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clouds

Imaggeo on Mondays: Cumulonimbus, king of clouds

Imaggeo on Mondays: Cumulonimbus, king of clouds

This wonderful mature thunderstorm cell was observed near the German Aerospace Center (DLR) Oberpfaffenhofen. A distinct anvil can be seen in the background meanwhile a new storm cell is growing in the foreground of the cumulonimbus structure. Mature storm cells like this are common in Southern Germany during the summer season. Strong heat, enough moisture, and a labile stratification of the atmosphere enables the development of this exciting weather phenomenon.

Description by Martin Köhler, as it first appeared on imaggeo.egu.eu.

Imaggeo is the EGU’s online open access geosciences image repository. All geoscientists (and others) can submit their photographs and videos to this repository and, since it is open access, these images can be used for free by scientists for their presentations or publications, by educators and the general public, and some images can even be used freely for commercial purposes. Photographers also retain full rights of use, as Imaggeo images are licensed and distributed by the EGU under a Creative Commons licence. Submit your photos at http://imaggeo.egu.eu/upload/.

Imaggeo on Mondays: Refuge in a cloudscape

Imaggeo on Mondays: Refuge in a cloudscape

The action of glaciers combined with the structure of the rock to form this little platform, probably once a small lake enclosed between a moraine at the mountain side and the ice in the valley.

Now it has become a green haven in the mountain landscape, a perfect place for an alp. In the Alps, stratus clouds opening up on autumn mornings often create gorgeous light display.

That day, some of the first light landed on this exact spot, while the mountain shadows still covered the valley bottom.

Description by Julien Seguinot, as it first appeared on imaggeo.egu.eu

Imaggeo is the EGU’s online open access geosciences image repository. All geoscientists (and others) can submittheir photographs and videos to this repository and, since it is open access, these images can be used for free by scientists for their presentations or publications, by educators and the general public, and some images can even be used freely for commercial purposes. Photographers also retain full rights of use, as Imaggeo images are licensed and distributed by the EGU under a Creative Commons licence. Submit your photos at http://imaggeo.egu.eu/upload/.

Extraordinary iridescent clouds inspire Munch’s ‘The Scream’

Screaming clouds

Edvard Munch’s series of paintings and sketches ‘The Scream’ are some of the most famous works by a Norwegian artist, instantly recognisable and reproduced the world over. But what was the inspiration behind this striking piece of art?

The lurid colours and tremulous lines have long been thought to represent Munch’s unstable state of mind; a moment of terror caught in shocking technicolour. At the same time, scientists have recently identified the connection between the great works of artists such as William Turner and the red and orange sunsets which can be a result of the global impact of volcanic aerosols. However, research presented this week at the European Geosciences Union General Assembly in Vienna by atmospheric scientists in Oslo Norway, suggests that the painting might show us evidence of something much stranger, and rarer – nacreous clouds.

Nacreous or mother-of-pearl clouds, are an extremely rare form of cloud created 20-30km above sea level – in the polar stratosphere when the air is extremely cold (between -80 and -85 degrees centigrade) and exceptionally humid,. So far observed mostly in the Scandinavian countries, these clouds are formed of microscopic and uniform particles of ice, orientated into thin clouds. When the sun is below the horizon (before sunrise or after sunset), these clouds are illuminated in a surprisingly vibrant way blazing across the sky in swathes of red, green, blue and silver. They have a distinctive wavy structure as the clouds are formed in the lee-waves behind mountains.

In 2014, these clouds were seen again over the skies of Oslo and given their extreme colouration and unexpected appearance, a photographer, Svein Fikke, immediately thought of Munch’s work. This perceived similarity between the mother of pearl clouds and the striking clouds and sense of tension in the painting is only reinforced when reading Munch’s writings about his experiences on the day that inspired the painting.

“I went along the road with two friends – the sun set

I felt like a breath of sadness –

– The sky suddenly became bloodish red

I stopped, leant against the fence, tired to death – watched over the

Flaming clouds as blood and sword

The city – the blue-black fjord and the city

– My friends went away – I stood there shivering from dread – and

I felt this big, infinite scream through nature”

                            Edvard Munch’s Diary Notes 1890-1892 (Tøjner and Gundersen, 2013)

Scientists have, in the past, used artworks to infer environmental conditions; from paintings of the ‘frost fairs’ held on the River Thames that show the gradual environmental change in Europe, to the discovery that several artists depict the influence of volcanic aerosols on global atmosphere in their paintings.

In a study conducted in 2007 (and 2014), scientists found that the visible impact that volcanic aerosols have on the atmosphere has in fact been recorded in the works of many of the great masters – particularly William Turner (Zerefos et al, 2007)). Several of Turner’s paintings depict sunsets with a distinct red/orange hue, distinct from his usual work of other years. This was correlated with significant volcanic eruptions in the same time period and the researchers found that these reddish paintings were all created in the years of, or immediately following, a major eruption (shown in the graph below).

Graph to show the relationship between colour and volcanic aerosols (a)The mean annual value of R/G measured on 327 paintings. (b)The percentage increase from minimum R/G value shown in (a). (c)The corresponding Dust Veil Index (DVI). The numbered picks correspond to different eruptions as follows: 1. 1642 (Awu, Indonesia-1641), 2. 1661 (Katla, Iceland-1660), 3. 1680 (Tongkoko and Krakatau, Indonesia-1680), 4. 1784 (Laki, Iceland-1783), 5. 1816 (Tambora, Indonesia-1815), 6. 1831 (Babuyan, Philippines-1831), 7. 1835 (Coseguina, Nicaragua-1835). 8. 1883 (Krakatau, Indonesia-1883). From Zerefos et al (2007).

For many years ‘The Scream’ was thought to also show the influence of a volcanic eruption, most likely the catastrophic eruption of Krakatoa in 1883 (described here by Volcanologist David Pyle), but whereas volcanic skies tend to tint the whole sky a red/orange, the skies in the scream have a distinct pattern, only seen in these extremely rare nacreous clouds.

How rare are they? Well, researcher Dr Helene Muri, a researcher based at the University of Oslo, who presented the research at the press conference, said that in her lifetime living mostly in Norway as an atmospheric researcher she has only seen them once. And what about Munch’s feeling of dread and ‘breath of sadness’?

Well, having a glowing swathe of iridescent petrol coloured clouds flare into bright relief after sunset, only for them to disappear 30 minutes later would be pretty shocking for any of us, even in our modern days of fluorescent streetlamps and light polluted skies.

By Hazel Gibson, EGU Press Assistant at the EGU 2017 General Assembly

GeoTalk: How are clouds born?

GeoTalk: How are clouds born?

Geotalk is a regular feature highlighting early career researchers and their work. In this interview we speak to Federico Bianchi, a researcher based at University of Helsinki, working on understanding how clouds are born. Federico’s quest to find out has taken him from laboratory experiments at CERN, through to the high peaks of the Alps and to the clean air of the Himalayan mountains. His innovative experimental approach and impressive publication record, only three years out of his PhD, have been recognised with one of four Arne Richter Awards for Outstanding Early Career Scientists in 2017.

First, could you introduce yourself and tell us a little more about your career path so far?

I am an enthusiastic atmospheric chemist  with a passion for the mountains. My father introduced me to chemistry and my mother comes from the Alps. This mix is probably the reason why I ended up doing research at high altitude.

I studied chemistry at the University of Milan where I got my degree in 2009.  During my bachelor and master thesis I investigated atmospheric issues affecting the polluted Po’ Valley in Northern Italy and since then I have always  worked as an atmospheric chemist.

I did my PhD at the Paul Scherrer Institute in Switzerland where I mainly worked at the CLOUD experiment at CERN. After that, I used the acquired knowledge to study the same phenomena, first, at almost 4000 m in the heart of the Alps and later at the Everest Base Camp.

I did one year postdoc at the ETH in Zurich and now I have my own Fellowship paid by the Swiss National Science Foundation to conduct research at high altitude with the support of the University of Helsinki.

We are all intimately familiar with clouds. They come in all shapes and sizes and are bringers of shade, precipitation, and sometimes even extreme weather. But most of us are unlikely to have given much thought to how clouds are born. So, how does it actually happen?

We all know that the air is full of water vapor, however, this doesn’t mean that we have clouds all the time.

When air rises in the atmosphere it cools down and after reaching a certain humidity it will start to condense and form a cloud droplet. In order to form such a droplet the water vapor needs to condense on a cloud seed that is commonly known as a cloud condensation nuclei. Pure water droplets would require conditions that are not present in our atmosphere. Therefore, it is a good assumption to say that each cloud droplet contains a little seed.

At the upcoming General Assembly you’ll be giving a presentation highlighting your work on understanding how clouds form in the free troposphere. What is the free troposphere and how is your research different from other studies which also aim to understand how clouds form?

The troposphere, the lower part of the atmosphere, is subdivided in two different regions. The first is in contact with the Earth’s surface and is most affected by human activity. This one is called the planetary boundary layer, while the upper part is the so called free troposphere.

From several studies we know that a big fraction of the cloud seeds formed in the free troposphere are produced by a gas-to-particles conversion (homogeneous nucleation), where different molecules of unknown substances get together to form tiny particles. When the conditions are favourable they can grow into bigger sizes and potentially become cloud condensation nuclei.

In our research, we are the first ones to take state of the art instrumentation, that previously, had only been used in laboratory experiments or within the planetary boundary layer, to remote sites at high altitude.

Federico has taken state of the art instrumentation, that previously, had only been used in laboratory experiments or within the planetary boundary layer, to remote sites at high altitude. Credit: Federico Bianchi

At the General Assembly you plan on talking about how some of the processes you’ve identified in your research are potentially very interesting in order to understand the aerosol conditions in the pre-industrial era (a time period for when information is very scarce). Could you tell us a little more about that?

Aerosols are defined as solid or liquid particles suspended in a gas. They are very important because they can have an influence on the Earth’s climate, mainly by interacting with the solar radiation and cooling temperatures.

The human influence on the global warming estimated by the Intergovernmental Panel for Climate Change (known as the IPCC) is calculated based on a difference between the pre-industrial era climate indicators and the present day conditions. While we are starting to understand the aerosols present currently, in the atmosphere, we still know very little about the conditions before the industrial revolution.

For many years it has been thought that the atmosphere is able to produce new particles/aerosol only if sulphur dioxide (SO2) is present. This molecule is a vapor mainly emitted by combustion processes; which, prior to the industrial revolution was only present in the atmosphere at low concentrations.

For the first time, results from our CLOUD experiments, published last year,  proved that organic vapours emitted by trees, such as alpha-pinene, can also nucleate and form new particles, without the presence of SO2. In a parallel study, we also observed that pure organic nucleation can take place in the free troposphere.

We therefore have evidence that the presence of sulphur dioxide isn’t necessary to make such a mechanism possible. Finally, with all this new information, we are able to say that indeed, in the pre-industrial era the atmosphere was able to produce new particles (clouds seeds) by oxidation of vapors emitted by the vegetation.

Often, field work can be a very rewarding part of the research process, but traditional research papers have little room for relaying those experiences. What were the highlights of your time in the Himalayas and how does the experience compare to your time spent carrying out laboratory experiments?

Doing experiments in the heart of the Himalayas is rewarding. But life at such altitude is tough. Breathing, walking and thinking is made difficult by the lack of oxygen at high altitudes.

I have always been a scientists who enjoys spending time in the laboratory. For this reason I very much liked  the time I spent in CERN, although, sometimes it was quite stressful. Being part of such a large international collaboration and being able to actively do science was a major achievement for me. However, when I realized I could also do what I love in the mountains, I just couldn’t  stop myself from giving it a go.

The first experiment in the Alps was the appetizer for the amazing Himalayan experience. During this trip, we first travelled to Kathmandu, in Nepal. Then, we flew to Luckla (hailed as one of the scariest airport in the world) and we started our hiking experience, walking from Luckla (2800 m) up to the Everest Base Camp (5300 m). We reached the measurement site after a 6 days hike through Tibetan bridges, beautiful sherpa villages, freezing nights and sweaty days. For the whole time we were surrounded by the most beautiful mountains I have ever seen. The cultural element was even more interesting. Meeting new people from a totally different culture was the cherry on the cake.

However I have to admit that it was not always as easy as it sounds now. Life at such altitude is tough. It is difficult to breath, difficult to walk and to install the heavy instrumentation. In addition to that, the temperature in your room during nights goes well below zero degrees. The low oxygen doesn’t really help your thinking, especially we you need to troubleshoot your instrumentation. It happens often that after such journey, the instruments are not functioning properly.

I can say that, as a mountain and science lover, this was just amazing. Going on a field campaign is definitely the  best part of this beautiful job.

To finish the interview I wanted to talk about your career. Your undergraduate degree was in chemistry. Many early career scientists are faced with the option (or need) to change discipline at sometime throughout their studies or early stages of their career. How did you find the transition and what advice would you have for other considering the same?

As I said before, I studied chemistry and by the end of my degree my favourite subject moved to atmospheric chemistry. The atmosphere is a very complex system and in order to study it, we need a multidisciplinary approach. This forced me to learn several other aspects that I had never been in touch with before. Nowadays, I still define myself as a chemist, although my knowledge base is very varied.

I believe that for a young scientist it is very important to understand which are his or her strengths and being able to take advantage of them. For example, in my case, I have used my knowledge in chemistry and mass spectrometry to try to understand the complex atmospheric system.

Geotalk is a regular feature highlighting early career researchers and their work.