Author: Sally Woodhouse

The impact of atmospheric model resolution on the Arctic

Sally Woodhouse1 Comment

Email: sally.woodhouse@pgr.reading.ac.uk

The Arctic region is rapidly changing, with surface temperatures warming at around twice the global average and sea ice extent is rapidly declining, particularly in the summer. These changes affect the local ecosystems and people as well as the rest of the global climate. The decline in sea ice has corresponded with cold winters over the Northern Hemisphere mid-latitudes and an increase in other extreme weather events (Cohen et al., 2014). There are many suggested mechanisms linking changes in the sea ice to changes in the stratospheric jet, midlatitude jet and storm tracks; however this is an area of active research, with much ongoing debate.

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Figure 1. Time-series of September sea ice extent from 20 CMIP5 models (colored lines), individual ensemble members are dotted lines and the individual model mean is solid. Multi-model ensemble mean from a subset of the models is shown in solid black with +/- 1 standard deviation in dotted black. The red line shows observations. From Stroeve et al. (2012)

It is therefore important that we are able to understand and predict the changes in the Arctic, however there is still a lot of uncertainty. Stroeve et al. (2012) calculated time series of September sea ice extent for different CMIP5 models, shown in Figure 1. In general the models do a reasonable job of reproducing the recent trends in sea ice decline, although there is a large inter-model spread and and even larger spread in future projections. One area of model development is increasing the horizontal resolution – where the size of the grid cells used to calculate the model equations is reduced.

The aim of my PhD is to investigate the impact that climate model resolution has on the representation of the Arctic climate. This will help us understand the benefits that we can get from increasing model resolution. The first part of the project was investigating the impact of atmospheric resolution. We looked at three experiments (using HadGEM3-GC2), each at a different atmospheric resolutions: 135km (N512), 60km (N216) and 25km (N96).

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Figure 2. Annual mean sea ice concentration for observations (HadISST) and the bias of each different experiment from the observations N96: low resolution, N216: medium resolution, N512: high resolution.

The annual mean sea ice concentration for observations and the biases of the 3 experiments are shown in Figure 2. The low resolution experiment does a good job of producing the sea extent seen in observations with only small biases in the marginal sea ice regions. However, in the higher resolution experiments we find that the sea ice concentration is much lower than the observations, particularly in the Barents Sea (north of Norway). These changes in sea ice are consistent with warmer temperatures in the high resolution experiments compared to the low resolution.

To understand where these changes have come from we looked at the energy transported into the ocean by the atmosphere and the ocean. We found that there is an increase in the total energy being transported into the Arctic which is consistent with the reduced sea ice and warmer temperatures. Interestingly, the increase in energy is being transported into the Arctic by the ocean (Figure 3), even though it is the atmospheric resolution that is changing between the experiments. In the high resolution experiments the ocean energy transport into the Arctic, 0.15 petawatts (PW), is in better agreement with observational estimates, 0.154 PW, from Tsubouchi et al. (2018). Interestingly, this is in contrast to the worse representation of sea ice concentration in the high resolution experiments. (It is important to note that the model was tuned at the low resolution and as little as possible was changed when running the high resolution experiments which may contribute to the better sea ice concentration in the low resolution experiment.)

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Location of ocean gateways into the Arctic. Red: Bering Strait, Green: Davis Strait, Blue: Fram Strait, Magenta: Barents Sea
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Figure 3. Ocean energy transport for each resolution experiment through the four ocean gateways into the Arctic. The four gateways form a closed boundary into the Arctic.

We find that the ocean is very sensitive to the differences in the surface winds between the high and low resolution experiments. In different regions the differences in winds arise from different processes. In the Davis Strait the effect of coastal tiling is important, where at higher resolution a smaller area is covered by atmospheric grid cells that cover both land and ocean. In a cell covering both land and ocean the model usually produces wind speeds to low for over the ocean. Therefore in the higher resolution experiment we find that there are higher wind speeds over the ocean near the coast. Whereas over the Fram Strait and the Barents Sea instead we find that there are large scale atmospheric circulation changes that give the differences in surface winds between the experiments.

References

Cohen, J., Screen, J. A., Furtado, J. C., Barlow, M., Whittleston, D., Coumou, D., Francis, J., Dethloff, K., Entekhabi, D., Overland, J. & Jones, J. 2014: Recent Arctic amplification and extreme mid-latitude weather. Nature Geoscience, 7(9), 627–637, http://dx.doi.org/10.1038/ngeo2234

Stroeve, J. C., Kattsov, V., Barrett, A., Serreze, M., Pavlova, T., Holland, M., & Meier, W. N., 2012: Trends in Arctic sea ice extent from CMIP5, CMIP3 and observations. Geophysical Research Letters, 39(16), 1–7, https://doi.org/10.1029/2012GL052676

Tsubouchi, T., Bacon, S., Naveira Garabato, A. C., Aksenov, Y., Laxon, S. W., Fahrbach, E., Beszczynska-Möller, A., Hansen, E., Lee, C.M., Ingvaldsen, R. B. 2018: The Arctic Ocean Seasonal Cycles of Heat and Freshwater Fluxes: Observation-Based Inverse Estimates. Journal of Physical Oceanography, 48(9), 2029–2055, http://journals.ametsoc.org/doi/10.1175/JPO-D-17-0239.1

APPLICATE General Assembly and Early Career Science event

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On 28th January to 1st February I attended the APPLICATE (Advanced Prediction in Polar regions and beyond: modelling, observing system design and LInkages associated with a Changing Arctic climaTE (bold choice)) General Assembly and Early Career Science event at ECMWF in Reading. APPLICATE is one of the EU Horizon 2020 projects with the aim of improving weather and climate prediction in the polar regions. The Arctic is a region of rapid change, with decreases in sea ice extent (Stroeve et al., 2012) and changes to ecosystems (Post et al., 2009). These changes are leading to increased interest in the Arctic for business opportunities such as the opening of shipping routes (Aksenov et al., 2017). There is also a lot of current work being done on the link between changes in the Arctic and mid-latitude weather (Cohen et al., 2014), however there is still much uncertainty. These changes could have large impacts on human life, therefore there needs to be a concerted scientific effort to develop our understanding of Arctic processes and how this links to the mid-latitudes. This is the gap that APPLICATE aims to fill.

The overarching goal of APPLICATE is to develop enhanced predictive capacity for weather and climate in the Arctic and beyond, and to determine the influence of Arctic climate change on Northern Hemisphere mid-latitudes, for the benefit of policy makers, businesses and society.

APPLICATE Goals & Objectives

Attending the General Assembly was a great opportunity to get an insight into how large scientific projects work. The project is made up of different work packages each with a different focus. Within these work packages there are then a set of specific tasks and deliverables spread out throughout the project. At the GA there were a number of breakout sessions where the progress of the working groups was discussed. It was interesting to see how these discussions worked and how issues, such as the delay in CMIP6 experiments, are handled. The General Assembly also allows the different work packages to communicate with each other to plan ahead, and for results to be shared.

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An overview of APPLICATE’s management structure take from: https://applicate.eu/about-the-project/project-structure-and-governance

One of the big questions APPLICATE is trying to address is the link between Arctic sea-ice and the Northern Hemisphere mid-latitudes. Many of the presentations covered different aspects of this, such as how including Arctic observations in forecasts affects their skill over Eurasia. There were also initial results from some of the Polar Amplification (PA)MIP experiments, a project that APPLICATE has helped coordinate.

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Attendees of the Early Career Science event co-organised with APECS

At the end of the week there was the Early Career Science Event which consisted of a number of talks on more soft skills. One of the most interesting activities was based around engaging with stakeholders. To try and understand the different needs of a variety of stakeholders in the Arctic (from local communities to shipping companies) we had to try and lobby for different policies on their behalf. This was also a great chance to meet other early career scientists working in the field and get to know each other a bit more.

What a difference a day makes, heavy snow getting the ECMWF’s ducks in the polar spirit.

Email: sally.woodhouse@pgr.reading.ac.uk

References

Aksenov, Y. et al., 2017. On the future navigability of Arctic sea routes: High-resolution projections of the Arctic Ocean and sea ice. Marine Policy, 75, pp.300–317.

Cohen, J. et al., 2014. Recent Arctic amplification and extreme mid-latitude weather. Nature Geoscience, 7(9), pp.627–637.

Post, E. & Others, 24, 2009. Ecological Dynamics Across the Arctic Associated with Recent Climate Change. Science, 325(September), pp.1355–1358.

Stroeve, J.C. et al., 2012. Trends in Arctic sea ice extent from CMIP5, CMIP3 and observations. Geophysical Research Letters, 39(16), pp.1–7.

Royal Meteorology Conferences

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From 3rd-6th July 2018 the Royal Meteorological Society (RMetS) held two national conferences at the University of York. The Atmospheric Science Conference, joint with NCAS, started off the week and brought together scientists to present and discuss the latest research findings in weather, climate and atmospheric chemistry. The following two days brought the RMetS Student Conference. Both events were well attended by PhD students from Reading and provided a great opportunity to share our work with the wider scientific community.

For a summary of the work presented by Reading students, stick around until the end of the blog!

Atmospheric Science Conference 2018

Weather, Climate and Air Quality

Many of the presentations focused on seasonal forecasting with Adam Scaife (Met Office) giving a keynote address on “Skilful Long Range Forecasts for Europe”. He presented an interesting analysis on the current progress of predicting the North Atlantic Oscillation showing that there is skill in current predictions which could be improved even further by increasing ensemble size. Adam was also awarded the prestigious Copernicus Medal at the conference dinner. Another notable talk was by Reading’s own Ed Hawkins, who presented the benefits of using citizen scientists to rescue weather records. A summary of Ed’s presentation can be accessed below, and you can read more about research involving Citizen Science in Shannon Jones’ blog.

The poster sessions at the conference also gave a great opportunity to look at the breadth of work going on in institutions around the UK. It was also a great time to catch up with colleagues and forge new academic connections.

One of the highlights of the conference was having the conference dinner in the National Railway Museum. This was a fantastic yet surreal location with dining tables set up in the station hall overlooking a suite of old steam trains . The event was made even better by watching England‘s quarter-final world cup game!

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Evolution of Science: Past, Present and Future

Students & Early Career Scientist Conference

The student conference is open to all students with an interest in meteorology, from undergraduate to PhD and early career scientists. The conference aimed to give students the opportunity to meet each other and present their work at an early stage in their career before attending other academic conferences. For many of those attending from Reading this was their first time presenting research at an event outside of the department and provided a great experience to communicate their work with others. Work presented varied from radiative forcing to normal empirical modes (summaries of talks are below). There were also a number of keynote speakers and workshops aimed at addressing the current challenges in atmospheric sciences and skills that are important for researchers.

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Rory Fitzpatrick, presenting on skills for writing as an academic. “I have the Best Words” – How to write articles that impact bigly”

https://twitter.com/jominicdones/status/1015191296334548993

Of course there was also time for socialising with an ice-breaker dinner and pub quiz  and a formal Conference dinner on the Thursday. This was the second student conference I have attended and it was a really great place to discuss my work and meet other students from around the country. I have also attended other academic events with several people that I met at the conference last year, it’s always great to see a friendly face!

The student conference is organised by a committee of students from around the UK. Being on the committee was a great opportunity to learn more about how conferences work and to practice skills such as chairing sessions. It has also been great to get to know lots of different people working within meteorology. If you’re interested in helping organise next year’s conference please do get in touch with Victoria Dickinson at RMetS (Victoria.Dickinson@rmets.org) or if you’re thinking about attending then you can start by joining the society where you’ll hear about all the other great events they host.

Highlights of the work presented by Reading students:

Godwin Ayesiga presented work on the convective activity that connects Western and Eastern equatorial Africa. Investigating how intraseasonal modes of variability influence intense rainfall.

Matt Priestley presented an assessment of the importance of windstorm clustering on European wintertime insurance losses. More details of this work can be found here.

Lewis Blunn presented his work looking into the ‘grey zone’ of turbulence at model grid scale lengths of 100 m – 1 km. At these scales turbulence is partially resolved by the grid but still needs to be partially parameterised. Lewis finds that spurious grid scale features emerge at scales where turbulence is partially resolved. Model results are poorer in this ‘grey zone’ than when turbulence is fully resolved or fully parameterised.

Alec Vessey presented his work evaluating the representation of Arctic storms in different reanalysis products. He found that there is a difference between different reanlysis and so care should be taken when using these products to analyse Arctic storms.

Dominic Jones presented a technique for extracting modes of variability from atmospheric data, and a test dataset that has been developed to use this technique to examine the relationship of modes of variability associated with the jet-latitude.

Rachael Byrom presented a motivation for quantifying methane’s shortwave radiative forcing. Her work demonstrated a need to use a high resolution narrow-band radiation model to accurately calculate forcings in atmospheric models.

Andrea Marcheggiani presented a poster on the role of resolution in predicting the North Atlantic storm track. An energy budget of the winter climatology (DJF 1979-2018) was presented.

Sally Woodhouse presented her work on the impact of resolution on energy transports into the Arctic. She has found that increasing atmospheric resolution increases the energy transport in the ocean to better agree with observations.

Kaja Milczewska presented work on evaluating the inaccuracies of predicting air quality in the UK.

Having recently passed her viva, Caroline Dunning’s presentation was on precipitation seasonality over Africa under present and future climates. Caroline has developed a new methodology for determining the beginning and end of the wet season across Africa. This has been applied to CMIP5 model output to look at future changes in wet seasons across Africa under climate change.

Polar Prediction School 2018

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From 17th-27th April three Reading students trekked to the to the far north to attend the APECS Polar Prediction School at the Abisko Research Station. The aims of this course were to provide a general education in the Polar climates, from ocean and ice to atmosphere to help the participants understand the issues of prediction in polar regions and contribute to the current academic push to improve our understanding and forecasting skill of these regions.

 

 

 

Abisko research station is situated 68°N on the banks of lake Torneträsk, the sixth longest lake in Sweden. Frozen from approximately December to June the lake provided a great base for experiencing taking observations of the poles. On the first full day we put up a met mast which we then used data from to explore boundary layer turbulence. Drilling the holes for the guy ropes to find the ice was still a metre thick was rather reassuring after people had stripped down to t-shirts in the sun.

Throughout the week we also launched multiple radiosondes which was another excellent excuse to spend some time drinking in the scenery. This caused a stir when there was an ice-fishing competition on the lake, so several local school children ended up assisting with the launch.

 

 

 

 

After a week packed full of lectures, from sea-ice dynamics to observations from an ice breaker, on the Sunday in the middle of the school we had the day off. Most people took this as a chance to explore a bit further afield. A few of us rented snowshoes which turned out to be an excellent idea as there were plenty of places where the snow was still a meter thick. However difficult the terrain the scenery was 100% worth it, and the kanelbullar in our packed lunches certainly helped keep us going.

 

 

This was followed by another week of lectures, covering boundary layers, clouds and much more. We also spent time working on our science communication, both to other scientists and the general public. This culminated with everyone giving a 1 minute “Frostbyte” presentation of their work.

The course was a great chance to learn about the polar climate more broadly which has been helpful in putting my PhD work in context. It’s also great to be able to say I have been to the Arctic when people ask in the future!

PPS2018_group

A big thank you to APECS, APPLICATE and the Polar Prediction Project for supporting the course as well as all the staff who gave their time to speak. More details about the course can be found here.

A week at COP23

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From the 6th -17th of November the UNFCCC’s (United Nation Framework Convention on Climate Change) annual meeting or “Conference of the Parties” – COP took place. This year was COP23 and was hosted by Bonn in the UN’s world conference centre with Fiji taking the presidency.

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Heading into the Bonn Zone on the first day of the COP. The Bonn Zone was the part of the conference for NGO stands and side events.

As part of the Walker Institutes Climate Action Studio another SCENARIO PhD and I attended the first week of the COP while students back in Reading participated remotely via the UNFCCC’s YouTube channel and through interviews with other participants of the COP.

There are many different components to the COP, it is primarily the meeting of a number of different international Climate agreements with lots of work currently being done on the implementation on the Paris Agreement. However it is also a space where many different civil society groups doing work connected to or impacted by climate change come together, to make connections with other NGOs as well as governments. This is done in an official capacity within the “exhibition zone” of the conference and with a vast array of side events taking place throughout the two weeks. Outside of these official events there are also many demonstrations both inside and outside of the conference space.

Demonstrations in the Bonn Zone

As an observer I was able to watch some of the official negotiations. On the Wednesday I attended the SBSTA (Subsidiary Body for Scientific and Technological Advice) informal consultation on research and systematic observations. It was an illuminating experience to see the negotiation process in action. At times it was frustrating to see how picky it feels like the negotiation teams can be, however over the week I did have a newfound appreciation for the complexity of the issues that are having to be resolved. This meeting was based on writing a short summary of the IPCC report and other scientific reports used by the COP, and so was less politically charged than a lot of the other meetings. However this didn’t stop an unexpected amount of debate over whether to include examples such as carbon-dioxide concentrations.

One of the most useful ways to learn about the COP was by talking to the different people and groups who we met at COP. It was interesting to see the different angles with which people were approaching the COP. From researchers who were observing the political process, to environmental and human rights NGO’s trying to get governments to engage with issues that they’re working on.

Interviewing other COP participants at the Walker Institutes stand

A particular highlight was the ex-leader of the Green Party Natalie Bennett, she spoke with us and the students back in Reading about a wide range of topics, from women’s involvement in the climate movement to discussing my PhD.

Kelly Stone from Action Aid provided a great insight into how charities operate at the COP. She spoke of making connections with other charities, often there are areas of overlap between their work but on other issues they had diverging opinions. However these differences have to be put aside to make progress on their shared interests. Kelly also discussed how it always amazes her that people are surprised that everyone who attends COP does not agree on everything, “we’re not deciding if climate change is real”. The issues being dealt with at the COP are complex dealing with human rights, economics, technology as well as climate change. Often serious compromises have to be made and this must be done by reaching a consensus between all 197 Parties to the UNFCCC.

To read more about the student experience of COP and summaries of specific talks and interviews you can view the COP CAS blog here. You can also read about last years COP on this blog here.

Clockwise from top left: The opening on the evening of Monday 6th November showed Fiji leaving its own mark as the President of the conference. The Norwegian Pavilion had a real Scandi feel, while the Fiji Pavilion transported visitors to a tropical island.

 

Adventures in Modelling – NCAS Climate Modelling Summer School

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At the beginning of September 3 PhD students from Reading, including myself, went to Cambridge to attend the NCAS Climate Modelling Summer School. This is an annual event aimed at PhD students and early career scientists who want to develop their understanding of climate models, with topics covering parameterisations to supercomputers.

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Staff and students of the course pose outside the Chemistry department, which played host to morning lectures

The course ran over two weeks with lectures on the components of climate models in the morning, covering fundamental dynamics and thermodynamics, numerical methods and different parameterisations. This was followed by an afternoon of computer practicals and then more topical lectures in the evening, such as “User engagement in climate science” and “The Sun and Earth’s climate system”. The lectures were very fast paced but this was a great opportunity to cover so many topics in a short space of time and get a grounding in lots of different topics that I will definitely be looking over in future. A poster session on the second evening gave us the chance to learn about other people’s work and make connections with other people starting out their careers in climate science, including a few readers of the blog, that will hopefully last throughout our careers.

One of the highlights of the course was the chance to run some (rather interesting) experiments with an earth system model. This involved breaking into groups with each being given a different project. It was exciting to go  through the whole process of having an idea, developing a hypothesis, thinking of specific experiments to answer the hypothesis and then analysing the results in just a week – something that takes much longer when you’re doing a PhD! My group worked on the Flat Earth experiment, which looked at the effect of removing all of the earth’s orography not, to our dismay, turning the earth into a flat disk. I learned a lot about how to run models, something which I have never done even though I use the output. It also developed my understanding of different climate processes that I don’t work with such as the monsoons, and even dynamical vegetation.

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Flat earth experiment looking at the change in the monsoon winds

Throughout the course we stayed at St Catharine’s College. Right in the centre of Cambridge it quickly felt like a home from home, keeping us well fed to get through the intense science. Although the weekend was rainy, apparently breaking a run of excellent weather for the school, we still had plenty of time to explore beautiful Cambridge. A few people were even brave enough to go punting!

An interesting, hectic and inspiring two weeks later we may have been glad to head back to Reading for a good sleep but having thoroughly enjoyed the summer school.

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The beautiful St Catharine’s College, image from http://www.caths.cam.ac.uk/

 

Summer Barbecue and Ceilidh

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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.