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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.

Imaggeo on Mondays: Isolated storm

Imaggeo on Mondays: Isolated storm

Clouds and storms are formed when warm, moist air rises. This causes the air to expand and cool: forming clouds as the moisture condenses onto particles suspended in the air (called cloud condensation nuclei). Normally, air rises from surface heating, or when warm and cold air pockets collide, or if air is pushed upwards when passing over hills or mountains. If this heating, and subsequent rising, is rapid enough then thunderstorms can form.

This imaggeo on Mondays photo shows an isolated thunderstorm roughly 50 km North of Vienna. The difference between an isolated thunderstorm and scattered storms is how much coverage the clouds have over a given area. If less than 10-20 % is covered then these storms are described as isolated. Scattered storms occur when coverage is at least 30-50 %. These storms can lead to downpours lasting a few minutes that then leads to sunny spells, only to have another rain storm occur again shortly afterwards.1

Globally, there are roughly 16 million thunderstorms each year, and at any given moment, there are ~2,000 thunderstorms in progress.2 The visible dark grey anvil shape and the fact that the lighter clouds above appear to be being ‘pulled into’ the storm suggests that this is a ‘severe’ thunderstorm. This means that the storm is self-supporting3 and can cause more extreme impacts than a normal thunderstorm. Rainfall is more intense and can cause flash flooding. In some cases, hail over 2.5 cm large can fall and tornados can even be formed.4 For more information about severe thunderstorms please check out the further reading list below.

By Sarah Connors, EGU Science Policy Officer

Further reading / sources

[1] – Aerostorms Scattered vs. Thunderstorms – http://www.aerostorms.com/scattered-vs-isolated-thunderstorms-what-is-the-difference/

[2] – Thunderstorm Basics – http://www.nssl.noaa.gov/education/svrwx101/thunderstorms/

[3] – Royal Meteorological Society Thunderclouds presentation – http://www.met.reading.ac.uk/~sgs02rpa/CONTED/WEATHER09_thunder.pdf

[4] – Frequently Asked Questions About Thunderstorms – http://www.nssl.noaa.gov/education/svrwx101/thunderstorms/faq/

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/.

Geosciences Column: Recent and future changes in the Greenland Ice Sheet

Geosciences Column: Recent and future changes in the Greenland Ice Sheet

Over the past few decades, the Arctic region has warmed more than any other on Earth. The Greenland Ice Sheet is losing mass faster than ever before, and is expected to keep melting with consequences for global sea-level rise and ocean circulation. At a media briefing, during the EGU’s General Assembly in April (stream it here), researchers presented new results on the factors that influence the Greenland Ice Sheet’s rapid and profound changes – from glacial lakes to clouds and snow darkening.

The vast expanse of the Greenland Ice Sheet covers an area of 1.71 million km2 (approximately a tenth of the size of Russia), and holds a staggering volume of ice: 2.85 million km3. The ice sheet is only rivalled in size by one other: the Antarctic Ice Sheet. Scientist have calculated that the Greenland Ice Sheet stores enough freshwater to raise sea level by 7.4m, should all the ice melt, so understanding what causes the ice to melt now and in the future is critical!

The importance of clouds

When you think of clouds, you probably think of them as purveyors of rain and bad weather. But that is not all; clouds form an intrinsic part of the climate system which is more complex than simply how they affect day to day weather. In Greenland, (as elsewhere across the globe), clouds are a source of precipitation, bringing all-important snow which accumulates on the ice sheet and makes it grow in size.

Southern Tip of Greenland.  Satellite Image by  NASA. Source: Wikimedia Commons

Southern Tip of Greenland. Satellite Image by NASA. Source: Wikimedia Commons

Clouds also affect temperatures: on a clear day you’ll feel the warmth of the sun on your back, but as night falls temperatures start dropping quickly as heat is lost to the atmosphere. However, if in the late afternoon the clouds started rolling in, the night would be warmer, as clouds stop heat being lost to the atmosphere. If they stick around long enough though, they promote cooling, as they reflect sunlight away from the Earth’s surface.

“On a global scale, clouds (on average) tend to cool the Earth’s surface, but there are many regional differences”, explained Kristof Van Tricht,(a PhD student at the University of Leuven in Belgium), during the press conference.

It turns out that, in Greenland, the warming effect of clouds dominates, and warming of the surface encourages melting of the ice sheet. However, the remoteness of the area means that direct observations of just how much the clouds warm the surface and to what extent this impacts on the ice sheet has been limited. Until now.

Using satellite observations, Van Tricht and his team have been able to study the warming effect of clouds in more detail than ever before. Their models show that, in the presence of clouds, the Greenland Ice Sheet can be up to 1.2°C warmer, which can cause substantial melting. Compared to models ran without cloud cover, the ice sheet could melt up to 38% more. This equates to 12% more runoff from the ice sheet into the oceans, solely due to the presence of clouds.

Predictions of what the findings mean for the ice sheet in the future are tricky though. The scientists’ model is based on real-time observations and so it isn’t possible to look into the future. For that, improved cloud model simulations are needed.

Beautiful lakes

Lakes form, seasonally, on the surface of the Greenland Ice Sheet as a result of run-off water pooling in depressions in the ice. Although beautiful to look at, because they are darker than the surrounding ice, they attract more heat. The lakes also drain sporadically, and when they do, some of the water they hold drains through the ice making its way to the base of the ice sheet. Once there, the water lubricates the base of the ice sheet and promotes it to flow more easily and quickly towards the ocean. Combined, these two effects affect the dynamics of the ice sheet.

 Drained Supraglacial Lake Bed. This lake has drained through the bottom for several years in a row. The large block was initially formed in summer of 2006, but large cracks run through it from subsequent lake drainages.  Credit: Ian Joughin (distributed via  imaggeo.egu.eu )

Drained Supraglacial Lake Bed. This lake has drained through the bottom for several years in a row. The large block was initially formed in summer of 2006, but large cracks run through it from subsequent lake drainages.
Credit: Ian Joughin (distributed via imaggeo.egu.eu )

At present, the lakes generally form within the ablation zone – the low-altitude regions towards the edges of the ice sheets where ice is lost through melting, evaporation, calving and other processes – where it is already warmest on the ice sheet.

At the press conference, Andrew Sheperd presented research carried out by Amber Leeson, on how the location on the ice at which the supraglacial (meaning they form on the surface of the ice) lakes form might change with a warming climate and what this means for the Greenland Ice Sheet.

As the climate warms, higher altitude regions on the ice sheet will too. Through building a hydrological model, Leeson found that the lakes spread father inland. According to Leeson’s simulation

“by 2050, the lakes have spread about 50 to 100 km further inland, so more of the ice sheet is potentially exposed to this lubrication effect,” added Shepard.

This is equivalent to an estimated 48–53% increase in the area over which they are distributed across the ice sheet as a whole.

Previous studies of how the ice sheet might respond to a warming climate do not consider the effects of the added melt water volume at the base of the ice sheet as a result of more lakes at the surface. Leeson’s findings mean that these models need to be re-run so that scientists can fully understand the potential implications. This is particularly true in terms of the lubrication effect at the base of the ice and whether the ice will more readily slip towards the oceans, potentially heightening the risk of sea level rise.

 By Laura Roberts, EGU Communications Officer

 

Further reading and information

You can stream the full press conference by following this link: http://client.cntv.at/egu2015/PC9.

Details of the speakers at the press conference are available at: http://media.egu.eu/press-conferences-2015/#greenland

This blog post presents only some of the findings which were discussed during the press conference. Other aspects of this press conference where covered in the media, you can find more on those here and by following this link.

Kristof Van Tricht, Gorodetskaya, I.V., L’Ecuyer, T. et al. Clouds enhance Greenland ice sheet mass loss, Geophysical Research Abstracts Vol. 17, EGU2015-12737-1, 2015 (conference abstract).

Amber A. Leeson, Sheperd, A., Briggs, K. et al. Supraglacial lakes on the Greenland ice sheet advance inland under warming climate, Nature Climate Change, 5, 51–55, doi:10.1038/nclimate2463, 2015.

Amber A. Leeson, Sheperd, A., Briggs, K. et al. Supraglacial lakes advance inland on the Greenland ice sheet under warming climate, Geophysical Research Abstracts, Vol. 17, EGU2015-934-1, 2015 (conference abstract).

Imaggeo on Mondays: Fuelling the clouds with fire

Wildfires frequently break out in the Californian summer. The grass is dry, the ground parched and a small spark can start a raging fire, but burning can begin even when water is about. Gabriele Stiller sets the scene for a blaze beside Mono Lake, exploring the events that got it going and what it may have started in the sky… 

While on shores of Mono Lake in the summer of 2012, I spotted something strange in the distance: a great blaze on the other side of the lake. We were on a trip through the southwestern states (a long tour through California, Nevada, Utah and Arizona). All the days before we had been continuously accompanied by thunderstorms that broke out during the afternoon. The photo was taken before the daily thunderstorm, and the large convective system already hinted to the next storm to come – and indeed it did, just a few hours later.

Desert fires close to Mono Lake, California. (Credit: Gabriele Stiller via imageo.egu.eu)

Desert fires close to Mono Lake, California. (Credit: Gabriele Stiller via imageo.egu.eu)

It was not clear if this convective cloud system was generated by uplift of heated air initiated by the fire, a process known as pyro-convection, or if it was simply a coincidence. After all, thunderstorms were a regular occurrence throughout our trip. This could have been the storm of the day, and the related convection could have transported the air and smoke from the fire upwards. Or a combination of both could have been behind it. The cumulus cloud was quite isolated, with clear sky surrounding it, but you can already see a small anvil developing (the area where ice is formed in the cloud) above the cauliflower-like cumulus – a hint towards a developing thunderstorm. Such a development would make the cloud into a cumulonimbus cloud.

So what caused the blaze? On 8 August 2012, the wildfire was started through lightning ignition by a thunderstorm coming from the Sierra Nevada, and it burned for several days on open grassland, far from human infrastructure. Due to these circumstances, firefighting was not particularly difficult for the authorities. However, more than 13000 acres were burned, and more than 500 people fought the fire. One of the priorities was to keep the amount of sage-grouse habitat burned to a minimum.

By Gabriele Stiller, Karlsruhe Institute of Technology, Karlsruhe, Germany

Imaggeo is the EGU’s open access geosciences image repository. Photos uploaded to Imaggeo can be used by scientists, the press and the public provided the original author is credited. Photographers also retain full rights of use, as Imaggeo images are licensed and distributed by the EGU under a Creative Commons licence. You can submit your photos here.