Archive | Atmospheric Sciences RSS feed for this section

Imaggeo on Mondays: Cordillera del Paine

9 Jul

Cordillera del Paine by Martin Mergili, distributed by EGU under a Creative Commons licence.

Images such as the one above inspire scientists and nature lovers alike. This photograph, showing a Chilean landscape with elements representative of various Earth-science disciplines, is simply stunning. In a beautiful mix of shapes and colours, a quiet lake with floating icebergs appears tucked in between a roughed mountain in the background and a colourful double rainbow in the foreground.

The photographer, Martin Mergili of the University of Natural Resources and Life Sciences in Vienna, captured this inspiring scenery during a holiday trip a few years ago. The photo shows the eastern edge of the southern part of Cordillera del Paine, a “small but spectacular” mountain group in the Torres del Paine National Park, which is located in Chilean Patagonia almost 2,000 kilometres south of Santiago de Chile.

“The prominent peaks visible in the left portion of the image are the Cuernos del Paine,” Martin explains. “The rainbow in the foreground is not just decoration, it reflects the ever-changing weather patterns characteristic of that area. Even though it is located in the rainshade of the Cordillera at the edge of the semi-arid Patagonian lowlands, the westerlies bring a lot of moist air from the Pacific Ocean. The icebergs in the lake in the foreground (Lago Grey) originate from the large Glaciar Grey calving into the lake.”

More stunning images of this and other landscapes are available from Martin’s website.

Imaggeo is the online open access geosciences image repository of the European Geosciences Union. Every geoscientist who is an amateur photographer (but also other people) can submit their images to this repository. Being open access, it can be used by scientists for their presentations or publications as well as by the press. If you submit your images to imaggeo, you retain full rights of use, since they are licenced and distributed by EGU under a Creative Commons licence.

Imaggeo on Mondays: Sequoias in full moon

25 Jun

Sequoias in full moon by Michael Prather, distributed by EGU under a Creative Commons licence.

The Sequoia National Park in Sierra Nevada, California, is one of the most beautiful wilderness areas in the United States. The park, spanning over 1,600 square kilometres, is home to high mountains, deep canyons, and long and pristine caves. But its most distinct feature are giant sequoias, the world’s largest trees.

Sequoias (Sequoiadendron giganteum) grow to an average height of 50 to 85 metres and have typical diametres of six to nine metres. The Sequoia National Park is home to General Sherman, the world’s largest (in volume) living tree, calculated to have a volume close to 1,500 cubic metres.

The giant trees frame a beautiful starry sky in this photo by Michael Prather. He took this picture in February 2010 during a family holiday to the Wuksachi area of the Sequoia National Park. He explains that the picture was taken the night after a very heavy snow storm. “We spent the weekend in Wuksachi, getting hit with about 24″ [~60cm] of snow overnight. The snow on the trees was heavy and lit up like daylight by the moon.  I was surprised to be able to see Orion so clearly with the near-full moon, but the sky was very clear.”

The lower half of the constellation of Orion is visible at the top centre of the photograph. The three stars that make up the belt of The Hunter appear clearly, and a more careful viewing also reveals the fuzzy Orion nebula – the middle of the three ‘stars’ south of the belt.

Imaggeo is the online open access geosciences image repository of the European Geosciences Union. Every geoscientist who is an amateur photographer (but also other people) can submit their images to this repository. Being open access, it can be used by scientists for their presentations or publications as well as by the press. If you submit your images to imaggeo, you retain full rights of use, since they are licenced and distributed by EGU under a Creative Commons licence.

Imaggeo on Mondays: Halo

11 Jun

Halo by Farahnaz Khosrawi, distributed by the EGU under a Creative Commons License

“Ring around the sun or moon brings rain or snow upon you soon.” Before the development of meteorology, visible atmospheric phenomena, such as halos, were used to forecast the weather. Though meteorological prediction has come a long way since then, these extraordinary halos really do appear in the sky on otherwise ordinary days, a lesson learned by Farahnaz Khosrawi when she saw the sun rise on a cold Swedish morning.

Khosrawi, an Associate Professor at the Department of Meteorology, University of Stockholm, recalls her trip to the office, “A wonderful halo was visible [around the sun] in the early morning of 8 December 2010. It was a very cold winter morning in Stockholm with temperatures around -20 C. The picture was taken in front of the university on my way to work. I couldn’t believe my eyes when I saw this wonderful huge halo. I was so glad that I had my camera with me. I never have seen such an halo before and who knows when I will have the chance to see one again.”

Like rainbows, halos are beautiful optical phenomena. However, unlike rainbows, where sunlight hits atmospheric water droplets, halos are formed when light is reflected and refracted by ice crystals in the thin, wispy cirrus clouds high up in the upper troposphere (5–10 km altitude). Khosrawi explains, “The shape and size of the ice crystals determines the appearance of the halo. The halo produced by the ice crystals appears as an arc or spot in the sky. Many halos occur near the sun but others appear elsewhere and can even appear in the opposite part of the sky.”

Two ‘sundogs’, another atmospheric phenomena that takes the shape of two bright spots of light to the left and right of the sun, are also visible in this stunning picture.

Imaggeo is the online open access geosciences image repository of the European Geosciences Union. Every geoscientist who is an amateur photographer (but also other people) can submit their images to this repository. Being open access, it can be used by scientists for their presentations or publications as well as by the press. If you submit your images to imaggeo, you retain full rights of use, since they are licenced and distributed by EGU under a Creative Commons licence.

Geosciences column: The evolution of the air

5 Jun

After a couple of months of absence, GeoLog is once again hosting the Geosciences column. This month we have no less than two posts highlighting recent research in the Earth sciences. In the first of this month’s columns, Amanda Gläser-Bligh writes about recent research on the regulation of the air published in the EGU journal Solid Earth.

If you’d like to contribute to GeoLog, please contact EGU’s Media and Commmunications Officer, Bárbara T. Ferreira at media@egu.eu.


What if the Earth had a thermostat that kept temperatures in the correct range to maintain life? In a recent paper published in Solid Earth, Euan Nisbet of London’s Royal Holloway and his collaborators propose just that.

Despite ups and downs in the atmospheric temperatures over geologic time, the Earth system seems to have maintained an equilibrium temperature of around 15°C. The global temperature appears to be able to correct itself up and down, much like an airplane constantly corrects its route, or a thermostat maintains a given temperature in a room. But how is the atmosphere being regulated on the planet, and who or what is selecting the temperature? An enzyme named rubisco seems to hold the answer.

What regulates the atmospheric composition of the Earth? (Photo: The sky from a plane after sunset, by Konstantinos Kourtidis. Distributed by EGU under a Creative Commons licence.)

Rubisco is one of the most commonly occurring enzymes on the planet: “When you eat your breakfast, you are most likely eating some rubisco,” Nisbet points out. The enzyme occurs in most green matter, having the important role of regulating CO2 intake to be used in photosynthesis, which in turn helps control atmospheric pressure by changing the CO2:O2 ratio.

The enzyme is responsible for the amount of carbon capture from CO2, and it is possible that rubisco’s selection of CO2 in preference to O2 controls the amounts of CO2 taken up by plants and algae, which is changing according to atmospheric conditions. This implies that rubisco itself determines the balance of CO2 and O2 in the air. The theory proposed by Nisbet and collaborators is that natural selection comes into play and causes the photosynthesizing organisms to pull down enough, but not too much, CO2 out of the atmosphere. This creates what is known as the Goldilocks effect: a planet that is not too hot and not too cold, but just right to sustain life.

There is a strong debate as to whether the atmospheric composition has been controlled by organic or inorganic elements. Nisbet and his team claim that while the system is biologically led, the process is a mixture of the two with inorganic chemistry working together with underlying biological trends.

Together with the changes occurring in the Sun, which was much weaker in the past, the greenhouse effect has reduced over time to compensate for this increase in solar temperatures. The suggestion is that rubisco evolution is the main driver of this shift and has created a stable system to maximize biological survival.

Additionally, because rubisco is a biological control, the response to challenging changes in atmospheric conditions (such as a massive volcanic outpouring of CO¬2) can occur rather rapidly when compared to inorganic processes, such as silicate erosion which also absorbs CO2.

To view what the scientific community had to say about the paper, check the article’s interactive discussion. ‘The regulation of the air: a hypothesis’ is the all-time most commented paper on Solid Earth Discussions.

By Amanda Gläser-Bligh, geologist and freelance writer

Publications by the EGU

10 May

The EGU is responsible for 14 Open Access journals, all freely available online

Since 2001, the EGU and Open Access publishing house Copernicus Publications has published a growing number of successful geoscientific journals. These include 14 peer-reviewed Open Access journals, of which 11 have a Thomson Reuters Impact Factor, placing them in the top echelon of their respective discipline. EGU also publishes a host of other materials available in paper and online. As a signatory of the Berlin Open Access Declaration (2003), the EGU is committed to making all their publications freely available.

The EGU’s Open Access scientific journals are:


Stock market crash hits EGU General Assembly shocker!

2 May

Today’s guest post is the second written at the 2012 General Assembly by Michelle Cain, postdoctoral researcher at the University of Cambridge, United Kingdom. Her first covered megacities.

It seems the global economic downturn is so pervasive that it has even hit the Earth sciences! I’ve been to a few talks now that have mentioned the downturn/recession/crisis/apocalypse (delete as appropriate), mainly with reference to emissions of pollutant species or greenhouse gases. I guess this is one of the few good-news stories to come from the bottom falling out of the world’s economy. With no money to burn, production and therefore emissions decreased, thus slowing emissions – ever so slightly.

On Tuesday, Jintai Lin presented some work on NO2 columns measured from space, which he used to back out the NO2 emissions coming from China. (NO2 is itself toxic, and a precursor for ozone, which is a greenhouse gas and is harmful for animal and plant health.) His analysis of the seasonal variation in NO2 showed that the emissions were dominated by anthropogenic sources. Presenting a time series of NO2 columns from satellites, he showed the unmistakable signal from the Chinese economic downturn in 2008-9 (see Lin and McElroy 2011, ACP), and he showed the same signal in aerosol optical depth (a marker for PM2.5 – see my previous blog post for a definition). But this was not to last, as the NO2 caught up again after about a year and a half.

Is recession good for the environment? English Landscape by Norbert Krupp. Distributed on Imaggeo.net by EGU under a Creative Commons license.

Then on Wednesday, Patricia Castellanos showed a similarly striking graph of a stock index (I didn’t catch which one) on the same axes as measures of European industrial activity and road transport. As you might have guessed, they correlated perfectly, all dropping off the edge of a cliff over the space of a few months in 2008. By dropping off a cliff, I mean a 20% decrease in industrial activity and 15% decrease in commercial road transport. Castellanos summarised this effect with what I found to be a surprising finding: NOx is 10-50% lower now than it was in 2004 (that’s not the surprising bit), and at least half of this reduction was due to the recession.

So, for all the EU’s hard work in making policies and targets for air quality, in regulating vehicle emissions and all the other things they are doing to improve the air we breathe, it has at most been as “good” as the recession for reducing NO2 levels. If they are really serious about air quality, policy makers would be wise to reconsider their attitude to economic growth…

By Michelle Cain, University of Cambridge

Imaggeo on Mondays: Hurricane season, from above

30 Apr

Hurricane Season 2010, distributed by EGU under a Creative Commons licence.

From space, planet Earth resembles a glassy blue marble, a term that was first used to describe a photograph of the Earth taken by the Apollo 17 crew on their way to the moon in 1972. Aside from providing stunning views of our planet, images of the Earth taken from above can also be used for meteorological observations. This beautiful photograph, taken by the Meteosat Second Generation (MSG) satellite, is a case in point.

Maximilian Reuter, who submitted the picture to the Imaggeo database describes it in detail. “This image shows a snapshot of the hurricane season 2010.  It was taken on August 28 that year from the MSG satellite in a geostationary orbit 36,000 km above the equator at 0°E. La Niña conditions favoured lower wind shear over the Atlantic Basin. This allowed storm clouds to grow and organise. Atlantic hurricanes often follow a typical path from Africa across the Atlantic to the east cost of the US. Along this way one can see the Category 4 hurricanes Earl and Danielle as well as the developing tropical storm Fiona. Often the remnants of hurricanes become North Atlantic low-pressure systems which are moving towards Europe.”

Reuter, a researcher at the Institute of Environmental Physics, University of Bremen, also provided a labelled image where the hurricane tracks are highlighted. The image, seen below, is part of the Moments from Space collection. Details on the generation of Moments from Space true-colour images have been published in the International Journal of Remote Sensing.

Highlighted hurricane tracks (source: http://www.moments-from-space.com)

Imaggeo is the online open access geosciences image repository of the European Geosciences Union. Every geoscientist who is an amateur photographer (but also other people) can submit their images to this repository. Being open access, it can be used by scientists for their presentations or publications as well as by the press. If you submit your images to imaggeo, you retain full rights of use, since they are licenced and distributed by EGU under a Creative Commons licence.

Megacities at EGU2012

26 Apr

Today’s guest post comes from Michelle Cain, postdoctoral researcher at the University of Cambridge, United Kingdom.

Almost a whole day’s worth of sessions on megacities – where to begin? I certainly couldn’t pick just one talk to write about, so here’s a mish-mash of the session in general and a few talks in particular.

First things first: what is a megacity? Officially defined (by who, I don’t know) as a city of 5 million people or more, there are only two of them in Europe (London and Paris), and both are among the most polluted cities in Europe. There are other European places that embody megacity characteristics without adhering to the strict definition, so the MEGAPOLI project has focused on two of these alongside the two bona-fide megacities. The Po Valley in Italy, surrounded by mountains on three sides, is populated by 16 million people and contains 37% of the country’s industry. The mountains disrupt the large-scale meteorology so that local winds are often slack, which combines with the high levels of industrial, agricultural and residential emissions to cause worse air quality than in either Paris or London.

Loss in life expectancy (months) attributable to exposure to anthropogenic PM2.5 for year 2000 emissions (Source: EC, IIASA)

The air quality is similarly poor in the Rhine-Ruhr valley in Germany, an industrial region with about 10 million inhabitants. This region suffers not only from local emissions, but often from pollution transported from London, Paris and the Netherlands in the prevailing winds. (Thanks to the MEGAPOLI website for the info about these locations).

The reasons why these non-megacities have been brought into the fold highlight the complexities of trying to understand what might happen in the coming years as the world becomes increasingly urbanised. It’s not only the amount of stuff being pumped into the atmosphere that causes air quality issues. It’s equally how much stuff gets vented out of the boundary layer (the lowest layer of the atmosphere, where people live), and how much gets washed out in rain. And what happens to the stuff before it gets removed? And this is not even considering the climate impacts of all this stuff is getting higher up into the atmosphere, where it has a longer lifetime and can be transported long distances, potentially also affecting air quality downwind. All these interactions could be broadly categorised into: emissions, boundary layer meteorology, deposition, chemistry, global transport, and climate.

Several talks in the session were related to emissions evaluations, as how can we hope to understand anything if we’re putting the wrong amount of stuff into the atmosphere? Any by “stuff”, I mean NOx (the sum of NO and NO2, which are pollutants emitted from both anthropogenic and natural sources, and can react to produce ozone, which has adverse health effects) and particulates (the shorthand for particulate matter is PM2.5/PM10 for those with a radius less than 2.5/10 microns, also bad for health), as these were the main topics in the session.

Generating emissions inventories is no trivial task, as is evidenced by the continual work going in to this area. In his talk, S Sahu described the development of an emissions inventory for Delhi and the surrounding areas, which is home to a staggering 30 million people in an area of 70 km x 65 km. For 6 months, an army of 250 students surveyed the residents and businesses to determine a sample of the emission-generating activity in the region. They combined this new data with the existing literature and government statistics to develop a GIS-based emissions inventory. Their results showed that there are 5.7 million vehicles on the roads, and 1.5 million living in slums and cooking with wood, kerosene or LPG (in order of decreasing precedence). The PM2.5 emissions total was 68.1 Gg/year, the largest portion of which was from transport at 30.25 Gg/year. Wind-blown dust and residential emissions were also large contributors. The inventory was used to forecast for the Commonwealth games in 2010 and is currently available for both science and policy uses.

Policy issues were the driver behind R Friedrich’s talk, which directly addressed questions of whether air quality policies could result in the desired policy outcome – surely an important factor in decision-making. As part of the EU MEGAPOLI project, his work took a “full chain approach”, whereby the scenario with and without the policy measure was modeled to determine the effectiveness of a policy. The reference scenario assumes the current EU energy and climate package was taken forward. Then each policy was added to the model, and the difference can be described in monetary terms or by DALYs (disability adjusted life years).

The study generated some surprising results. Twenty four policy measures were ranked in terms of avoided DALYs for Paris, and the best measure by this metric was to change to efficient combustion of gaseous fuels (which generate less PM than wood), followed by biomass fuels. However, different metrics paint a different picture. Calculating the efficiency of each measure in monetary terms put coke dry quenching (as opposed to wet quenching which generates PM) in the top spot, followed by use of biofuels, use of district-wide heating networks, an aviation kerosene tax and a switch to electric vehicles. The least efficient measure was a passenger car toll (which, for example, London has had since 2003). Interestingly, the implementation of a low emissions zone was shown to have a negative or neutral effect. On the other hand, the speaker recommended the improvement of traffic management as an efficient measure.

Another EU project, CityZEN, also linked the science with policy needs by producing some 2 page policy briefs on ozone, PM, observations and the East Mediterranean air pollution hotspot, and was discussed by several speakers. Other talks and poster covered the links between meteorology and chemistry, observations and models, but I’m afraid this is all I have time for… See you next time, on the GeoLog.

By Michelle Cain, University of Cambridge

Imaggeo on Mondays: Seeing double

27 Feb

Double rainbow over a Tibetan Plateau lake by Janneke IJmker, distributed by EGU under a Creative Commons licence.

On 6 September 2009, monsoon clouds had built up throughout the day over the Donggi Cona lake in central China. Janneke IJmker, now a researcher at Deltares in the Netherlands, was doing fieldwork there as part of her PhD at RWTH Aachen University in Germany. By dinner time, the sun shone on raindrops from the clouds producing a magnificent double rainbow over the lake, which IJmker captured with her camera.

“The photograph was taken during a fieldwork study of Holocene climate variations in the Donggi Cona lake catchment on the north-eastern Tibetan Plateau. Monsoon clouds and intense solar radiation resulted in this double rainbow, nicely demonstrating the reversal of colours in the secondary rainbow,” IJmker noted.

Secondary rainbows are the result of a double reflection of sunlight inside the water droplets. This second reflection causes the colours of the secondary rainbow to be inverted, with blue on the outside and red on the inside, compared to the primary.

Imaggeo is the online open access geosciences image repository of the European Geosciences Union. Every geoscientist who is an amateur photographer (but also other people) can submit their images to this repository. Being open access, it can be used by scientists for their presentations or publications as well as by the press. If you submit your images to imaggeo, you retain full rights of use, since they are licenced and distributed by EGU under a Creative Commons licence.

Imaggeo on Mondays: Orange anvils

13 Feb

Orange anvils by Katja Weigel, distributed by EGU under a Creative Commons licence.

The anvils in this picture are not heavy steel or iron blocks but rather soft clouds coloured orange by the setting sun. The term is used to describe the upper part of a cumulonimbus or thunderstorm cloud that tends to spread out in an anvil shape as warm air bumps up against the bottom of the stratosphere (the atmospheric layer between 15-50 kilometres height).

Katja Weigel, a researcher at the Institute of Environmental Physics, University of Bremen, Germany took this picture at Mindil Beach in Darwin, Australia, shortly after sunset on 11 November 2005. She travelled there for the SCOUT-O3 (Stratospheric-Climate Interactions with Emphasis on the Upper Troposphere and Lower Stratosphere) campaign.

“The aim of the campaign was to observe and investigate transport into the stratosphere by strong tropical convection. The 11 November 2005 was the day before the research aircraft M55-Geophysika arrived in Darwin. Therefore, we did not take measurements in the clouds shown here but in and around similar clouds during the following weeks,” Weigel said.

More information about the SCOUT-O3 can be found in the campaign’s flyer, or in the special issue ‘SCOUT-O3 Tropics’ of the EGU journal Atmospheric Chemistry and Physics.

Imaggeo is the online open access geosciences image repository of the European Geosciences Union. Every geoscientist who is an amateur photographer (but also other people) can submit their images to this repository. Being open access, it can be used by scientists for their presentations or publications as well as by the press. If you submit your images to imaggeo, you retain full rights of use, since they are licenced and distributed by EGU under a Creative Commons licence.