Archive for the ‘meteorology’ Category
Japanese team sees gamma-ray pulse before lightning flash
First the gamma rays, then the flash
Physicists in Japan have made the best study yet of the gamma rays that are produced in the minutes leading up to a lightning flash. In addition, the team also observed for the first time emissions that ended abruptly less than a second before the exact moment the flash occurs. The finding provides important information about the relationship between the mysterious atmospheric accelerators that produce the gamma rays and the lightning that we see in the sky.
Physicists have known for some time that gamma rays are sometimes produced when lightning strikes. Indeed, gamma-ray pulses from thunderclouds that vary in length from sub-millisecond to several minutes have been detected for the last 30 years. Most researchers agree that there are two types of bursts: very short, higher-energy bursts that coincide with lightning; and longer, lower-energy pulses that are sometimes not associated with a specific lightning event. While all of these bursts are thought to be created when charged particles are accelerated by the huge electric fields that build up in a thundercloud, the exact mechanism – or mechanisms – that produce them remains a mystery.
In this latest study, Harufumi Tsuchiya of the RIKEN High-energy Astrophysics Laboratory and colleagues at several other Japanese institutes looked at data collected in 2010 by the Gamma-Ray Observation of Winter THunderclouds (GROWTH) experiment at the Kashiwazaki-Kariwa nuclear power plant. The experiment includes several different gamma-ray detectors that are used in tandem with plastic detectors – the latter ensuring that charged particles such as muons are not mistaken for gamma rays. The system detected gamma rays at energies between 40 keV and 30 MeV…..
…. Read more at http://physicsworld.com/cws/article/news/2013/jul/10/
Redefining the ampere with the help of graphene?
Electron pumps made from graphene work 10 times faster than similar pumps made from conventional 3D materials and can be used to generate larger currents. (Courtesy: M Connolly)
The world’s first single-electron graphene pump has been built by researchers at the UK National Physical Laboratory and the Cavendish Laboratory in Cambridge. The device could be used to redefine the standard unit of current, the ampere, in terms of the electron charge – a fundamental constant of nature.
The international system of units (SI) is made up of seven base units, which are the metre, kilogram, second, kelvin, ampere, mole and candela. The ampere, volt and ohm are the three fundamental units of electricity.
Although physicists have already come up with modern ways to represent the volt and ohm (through measurements of the Josephson voltage and quantum Hall resistance, respectively), there is no equivalent for the ampere. Indeed, today, the ampere is defined as the current which, when flowing through two parallel conductors one metre apart, exerts a certain force between the conductors. Directly realizing such a macroscopic definition of current is experimentally difficult, and the accuracy of the result also depends on other base units, such as the kilogram, which drifts with time.
Enter SEPs
Ideally, a new definition of the ampere would be based on an extremely accurate source of electric current, capable of delivering one electron at a time. A single-electron pump (SEP) could be ideal in this respect because it produces a flow of individual electrons by shuttling them into a quantum dot and emitting them precisely one at a time. A good SEP also pumps the electrons quickly, so a sufficiently large current is generated.
Until recently, two types of SEP were promising contenders: tunable barrier pumps made from semiconductors, which are fast, and so-called hybrid turnstiles made from superconductors, which can be mounted in parallel to make the output current larger. Although the most accurate, a third type of pump usually made from metallic islands is too slow for making a practical current standard, but the UK researchers have now improved its performance by making it from graphene, which is a semi-metal. Graphene is a sheet of carbon just one atom thick that has a honeycomb lattice structure….
…Read more at http://physicsworld.com/cws/article/news/2013/may/28/redefining-the-ampere-with-the-help-of-graphene
New insights into what triggers lightning
What initiates a lightning strike? In the image above, multiple cloud-to-ground and cloud-to-cloud lightning strikes are observed during a night-time thunderstorm. (Courtesy: NOAA)
Cosmic rays interacting with water droplets within thunderclouds could play an important role in initiating lightning strikes. That is the claim of researchers in Russia, who have studied the radio signals emitted during thousands of lightning strikes. The work could provide new insights into how and why lightning occurs in the first place.
Although most people have witnessed a flash of lightning during a thunderstorm at some point in their lives, scientists still do not completely understand what triggers the discharge in the first place. Lightning has been studied for hundreds of years, yet while many possibilities for observation are available – there are about 40 to 50 lightning strikes per second across the globe – predicting the onset of a strike is difficult…. Read more at http://physicsworld.com/cws/article/news/2013/may/07/new-insights-into-what-triggers-lightning
Paint by Particle
Satellites, balloon-borne instruments and ground-based devices make 30 million observations of the atmosphere each day. Yet these measurements still give an incomplete picture of the complex interactions within Earth’s atmosphere. Enter climate models. Through mathematical experiments, modelers can move Earth forward or backward in time to create a dynamic portrait of the planet. NASA Goddard’s Global Modeling and Assimilation Office recently ran a simulation of the atmosphere that captured how winds whip aerosols around the world. Such simulations allow scientists to better understand how these tiny particulates travel in the atmosphere and influence weather and climate. In this visualization, covering August 2006 to April 2007, watch as dust and sea salt swirl inside cyclones, carbon bursts from fires, sulfate streams from volcanoes—and see how these aerosols paint the modeled world.
NASA Snow Cover Maps
NASA has released a video that highlights where snow graced the Earth every month for over the past ten years.
http://youtu.be/WfHvujaE2hI
Read more: dailygalaxy.com
NPP Launch
NASA’s National Polar-orbiting Operational Environmental Satellite System Preparatory Project (NPP) spacecraft was launched aboard a Delta II rocket at 5:48 a.m. EDT today, on a mission to measure both global climate changes and key weather variables.
NPP is the first step for NASA in building the next generation Earth observing satellite system. The EOS (Earth Observing System) has provided many new insights in various aspects of Earth including clouds, oceans, vegetation, glaciers and atmosphere for over a decade. Now that the system is aging, a new generation of satellites are ready to take over.
NPP is an effort led by NASA’s Goddard Space Flight Center that is carrying the first of the new sensors that will be utilized as part of that next-generation system called the Joint Polar Satellite System (JPSS). The mission will continue critical weather and climate measurements by flying advanced sensor packages. NPP will measure various properties of the Earth’s atmosphere, land surface and oceans. Its five-year mission life will help to bridge critical weather data collection before JPSS is ready for operations in 2016.
Hurricane Rina from ISS
External cameras on the International Space Station captured views of Hurricane Rina at 2:39 p.m. EDT on Oct. 25, 2011, as the complex flew 248 miles over the Caribbean Sea east of Belize.
http://youtu.be/P4N1EX8i1CU
Global warming ‘confirmed’ by independent study
The Earth’s surface really is getting warmer, a new analysis by a US scientific group set up in the wake of the “Climategate” affair has concluded.
The Berkeley Earth Project has used new methods and some new data, but finds the same warming trend seen by groups such as the UK Met Office and Nasa.
The project received funds from sources that back organisations lobbying against action on climate change.
“Climategate”, in 2009, involved claims global warming had been exaggerated.
Emails of University of East Anglia (UEA) climate scientists were hacked, posted online and used by critics to allege manipulation of climate change data.
Fresh start
The Berkeley group says it has also found evidence that changing sea temperatures in the north Atlantic may be a major reason why the Earth’s average temperature varies globally from year to year.
The project was established by University of California physics professor Richard Muller, who was concerned by claims that established teams of climate researchers had not been entirely open with their data.
He gathered a team of 10 scientists, mostly physicists, including such luminaries as Saul Perlmutter, winner of this year’s Nobel Physics Prize for research showing the Universe’s expansion is accelerating.
Funding came from a number of sources, including charitable foundations maintained by the Koch brothers, the billionaire US industrialists, who have also donated large sums to organisations lobbying against acceptance of man-made global warming.
“I was deeply concerned that the group [at UEA] had concealed discordant data,” Prof Muller told BBC News.
“Science is best done when the problems with the analysis are candidly shared.”
The group’s work also examined claims from “sceptical” bloggers that temperature data from weather stations did not show a true global warming trend.
The claim was that many stations have registered warming because they are located in or near cities, and those cities have been growing – the urban heat island effect.
The Berkeley group found about 40,000 weather stations around the world whose output has been recorded and stored in digital form.
It developed a new way of analysing the data to plot the global temperature trend over land since 1800.
What came out was a graph remarkably similar to those produced by the world’s three most important and established groups, whose work had been decried as unreliable and shoddy in climate sceptic circles.
The Berkeley group's record of global land temperature mirrors existing ones closely
Two of those three records are maintained in the US, by the National Oceanic and Atmospheric Administration (Noaa) and National Aeronautics and Space Administration (Nasa).
The third is a collaboration between the UK Met Office and UEA’s Climatic Research Unit (CRU), from which the e-mails that formed the basis of the “Climategate” furore were hacked two years ago.
“Our biggest surprise was that the new results agreed so closely with the warming values published previously by other teams in the US and the UK,” said Prof Muller.
“This confirms that these studies were done carefully and that potential biases identified by climate change sceptics did not seriously affect their conclusions.”
Since the 1950s, the average temperature over land has increased by 1C, the group found.
They also report that although the urban heat island effect is real – which is well-established – it is not behind the warming registered by the majority of weather stations around the world.
They also showed that in the US, weather stations rated as “high quality” by Noaa showed the same warming trend as those rated as “low quality”.
‘Time for apology’
Prof Phil Jones, the CRU scientist who came in for the most personal criticism during “Climategate”, was cautious about interpreting the Berkeley results because they have not been published in a peer-reviewed journal.
“I look forward to reading the finalised paper once it has been reviewed and published,” he said.
“These initial findings are very encouraging, and echo our own results and our conclusion that the impact of urban heat islands on the overall global temperature is minimal.”
The Berkeley team has chosen to release the findings initially on its own website.
They are asking for comments and feedback before preparing the manuscripts for formal scientific publication.
In part, this counters the accusation made during “Climategate” that climate scientists formed a tight clique who peer-reviewed each other’s papers and made sure their own global warming narrative was the only one making it into print.
But for Richard Muller, this free circulation also marks a return to how science should be done.
“That is the way I practised science for decades; it was the way everyone practised it until some magazines – particularly Science and Nature – forbade it,” he said.
“That was not a good change, and still many fields such as string theory practice the traditional method wholeheartedly.”
This open “wiki” method of review is regularly employed in physics, the home field for seven of the 10 Berkeley team.
Bob Ward, policy and communications director for the Grantham Research Institute for Climate Change and the Environment in London, said the warming of the Earth’s surface was unequivocal.
“So-called ‘sceptics’ should now drop their thoroughly discredited claims that the increase in global average temperature could be attributed to the impact of growing cities,” he said.
“More broadly, this study also proves once again how false it was for ‘sceptics’ to allege that the e-mails hacked from UEA proved that the CRU land temperature record had been doctored.
“It is now time for an apology from all those, including US presidential hopeful Rick Perry, who have made false claims that the evidence for global warming has been faked by climate scientists.”
Ocean currents
The Berkeley group does depart from the “orthodox” picture of climate science in its depiction of short-term variability in the global temperature.
The El Nino Southern Oscillation (ENSO) is generally thought to be the main reason for inter-annual warming or cooling.
But by the Berkeley team’s analysis, the global temperature correlates more closely with the state of the Atlantic Multidecadal Oscillation (AMO) index – a measure of sea surface temperature in the north Atlantic.
There are theories suggesting that the AMO index is in turn driven by fluctuations in the north Atlantic current commonly called the Gulf Stream.
The team suggests it is worth investigating whether the long-term AMO cycles, which are thought to last 65-70 years, may play a part in the temperature rise, fall and rise again seen during the 20th Century.
But they emphasise that anthropogenic global warming (AGW) driven by greenhouse gas emissions is very much in their picture.
“Had we found no global warming, then that would have ruled out AGW,” said Prof Muller.
“Had we found half as much, it would have suggested that prior estimates [of AGW] were too large; if we had found more warming, it would have raised the question of whether prior estimates were too low.
“But we didn’t; we found that the prior rise was confirmed. That means that we do not directly affect prior estimates.”
The team next plans to look at ocean temperatures, in order to construct a truly global dataset.
By Richard Black – bbc.co.uk
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