoge and Lyon demonstrate for the first time that satellite images of dissolved organic matter may also help researchers approximate the mixing of surface-level ocean water during a hurricane or typhoon, allowing estimates of oceanic conditions that complement currently available sea surface temperature data. Such images provide information that is not currently used for meteorology or oceanography. The authors speculate that the observations can be used to estimate the depth of waters churned up by a strong, wind-driven storm, which could improve the tracking of hurricanes and perhaps could be used to learn more about the behavior of smaller weather conditions.

Title: Satellite observation of Chromophoric Dissolved Organic Matter (CDOM) variability in the wake of hurricanes and typhoons

Authors:
Frank E. Hoge, NASA Goddard Space Flight Center, Greenbelt, Maryland;
NASA Wallops Flight Facility, Wallops Island, Virginia;
Paul E. Lyon, EG&G Inc., NASA Wallops Flight Facility, Wallops Island, Virginia.

Source: Geophysical Research Letters (GL) paper: 10.1029/2002GL015114, 2002

A three-dimensional simulation of the conditions in the upper atmosphere may help researchers better predict the behavior of atmospheric gravity waves. Gravity waves can transfer energy and winds from the lower to upper sky, affecting the planetary climate.  Horinouchi et al. present the first results from a detailed gravity
wave model, showing the waves' generation, growth and size. Their analysis shows the properties of the waves from the ground to approximately 100 kilometers [60 miles], reaching into the mesosphere. Their simulation accounts for cumulus clouds, which can influence gravity wave patterns, and, unlike previous models,
shows with enhanced accuracy that the waves are broadly distributed in the troposphere and the lower parts of the stratosphere. The researchers' findings can be used to better determine baseline atmospheric conditions and to create more precise weather forecasts. 

Title: Convectively generated mesoscale gravity waves simulated throughout the middle atmosphere

Authors:
Takeshi Horinouchi, Takuji Nakamura, Kyoto University,  Uji, Japan;
Jun-ichi Kosaka, Hitechs, Inc., Toyama, Japan.

Source: Geophysical Research Letters (GL) paper: 10.1029/2002GL016069, 2002

"Dust devils" are a common part of the Martian environment, regularly sweeping by the Mars Pathfinder lander location and suspending clouds of red dust near the surface. Murphy and Nelli used surface pressure measurements from the lander to infer at least two such storms per day at its northern subtropical location.
The convective vortices averaged nearly 100 meters [300 feet] in diameter during the mid- to late-summer mission. Comparing previous estimates of the volume and dust content of individual convective gusts with the newly assumed storm frequency, the authors conclude that the vortices provide a near-constant background of dust in the atmosphere that can influence the planetary climate by scattering and reflecting sunlight and surface heat.

Title: Mars Pathfinder convective vortices: Frequency of occurrence

Authors:
James R. Murphy, Steven Nelli, New Mexico State University, Las Cruces, New Mexico.

Source: Geophysical Research Letters (GL) paper: 10.1029/2002GL015214, 2002
 

Abnormally dry conditions in the American Southwest during the summer of 1993 may be partially responsible for the devastating Midwest flooding during the same year along the Mississippi River. Pal and Eltahir analyzed soil moisture conditions in the United States and found that anomalously dry conditions can affect the jet stream and change the soil and climactic conditions in other parts of the country. During 1993, the authors propose, dry soil over northern Mexico led to a shift in cyclonic winds, sparking increased precipitation and pushing the maximum flooding over the Great Plains. The researchers also speculate that wet soil, which enhances flooding, can strengthen and anchor the winds in a particular area, affecting the conditions that can lead to local and large-scale flooding.

Title: Teleconnections of soil moisture and rainfall during the 1993 Midwest summer flood

Authors:
Jeremy S. Pal, Abdus Salam International Centre for Theoretical Physics, Trieste, Italy;
Elfatih A. B. Eltahir, Massachusetts Institute of Technology, Cambridge, Massachusetts.

Source: Geophysical Research Letters (GL) paper: 10.1029/2002GL014815, 2002

Increased sulfate aerosols from commercial airliners will affect tropospheric ozone levels and may lead to surface cooling while contributing to upper-atmospheric warming. Pitari et al. examined how sulfur in exhaust emissions from subsonic aircraft affects atmospheric chemistry by using two chemical models that, for the first time, can analyze the direct and indirect effects of atmospheric changes forced by aircraft emissions. The authors propose that sulfuric acid particles in aircraft fuel exhaust reduces the number of sulfate aerosols in the upper troposphere and enhances the chemical reactions on the particle's surface, which can reduce ozone levels. Unlike previous studies that had primarily focused on jet contrails and the effects on the climate from pollutants and emissions, the dual atmospheric model predicts how both chemical reactions and atmospheric particles are responsible for forcing climate change.

Title: Climate forcing of subsonic aviation: Indirect role of sulfate particles via heterogeneous chemistry

Authors:
Gianni Pitari, E. Mancini, University of L'Aquila, L'Aquila, Italy;
A. Bregman, Royal Netherlands Meteorological Institute, De Bilt, The Netherlands.

Source: Geophysical Research Letters (GL) paper: 10.1029/2002GL015705, 2002

Lightning storms on Earth are a major cause of electron loss in the Van Allen radiation belt, according to researchers studying the upper atmosphere and near-Earth space. Rodger and Clilverd present model results that suggest lightning-generated radio waves called "whistlers" hasten the depletion of charged Van Allen particles, causing them to rain down toward Earth and affect atmospheric conditions. Lightning creates an intense pulse of radio waves that escape into space, producing whistling radio tones that scatter Van Allen electrons. The researchers analyzed satellite observations from Antarctica that showed the loss of electrons from the inner radiation belt with each burst of radio waves, allowing them to determine the behavior of the particles in the Van Allen belt.

Title: Inner radiation belt electron lifetimes due to whistler-induced electron precipitation (WEP) driven losses

Authors:
Craig J. Rodger, University of Otago, Dunedin, New Zealand;
Mark A. Clilverd, British Antarctic Survey, Cambridge, United Kingdom.

Source: Geophysical Research Letters (GL) paper: 10.1029/2002GL015795, 2002

The majority of the haze over the Arabian Sea is caused by natural dust and sea-salt aerosols, rather than by man-made pollution. Satheesh and Srinivasan suggest that natural airborne particles from Arabia and the Sahara Desert contribute most of the dust, which affects the temperature, sunlight balance and solar energy over the region. The researchers analyzed multiple data sets that estimated the source of the aerosols over the ocean near the Indian subcontinent, finding that more than half of the thick blanket of natural particles that drift over India's land mass are transported by annual monsoon winds blowing from the ocean. The aerosol haze was previously believed to have migrated from South and Southeast Asia.

Title: Enhanced aerosol loading over Arabian Sea during the pre-monsoon season: Natural or anthropogenic?

Authors:
S. K. Satheesh, J. Srinivasan, Indian Institute of Science, Bangalore, India.

Source: Geophysical Research Letters (GL) paper: 10.1029/2002GL015687, 2002

A model of the North Atlantic circulation that uses 50 years of sea surface temperatures can predict weather patterns for the upcoming winter with surprising accuracy. Saunders and Qian examined the predictability of the North Atlantic Oscillation (NAO), which drives atmospheric variability and storm systems from the North American east coast to Europe. The researchers were able to infer the strength and variability of the NAO during its most active winter months between December and February, using sea surface temperature patterns recorded during the summer months (from June to October). Combining their knowledge with historical records dating back to 1950, the researchers were able to accurately predict the wintertime ocean current in more than two-thirds of the past 51 winters and in approximately 85 percent of the past 15 winters.

Title: Seasonal predictability of the winter NAO from north Atlantic sea surface temperatures

Authors:
Mark A. Saunders and Budong Qian, University College London, Surrey, UK.

Source: Geophysical Research Letters (GL) paper: 10.1029/2002GL014952, 2002

Mineral changes under high pressure and temperatures combined with the bending of a tectonic plate are the likely causes of multiple seismic zones within a fault area. Kelin Wang proposes that the two conditions are associated with the phenomenon of double and triple seismic zones observed in the Earth's crust. The
multiple zones have more than one area of sesismic activity. Researchers have analyzed the zones worldwide, establishing most of their properties, but have not been able to explain how they are formed. Wang's analysis suggests that while dehydration in the slow-moving plates enhances the possibility of brittle faulting, an
"unbending" process that straightens the normal curvature of stressed tectonic plates can create forces, like elevated fluid pressures, that create double or triple seismic zones.

Title: Unbending combined with dehydration embrittlement as a cause for double and triple seismic zones

Author:
Kelin Wang, Geological Survey of Canada, Pacific Geoscience Centre, Sidney, British Columbia, Canada.

Source: Geophysical Research Letters (GL) paper: 10.1029/2002GL015441, 2002

*****
Ordering information for science writers

Journalists and public information officers of educational and scientific institutions (only) may receive one or more of the papers cited in the Highlights by sending a message to Emily Crum at ecrum@agu.org, indicating which one(s). Include your name, the name of your publication, and your phone and fax number. State
whether you prefer to receive the paper(s) as pdf attachments by email or as a fax.

Others should send a request to service@agu.org, citing the doi of the paper (number beginning 10.1029/....), to order a copy of the paper.

The Highlights and the papers to which they refer are not under AGU embargo.
###