Summer Barbecue and Ceilidh

Every year the Meteorology Department holds a summer barbecue and ceilidh to celebrate the end of the academic year. Organised by a couple of PhD students, work has been going on behind the scenes for a couple of months. There’s a surprising amount of things to do for an event like this, with health and safety forms and events licenses to fill in as well as booking the band, trying to find 200 bread rolls, and ticket design and selling.

After what seems like an age the day of the barbecue finally arrived! The first job was to collect all the meat – trying to fit 160 burgers and sausages into the communal fridge finally put my tetris skills to good use. A day of bread slicing and salad prep followed until 4:30 arrived and all the PhD students were rounded up to transform the lawn next to the department into a summer party paradise. What looked like an explosion in a bunting factory, one extremely innuendo ridden marquee erection later and with the BBQs lit everything was ready for the guests.

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How many PhD students does it take to put up a marquee?

Primarily being a barbecue the food was of utmost importance. As the guests began to arrive the brilliant (or foolish) volunteers were hard at work keeping up with the demand for sausages and burgers. Fortunately the weather held out and we ended up with a rather glorious evening. It was lovely to be sat out on the sunny lawn with a glass of sangria surrounded by people enjoying an event that you’d put together. However we couldn’t just sit back and watch the clouds all evening, there was the Ceilidh to come.

Following rave reviews last year the Hogs Back Band made their triumphant return. For those not in the know a ceilidh is a party with folk music and traditional dances. I don’t know about you but I don’t have a repertoire of traditional folk dances memorised. Luckily for us the band came with a caller who explains all the dance, gives some interesting facts and helps pressure some ‘volunteers’ to get up and dance.

The first people on the dance floor were the kids and families, but after a couple of songs, some social pressure and a touch of dutch courage the students and staff started to get up. For a supposedly well educated group some of the dances caused us a bit of trouble; fortunately the band’s caller was on hand to put us to rights and publicly shame the group that were having the most trouble. Let me tell you dancing to a ceilidh is a proper work out! Good job there was a stack of desserts brought by some of meteorology’s excellent bakers to keep us going.

 

 

After the sun had set everyone was rounded up for the final dance, with a lot of galloping round a giant circle and spinning round we were almost done. Just tidying up and then back inside for the afterparty.

All in all it was a great event to get everyone together and get the students and staff to mix in a social setting. Watching your supervisor dancing a ceilidh with their children certainly helps you remember that they’re real people too. It’s so lovely to be part of such a sociable department and be reminded that there’s more to life than your PhD.

The ‘Roaring Forties’ and the Ozone Hole

Email: N.Byrne@pgr.reading.ac.uk

The ‘roaring forties’, often referred to as the ‘brave west winds’, are strong westerly winds in the Southern Hemisphere located between the latitudes of 40 and 50 degrees. These wild winds are some of the strongest on the planet and can traverse the globe at furious speeds, aided in part by the relative dearth of landmasses to serve as windbreaks. Their close companions, the ‘furious fifties’ and the ‘shrieking sixties’ represent regions of even stronger winds that affect the entire Southern Ocean. These strong and steady winds are the driving source of the primary Southern Ocean current (the Antarctic Circumpolar Current) and make it the largest ocean current on the planet.

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Figure 1: (Sourced from earth.nullschool.net.) Surface wind on 20-05-2017. Lighter colours represent regions of larger wind speeds.

The existence of these winds and ocean currents has long been known to sailors and in past centuries, they propelled ships at breakneck speed across the Pacific. In more recent times, vessels that will also travel this route include the British Antarctic Survey’s RRS Sir David Attenborough and the now infamous Boaty McBoatface! Research vessels such as these help contribute to our understanding of how the mid-latitude westerly winds interact with the Southern Ocean and the Antarctic climate, and whether there are any important feedbacks between these different components of the climate system. They are also an important source of evidence for how the climate is changing in one of the most remote places on Earth.

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Figure 2: (Sourced from BBC News.) Boaty McBoatface.

While the rapid increase in CO2 has received much attention for its role in surface climate change in many parts of the globe, in the Southern Hemisphere middle-high latitudes it is arguably ozone depletion (and the associated ozone hole) that has led to the largest changes in surface climate. This is primarily because of the recent discovery that there are important dynamical effects associated with the Antarctic ozone hole – namely a shift in the location of the ‘roaring forties’! This result was quite unexpected at the time of its discovery as it had previously been assumed that surface impacts associated with the Antarctic ozone hole were primarily radiative in nature. Much work in recent years has gone into improving our understanding of how these dynamical effects are transmitted to the surface and what might be the future implications for Southern Hemisphere climate (see references for more details). In any case, the observed impacts of the ozone hole on the westerly winds offer a sobering reminder of the potentially large (and unexpected!) changes that anthropogenic emissions can induce in our climate.

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Figure 3: (Sourced from Wikipedia.) Image of the largest Antarctic Ozone hole ever recorded over the Southern pole (September 2006).

References

Byrne, N. J., T. G. Shepherd, T. Woollings, and R. A. Plumb, (2017), Non-stationarity in Southern Hemisphere climate variability associated with the seasonal breakdown of the stratospheric polar vortex. J. Clim., in press. doi: 10.1175/jcli-d-17-0097.1.

Thompson, D. W. J., S. Solomon, P. J. Kushner, M. H. England, K. M. Grise, and D. J. Karoly, (2011), Signatures of the Antarctic ozone hole in Southern Hemisphere surface climate change. Nat. Geosci., 4: 741–749. doi:10.1038/ngeo1296.

Sting Jet: the poisonous (and windy) tail of some of the most intense UK storms

Email: a.volonte@pgr.reading.ac.uk

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Figure 1: Windstorm Tini (12 Feb 2014) passes over the British Isles bringing extreme winds. A Sting Jet has been identified in the storm. Image courtesy of NASA Earth Observatory

It was the morning of 16th October when South East England got battered by the Great Storm of 1987. Extreme winds occurred, with gusts of 70 knots or more recorded continually for three or four consecutive hours and maximum gusts up to 100 knots. The damage was huge across the country with 15 million trees blown down and 18 fatalities.

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Figure 2: Surface wind gusts in the Great Storm of 1987. Image courtesy of UK Met Office.

The forecast issued on the evening of 15th October failed to identify the incoming hazard but forecasters were not to blame as the strongest winds were actually due to a phenomenon that had yet to be discovered at the time: the Sting Jet. A new topic of weather-related research had started: what was the cause of the exceptionally strong winds in the Great Storm?

It was in Reading at the beginning of 21st century that scientists came up with the first formal description of those winds, using observations and model simulations. Following the intuitions of Norwegian forecasters they used the term Sting Jet, the ‘sting at the end of the tail’. Using some imagination we can see the resemblance of the bent-back cloud head with a scorpion’s tail: strong winds coming out from its tip and descending towards the surface can then be seen as the poisonous sting at the end of the tail.

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Figure 3: Conceptual model of a sting-jet extratropical cyclone, from Clark et al, 2005. As the cloud head bends back and the cold front moves ahead we can see the Sting Jet exiting from the cloud tip and descending into the opening frontal fracture.  WJ: Warm conveyor belt. CJ: Cold conveyor belt. SJ: Sting jet.

In the last decade sting-jet research progressed steadily with observational, modelling and climatological studies confirming that the strong winds can occur relatively often, that they form in intense extratropical cyclones with a particular shape and are caused by an additional airstream that is neither related to the Cold nor to the Warm Conveyor Belt. The key questions are currently focused on the dynamics of Sting Jets: how do they form and accelerate?

Works recently published (and others about to come out, stay tuned!) claim that although the Sting Jet occurs in an area in which fairly strong winds would already be expected given the morphology of the storm, a further mechanism of acceleration is needed to take into account its full strength. In fact, it is the onset of mesoscale instabilities and the occurrence of evaporative cooling on the airstream that enhances its descent and acceleration, generating a focused intense jet (see references for more details). It is thus necessary a synergy between the general dynamics of the storm and the local processes in the cloud head in order to produce what we call the Sting Jet .

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Figure 4: Sting Jet (green) and Cold Conveyor Belt (blue) in the simulations of Windstorm Tini. The animation shows how the onset of the strongest winds is related to the descent of the Sting Jet. For further details on this animation and on the analysis of Windstorm Tini see here.

References:

http://www.metoffice.gov.uk/learning/learn-about-the-weather/weather-phenomena/case-studies/great-storm

Browning, K. A. (2004), The sting at the end of the tail: Damaging winds associated with extratropical cyclones. Q.J.R. Meteorol. Soc., 130: 375–399. doi:10.1256/qj.02.143

Clark, P. A., K. A. Browning, and C. Wang (2005), The sting at the end of the tail: Model diagnostics of fine-scale three-dimensional structure of the cloud head. Q.J.R. Meteorol. Soc., 131: 2263–2292. doi:10.1256/qj.04.36

Martínez-Alvarado, O., L.H. Baker, S.L. Gray, J. Methven, and R.S. Plant (2014), Distinguishing the Cold Conveyor Belt and Sting Jet Airstreams in an Intense Extratropical Cyclone. Mon. Wea. Rev., 142, 2571–2595, doi: 10.1175/MWR-D-13-00348.1.

Hart, N.G., S.L. Gray, and P.A. Clark, 0: Sting-jet windstorms over the North Atlantic: Climatology and contribution to extreme wind risk. J. Climate, 0, doi: 10.1175/JCLI-D-16-0791.1.

Volonté, A., P.A. Clark, S.L. Gray. The role of Mesoscale Instabilities in the Sting-Jet dynamics in Windstorm Tini. Poster presented at European Geosciences Union – General Assembly 2017, Dynamical Meteorology (General session)

Prof. Tapio Schneider – Our Distinguished PhD Visiting Scientist.

Email: j.f.talib@pgr.reading.ac.uk

Every year PhD students from the Department of Meteorology at the University of Reading welcome a distinguished scientist in the field of environmental sciences. Previous scientists include Richard Rotunno (UCAR), Isaac Held (GFDL) and Susan Solomon (NOAA). This year’s honoured visitor was Professor Tapio Schneider from the climate dynamics research group from California Institute of Technology (Caltech), the academic home of NASA’s Jet Propulsion Laboratory. Tapio is a well-known contributor to our understanding of global climate dynamics and it was a pleasure to welcome him to our department.

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Prof. Tapio Schneider with some of the current PhD cohort.

Our visiting scientist programme in the department is an opportunity for PhD students to share and explain their research to an external visitor. It allows for PhD research to be looked at from a completely new perspective which will hopefully improve the PhD studies. In a typical PhD visiting scientist week, the visiting scientist meets students one to one, attends departmental research groups and presents work in departmental seminars.

Tapio Schneider presented two departmental seminars during his time with us titled How low clouds respond to warming: Observational, numerical and physical constraints and Model hierachies: From advancing climate dynamics to improving predictions. The latter of these seminars encouraged a discussion to rethink how we approach advancing our modelling capabilities. Tapio argued that the atmospheric modelling community had not fully engaged in the benefits that observations offer. He suggested that our goal should be a heirarchical system that integrates both observational data and models. We should look into creating “machine-learning” models, those which use observational data to improve our modelling capabilities through altering parameterisation schemes and radiative balance calculations at the top of the atmosphere (as two examples).

As already mentioned, the visiting scientist also meets with students one-to-one and it was highly beneficial for my own project to have a meeting with Tapio Schneider. We discussed papers released by himself alongside his former PhD student Tobias Bischoff (for example, The Equatorial Energy Balance, ITCZ position and Double-ITCZ bifurications) which concentrate on creating a diagnostic framework with which we can estimate the location and structure of the Inter-Tropical Convergence Zone (ITCZ). We discussed conclusions reached from my own aquaplanet simulations and how they relate to the proposed diagnostic framework. Keep an eye on the blog for a post coming soon on the developments in my own PhD project, (titled, what determines the location and intensity of the ITCZ?).

To bring this blog post to a close I would like to thank Professor Tapio Schneider for his time, knowledge and wisdom that he shared with the PhD cohort whilst at Reading. Thank you also to those from the University of Reading who supported Tapio’s visit. Feedback from the PhD cohort is extremely positive and I would highly recommend a similar scheme for other scientific departments.

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PhD social with the distinguished visitor.

Under-ice melt ponds in the Arctic

Email: n.e.smith@pgr.reading.ac.uk

The Arctic’s climate is one of those most rapidly changing globally, and as such the region has become a poster-child of climate change. Sea ice area is frequently used as an indicator of the rate of change of the system, providing striking visualisations of the rapidity of the change in recent years. The sea ice is also a driver of climate change, with areal cover greatly affecting the planet’s albedo and ice melt cooling and desalinating the Arctic ocean, altering circulation globally.

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Photo: Haakon Hop, Norsk Polarinstitutt

During the summer months, incoming solar radiation melts the surface layers of the sea ice. This melt water collects in hollows on the surface of the sea ice forming pools called melt ponds. Since the sea ice is porous, water from these ponds can percolate down or flow down through macroscopic flaws in the ice and out of the base of the ice. The melt water is relatively warm and fresh compared to the ocean below, so it floats between the ice and the ocean, gathering in pools beneath the sea ice called under-ice melt ponds. [1]

A couple of types of ice growth have been observed associated with these ponds. Most importantly, a sheet of ice can form at the interface between the pond and the ocean, completely isolating the fresh water from the ocean. As they create the illusion that they are the base of the sea ice, these sheets of ice are commonly referred to as ‘false bottoms’. [2]

We have developed a one-dimensional thermodynamic model of under-ice melt ponds to investigate how they affect their surroundings. We have carried out a number of sensitivity studies using this model, which have lead to some interesting conclusions about how these ponds evolve and affect the ice above them.

For example, the thicker the sea ice above an under-ice melt pond, the longer it takes to freeze due to a shallower temperature gradient above. As a result, more ice is gained due to under-ice melt ponds beneath thicker ice. This could be a positive feedback cycle, since we expect to see thinner ice on average as the Arctic warms, leading to less ice gained due to the ponds beneath it.

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We also see that, as well as the outcome observed in the field, in which the false bottom migrates upwards and thickens as it freezes through the pond, it can also ablate under certain conditions. For example, ponds that are relatively salty at the start of the simulation freeze more slowly, and the false bottom ablates before it is able to reach the base of the sea ice.

eguSens1

Our sensitivity studies show that under-ice melt ponds could be responsible for up to 7.9% additional ice thickness at the end of a 50 day simulation. This would equate to up to 3.2% more ice volume across the Arctic dependent on the area of the ice underlain by these pools.

Recently, we have coupled our under-ice melt pond model with a simple, zero-dimensional model of the oceanic mixed layer. Using this coupled model, we see that the false bottom ablates more rapidly than a slab of sea ice, releasing more fresh water into the mixed layer. This strong reduction of salinity causes a shallowing of the mixed layer. We are currently further investigating the effects that the ponds have on the ocean below them.

Under-ice melt ponds and false bottom insulate the sea ice from below and affect the basal fluxes of salt and fresh water into the mixed layer, and thicken the ice above them allowing less radiation to penetrate through from the surface. They are clearly significant to the mass balance of the ice and the ocean below them, yet are not currently accounted for in the sea ice components of climate models. A parameterisation of their effects would be useful to include.

[1] Notz, Dirk, et al. “Impact of underwater‐ice evolution on Arctic summer sea ice.” Journal of Geophysical Research: Oceans 108.C7 (2003).

[2] Martin, Seelye, and Peter Kauffman. “The evolution of under-ice melt ponds, or double diffusion at the freezing point.” Journal of Fluid Mechanics 64.3 (1974): 507-528.

Innovating for Sustainable Development

Email: Rachael.Byrom@pgr.reading.ac.uk

In 2016 the United Nations (UN) Sustainable Development Goals (SDGs) officially came into force to tackle key global challenges under a sustainable framework.

The SDGs comprise 17 global goals and 169 targets to be achieved across the next 15 years. As part of the ‘2030 Agenda’ for sustainable development, these goals aim to address a range of important global environmental, social and economic issues such as climate change, poverty, hunger and inequality. Adopted by leaders across the world, these goals are a ‘call for action’ to ensure that no one is left behind. However, the SDGs are not legally binding. The success of goals will rely solely on the efforts of individual countries to establish and implement a national framework for achieving sustainable development.

UN SDGs
The United Nation’s 17 Sustainable Development Goals

As part of the NERC funded ‘Innovating for Sustainable Development’ programme, students here in the Department of Meteorology were given the opportunity to explore and find solutions to key environmental challenges as outlined in the UN’s SDGs.

Run by the SCENARIO and SSCP doctoral training partnerships, the programme challenged students from a variety of disciplines and institutions to re-frame the SDGs from a multi-disciplinary perspective and to develop tangible, innovative solutions for sustainable development.

The programme began with an ‘Interdisciplinary Challenges Workshop’ where students participated in activities and exercises to review the importance of the SDGs and to consider their multi-disciplinary nature. Students were encouraged to think creatively and discuss issues related to each of the goals, such as: ‘Is this SDG achievable?’, ‘Are the goals contradictory?’ and ‘How could I apply my research to help achieve the SDGs?’

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Visual representations of SDG 5 and SDG 7

Following this, three ‘Case Study’ days explored a handful of the SDGs in greater detail, with representatives from industry, start-ups and NGOs explaining how they are working to achieve a particular SDG, their current challenges and possible opportunities for further innovation.

The first Case Study day focused on both SDG 7 – Affordable and Clean Energy and SDG 12 – Responsible Consumption and Production. For SDG 7, insightful talks were given by the Moving Energy Initiative on the issue of delivering energy solutions to millions of displaced people, and BBOXX, on their work to produce and distribute off-grid solar power systems to rural communities in places such as Kenya and Rwanda. In the afternoon, presentations given by Climate-KIC start up NER and Waitrose showcased the efforts currently being taken to reduce wasteful food production and packaging, while Forum for the Future emphasised the importance of addressing sustainable nutrition.

The second Case Study day focused on SDG 6 – Clean Water and Sanitation. Experts from WaterAid, De-Solenator, Bear Valley Ventures, UKWIR and the International Institute for Environmental Development outlined the importance of confronting global sanitation and water challenges in both developing and developed nations. Alarmingly, it was highlighted that an estimated 40% of the global population are affected by water scarcity and 2.4 billion people still lack access to basic sanitation services, with more than 80% of human activity wastewater discharged into rivers without going through any stage of pollution removal (UN, 2016).

Case study
Participants discussing ideas during the second Case Study day

The last Case Study day explored SDG 9 – Industry, Innovation and Infrastructure and SDG 11 – Sustainable Cities and Communities. A range of talks on building technologies, carbon neutral buildings and sustainable solar technologies were given, along with a presentation by OPDC on the UK’s largest regeneration project. The day finished off with an overview from the Greater London Authority about the London Infrastructure Map and their new approach to sustainable planning and development across the city.

The programme finished off with a second workshop. Here students teamed up to develop innovative business ideas aimed at solving the SDG challenges presented throughout the Case Study events. Business coaches and experts were on hand to offer advice to help the teams develop ideas that could become commercially viable.

On the 16th March the teams presented their business ideas at the ‘Meet the Cleantech Pioneers’ networking event at Imperial’s new Translation and Innovation Hub (I-HUB). An overview of the projects can be found here. This event, partnered with the Climate-KIC accelerator programme, provided an excellent platform for participants to showcase and discuss their ideas with a mix of investors, entrepreneurs, NGOs and academics all interested in achieving sustainable development.

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The final showcase event at Imperial’s I-HUB

Overall the programme provided a great opportunity to examine the importance of the SDGs and to work closely with PhD students from a range of backgrounds. Fundamentally the process emphasised the point that, in order for the world to meet the 2030 Agenda, many sustainable development challenges still need to be better understood and many solutions still need to be provided – and here scientific research can play a key role. Furthermore, it was made clear that a high level of interdisciplinary thinking, research and innovation is needed to achieve sustainable development.

Institutes

References:

UN, 2016: Clean Water and Sanitation – Why it matters, United Nations, Accessed 05 March 2017. [Available online at http://www.un.org/sustainabledevelopment/wp-content/uploads/2016/08/6_Why-it-Matters_Sanitation_2p.pdf]

Can we really use El Niño to predict flooding?

R. Emerton, H. Cloke, E. Stephens, E. Zsoter, S. Woolnough, F. Pappenberger (2017). Complex picture for likelihood of ENSO-driven flood hazard. Nature Communications. doi: 10.1038/NCOMMS14796

Email: r.e.emerton@pgr.reading.ac.uk

When an El Niño is declared, or even forecast, we think back to memorable past El Niños (such as 1997/98), and begin to ask whether we will see the same impacts. Will California receive a lot of rainfall? Will we see droughts in tropical Asia and Australia? Will Peru experience the same devastating floods as in 1997/98, and 1982/83?

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El Niño and La Niña, which see changes in the ocean temperatures in the tropical Pacific, are well known to affect weather, and indeed river flow and flooding, around the globe. But how well can we estimate the potential impacts of El Niño and La Niña, and how likely flooding is to occur?

This question is what some of us in the Water@Reading research group at the University of Reading have been looking to answer in our recent publication in Nature Communications. As part of our multi- and inter-disciplinary research, we work closely with the Red Cross / Red Crescent Climate Centre (RCCC), who are working on an initiative called Forecast-based Financing (FbF, Coughlan de Perez et al.). FbF aims to distribute aid (for example providing water purification tablets to prevent spread of disease, or digging trenches to divert flood water) ahead of a flood, based on forecasts. This approach helps to reduce the impact of the flood in the first place, rather than working to undo the damage once the flood has already occurred.

Photo credit: Red Cross / Red Crescent Climate Centre

In Peru, previous strong El Niños in 1982/83 and 1997/98 had resulted in devastating floods in several regions. As such, when forecasts in early 2015 began to indicate a very strong El Niño was developing, the RCCC and forecasters at the Peruvian national hydrological and meteorology agency (SENAMHI) began to look into the likelihood of flooding, and what FbF actions might need to be taken.

Typically, statistical products indicating the historical probability (likelihood [%] based on what happened during past El Niños) of extreme precipitation are used as a proxy for whether a region will experience flooding during an El Niño (or La Niña), such as these maps produced by the IRI (International Research Institute for Climate and Society). You may also have seen maps which circle regions of the globe that will be drier / warmer / wetter / cooler – we’ll come back to these shortly.

These rainfall maps show that Peru, alongside several other regions of the world, is likely to see more rainfall than usual during an El Niño. But does this necessarily mean there will be floods? And what products are out there indicating the effect of El Niño on rivers across the globe?

For organisations working at the global scale, such as the RCCC and other humanitarian aid agencies, global overviews of potential impacts are key in taking decisions on where to focus resources during an El Niño or La Niña. While these maps are useful for looking at the likely changes in precipitation, it has been shown that the link between precipitation and flood magnitude is nonlinear (Stephens et al.),  – more rain does not necessarily equal floods – so how does this transfer to the potential for flooding?

The motivation behind this work was to provide similar information, but taking into account the hydrology as well as the meteorology. We wanted to answer the question “what is the probability of flooding during El Niño?” not only for Peru, but for the global river network.

To do this, we have taken the new ECMWF ERA-20CM ensemble model reconstruction of the atmosphere, and run this through a hydrological model to produce the first 20th century global hydrological reconstruction of river flow. Using this new dataset, we have for the first time estimated the historical probability of increased or decreased flood hazard (defined as abnormally high or low river flow) during an El Niño (or La Niña), for the global river network.

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Figure 1: The probability of increased (blue) or decreased (red) flood hazard during each month of an El Nino. Based on the ensemble mean of the ERA-20CM-R 20th century river flow reconstruction.

The question – “what is the probability of flooding during El Niño?”, however, remains difficult to answer. We now have maps of the probability of abnormally high or low river flow (see Figure 1), and we see clear differences between the hydrological analysis and precipitation. It is also evident that the probabilities themselves are often lower, and much more uncertain, than might be useful – how do you make a decision on whether to provide aid to an area worried about flooding, when the probability of that flooding is 50%?

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Figure 2: Historical probability of increased / decreased flood hazard map for February, with overlay showing the typical impact map for winter during an El Nino. This highlights the complexity of the link between El Nino and flooding compared to the information usually available.

The likely impacts are much more complex than is often perceived and reported – going back to the afore-mentioned maps that circle regions of the globe and what their impact will be (warmer, drier, wetter?) – these maps portray these impacts as a certainty, not a probability, with the same impacts occurring across huge areas. For example, in Figure 2, we take one of the maps from our results, which indicates the probability of increased or decreased flood hazard in one month during an El Niño, and draw over this these oft-seen circles of potential impacts. In doing this, we remove all information on how likely (or unlikely) the impacts are, smaller scale changes within these circles (in some cases our flood hazard map even indicates a different impact), and a lot of the potential impacts outside of these circles – not to mention the likely impacts can change dramatically from one month to the next. For those organisations that take actions based on such information, it is important to be aware of the uncertainties surrounding the likely impacts of El Niño and La Niña.

“We conclude that while it may seem possible to use historical probabilities to evaluate regions across the globe that are more likely to be at risk of flooding during an El Niño / La Niña, and indeed circle large areas of the globe under one banner of wetter or drier, the reality is much more complex.”

PS. During the winter of 2015/16, our results estimated an ~80% likelihood of increased flood hazard in northern coastal Peru, with only ~10% uncertainty surrounding this. The RCCC took FbF actions to protect thousands of families from potentially devastating floods driven by one of the strongest El Niños on records. While flooding did occur, this was not as severe as expected based on the strength of the El Niño. More recently, during the past few months (January – March 2017), anomalously high sea surface temperatures (SSTs) in the far eastern Pacific (known as a “coastal El Niño” in Peru but not widely acknowledged as an El Niño because central Pacific SSTs are not anomalously warm) have led to devastating flooding in several regions and significant loss of life. And Peru wasn’t the only place that didn’t see the impacts it expected in 2015/16; other regions of the world, such as the US, also saw more rainfall than normal in places that were expected to be drier, and California didn’t receive the deluge they were perhaps hoping for. It’s important to remember that no two El Niños are the same, and El Niño will not be the only influence on the weather around the globe. While El Niño and La Niña can provide some added predictability to the atmosphere, the impacts are far from certain.

Presidente Kuczynski recorre zonas afectadas por lluvias e inund
Flooded areas of Trujillo, Peru, March 2017. Photo credit: Presidencia Peru, via Floodlist

Full reference:

R. Emerton, H. Cloke, E. Stephens, E. Zsoter, S. Woolnough, F. Pappenberger (2017). Complex picture for likelihood of ENSO-driven flood hazard. Nature Communications. doi: 10.1038/NCOMMS14796

Press Release: