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Atmospheric Sciences

atmospheric science

How can we use meteorological models to improve building energy simulations?

How can we use meteorological models to improve building energy simulations?

Climate change is calling for various and multiple approaches in the adaptation of cities and mitigation of the coming changes. Because buildings (residential and commercial) are responsible of about 40% of energy consumption, it is necessary to build more energy efficient ones, to decrease their contribution to greenhouse gas emissions.

But what is the relation with the atmosphere. It is two folds: firstly, in a previous post, I have already described what is the impact of the buildings / obstacles on the air flow and on the air temperature. Secondly, the fact that the climate or surrounding environment is influenced, there will be a significant change in the energy consumption of these buildings.  Currently, building energy simulation tool are using data usually gathered outside of the city and hence not representative of the local context. Thus it is crucial to be able to have necessary tools that capture both the dynamics of the atmosphere and also those of a building to design better and more sustainable urban areas.

In the present work, we have brought these two disciplines together by developing a multi-scale model. On the one side, a meteorological model, the Canopy Interface Model (CIM), was developed to obtain high resolution vertical profile of wind speed, direction and air temperature. On the other hand, an energy modelling tool, CitySim, is used to evaluate the energy use of the buildings as well as the irradiation reaching the buildings.

With this coupling methodology setup we have applied it on the EPFL campus, in Switzerland.  We have compared the modelling results with data collected on the EPFL campus for the year 2015. The results show that the coupling lead to a computation of the meteorological variables that are in very good agreement. However, we noted that for the wind speed at 2m, there is still some underestimation of the wind speed. One of the reason for this is that the wind speed close to the ground is very low and there is a higher variability at this height.

Comparison of the wind speed (left) and air temperature (right) at 2m (top) and 12m (bottom).

We intend to improve this by developing new parameterization in the future for the wind speed in an urban context by using data currently being acquired in the framework of the MoTUS project. One surprising result from this part of the study, is the appearance inside of an urban setup of a phenomena call Cold Air Pools which is very typical of valleys. The reason for this is the lack of irradiation reaching the surface inside of dense urban parts.

Furthermore, we have seen some interesting behaviour in the campus for some particular buildings such as the Rolex Learning Center. Buildings with different forms and configuration, reacted very differently with the local and standard dataset. We designed a series of additional simulation using multiple building configuration and conducted a sensitivity analysis in order to define which parameters between the wind speed and the air temperature had a more significant impact on the heating demand (see Figure 1). We showed that the impact of a reduction of 1°C was more important than a reduction of 1m s-1.

Figure 1. Heating demand of the five selected urban configurations (black dots), as function of the variation by +1°C (red dots) and -1°C (blue dots) of the air temperature, and by +1.5 m s-1 (violet dots) and -1.5 m s-1 (orange dots).

Finally, we also analysed the energy consumption of the whole EPFL campus. When using standard data, the difference between the simulated and measured demand was around 15%. If localized weather data was used, the difference was decreased to 8%. We have thus been able to reduce the uncertainty of the data by 2. The use of local data can hence improve the estimation of building energy use and will hence be quite important when building become more and more efficient.

Reference / datasets

The paper (Mauree et al., Multi-scale modelling to evaluate building energy consumption at the neighbourhood scale, PLOS One, 2017) can be accessed here and data needed to reproduce the experiment are also available on Zenodo.

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

http://www.esa.int/spaceinimages/Images/2015/01/Ecosystem_Earth

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!

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