2007 04 28
By Dave Dooling | science.nasa.gov
Above: Lightning over the Swiss Alps. Credit and copyright: Olivier Staiger.
Lightning is more than light and noise: It's an intense chemical factory that affects both local air quality and global climate. But how big is the effect? Researchers aren't sure. To answer the question they're developing a new technique to estimate the factory's output.
If successful, the method will be applied to the Geostationary Lightning Mapper (GLM) that will monitor the Western hemisphere from a next-generation weather satellite slated for launch in 2014.
"Atmospheric chemists are very interested in trace gases produced by lightning, particularly nitrogen oxides ('NOx' for short)," explains William Koshak, a lightning researcher at NASA's Marshall Space Flight Center. NOx includes nitric oxide (NO), a toxic air pollutant produced by automobile engines and power plants, and nitrogen dioxide (NO2), a poisonous reddish-brown gas with a sharp odor.
"We know that lightning is the most important source of NOx in the upper troposphere, where our weather takes place," Koshak continues. "NOx indirectly influences our climate because it partly controls the concentration of ozone (O3) and hydroxyl radicals (OH) in the atmosphere. Ozone is an important greenhouse gas, and OH is a highly reactive molecule that controls the oxidation of several greenhouse gases."
While the output from cars and industry can be measured, lightning is a wildcard in models of regional air quality and global climate because it is difficult to realistically model several important lightning characteristics--e.g., lightning energy and the thermochemical yield of NOx produced by a lightning stroke. As such, the global production rate of lightning NOx is still uncertain, and ranges anywhere from 2 to 20 teragrams per year (1 teragram = 1 trillion grams).
Below: The worldwide distribution of lightning strikes. Each flash produces a tiny puff of NOx, individually negligible, but adding up to as much as 20 trillion grams per year when summed over the entire globe.
"Fortunately, space-based atmospheric chemistry measurements made by NASA's Aura satellite provide a 'top-down' constraint on global chemistry and climate models," Koshak says. "With these new constraints, the best estimate to date is closer to 6 teragrams per year. However, more work must be done to better model lightning and other chemical processes before full confidence in this estimate is achieved."
To better understand lightning flash energy -- a critical parameter in lightning NOx production -- Koshak and his colleagues are using data from the Lightning Imaging Sensor (LIS) aboard the Tropical Rainfall Measuring Mission (TRMM) satellite and two arrays of ground instruments at NASA's Kennedy Space Center in Florida. LIS is a special camera that uses a very narrow spectral filter and other techniques to detect the lightning optical emissions during both day and night. The filter is centered near 777.4 nm, which is just below the deep red limit of human vision.
Their results will be reported in Lightning charge retrieval: dimensional reduction, LDAR constraints, and a first comparison with LIS satellite data, a paper recently accepted for publication in the Journal of Atmospheric & Oceanic Technology of the American Meteorological Society. His co-authors are E. Philip Krider, Natalie Murray, and Dennis Boccippio.
"The idea is to investigate what correlation may exist between the optical characteristics of flashes seen by LIS vs. ground-based lightning measurements at Kennedy. The ground-based sensors allow us to probe deep within the thundercloud to determine the geometry of the lightning channel, the charges deposited by the flash, and the energy of the flash. The key is to see if the space-based optical measurements can be related to the ground-based flash energy estimates. If this can be done, it would be possible to use sensors in space to remotely retrieve flash energetics over a much larger region of the globe," says Koshak.
Above: Koshak and colleagues are using data from the Lightning Imaging Sensor (LIS) aboard the Tropical Rainfall Measuring Mission (TRMM) satellite to study lightning NOx production. [TRMM] [LIS]
"It's a formidable task, and this is just a preliminary look," he says of the forthcoming paper. The cloud medium is variable and therefore scatters the light emitted from lightning in complex ways. Energetic flashes embedded deep within an "optically thick" thundercloud could appear relatively dim to a space sensor, while weak-energy flashes occurring near cloud-top could appear relatively bright. All these complexities must be unraveled, and it is "tricky business."
Ultimately Koshak hopes to provide a technique that will use GLM data to estimate lightning flash energy. "In practice we'll do it in a statistical fashion. We would like to give the atmospheric chemistry modelers a realistic probability distribution function for lightning flash energies that they can use in their models to better simulate lightning (be it ground or cloud flashes)."
From that, scientists will start to better understand the global production of one of the key pollutants in the atmosphere pertinent to global climate and air quality.
Read more: http://science.nasa.gov/headlines/y2007/27apr_nox.htm?list109322
Lightning causes smudges in Saturn's rings
Why The Electric Universe Matters
The Dragon and the Pearl
Red Ice Creations Radio - Donald E. Scott - The Electric Sky
Red Ice Creations Radio - Donald E. Scott - The Electric Sky (Subscriber)
Satellites Track Strange 'Earth Energy'
The Balloon goes up over lightning!
Columbia downed by Megalightning
Libya's Kebira Crater
Electric Universe: A Cosmology for the 21st Century
Latest News from our Front Page
Former Chief Security Officer for NewsCorp: N. Koreans Not Behind Sony Hack, Interview Leak
Hemanshu Nigam, a former federal prosecutor and former chief security officer for NewsCorp/Fox studios, says North Korea isn’t behind the Sony Hack.
Nigam gave several bullet points for why the hack was likely an inside job.
Attack code borrowed from a previous attack on Seoul, that’s why it’s in Korean. Private hackers typically borrow malicious code from other hackers.Nations state attacks follow ...
Sony Fires Back at Obama: Actually We Did Call the White House – Several Times
Sony fired back at Obama after the press conference saying they had several conversations with the Obama White House before and after the movie was canceled.
Via The Hollywood Reporter:
After President Obama criticized Sony for its decision to cancel The Interview's release after theater chains decided not to show the film, the studio has issued a statement elaborating on the move.
The Bankster International
Geopolitical analysis, the art of explaining power relationships through the prism of impersonal geography, can be a helpful tool for observers of the Great Game – but it also has its limitations. A case in point is the renewed US-Russia confrontation. Think tanks and policy insiders easily sell the narrative that from the dark days of the Cold War to ...
Another banker dies under suspicious circumstances
52-year-old Belgian Geert Tack – a private banker for ING who managed portfolios for wealthy individuals – was described as ‘impeccable’, ‘sporty’, ‘cared-for’, and ‘successful’ and so as Vermist reports, after disappearing a month ago, the appearance of his body off the coast of Ostend is surrounded by riddles…
Impeccable. Sporty. Cared for. Successful. Just some qualifications that are attributed to ...
NATO increases military presence on Russia’s borders
The Pentagon has confirmed the military buildup along Russia’s borders to ensure long-term “peace and stability” in the region.
Earlier Moscow accused NATO of a sharp increase in air activity and intelligence flights in the border zone.
Replying to RIA Novosti’s query on the increased number of NATO flights around Russia’s borders, a Pentagon representative told the news agency that the military ...
|More News » |