Can a 3D radar composite reliably represent ZDR columns?

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Brian Lo – brian.lo@pgr.reading.ac.uk 

Differential reflectivity (ZDR) is the difference in measured backscatter from emitted radio waves in the horizontal and vertical polarisations. It is an observable available from dual-polarisation radars. Conventional single-polarisation radars usually offer reflectivity ZH only which is the intensity of backscatter in the horizontal polarization available from conventional radars. The addition of measuring ZDR allows for hydrometeor type classification. In other words, we could tell between large round tumbling hail which gives near zero ZDR from large oblate raindrops that give highly positive ZDR (Kumjian, 2013a). Strong updrafts contribute to severe convective development by lofting large hydrometeors like raindrops into higher parts of the storm, giving ZDR column signatures. A differential reflectivity (ZDR) column is defined as “a region of enhanced ZDR as situated above the 0◦C level” (Kumjian, 2013b) and are known to be useful in informing forecast warning decisions (e.g. Kuster et al., 2019, 2020).

The UK Met Office has fully upgraded all 15 C-band radars as of January 2018 to have dual-polarisation capabilities. The Met Office also composites data from this radar network to provide three-dimensional gridded products covering the entirety of the UK (Scovell and al-Sakka, 2016). Whereas a single radar would only be able to detect hydrometeors as high as its highest scan elevation, thus leaving the so-called “cone of silence” aloft closest to the radar, the composite permits nearby radars to fill in these regions of missing observations. To harness the greater spatial domain of the 3D radar composite constituting data from multiple overlapping radars, the composite was upgraded to include ZDR to investigate the operational potential of using ZDR columns. But, how do we know ZDR columns can be reliably detected within this 3D radar composite? 

The work described in this post is to verify ZH and ZDR generated by the Met Office compositing process against range-height indicator (RHI) scans from Chilbolton Advanced Meteorological Radar (CAMRa), otherwise known as the world’s largest steerable meteorological research radar (see Figure 1). RHI scans are carried out by varying a radar antenna’s elevation angle but with the azimuth angle held constant. ZDR columns are often narrow features that may challenge the limited resolution (1km in the horizontal) of the radar composite.

Figure 1: The 25 m antenna of the Chilbolton Advanced Meteorological Radar (CAMRa) located at the Chilbolton Observatory. 

CAMRa is a suitable truth owing to it being well-calibrated to within 0.1dB of ZDR, its extremely narrow beamwidth of 0.28◦, high range resolution of 75m and high resolution elevations of 0.11deg within RHIs. In contrast, the composite is made of operational radar data of lower resolution and the compositing process could further degrade the accuracy of the data. Thus its ZDR output has to be verified.

Vertical cross sections of the radar composite

Figures 2a and 2d are RHI scans carried out by CAMRa, covering elevations from 0.02 to 10.0◦. These two figures captured an evolving convective system on 7 June 2016 at 1651Z (Figure 2e) and on 1 October 2019 at 1526Z (Figure 2f). The fine range resolution of 75m captured multiple intense reflectivity cores exceeding 40 dBZ with accompanying overshooting tops.

Figures 2b and 2e are pseudo-RHIs produced from the compositing process of the Chenies and Thurnham operational C-band radars. Both radars were chosen for the compositing process as their overlapping sampling regions offered coverage for the convective system scanned by CAMRa. Instead of generating the usual 3D composite with 1 km and 500 m of horizontal and vertical grid spacing respectively, the compositing software was modified in this verification process to interpolate C-band radar data onto a 2D grid along the CAMRa scan azimuth with the same grid resolutions thus producing the so-called pseudo-RHI plots. 

Figure 2: RHI plots of radar reflectivity ZH scanned by CAMRa (a,d) and corresponding pseudo-RHI plots derived from the original Met Office radar compositing process (b,e) and with azimuthal correction applied (c,f). The top and bottom rows each corresponds to observations on 07 June 2016 but at 1603Z and 1651Z respectively. 

However, the preliminary inspection of the pseudo-RHI plots reveals a serious vertical discontinuity of interpolated data. Such an issue would disrupt the automatic detection of vertically extending signatures such as ZDR columns. This problem is seen at around 70 and 100km down range in Figure 1b and 90km down range in Figure 2e. The displacement observed here suggests that the spatial location of storms could be misrepresented on the order of 5 km. What could have caused this problem?

Correction of spatial location of radar beams in compositing software 

Through scrutiny of the Met Office compositing software, I found an error with how radar azimuths were used in the compositing process. In the pre-exisiting compositing software,  radar azimuths would be formulated as azimuthal equidistant projection coordinates relative to the radar site, then directly transformed onto British National Grid coordinates. However, it was overlooked that Met Office radar azimuths are recorded with respect to British National grid north, whereas azimuthal equidistant projection coordinates require azimuths to be relative to true north. The deviations of up to a few degrees between the norths can lead to a horizontal displacement of radar data of at least a few kilometres at a range of 100km from a radar site. Lesson learnt: Attention to small details can have a large impact later on! 

To fix this problem, grid convergence (Ordnance Survey, 2018) is added to all radar azimuths such that radar azimuths are adjusted with respect to true north before undergoing transformation into British National Grid coordinates. The effect of implementing such a correction can be seen in Figures 1c and 1f, where reflectivity values interpolated from two separate C-band radars result in a vertically continuous intense reflectivity core. There could still be mismatches on a smaller scale owing to radar scans happening at different times while the storm was being advected. With the radar composite corrected, is ZDR well represented? 

Visual comparison of ZDR

Both Chenies and Thurnham radars used for generating pseudo-RHIs were upgraded to have dual polarimetric capability since March 2013. This allows the generation of ZDR pseudo-RHI plots as shown in Figures 2c and 2b, which can be qualitatively compared with CAMRa scans in Figures 2a and 2d on 7 June 2016 at 165136Z and on 1 October 2019 at 152641Z respectively.

Figure 3: RHI plots of radar differential reflectivity ZDR scanned by CAMRa (a,b), corresponding pseudo-RHI plots derived from the radar composite (c,d) and MAXDBZ plan views in (e,f). In the plan views, the red cross marks the position of CAMRa. The black line is the azimuth of CAMRa for the RHI scan. Black dots are separated by 20km with the first and last black dot corresponding to the plotted range of the RHIs. The top and bottom rows each corresponds to observations on 07 June 2016 at 1651Z and 01 Oct 2019 at 1526Z respectively. The freezing height was 3.0 km in the June case and 2.2 km in the October case. 

Considering the observed ZDR column is approximately 95 km down range from the radar, a displacement of 0.6◦ is 1km of distance in the horizontal. Such a distance corresponds to the sampling resolution of the radar composite. The C-band operational radars also have a wider beamwidth of 1.1◦ and are unable to observe fine details unless the ZDR column is situated close to one of the radars. Thus, the discrepancy in intensity and height in Figure 2 is expected, owing to the differences in sampling resolutions between CAMRa and the radar composite. The operational radar composite, which combines measurements from radars at various ranges, is capable of detecting ZDR column features at a coarser resolution, whereas CAMRa is used to study fine details of the column structures with high precision in individual case studies. 

We have shown that outputs from CAMRa captured sub-kilometre features such as the width of ZDR columns and their horizontal structures within a cell are too fine to be resolved by the composite. Despite the resolution limitations of operational radars and having done other tests not mentioned in this post, we are confident that the radar composite can be exploited to reliably capture the presence of ZDR columns at a horizontal spatial resolution of 1 km alongside an indication of their maximum heights. 

References

Kumjian, M. R. (2013a). “Principles and Applications of Dual-Polarization Weather Radar. Part I: Description of the Polarimetric Radar Variables”. Journal of Operational Meteorology 1.20, pp. 243–264. doi:10.15191/nwajom.2013.0120 

Kumjian, M. R. (2013b). “Principles and applications of dual-polarization weather radar. Part II: Warm- and cold-season applications”. Journal of Operational Meteorology 1.20, pp. 243–264. doi:10.15191/nwajom.2013.0120 

Kuster, C. M. et al. (2019). “Rapid-update radar observations of ZDR column depth and its use in the warning decision process”. Weather and Forecasting 34.4, pp. 1173–1188. doi: 10.1175/WAF-D-19-0024.1 

Kuster, C. M. et al. (2020). “Using ZDR Columns in Forecaster Conceptual Models and Warning Decision Making”. Weather and Forecasting, pp. 1–43. doi: 10.1175/WAF- D-20-0083.1 Ordnance Survey (2018). A Guide to Coordinate Systems in Great Britain. Accessed: 16-1-2024 

Scovell, R. and H. al-Sakka (2016). “A Point Cloud Method for Retrieval of High-Resolution 3D Gridded Reflectivity from Weather Radar Networks for Air Traffic Management”. Journal of Atmospheric and Oceanic Technology 33.3, pp. 461–479. doi: https://doi.org/10.1175/JTECH-D-15-0051.1 

Good morning Baltimore! AMS 2024

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Isabel Smith – i.h.smith@pgr.reading.ac.uk

Hannah Croad – h.croad@pgr.reading.ac.uk

In January 2024, Isabel Smith and Hannah Croad attended the 104th American Meteorological Society (AMS) annual meeting in Baltimore, Maryland. As fourth-year PhD students this was something of a “last hurrah” of our PhDs (with the remainder of our project monies and carbon budgets being used up), representing a fantastic opportunity to see the latest research happening in meteorology, meet other scientists working in our respective fields, and present our own work to a large audience at this late stage in our projects.

We arrived in Baltimore on the Friday before the conference started, navigating the busy streets near the Inner Harbour in a thick fog to find our hotel. The many plumes of steam coming from vents in the street were somewhat disconcerting, but it turns out this is the result of an underground steam pipe system and is completely safe. As exciting as this was, Baltimore is slightly lacking in terms of other tourist attractions, so on the Saturday we chose to visit Washington DC, only a 1-hour train ride away. We had a great day wandering about the capital city, visiting the Smithsonian’s National Air and Space Museum, and seeing all the iconic monuments including the Capitol building and the White House. Back in Baltimore on the Sunday, there was a buzz about the city as Baltimore’s NFL Ravens team were hosting the Kansas City Chiefs. Although we did not attend the game, and the Ravens lost, it was a great honour to be within a mile radius of Taylor Swift.

Figure 1: Posing for a selfie in front of the Capitol building in Washington DC whilst the sun made a brief appearance.

The conference started on Sunday, with registration (where we picked up some cool lanyards), speeches from outgoing and incoming AMS presidents, student posters, and an interesting panel discussion about how the two sides of American politics must come together in the fight against climate change. It was also great to meet up with two first-year PhD students from the department, Karan Ruparell and Robby Marks, for who this was the first international conference of their PhD.  

Figure 2: PhD students (from left to right: Karan, Hannah, Robby, Isabel) from the University of Reading at the AMS 2024 annual meeting with the climate-striped-inspired logo.

The main conference programme was scheduled from Monday to Thursday. The size of the conference was overwhelming, with up to 40 parallel sessions at any one time amongst the many different mini- conferences and symposia. Hence, it was important to research which sessions you wanted to go to in advance.  We did this using the AMS app, although it was rather slow and buggy (AMS if you’re reading this, please improve for next year). Isabel attended the 4-day symposium on Aviation, Range and Aerospace meteorology (ARAM), being held in the same room of the conference center each day. In contrast, Hannah attended many different sessions and so was continuously moving between different rooms, with the highlights being the Daniel Keyser symposium on synoptic-dynamic meteorology on Monday and the Polar symposium on Thursday. 

The biggest day of the conference for us was Thursday, as we were both going to be presenting our work. Starting bright and early, Isabel gave an oral presentation in the ARAM symposium, talking about her work on trends in aviation scale turbulence. In the afternoon, Hannah presented a poster in the Polar symposium, talking about her climatology of summer-time Arctic cyclones. We found it interesting to compare the two different presentation formats. For oral presentations your research is likely to reach more people as you have a captive audience for 12 minutes, but the format is more nerve-wracking and there is only limited time for questions and discussion. Less people are likely to visit a poster, but the 1.5 hour format allows for longer and more in-depth discussion with those who do approach you (assuming your poster survives the flight in your suitcase of course). Regardless of the format, we both really enjoyed sharing and discussing our work with other scientists and found the day to be thoroughly rewarding. 

Figure 3: Isabel giving her presentation in the ARAM symposium.
Figure 4: Hannah (left) presenting her poster at the Polar symposium. 

In summary, we both had a fantastic time at the AMS 2024 annual meeting. Not only did we enjoy and learn a lot from the conference talks and posters, it was also great to catch up with current and ex-students from the department, old friends and lecturers from our time at the University of Oklahoma as undergraduate students, and to make new contacts in our respective fields. Although large conferences like AMS can be daunting, attending gives you an appreciation of the wide variety of research happening all over the world, conducive to a stimulating and inspiring atmosphere. They also provide fantastic opportunities to network and to learn new things outside of your immediate research topic. Hence, we would both recommend attending a big conference like AMS if you get the chance to do so in your PhD! 

POST fellowship at UK Parliament on carbon offsetting

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Helen Hooker – h.hooker@pgr.reading.ac.uk

What is POST?

The Parliamentary Office for Science and Technology (POST) is a research and knowledge exchange service at UK Parliament. POST uses the best available research evidence and information to inform the legislative process and scrutiny of Government. POST advisors and fellows create POSTnotes and POSTbriefs on hot topics of interest to MPs and peers (members of the House of Lords) that are published online. Members may use information from POST publications during committee meetings or debates in Parliament.

The POSTnote process

POST fellows work for three months on an assigned topic outside of their usual area of research. The research is rapid! Fellows quickly identify experts from Academia, NGOs, Industry, and Government departments to speak to, and try to think of insightful questions to ask.

I was assigned the topic of carbon offsetting – yay! I interviewed almost 40 people that varied from those working with Indigenous Peoples in Guyana to others working with farming communities on Biochar (the carbon rich remains of super-heated organic material) research in the UK.

What is carbon offsetting?

A carbon credit is a token representing the avoidance, reduction or removal of atmospheric greenhouse gases (GHG), measured in tonnes of carbon dioxide equivalent (tCO2e). There are three main outcomes for projects creating carbon credits: Avoided emissions, for example by preventing deforestation and forest degradation; Reduced emissions, for example by restoring peatlands; and Removal and storage of CO2, for example by direct air capture or restoring forests. Businesses and individuals can purchase credits on the voluntary carbon market and may use them to offset their own emissions.

After lots of reading and reference gathering, the impartial POSTnote is drafted at around 3500 words and includes 100+ references. Internal and (a monster) external review follow (the draft note is sent to all contributors for comment) before final publication.

Working at Parliament

It was great to be a part of a team of POSTies, some seconded to select committees such as the Environmental Audit Committee or the Library. Others worked on different POSTnote topics like Green skills, AI in education and The future of fertiliser use. Westminster Palace is beautiful, awe-inspiring and a motivating place to work. There are lots of opportunities to enter ballots for activities and events. I was fortunate to attend the State Opening of Parliament (from the pavement, the King definitely waved at me), visit the archive tower (I counted nearly 300 steps up 12 floors and saw the original Freedom of Information Act 2000), and sing Christmas carols in Mr Speakers House.

Summary

I applied for a POST fellowship to learn more about policy and how research can have an impact. I loved the learning process, and I will use it in my research going forwards. I would like to thank SCENARIO DTP for funding the opportunity.

sshRACC: The Making Of

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Once upon a time, in the first week of term, last year’s panto organisers Jen Stout and Caleb Miller came to HP180 to ask if we (Catherine Toolan, Rosie Mammatt, and Hette Houtman) wanted to organise this year’s panto. Duty called, and we answered. We swiftly set out to start the preparations for this prestigious event.  

We set week 3 as the deadline to decide what story we would parody (2 weeks behind schedule). Luckily, some brainstorming on the (slightly hungover) morning after last year’s panto afterparty had already produced a strong candidate: Shrek. We agreed that the plot would be hard to adapt, but the potential for great songs would more than make up for it. During a general assembly of PhD students, it was decided almost unanimously that Shrek was the best we could come up with (sorry Rhiannon, maybe you can do Stratatouille next year). And so it was that Thorwald Stein came to be portrayed as an ogre. 

Plot

By week 8 (5 weeks behind schedule) the plot was finally ironed out. 

Thorwald Stein, a happy and eco-friendly researcher, is having a meeting with PhD student DonkeyBrian Lo, when a horde of fairytale characters barge into his swam-, err office. They bring the news that head of department, Lord Charquaad-Perez, has turned off the heating in most of the building to cut down on carbon emissions! When Thorwald demands an end to this nonsense, Lord Charquaad-Perez tells Thorwald he can have the heating back on if he brings down the dreaded FAAM-dragon, which is breathing out loads of carbon and taking up most of their carbon budget.  

Thus, Thorwald and his trusty companion DonkeyBrian set out on this quest to bring back peace to the department. They are joined by Lord Charquaad’s minion, Chris in Westboots, who keeps an eye on things for his master. When they finally reach the far, far away land of Wessex and spot the FAAM-dragon, they discover that world-renowned climate scientist FionEd Hawkins is trapped on it! As is panto tradition, Maarten Ambaum (portrayed as Prince Charming) tells our heroes that his textbook on thermal physics contains the secrets they need to bring down the plane. But alas, all its copies have been stolen from the library! Luckily, in an ode to the retiring SCENARIO DTP coordinator Wendy Neale and her seemingly magical powers in keeping this department running, Fairy Wendymother comes to the rescue. She waves her magic wand and down comes the dreaded FAAM-dragon. 

After a long journey (made even longer because their newly set travel carbon budget ran out on the way back), the crew return to the department. Thorwald and FionEd set out to cut down the department’s carbon emissions even further, but are thwarted by Lord Charquaad-Perez, who promises FionEd 3TB of storage on the sshRACC if she works on a paper with him instead of attempting to reduce the department’s carbon emissions. 

A fight ensues, and in the chaos Lord Charquaad-Perez is taken prisoner by the FAAM dragon. Thorwald and FionEd sneak into Lord Charquaad’s office and discover that it wasn’t FAAM but he himself who had been using up 80% of the budget – on Virgin Galactic tourist flights to the stratosphere! “That man must really love the stratosphere”, FionEd rightly says. 

With Lord Charquaad’s silly emissions no longer an issue, and the implementation of some ingenious emission-reducing measures from FionEd and Thorwald (like reusable coffee cups), the department becomes truly green, and can finally live la vida eco.  

Songs 

“Live la vida eco? What’s that?”, we hear you ask. Livin’ la vida eco was an adaptation of the absolute banger of a song by Ricky Martin, on which we ended the panto. And it wasn’t the only bop to be played by the band that night: All-Star by Smash Mouth (‘Ed Hawkins once told me the world is gonna warm up’), Funkytown by Lipps Inc. (‘Won’t you get me some heating now?’), Holding out for a hero by Bonnie Tyler (‘I need you Wendy’), I’m a believer by Smash Mouth (‘Donkey made me change, now I’m a lot cleaner’), and finally Sk8er Boi by Avril Lavigne (‘Working on papers she’s all alone’ – we will admit this one didn’t make a lot of sense, but we just wanted to play the song). All killer, no filler. 

Once again, Flynn Ames and his protege Nathaniel Edward-Inatimi did a superb job of organising the band. Their incredible talent and months of practise meant that by the time the song rehearsals came around (just two weeks before the show), they sounded amazing. The singers, however, did not. But after a few rehearsals, we’d come out of our shells and were able to put out a (hopefully) respectable performance!  

A special thanks must also go to Beth Saunders for her many years of panto knowledge, insane drumming skills and helping us get back into the swing of live pantos after the covid years. You’ll be missed next year! 

Casting  

The job of casting the roles this year seemed to be too easy. First year Robby Marks’ fatal “I don’t mind” remark led to him becoming the title character. Similar mistakes from Niamh O’Callaghan, who u-turned from “absolutely not” to “oh go on then” in a matter of seconds, led to her becoming the esteemed climate scientist FionEd Hawkins.  

As many of the other parts had relatively few lines, it was great to have so many students wanting to get involved. This led to a great atmosphere both on and off stage – we’re hoping this enthusiasm is still there when we start looking for next year’s organisers… 

The Night of the Panto  

Tickets had been sold (about 150 of them!). Props had been made, songs had been practised. The backstage cupboard was full, Robby’s face had been painted green. The cast were assembled and waiting at 5pm sharp. But wait – who was this in the Madejski lecture theatre? Surprise! An unexpected law lecture until 6pm!  

With the doors due to open at 7pm, we were feeling the pressure. Thankfully, due to a fair amount of preparation earlier in the day between lectures, many of the time- consuming tasks like setting the band up had already been done. With all hands- on deck and some tactical delaying of the audience (by keeping them by the buffet for longer) we were ready to go by 7.15.  

The first act was underway and the performance was going well. Nobody had forgotten their lines (yet). At the end of the first act, a quick glance at the watch relieved that we’d whistled through it in under half an hour… eek! 

Fortunately, we had three fantastic interval acts to keep us entertained in the break. Blair McGinness revealed the results of the Big Biscuit Bracket 2023 – why did more than half of you vote for bourbons over chocolate leibniz? Next came the latest episode of Jon Shonk’s much-anticipated Mr Mets series, which was as fantastic as ever. And finally, Chris Scott serenaded us with a handwritten ditty about the fake panto poster on the second floor window, supported by his dancer/backing singer(?) Matt Owens. 

It was time for the second act to get underway. The end of many months of (behind schedule and therefore slightly panicked) writing and rehearsing was in sight, and the performance was wrapped up with a rousing version of Ricky Martin’s famous Livin’ la Vida Eco. Applause was demanded by our cupboard signs, the audience delivered! 

Afterwards, it was time for the swiftest take down you’ve ever seen and a night on the tiles, I mean in the coffee room, with DJ Shonk! 

Some of the phenomenal cast and crew that brought sshRACC to the stage

Reflections  

After lots of hard work, many to-do lists, and more than a few days of PhD research missed, it was very rewarding to see everyone’s efforts come together on the night and to contribute to a long-standing department tradition. Once again, we were reminded that our department is full of people with talents that lie well outside of the field meteorology! We are also proud to say that we delivered (probably) the cheapest evening out in Reading – we believe the panto has remained at the same bargain price of £5 per adult since its beginning in 1992… 

Did we enjoy the experience? Yes, we did. Do we want jobs as directors or producers on the West End? No thank you! 

We would like to thank everyone who attended, contributed to, performed in or supported the panto in any way, shape or form. There are too many of you to list here, so just know that your efforts are appreciated! 

AGU in Sunny San Francisco

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Flynn Ames - f.ames@pgr.reading.ac.uk

For my first (and given carbon budgets, possibly the last) in-person conference of my PhD, I was lucky enough to go to AGU (American Geophysical Union Conference) in December 2023, taking place in San Francisco, California. As my first time in America, there was a lot to be excited about. As my first time presenting at a conference, there was a lot to be nervous about. So what did I discover?

To echo the previous year’s post: AGU is big. I mean really big. I mean seriously (please take me seriously) its huge. The poster hall was the size of an aircraft hangar – poster slots were numbered from 1 to over 3000, with each slot used by a different person for each day. Dozens of talk sessions were held at any time simultaneously across the three separate buildings (that thankfully were very close to each other), commencing anytime from 8am to 6pm, Monday to Friday. I was recommended the AGU app and would (uncharacteristically) do the same as it was very helpful in navigating the sessions. I’d also recommend properly planning what you want to attend in advance of the conference – it is very easy to miss potentially relevant sessions otherwise.

The poster hall from two different angles on Monday Morning (left) and Friday evening (right).

The keynote lectures (one per day) were like something out of Gamescom or E3. They always started with flashy, cinematic vignettes. Hosts and speakers had their own entrance theme song to walk out on stage to, whether that be Katy Perry ‘Fireworks’ or Johnny Cash ‘Ring of Fire’ (and of course, they had the cliche teleprompter from which to read). Some Keynote talks were OK in terms of content, but others were definitely a miss, seemingly prioritising style over substance or referring to subject matter in too abstract a way, so that it was difficult to gauge what the take home message was meant to be. I’d say attend at least one for the experience but skip the rest if they don’t appeal to you.

There were also miscellaneous activities to partake in. Exhibition Hall F was where you could find stalls of many research organisations, along with any American or Chinese university you can name (NASA had a cool one with some great graphics). In that same place you could also get a free massage (in plain sight of everyone else) or a professional headshot (which I tried – they brushed something on my face, I don’t know what it was) or even hang out with the puppies (a stall frequented by a certain Met PhD student). You could say there was something for everyone.

I wasn’t the only one needing rest after a long day of conferencing.

I found poster sessions to be far more useful than talks. Most talks were eight minutes long, with a red light switching on after seven. With these time constraints, presenters are often forced to assume knowledge and cram in content and slides. The presentations can be hard to follow at the best of times, but especially when you yourself are presenting later in the week and all you can do is watch and wait for that red light, knowing that it will be deciding your fate in days to come. In contrast, posters can be taken at one’s own pace – you can ask the presenter to tailor their “spiel” to you, whether that’s giving a higher-level overview (as I asked for 100% of the time) or skipping straight to the details. You get a proper chance to interact and have conversations with those doing work you’re interested in, in contrast to talks where your only hope is to hunt down and corner the presenter in the few microseconds after a session ends.

With that said, there were many great talks. Some of the coolest talks I attended were on existing and future mission concepts to Europa (moon of Jupiter) and Enceladus (moon of Saturn) respectively, which has tangential relevance to my own project (icy moon oceanography – probably best left for a future post). In these talks, they discussed the science of the upcoming Europa Clipper mission, along with a robotic EEL concept (like a robot snake) for traversing within and around the icy crevasses on Enceladus’s surface. It was really cool (and very lucky) getting to interact with people working on Europa Clipper and the current Juno mission orbiting Jupiter. Given the time taken between a mission’s proposal, getting (and sometimes losing) funding, planning, construction, and eventual launch and arrival, many of these scientists had been working on these missions for decades! 

My own talk was scheduled for the final conference day (given the luck with everything else, I won’t complain) at 8:40 am. While seemingly early, I struggled to sleep beyond 3:30am most days anyway owing to jet lag so by 8:40am, stress ensured I was wide awake, alert, and focused. 

The talk was over in a flash – I blinked and it was done (more or less).

The most academically helpful part of the conference was the conversations I had with people about my work after the talk. This was my main take away from AGU – that getting to know people in your field and having in-depth conversations really can’t have been achieved by reading someone’s paper, or even sending an email. Meeting in-person really helps. A poster session can thankfully make this feel very natural (as opposed to just randomly walking up to strangers – not for me…) and is therefore something I recommend taking advantage of. Besides, if they’re presenting a poster, they’re less able to run away, even if they want to.

A quick bullet point list of other things I learned (and didn’t) while at AGU:

Things I learned:

  • Apparently, PhD students having business cards is normal in America? – I got handed one during a dinner and the whole table didn’t understand why I was confused
  • NO BISCUITS DURING COFFEE BREAKS in America – probably because you can’t get biscuits easily in America. Regardless, my stomach deemed this a poor excuse.
  • Food portions are, in general, much bigger – surely to make up for the lack of biscuits during coffee breaks.

Things I didn’t learn:

  • How the automatic flush mechanism worked in the conference venue toilets (I really tried)
  • Given there were dozens of sessions happening simultaneously at the conference, probably many other things.

After AGU finished, I was lucky enough to spend extra time in San Francisco. The city really has a piece of everything: fantastic walks near the Golden Gate and coastal area, the characteristic steep streets and cable cars, lots of great places to eat out (great for vegans/vegetarians too! :)), and they had unexpectedly good street musicians. The weather was very nice for December – around 18 degrees. I even got sunburned on one of the days. Public transport is great in San Francisco and getting around the city was no issue.

Some of the various sights (and only pictures I took) in San Francisco.

But San Francisco also appears to be a city of extremes. There are mansions near the beach in an area that looks like a screenshot from Grand Theft Auto Five. Meanwhile in the city itself, the scale of homelessness is far beyond anything I’ve observed here in the UK. I’d very frequently walk past people with large trolleys containing what appeared to be all their belongings. Nearby the Tenderloin district, pitched tents on the pathways next to roads were common, with people cooking on gas stoves. The line to what appeared to be one soup kitchen stretched outside and round the corner. Drug use was also very noticeable. I frequently spotted people slumped over in wheelchairs, others passed out in a subway station or outside a shop. People pass by as if no-ones there. It’s one thing hearing about these issues, but it is eye-opening to see it.

Overall, attending AGU in San Francisco was an experience I will not forget and certainly a highlight of my PhD so far – I’m very grateful I was able to go! Next year’s AGU will take place in Washington DC from 9th-13th December. Will you be there? Will you be the one to write next years AGU post?  Stay tuned to the Social Metwork (and for the latter, your email inbox) to find out.

The Weather Game

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Ieuan Higgs – i.higgs@pgr.reading.ac.uk

It’s a colder-than-usual, early October Friday afternoon in the PhD offices of Brian Hoskins. The week is tired, motivation is waning and most importantly – Sappo is only 30 minutes away. As the collective mind of each office meanders further and further from work, someone inevitably pipes up with:

“Has anyone done their weather game predictions this week?”

Some mutterings might move around the room – grumbling about the unpredictability of rainfall in Singapore, or a verbal jab at the cold front that decided to move across Reading about 6 hours too early – until, as predictably as ENSO, a first year cautiously asks,

“…What’s the weather game?”

Which is then met with a suitable response, such as:

“The Weather Game? It’s a bit like fantasy football, but for us weather nerds – you’re going to love it!”. 

At least, that’s how I like to describe it.

The game was hotly contested this Autumn, with huge sign-up and participation across the entire term.

A particular shoutout to the Undergraduates, who were out in force and took 50% of the top 10 spots!

Plotting the cumulative scores for the top 32 players of the term, we are treated to a blindingly colourful cascade (thanks excel?) of points totals:

From this, it is clear that our eventual winner had led the pack for a solid five weeks by the competition end – although I’m sure they were a little nervous in those final two weeks. We can also see the dreaded “flatline” – players who clearly got off to a good start but then, for whatever reason, never submitted another prediction for the remainder of the game. Another interesting feature of these plots is the occasional downward bump – a symptom of the dreaded negative score, which were (thankfully) relatively few and far between.

The illustrious awards ceremony was held in WCD on the 8th of December. Category winners were treated to a bar of tasty chocolate, and the overall winner was gifted a delightful little ThermoPro Bluetooth Thermometer & Hygrometer. This seemed an ideal prize for students who might want check if their flat-share thermostat is being undemocratically switched on while they are out at lectures. Of course, a wooden spoon was given to the last place that played at least 8 of the 10 weeks (and if you’re having that much fun with the weather – can you really ever lose?).

With all of that said, we now put our winners’ names in lights (or on the blog) – immortalising them in the records of Weather Game glory.

Wooden Spoon: Catherine Toolan

Oil and Gas – 66.8 points – 32nd place

Best Pseudonym: Meg Stretton

The SIF Lord

External: Thomas Hall

Noctilucent – 518.6 points – 2nd place

Postgraduate: Caleb Miller

I own a sphere – 414.4 points – 8th place

Staff: Patrick McGuire

WindyCrashLandingOnYou – 432.4 points – 7th place

Overall Winner: Nathan Ng

Come Rain or (Keith) Shine – 534.3 points – 1st place

The Weather Game will be back in Spring of 2024. We are excited to run it, and hope to see many new and familiar faces (well, pseudonyms) there.

Mr Weathers

Ieuan Higgs and Nathan Edward-Inatimi

WesCon 2023: From Unexpected Radiosondes to Experimental Forecasts

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Adam Gainford – a.gainford@pgr.reading.ac.uk

Summer might seem like a distant memory at this stage, with the “exact date of snow” drawing ever closer and Mariah Carey’s Christmas desires broadcasting to unsuspecting shoppers across the country. But cast your minds back four-to-six months and you may remember a warmer and generally sunnier time, filled with barbeques, bucket hats, and even the occasional Met Ball. You might also remember that, weather-wise, summer 2023 was one of the more anomalous summers we have experienced in the UK. This summer saw 11% more rainfall recorded than the 1991-2020 average, despite June being dominated by hot, dry weather. In fact, June 2023 was also the warmest June on record and yet temperatures across the summer turned out to be largely average. 

Despite being a bit of an unsettled summer, these mixed conditions provided the perfect opportunity to study a notoriously unpredictable type of weather: convection. Convection is often much more difficult to accurately forecast compared to larger-scale features, even using models which can now explicitly resolve these events. As a crude analogy, consider a pot of bubbling water which has brought to the boil on a kitchen hob. As the amount of heat being delivered to the water increases, we can probably make some reasonable estimates of the number of bubbles we should expect to see on the surface of the water (none initially, but slowly increasing in number as the temperature of the water approaches the boiling point). But we would likely struggle if we tried to predict exactly where those bubbles might appear. 

This is where the WesCon (Wessex Convection) field campaign comes in. WesCon participants spent the entire summer operating radars, launching radiosondes, monitoring weather stations, analysing forecasts, piloting drones, and even taking to the skies — all in an effort to better understand convection and its representation within forecast models. It was a huge undertaking, and I was fortunate enough to be a small part of it. 

In this blog I discuss two of the ways in which I was involved: launching radiosondes from the University of Reading Atmospheric Observatory and evaluating the performance of models at the Met Office Summer Testbed.

Radiosonde Launches and Wiggly Profiles

A core part of WesCon was frequent radiosonde launches from sites across the south and south-west of the UK. Over 300 individual sondes were launched in total, with each one requiring a team of two to three people to calibrate the sonde, record station measurements and fill balloons with helium. Those are the easy parts – the hard part is making sure your radiosonde gets off the ground in one piece.

You can see in the picture below that the observatory is surrounded by sharp fences and monitoring equipment which can be tricky to avoid, especially during gusty conditions. In the rare occurrences when the balloon experienced “rapid unplanned disassembly”, we had to scramble to prepare a new one so as not to delay the recordings by too long.

The University of Reading Atmospheric Observatory, overlooked by some mid-level cloud streets. 

After a few launches, however, the procedure becomes routine. Then you can start taking a cursory look at the data being sent back to the receiving station.

During the two weeks I was involved with launching radiosondes, there were numerous instances of elevated convection, which were a particular priority for the campaign given the headaches these cause for modellers. Elevated convection is where the ascending airmass originates from somewhere above the boundary layer, such as on a frontal boundary. We may therefore expect profiles of elevated convection to include a temperature inversion of some kind, which would prevent surface airmasses from ascending above the boundary layer. 

However, what we certainly did not expect to see were radiosondes appearing to oscillate with height (see my crude screenshot below). 

“The wiggler”! Oscillating radiosondes observed during elevated convection events.

Cue the excited discussions trying to explain what we were seeing. Sensor malfunction? Strong downdraughts? Not quite. 

Notice that the peak of each oscillation occurs almost exactly at 0°C. Surely that can’t be coincidental! Turns out these “wiggly” radiosondes have been observed before, albeit infrequently, and is attributed to snow building up on the surface of the balloon, weighing it down. As the balloon sinks and returns to above-freezing temperatures, the accumulated snow gradually melts and departs the balloon, allowing it to rise back up to the freezing level and accumulate more snow, and so on. 

That sounds reasonable enough. So why, then, do we see this oscillating behaviour so infrequently? One of the reasons discovered was purely technical. 

Most retrieving stations are set to stop collecting data when they measure that the radiosonde is descending, as this is typically assumed to be caused by the balloon being popped. So there actually may be more of these events than we expect, we just haven’t been observing them. Another, more speculative reason could be the conditions which favour large amounts of snow to develop at mid-levels. In each of the three launches where we observed oscillating profiles, the weather we were measuring was associated with elevated convection which often leads to deeper ascent than surface-based convection. 

If you would like to read more about these events, a paper is currently being prepared by Stephen Burt, Caleb Miller and Brian Lo. Check back on the blog for further updates!

Humphrey Lean, Eme Dean-Lewis (left) and myself (right) ready to launch a sonde.

Met Office Summer Testbed

While not strictly a part of WesCon, this summer’s Met Office testbed was closely connected to the themes of the field campaign, and features plenty of collaboration. 

Testbeds are an opportunity for operational meteorologists, researchers, academics, and even students to evaluate forecast outputs and provide feedback on particular model issues. This year’s testbed was focussed on two main themes: convection and ensembles. These are both high priority areas for development in the Met Office, and the testbed provides a chance to get a broader, more subjective evaluation of these issues.

Group photo of the week 2 testbed participants.

Each day was structured into six sets of activities. Firstly, we were divided into three groups to perform a “Forecast Denial Experiment”, whereby each group is given access to a limited set of data and asked to issue a forecast for later in the day. One group only had access to the deterministic UKV model outputs, another group only had access to the MOGREPS-UK high-resolution ensemble output, and the third group has access to both datasets. The idea was to test whether ensemble outputs provide added value and accuracy to forecasts of impactful weather compared to just deterministic outputs. Each group was led by one or two operational meteorologists who navigated the data and, generally, provided most of the guidance. Personally, I found it immensely useful to shadow the op-mets as they made their forecasts, and came away with a much better understanding of the processes which goes into issuing a forecast.

Next, we performed a similar activity only this time using outputs from a new tool called IMPROVER. IMPROVER is designed to blend the various model outputs and present the strongest aspects of each one in a single set of visualisations. Once again, it was really interesting to see how the neighbourhood processing included within IMPROVER was used to provide additional confidence to the forecasts issued from the previous activity. After this, we would get a brief update from the current WesCon director about the current goings-on with the field campaign. Some time was also very graciously set aside during these sessions to let the students in the testbed present some of their work.

After lunch, we would begin the ensemble evaluation activity which focussed on subjectively evaluating the spread of solutions in the high-resolution MOGREPS-UK ensemble. Improving ensemble spread is one of the major priorities for model development; currently, the members of high-resolution ensembles tend to diverge from the control member too slowly, leading to overconfident forecasts. It was particularly interesting to compare the spread results from MOGREPS-UK with the global MOGREPS-G ensemble and to try to understand the situations when the UK ensemble seemed to resemble a downscaled version of the global model. Next, we would evaluate three surface water flooding products, all combining ensemble data with other surface and impact libraries to produce flooding risk maps. Despite being driven by the same underlying model outputs, it was surprising how much each model differed in the case studies we looked at. 

Finally, we would end the day by evaluating the WMV (Wessex Model Variable) 300 m test ensemble, run over the greater Bristol area over this summer for research purposes. Also driven by MOGREPS-UK, this ensemble would often pick out convective structure which MOGREPS-UK was too coarse to resolve, but also tended to overdo the intensities. It was also very interesting to see the objective metrics suggested that WMV had much worse spread than MOGREPS-UK over the same area, a surprising result which didn’t align with my own interpretation of model performance.

Overall, the testbed was a great opportunity to learn more about how forecasts are issued and to get a deeper intuition for how to interpret model outputs. As researchers, it’s easy to look at model outputs as just abstract data, which is there to be verified and scrutinised, forgetting the impacts that it can have on the people experiencing it. While it was an admittedly exhausting couple of weeks, I would highly recommend more students take part in future testbeds!

International symposium of data assimilation 2023

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Laura Risley – l.risley@pgr.reading.ac.uk

The 9th international symposium of data assimilation (ISDA) was held in Bologna, Italy this October. Firstly, what is data assimilation? Data assimilation is the process of combining observed data with a numerical model. It also considers the errors present in both and produces the best estimate of the current state of the system. Data assimilation is used in various fields such as ocean modelling and numerical weather prediction. As such it has become an extremely important technique with high impact. ISDA is one of the largest gatherings of data assimilation scientists from across the world, and this year’s conference was no exception.  

Figure 1: All talks over the course of the week were held in this room. Here is also a snippet of the schedule.

The conference took place over 5 days, each packed full of talks. There were no parallel sessions and so attendees were able to go to all 73 talks during the day! The conference didn’t stop there as there were two posters’ sessions on the Tuesday and Thursday evenings, as well as a gala dinner on the Wednesday evening which we were all invited to. This was held in the Palazzo Pepoli – the museum of the history of Bologna. A unique venue that we were fortunate enough to be able to explore before a delicious meal. 

Attendees of ISDA came from various institutions. These included ECMWF, RIKEN, Penn State, The Met Office UK, CERFACS, DWD and many more. It was a truly global affair. The University of Reading was represented by members of the Data Assimilation Research Centre (DARC). Presentations were given by staff – Sarah Dance, Alison Fowler, Yumeng Chen and Ivo Pasmans, whereas PhD students presented posters – myself, Ieuan Higgs and Helen Hooker. The poster sessions were a great opportunity to discuss our work with people from various disciplines, but all interested. I found the experience extremely useful and very enjoyable, despite being quite nervous before the session. Poster sessions are a great chance to not only share your work with others but ask for advice from experts. Although it feels daunting talking to those who are far more experienced in data assimilation, you soon realise that everyone is there to learn and help each other. It is a supportive and friendly environment!  

Figure 2: PhD students from DARC presenting posters at ISDA (me, Ieuan Higgs and Helen Hooker).  

The conference, centred on data assimilation, covered a variety of topics from parameter estimation in earthquake models; lightning data assimilation; non-linear data assimilation and anchor observations – just to name a few! Machine learning took centre stage this year with researchers highlighting both the pitfalls and the advantages of incorporating machine learning techniques within data assimilation. 

The conference has previously been held in various locations such as Reading, Munich and Fort Collins. This year it was held in Bologna, Italy and organised by Alberto Carrassi. Bologna is a wonderful city, full of historic buildings and food. Lots and lots of food. I felt very lucky to have been able to take my first trip over to Italy for the conference. 

Figure 3: Some sights from Bologna!  

Overall, it was a fantastic week of ensemble Kalman filters, cost functions, covariance matrices, localisation, pizza, and pasta. I learnt a lot about data assimilation; how vast the applications are and how much I still have to discover in the future. ISDA 2024 will be held in Kobe, Japan!