Extreme weather
The word winter apparently comes from the Germanic ‘wintar’ which in turn is derived from the root ‘wed’ meaning ‘wet’ or water’, and so signifies a wet season. An entirely apt description for the winter of 2023/24!
The word winter apparently comes from the Germanic ‘wintar’ which in turn is derived from the root ‘wed’ meaning ‘wet’ or water’, and so signifies a wet season. An entirely apt description for the winter of 2023/24!
Meteorologically-speaking, winter as a season starts on December 1st and ends at the end of February. Agronomically, I always tend to associate the beginning of November as the start of winter because that’s when we tend to see a marked dip in air and soil temperature. We also see a pronounced dip in DLI (Daily Light Interval) levels in the last week of October as days shorten and nights lengthen!
However the media describe it, last winter was a shocker, with England enduring the wettest 18 months since 1836 and many areas of the U.K receiving >170% of the1991-2020 average rainfall. It isn’t just the rain that has caused an issue, it was also unseasonably warm, with December ’23 and February ’24 in particular posting record monthly air temperatures.
First up, let’s look at some climatic stats from four locations across the U.K, courtesy of the Davis weather station network I work with. I picked Bath, Sevenoaks, Milton Keynes and Manchester.
Before I do, I think it is pertinent to put out that although we very obviously have had a lot of rain, my objective was to try and determine whether there was anything different about this winter’s weather patterns and resulting rainfall.
The first significant difference concerning winter 2023/24 was the sheer number of storm systems the U.K & Ireland experienced. Left is a comparison between the last two autumn/winters.
The storm season runs from the beginning of September to the end of August. You can clearly see that we had eleven named storm systems last winter vs. just four the year before, and two of those occurred in the summer (as I found out to my cost in a campervan during Storm Betty!!).
Source – U.K Storm Centre, The Met Office
(metoffice.gov.uk/weather/warnings-and-advice/uk-storm-centre/index).
In the chart above, I have added the ‘nature’ of the storm system including its path and the main area affected in the U.K & Ireland. I also think it is pertinent to point out that we have had plenty of low pressure systems (and therefore rain) last winter, without them being named as a storm system.
To answer the many questions I had/have about last winter’s weather patterns and their potential cause, I turned to Sebastian Schlögl, head of Meteorology at Meteoblue AG. Meteoblue (meteoblue.com) is the weather company I have worked with since 2009 and I am indebted to Karl Gutbrod, CEO, for his support through my career.
So why so many storms last winter?
To understand the answer to this question, you need to know about the jet stream. We (the U.K & Ireland) lie on the path of the polar jet stream and its ‘behaviour’ is inextricably linked with our weather. When it flows strongly, it is responsible for pushing weather systems across The Atlantic and, when it weakens, it can meander, forming troughs and peaks in which weather systems can get stuck or blocked. To understand this better, go to this link; (metoffice.gov.uk/weather/learn-about/weather/how-weather-works/high-and-low-pressure/blocks). These blocked weather systems are often associated with extreme weather events, be that rainfall or heatwaves.
Here’s Sebastian’s take on my question.
“During an El Niño phenomena, the temperature gradient between the Tropics and the Polar region increases, through which the Jet stream gets stronger. It can bring more low pressure systems, causing a weak decrease in air temperature in the temperate latitudes.”
So, we have a potential link with El Niño, the warming event that takes place in the Pacific and, to boot, something that occurred recently. The majority of storms we experienced were indeed Atlantic storms that followed a traditionally strong jet stream path across the west of Ireland U.K. There were though other Atlantic storms that didn’t follow the normal track/path and occurred when the jet stream flow was weaker. These storms came in across The Bay of Biscay and tended to affect the southeast of Ireland and southern half of the U.K.
The storms that formed further south and tracked in across The Bay of Biscay were the most devasting from a flooding perspective, namely Storms Babet, Ciarán and Henk.
Why was this?
Well, firstly because they were associated with a trough pattern in the jet stream; they were slower moving, meaning we tend to get more rain and, I believe, more intense rainfall.
They also appear to have more energy associated with them and that may be because of a process called ‘Cyclogenesis’ where a storm system intensifies. I wondered if sea temperature had an effect, so I looked at three different locations using the brilliant MyOcean Pro tool on the Copernicus.eu website. Find it here
At the start of the year, the sea temperature in The Bay of Biscay was 13.369°C, compared to 10.589°C off the coast of Cornwall and 11.027°C off the west coast of Ireland. Warmer air holds more water vapour; for every 1°C increase in air temperature, the amount of water vapour the atmosphere can hold increases by 7%. I would theorise that the higher sea temperature and slow-moving track of the storm system allows it to build more energy. (Note - the famous hurricane of 1987 followed the same track into the south of England and underwent Cyclogenesis on the way).
Source – Copernicus.eu
Let us now look (image below) at the actual rainfall stats from the four locations I have chosen compared to winter 2022/23 and the 1991-2020 anomaly.
As with any weather statistics, we can see drier and wetter months, but the stand outs were December ’23 and February ’24, which showed significantly more rain than the prior year (remembering of course that February ’23 was one of the driest ever). All locations showed more rainfall than the same period, prior year and the 1991-2020 long term average, with some big differences for the period December to February.
Is that the whole story though?
The simple answer is no, because what we saw was more flooding, more saturated rootzones and, as we moved into spring, more growth that we could not keep on top of because you couldn’t get machinery onto the areas to cut. I looked into number of wet days, number of consecutive dry days, but surprisingly there wasn’t a consistent trend, year-on-year.
For sure, we also know that with a wetter summer in 2023, followed by a wet autumn/winter AND spring, the actual ground water levels were much higher than the previous winter, so there was less place for water to go in the first place.
The final parameter I looked into was rain rate (in terms of mm per hour) because it is this that causes issues with flooding, bunker wash, etc. If the rain rate is too high, it can overwhelm the infiltration rate of the rootzone it is falling on.
Pictured below are the number of heavy (≥7.5mm per hour) and violent (≥50 mm per hour) rain rate events at the four locations from the beginning of September to the end of February, recorded by a Davis Vantage Pro weather station.
The above analysis clearly shows that in three out of four locations, there were more heavy rainfall events as defined by the rain rate. In two out of the four locations, there were also more violent rainfall events. I don’t think it is any accident that the two locations with the most violent rainfall events, Sevenoaks and Bath are both close to the point where storms make landfall across the south and southwest of England and, of course, are warmer on average than Milton Keynes and Manchester.
So, my conclusion is that in some locations (Manchester) we just had more rain, plain and simple, but in others, not only did we have more rain, but the rain rate it fell at, and the frequency of heavy/violent rainfall events increased.
One last meteorological question... Is this phenomenon related to climate change?
I’ll leave that answer to Sebastian Schlögl from Meteoblue…
“Now, there are several connections between the Jet Stream, the weather and the climate change. Recent publications from scientific experts suggest that the Jet Stream will meander more with climate change, because the arctic region becomes warmer, faster. That causes the temperature gradient between the polar region and the equator to decrease, which could further cause the Jet Stream winds to become less strong.
This leads to a stronger meandering of the Jet Stream, so the amplitudes of the Jet Stream waves become stronger. That might lead to a longer persistence of weather situations than usual, occasionally resulting in, for example, long heat waves or continuous rain. But, keep in mind, that even with future predictions of climate change, the monthly positive anomalies of rain you have observed in Britain last winter are very difficult to directly link to long-term Jet Stream shift, because the latter is more a climate-related issue. Monthly positive anomalies of rain in Great Britain could additionally be caused by many other factors which interact with each other in a very complex way.”
Turning to the agronomic consequences of the above, there are many, varied and entirely dependent, as we can see, on which part of the U.K & Ireland your facility is located in.
Intense rainfall events are by their very nature extremely localised, with large differences in rainfall between two sites just a few miles away. Alongside rainfall, we also had a very mild, some would say warm, winter and the continual growth this provided has caused issues with respect to maintenance, but this is a two-sided coin because growth is not only an issue, but an opportunity. Something I hope to discuss in my next article.
To be able to deal with significantly more rainfall events AND more intense rainfall, it comes down to soil type, rootzone characteristics and surface organic matter levels. Surface organic matter is the first consideration and we aren’t just talking about %’s here. If the nature of the surface organic matter is compacted, with a low level of topdressing through the profile, then it will provide the primary barrier to water movement regardless of the actual % O.M stated on a physical analysis report. After that, we have the ameliorated rootzone (hopefully L2 and L3 in my aeration image above) and finally the drainage layer. This is a complicated topic because obviously there is huge variability in soil type across a facility and the areas that are managed/unmanaged. One area that intrigues me is how rootzones are actually performing from an infiltration rate perspective vs. the actual rainfall intensity we are experiencing nowadays. Finally, we have plant growth regulator timing and usage, disease management and nutrition as the other significant considerations to discuss.
The author
Mark Hunt has worked in plant nutrition and disease management R&D over the last thirty years. He joined Prodata Weather Systems in 2021 and continues to share his expertise and advice of weather analytics to turfcare professionals. weatherstations.co.uk
It’s not the weather for a promotion
Peter Smith was recently appointed as head greenkeeper at Bathgate Golf Club, however, due to the challenging weather, his first year in charge has been one he wants to forget.
Throughout the last ten years, the average rainfall in winter at Bathgate has increased from 502mm to 831mm in 2023 and Peter thinks it will keep increasing…
Due to increased rainfall, Peter has struggled to make and sustain plans to improve the course. “You make plans a day in advance and then it rains twice as much as you expected, so you then have to scrap that plan. More often than not, you won’t be able to do any work because of the ground being saturated and flooded, which massively impacts general maintenance and projects; we’ve had nearly 800mm of rain throughout the last five months!”
The team had planned to do a bunker programme and a green reshape in order to improve the course throughout the winter, but unfortunately these are still incomplete. Peter told us why: “We tried to beat the weather by starting the projects in October, but because of the insistent weather we couldn’t progress anything for a good few months.”
Restricted golf
Another factor of the increased rainfall is the closure of the course and Peter has taken a cautious approach: “We have been shut a lot more this year compared to the previous years, as I have tried to protect the course. I wanted it to be ready for the summer and most members were accepting of this at the beginning. That is what we need as greenkeepers, especially when the weather is against us.”
“However, after a couple of months of closing the course, we started to get pressure from members. Sometimes, it is out of your hands and closing is the best thing to do, but members became more and more impatient. The greens committee were full of support for Peter and his team: “They knew what we were trying to achieve, but there is only so much work you can do in the rain. We have people on the committee who have been members for fifty years and never seen it as wet as this winter.”
A learning curve
Despite the weather challenges, Peter is seeing the positives of his damp first year in charge: “It has been good to be in the worst case scenario and I have definitely learnt the areas where the course struggles with rainfall. I hope next year won’t be as hard as this one, but the weather appears to be getting worse every year. We will rearrange our schedule and try and do work earlier by starting projects at the end of September. This weather is the norm moving forward and those in turf care must plan around it.”
Looking after the team
With the weather being challenging, the club have invested into looking after the greens team. Peter concluded: “We purchased waterproof clothing for the staff which has given them more encouragement to get out and do the work, despite the challenging conditions.
It can be a long day out in the rain, but the spirit of the team has increased due to the improvement of workwear.”
Surfactants used year-round
Climate change is predicted to bring hotter, drier summers accompanied by wetter weather patterns and more frequent, heavier, downpours.
Over the past few years, this prediction has been playing out right across Europe, with more intensive periods of heat and drought alongside more frequent periods of heavy rainfall. The past 12 months have been particularly challenging for anyone maintaining sports and amenity turf, with continually saturated soils making it extremely difficult to present playing surfaces to usual standards.
Consequently, these changing weather patterns have altered the way turf managers are using surfactants. Rather than the focus being solely on improving the effectiveness of applied irrigation and managing drought stressed turf, surfactants are now being used year-round. Aquatrols have developed surfactants proven to improve surface infiltration and reduce run-off during wetter periods of the year. Chemistries are now available to move water more quickly through saturated soils and improve surface infiltration rates on already wet ground.
In autumn and winter, maintaining as dry a turf surface as possible is key - not only for keeping sports surfaces firm and in play, but also to reduce potential for disease and organic matter build-up. Consequently, the use of surfactants now have a role to play in soil water management year-round, enabling turf managers to better cope with these more challenging conditions.
For Aquatrols, we have had to consider how the unpredictable weather patterns impact our operations. One response has been for us to increase warehousing capabilities both in the UK and Europe. This ensures that we have the right surfactants available at the right time for our distributors and their customers - regardless of what the weather brings.
Emma Beggs - Portfolio Manager Aquatrols Europe Ltd