Atmospheric Sciences

Atmospheric Sciences

How does weather affect volcanoes?

How does weather affect volcanoes?

I was taking a plane trip home recently. To kill the time I got talking with the person sitting next to me and naturally one of their first questions was to ask me what I did for a living. To avoid a complicated discussion about the nuances of my research I summarised – ‘I am a volcanic meteorologist’. They were interested and wanted to know all about how volcanoes affect the weather, my opinion on ‘that Icelandic eruption’ and told me some slightly left-field opinions on climate change. It was an interesting chat and it got me thinking, volcanoes seem to have several well known impacts on weather but can weather have an impact on volcanoes?

At first it appears quite strange that something seemingly so solid can be altered by atmospheric processes. But in the case of mudflows this is exactly what can happen – rain mixing with soil causing soft wet mud to slide down a hill. In the case of volcanoes, a lahar can form, a mudflow consisting of volcanic debris with the consistency of wet concrete which cascades down the slopes of a volcano.

Water has also been known to trigger rockfalls by getting into the cracks between rocks and weakening them. This same erosion process can erode scree from the summit of a volcano.

Lava domes (a roughly circular shaped mound created from the slow extrusion of lava from a volcano) are known to grow in the absence of rainfall. When it rains water seeps into the cracks between rocks in the lava dome. The lava dome is very hot so rain instantly vapourises. Hence a large rain rate is needed to get further inside cracks in the rocks. Once deep inside, the rainwater vapourises into high pressure steam as it encounters temperatures in excess of 300 C. This destabilises the lava dome and sometimes leads to a collapse.

A collapsing lava dome creates a pyroclastic flow, a high-density mix of volcanic rocks and gas travelling down the slopes of a volcano at high speed and destroying almost everything it its path. A 2001 lava dome collapse is thought to have been triggered by rainfall.

Excessive rainfall can and does impact volcanoes. Having said this hurricanes and other large storms, having a rainfall rate needed to cause water to seep into the lava dome of a volcano are mostly found in the tropics.

Do you know of any other cases of weather affecting volcanoes? The author would be interested to know – please post your suggestions in the comments.

Atmospheric Modelling with Meso-NH

Atmospheric Modelling with Meso-NH

Twice a year in Toulouse Meteo-France runs a tutorial on Meso-NH – the non-hydrostatic mesoscale atmospheric model of the French research community. Last week I was fortunate enough to attend their autumn 2015 tutorial. But, what is this model and was the tutorial useful?

Atmospheric models solve the governing equations for atmospheric motions. This allows us, for example, to forecast future atmospheric conditions, to study past climates or even to visualise tiny features over a range of a few tens on metres. Over the last 90 years atmospheric models have developed from a thought concept to low resolution global simulations to high resolution models being able to simulate all kinds of small scale meteorological phenomena. The last of these achievements has been made within the last 15 years using a set of equations and assumptions known as non-hydrostatic modelling.

A non-hydrostatic model is quite simply one in which the atmosphere is not assumed to be in hydrostatic equilibrium. This means that high resolution features can be simulated such as small-scale convection. Processes that are very small or too complex are simulated via parametrisations whereby each small process is represented by relating them to variables at a resolution that the model can resolve. In this way very complex models can be built up simulating many small features of the atmosphere. A mesoscale model has sufficiently high resolution that it can simulate mesoscale weather features.

There are many different non-hydrostatic mesoscale models with different parametrisations for different applications and they are run by different organisations across the world. Recent increases in computing capacity have meant that the complexity of these models is greater than ever before. There are many popular non-hydrostatic mesoscale models including but not limited to the Weather Research and Forecasting Model (WRF), Unified Model (UM), and Meso-NH. This is definitely not the place to start a debate on the drawbacks of different models! However a feature of many but not all of these models is that they are open source, the programming code used to run them is available for modification or enhancement by anyone, this is great for the development of new parametrisations.

The Meso-NH tutorial was split over three days, the first spent on theory about the model. The second was concerned with theory and practise with an idealised atmosphere over fictitious terrain. The third concentrated just on theory and practise with an actual case study of a real meteorological event. Approaching the tutorial in French as a non-native speaker was initially daunting but there are English subtitles and all the documentation is provided in English – this is no excuse not to become fully immersed in this model. Meso-NH is by no means a basic model and the learning curve is steep but coming from a background in a different non-hydrostatic mesoscale model (WRF) it was very intuitive. Impressive features of the model included the breadth of options for the details of different parametrisations and the post-processing display and interpretation options for the model simulations.

Why should we care about a building’s energy consumption?

Why should we care about a building’s energy consumption?

From the 9th to the 11th of September the Solar Energy and Buildings Physics laboratory is hosting the CISBAT conference. This international meeting is seen as a leading platform for interdisciplinary dialog in the field of sustainability in the built environment. More than 250 scientists and people from the industry will be at EPFL in Lausanne to talk about topics from solar nanotechnologies to the metabolism in urban districts.

But how is this related to Atmospheric Science really? As you might know, this year the United Nations Climate Change Conference COP21 meeting will be held in Paris and the focus is to try to limit the global temperature increase to 2ºC. Switzerland has already submitted its proposal regarding its future emission and aims at reducing it by 50% by 2030. Many other countries have done the same, but NGO’s are saying that the most important greenhouse gas (GHG) emitters are not going far enough in their proposals to limit the temperature increase.

So what are the sectors where we can decrease our energy consumption, improve the efficiency and decrease our GHG emissions? If we look at France for example, the building sectors consumes about 44% of the final energy use. From these 44%, around 70% is used only for the thermal comfort on the occupants.


inbuildings Energy use for each sector (top) and inside buildings (bottom) adapted from French Environmental Energy Agency (Image credit: D. Mauree, 2014)

This conference is also an official presentation platform for the Swiss Competence Center for Energy Research “Future Energy Efficient Buildings & Districts” (FEEB&D). This project aims is to reduce the end energy demand of the Swiss building stock by a factor of five during the next decades thanks to efficient, intelligent and interlinked buildings.

From the figures above we have seen that there is here a huge potential to decrease our energy consumption. First we can improve the insulation of the buildings to enhance their efficiency. Several countries have implemented financial incentives to incite renovation but have also introduced tighter thermal regulations to decrease energy use in new and refurbished buildings.

In this conference, we will also be talking about the integration of renewable energies (RE) (solar PV, thermal, algae, wind, …). The idea of course is to improve the penetration of RE in urban areas so as to decrease our dependency on fossil fuels and hence of course reduce our GHG emissions. In order to reach this objective, it is then necessary to optimize their installations in order to see how we can reach the greatest autonomy possible with RE and the usage of storage solutions.

Among other subjects that will be presented during this meeting are model predictive control and daylighting and electric lighting. We will also address some issues related to urban simulation (you can have a look at a former blog post on this subject) / ecology and metabolism. Have a look at the CISBAT website and follow us on Twitter. I will also try to LT the conference with #cisbat15.

Urban Climate

Urban Climate

The 9th International Conference on Urban Climate and the 12th Urban Environment Symposium are taking place this week in the “Pink City” Toulouse. With the 21st Conference of Parties (COP21) which will be held in December in Paris, the obvious focus topic for the urban climate conference is the mitigation and adaptation to climate change in urban environment.

But, first of all, why should we even care about the urban climate and environment? One of the most important phenomena related to the urban climate that was first described by Luke Howard (1833) is the Urban Heat Island. This effect is caused by the accumulation of heat due to the various construction materials (asphalts, tiles, bricks…) used in urban areas. At night the urban areas hence cool less than in a natural environment and this leads to a higher temperature than the surrounding rural areas (see Figure). The difference in temperature can be up ot 8 degrees for some cities and for particular period during the year. Besides the presence of buildings also cause a modification of the wind pattern in cities.

One “simple” example of the significant impact of these effects is for example change the heating /cooling use in cities. Building energy demand is directly correlated with the outside air temperature but also to the wind speed. Thus, as the temperature is higher in urban areas, there is a greater need for cooling demand in temperate or arid climate. However, even in moderate climate, during long heat wave (and this is expected to become more frequent with climate change!) it can be expected that the cooling energy demand will increase.

Since 2010, over 50% of the world population lives in urban areas and this figure is expected to rise to 75% in 2050 (UN, 20121). As more people live in cities, this means that the cities need to grow to accommodate for the additional population. Urban expansion and densification as well as the decrease in agricultural land are crucial development issues that need to be addressed.

This means that we have to understand the various processes influencing the meteorological parameters in these areas. Model and simulation tools are ways to understand these complex problems and can be very useful tools for decision makers as it is an easier way to analyse different planning scenarios. Many scientists are also working on monitoring and measuring various meteorological parameters with traditional equipment but also with newer methods using mobile phones and other sensors.

The combined effects mentioned above can raise a number of questions:

  1. With climate change in mind, how do we build more buildings consuming less energy to accommodate for the increasing population?
  1. We have seen, for ex. in the summer 2003, that a long heat wave can increase significantly the number of deaths among vulnerable urban population (elder and younger people as well as people with respiratory problems). How do we then make sure that the thermal comfort of the inhabitants is satisfied in cities?
  1. Finally, how do we make sure that we build, design and plan more sustainable cities to decrease the impact of air pollution, to integrate more green and vegetated spaces…

All of these questions are very difficult to answer as they are a combination of scientific research questions but also of policy and planning decision. Scientists and planners should hence work together to build more sustainable cities and to provide meaningful implementation of the different research solutions.

1UN. World Urbanization Prospects: The 2011 Revision, CD-ROM Edition. Technical report, Department of Economic and Social A_airs, Population Division, 2012.

What is the biggest air pollution event in the modern era?

What is the biggest air pollution event in the modern era?

It’s hard to think of the scale of the biggest air pollution event in the modern era. Immediately my mind conjures up memories of black and white photographs of the Great London Smog of 1952. Then I start thinking bigger, how about the 1.2 billion vehicles world-wide on the road churning out nitrogen dioxide every single day? Well these are a drop in the ocean compared with bigger industrial polluters. A recent study by the World Health Organisation pegged the financial damage to Europe by anthropogenic air pollution in 2010 at a whopping €2 Trillion. However all of these anthropogenic pollution events pale in comparison compared with mother Earth. A single volcano, Mt. Etna in Sicily has been known to emit the same amount of sulphur in a year as all of French industry.

So, perhaps we just need to find the biggest volcanic eruption in the modern era? This is the 1815 Tambora eruption, the biggest in the last 10,000 years. Actually, no – how explosive a volcanic eruption is and the amount of potentially harmful sulphur dioxide it emits are not always related and even then the dangers these pose to humans depend on weather conditions. In the modern era there is one natural contender: pumping out 15 times more sulphur as the whole European region in 2010, the 1783 volcanic eruption of Laki.

The eruption carried gases into the atmosphere to the start of the tropopause. This is not abnormal, the 2010 eruptions of Eyjafjallajökull followed the same path. What was different from other eruptions was the amount of gas. The Laki eruption carried an estimated 8 million tons of poisonous hydrofluoric acid and 120 million tons of sulphur dioxide into the atmosphere. Here the gases entered the jet stream; a narrow band of intense winds found at about 16 km altitude and this had far-reaching effects.

A high pressure area over Iceland at the time of the eruption caused the poison ridden winds to move south-east and subside over Europe. This resulted in many thousands of deaths because sulphur dioxide gas reacts with moisture in lungs to form sulphurous acid.

High pressure blocking over Iceland (1783)

High pressure blocking over Iceland (top-left) during Laki eruption caused eruption clouds to move over Europe. Image adapted from: Thordarsson and Self (2003).

The ‘Laki haze’ did not dissipate due to hot weather until the autumn and acted like a heat blanket creating convection from increased surface heating resulting in thunderstorms. This directly led to severe flood damage in central Europe. Crop and livestock damage followed. A famine began in Iceland where most of the livestock died from skeletal fluorosis; a condition caused by ingesting fluoride which leads to decreased bone strength, increased risk of fractures and impaired mobility.

This one event weakened the African monsoon circulation leading to less precipitation over the Sahel and resulting in an Egyptian famine due to a shortage of water in the Nile. The Chalisa famine in India occurred also the same year and resulted in 11 million deaths on the subcontinent. However the second of these famines can also be linked to changing El-Niño conditions over the preceding years. The volcanic eruption gases on the atmosphere were as far reaching as North America where there was reported to be ice in the Gulf of Mexico.

A cycle of unusual seasons continued for several years after and caused huge global economic hardship which has been thought to be one of the drivers behind the French Revolution. The large amounts of Sulphur dioxide that remained in the atmosphere may have caused global average temperatures to fall by 1°C for the next couple of years. About 6 million people died as a result of the eruption, either directly or indirectly – this was about 1% of the world’s population at the time.

The Laki 1783 eruption is troubling. In the popular imagination big explosive volcanic events are the most devastating and cone shaped volcanos like Krakatoa are more embedded in our consciousness. However a lesser-known less explosive volcano, if well placed in terms of weather patterns, could potentially be more devastating. If an event like the Laki eruption were to happen again we could expect cold weather and maybe a year without summer. Modern volcanic monitoring practises could help us prepare for such an event but its global nature would still be very disrupting to our lives.

An unlikely choice between a gasoline or diesel car…

An unlikely choice between a gasoline or diesel car…

I have recently been confronted with the choice of buying a “new” car and this has proved to be a very tedious task with all the diversity of car that exists on the market today. However, one of my primary concerns was, of course, to find the least polluting car based on my usage (roughly 15000km/year).

Cars (or I should say motor vehicles) pollution is one of the major sources of air pollution (particulate matter, soot, NOx, …) in urban areas. These often cause, during both winter and summer seasons, long and prolonged exposition to ozone or PMs which can have significant effect on the health of urban population. Besides, vehicles are also one of the most important sources of greenhouse gases emissions (around 30%). Extensive research in various areas (air pollution and monitoring in urban areas, efficiency of motor vehicles, mobility and public transportation, urban planning,…) are thus being conducted to help reduce the exposition to dangerous pollutants and emissions of GHG.

Manufacturers have been more and more constrained by new regulations to decrease the pollutant emissions (with EURO6 norm now in the EU) and the increase the efficiency of motor vehicles. Governments around the world and more particularly in Europe, after the financial crisis of 2007/2008 have introduced new subsidies to incite people to buy new more energy efficient vehicles. One of the main issues here is that often the more efficient vehicles are not necessarily the less polluting vehicles. Policies have been based on GHG emissions from vehicle consumption without consideration of the full life cycle cost and analysis and also on other pollutants emissions.

Thus if we take for example an electric car, the GHG emissions (and also other pollutants) are pretty low or close to zero as there are none released by the car itself. But we also need to evaluate the emissions from the electricity power plant (most likely to be a centralized one based on either fossil fuel or nuclear energy). Furthermore if the life cycle cost of the battery in such cars, are taken into consideration, the picture is not so black and white anymore as it has been pointed out by numerous studies (ADEME – sorry for the French link!). Besides electric vehicle remain quite expensive and not really adapted to all usage.

If we compare both diesel and gasoline cars, then it becomes a bit more tedious. Diesel engines consumes generally less than gasoline one. However their PM emissions, for example, can be quite high and hence they need really efficient filters to get rid of these pollutants. More stringent regulations have forced manufacturers to improve significantly the quality of the air coming out of their diesel engines but still remain on average more polluting than gasoline cars. Countries, like France, that have strongly subsidized the use of diesel in the past, are now finding it quite difficult to phase out these types of cars. And besides they are more efficient and hence emits lets GHG.

Coming back to my choice of cars then… The choice for me in the end was then between the long term or short term benefits. Using a gasoline car or an electric car (in a country where the energy is coming from renewables!) would be more ecologically sound if we drive mostly in urban areas. However if you are thinking about the long term benefits (with climate change) then you should probably opt for a more efficient diesel car.

All of this, points out that research still need to be conducted and new innovative ideas are really needed (like Elon Musk’s battery, maybe?) so as to bridge the enormous gap between having an efficient car, the life cycle analysis and living in a pollution-free urban environment. But of course…, the best solution is to use public transport or bikes… well this is not always possible!

How we might lose the battle against climate change … or against any other environmental problem?

How we might lose the battle against climate change … or against any other environmental problem?

This would not be a blog about atmospheric science if I did not talk about climate change. But I won’t be talking about the science of climate change… there are numerous blogs including here that will talk much better about this. The problem that will be addressed here does not only refer to the “battle” we are currently facing with climate but also numerous other environmental issues (smog, PM2.5 / PM10 pollution, endocrine/ hormone disruptors, pesticides…). For most of these environmental issues, extensive research is already conducted in Atmospheric sciences but these are also tackled in social and economic sciences as well. However, most of the policies in place right now fail to address these issues which are really urgent matter and humans (and other form of life as well) are losing million of hours of life expectancy and hence costing billion of euros to the community.

My point here is that there is a huge gap between what the scientific community understands (and is of course continuing to study) and what is perceive as a threat by the public. More and more scientists engage in outreach programmes and try to convey their findings about their research to the public. One of the other methods scientists use nowadays is more generally known as “open science” where researchers make their data and findings (for ex. with articles) freely available. However it seems that although these practices have been in place for a couple of years / decades, the gap still exists. Either the public has the perception that scientists are totally disconnected from their reality or they do not feel the urgency to take actions to address these issues (because most likely we do not “feel” or “see” the direct impact of the such pollution problems – in the case of climate change we are talking mostly about long term effect on sea level, biodiversity…).

The second issue lies with what kind of policy to put in place based on the findings from the scientific community. Although the aim of science is primarily to understand the “how” and the “why” of questions, it is crucial now for us to take a more firm stand on these issues. Several discussions have already been taking place within the scientific community to decide on whether it is the role of scientist to act as an advocate for a change in policy. For ex. if my research is on climate change and my findings show that human greenhouse gas (GHG) emissions are responsible for the current climate change, is it my role as a researcher to say “loud and clear” that I think we should decrease drastically our GHG emissions? Some scientists think that this is not our role, as we need to be impartial and hence we cannot engage in advocacy. I have to disagree here as we are indeed the most well placed persons to take such stands.

However, I think it is also now crucial for universities and research institutes, to develop new ways (or totally new separate departments) in order to engage with the public and share the knowledge. It is not possible, when the extent of knowledge is so vast, in so many topics, that there are still many areas on which the public / government and the scientific community are in such disagreement. Various situations, in the past, have caused tremendous suffering (for ex. high death and cancer rate in the case of asbestos) and could have been prevented, because the scientific knowledge was here but there was intense lobbying and a lack of political will to change things (it took about 50 years for France to officially ban asbestos after it has been recognized as the origin of pathological diseases).

In view of these situations, policy change will definitely come when the public “knows” and can hence ask for a change with their local / national / international governments. This bottom-up approach seems to be the most likely way with which we will be able to address these environmental issues in the future. The problem here is that we (scientists in general) have to ask ourselves why is it that our research influence so marginally policies that are put in place. Are we not engaging with the public enough? Should we share our results/findings differently? Are international organisations the best way to find consensus on such topics? I agree that scientists cannot solve all the problems of the world but the research community is one of the pillars of the society and should engage as such in the debates the society is facing. Although I started with a very bleak perspective (and for now this seems to be the case with many challenges we are facing) there is still some hope for the future. We will see, for ex., in the COP21 international meeting if an agreement will be reached on the climate change topic… but I have serious doubts about this being the case.

Welcome to the AS division blog

Ecosystem Earth. Copyright ESA/NASA


The Atmospheric Sciences Division of the EGU is launching its new blog. This blog hopes to address a number of topics, as well as the major challenges, related to the atmospheric sciences. In this introductory post, I would like to present some of the topics we will address here and also some hurdles the scientific community is trying to overcome.

First, let’s agree on some definitions. Atmospheric science is a field which studies the various processes which are taking place in the fluid layer above the surface of a planet. This can include a a range of topics : Atmospheric Chemistry (“is the study of the composition of the atmosphere, the sources and fates of gases and particles in air, and changes induced by natural and anthropogenic processes”), Atmospheric Dynamics (“involves observational and theoretical analysis of all motion systems of meteorological significance, including such diverse phenomena as thunderstorms, tornadoes, gravity waves, tropical hurricanes, extratropical cyclones, jet streams, and global-scale circulations”), Atmospheric Physics (“is the application of the fundamental laws of physics to the systems and the phenomena hosted by the subtle thin layer of gases and vapors surrounding a planet”) and Climatology (“which represents the composite of day-to-day weather over a longer period of time”). Although these definitions might seem a tiny bit rudimentary they give a grasp of how vast this field can be. It is popular belief that atmospheric science is applied mainly to the Earth but extensive research isalso taking place on other celestial bodies.

Secondly, let’s take a look at the major research challenges that we are facing in this field. Data collection and assimilation are an inherent problem in all research but particularly important in this field. The amount of data to be collected and analysed is significant with regards to the systems (e.g. Earth’s atmosphere) we are looking at. Furthermore weather and climate processes are very complex to model due to the non-linear processes (e.g. fluid mechanics, feedbacks…). These models are crucial in understanding the phenomena and for an enhanced prediction for the future. Developing and developed countries alike, faces air pollution problems. Models have significantly improved in this aspect but still need to be improved to tackle the new challenges (e.g. indoor air-pollution, biomass burning, …). These are also very closely related to urban climate and boundary layer and small scale processes (turbulence…). I only mention a few tasks we need to address but of course there are a significant number of others (e.g. ozone layer, extreme events, cloud physics, …).

Finally, to conclude there is also one significant obstacle that we are also facing and this is policy making and application of some research programmes. Even if models and significant research exist in a certain field this does not mean that policy makers will base their decisions on the outcome of a research project. It is thus also vital to address societal complexity through research and also to use outreach as a means to reach a vast audience to promote the goals of our research programmes.

In the future, we hope to present some of the research programmes that are currently being done in this field and to show how we intend to address present and future challenges. Please feel free to comment below and we also welcome guest bloggers, so do not hesitate to contact us if you want to contribute. We look forward to having an amazing ride with you!