This is a revised version of an article written originally in 2018 to story the project, edited and published in Now Then as Rain: Chasing Sheffield’s rain shadow.
At nineteen, an attic bedroom at the top of Crookes on the western edge of Sheffield gifted me a panoramic view looking east into the city. That was in 2011. It was the first house I’d lived in with friends after leaving student halls. I spent a lot of time leaning out the skylight smoking hand-rolled cigarettes and soaking up the freedom of the view.
Over the neighbouring rooftops, the view dropped off down into the valley of the city, flattening out northwest to the Tinsley viaduct and beyond. Across the other side of the city, another hill rose up with a snaking tramline leading up behind Park Hill flats.
I began to recognise the predictability that clouds would float straight over my head from behind the house and sink as they dipped into the natural bowl of the city. They’d come over from the Peak District, which started not far beyond the other side of the house, having fizzed into and out of existence in moist air over hundreds of miles across the Atlantic, Ireland and Manchester. A couple of times, I saw it rain without a cloud in the sky; pure blue air and crystalline rain.
From the house, it was about a ten-minute walk in the direction of the Peak District over to Bolehills Park. A ‘bole hill’, I later learned, is the name for a hillside where metallurgists smelted lead in open-air furnaces, drawing on the energy of strong persistent winds. Following a contour line around 200 metres, from Bolehill Park, you get stunning views out west across the edge of the Peak District. I’d walk over to the park, alone and with friends, and often see banks of clouds lined up neatly north to south along the backbone of the Peaks.
A few years later in 2014, I was working part-time at the Hallamshire House, a pub just round the hill from Crookes, and studying for a Master’s degree in science communication. Instead of doing a written thesis, we were given the option of creating a piece of content for our final project. The idea hadn’t fully formed, but I was curious and figured a documentary could be a way to explore the patterns I’d started noticing in the skies.
Weather coming over from Manchester and the Peaks would often leave Sheffield drier than we’d have forecast. Sometimes the rain never arrived, or it’d be lighter than predicted. We’d also get more sunshine and less cloud cover. A glade of blue would sometimes appear over the city within a blanket of clouds. These events made me ask: were the Peaks doing something to protect us from the weather?
Over the following months, through the summer of 2014, I attempted writing, filming, and editing a short documentary, alongside conducting some research into the science and formulating a thesis. With equipment loaned from the journalism department and a small budget from the university to cover my travel, I tried capturing the story of my investigations into the region’s climate in the documentary I called, Chasing Sheffield’s Rain Shadow.
The Central Library in Sheffield was one of the starting points for my research. One of my grandmothers used to take me and my sister there during the school holidays, and I had a feeling it might hold some clues. I gathered a shortlist from the online database and a librarian helped me find the books. A few of the works were short, independently published accounts of the regional weather. Others featured work from scientists at the city’s universities.
In a fabric-bound book published in 1956, ‘Climate in Sheffield and its Region’, Alice Garnett, a Professor of Geography at Sheffield University, the first woman to be voted in as President of the Institute of British Geographers in 1966, noted the earliest mention I found of a ‘rain shadow’ explaining Sheffield’s relative dryness compared to Manchester and the Peaks.
A rain shadow describes a phenomenon in the skies and its outcomes across the land. It’s a metaphor of sorts, trying to capture a description of the causes for locations on either side of a mountain range in the path of a prevailing wind tending to have a noticeable difference in rainfall. In characteristic examples, a rain shadow paints a stark difference in vegetation on either side of a range – down the coastline of California, for example, you can trace the Sierra-Cascades by following the green around San Francisco to their west and the deserts of Nevada to their east.
Travelling with a prevailing wind, when air reaches a range of mountains or hills, it gets lifted and buffeted upwards. In the lowest layer of the atmosphere, there’s less pressure in the air and it’s usually colder the higher you go. Water vapour in the air tends to cool as it rises, condensing into droplets, clouds, and eventually rain. Driven on by winds and the rotation of the earth, the air and clouds eventually make it up and over the other side of the range. As the air descends, it warms again. Water in the clouds evaporates, leaving a metaphorical shadow of rain where it should have fallen before descending. Only at sunset could there be a shadow from a rain shadow.
The weather is notoriously complex and unpredictable. Many local and global elements influence it. The mechanisms underpinning and triggering orographic precipitation, the technical term for rain influenced by elevated terrain, are not as simple as I’ve described. Larger-scale storms and frontal weather systems will barrel through a region and over a mountain range. Convection bubbles up heat from the land into explosive, localised rain showers in both the presence and absence of hills.
As an idea, a rain shadow attempts to describe mechanisms through which rainfall and clouds are reduced or blocked on the downwind, leeward, side of a mountain range.
It was these ideas I followed, searching to figure out why Sheffield seemed to often be blessed with better weather than the forecasts predicted. Or, if you look at it that way, why it’s often so rainy in Manchester.
Conversations with friends, family, locals at the Hallamshire House, and people I interviewed for the documentary at Sharrow Vale market revealed experiences of orographic weather in the region. A beekeeper told me how hard it was caring for his heather-loving hives in heavy rainfall they often get out at the edge of the Peaks. A retired RAF pilot taught me about atmospheric waves in the wake of hills he’d ride on the flight back to base. A homebrewer recommended an ale from a brewery in the Peaks they’d recently named Rain Shadow. And a couple of dog walkers recounted trips to rainy reservoirs at the edge of the city returning to streets as dry as bones.
A conversation with a friend studying engineering at the time resonated with a book I found in the Central Library. It was from 1976, titled ‘Urban Development and Planning of Sheffield Since the Beginning of the Industrial Era’. They both told similar versions of a story, where to avoid the pollution from the factories and industry blowing most regularly across to the east, people who could afford it built and lived in houses in the west of the city. It’s a similar story that shaped urban development across many cities in Europe.
The consequences of the prevailing westerly we get over the British Isles can also be seen in the distribution of health and wealth across our cities. Even today, you can see divides across Sheffield. Danny Dorling’s Tale of Two Cities mapped this out for Sheffield, highlighting the unequal distribution of health and wealth across the east and west of the city.
With a clearer idea about rain shadows and Sheffield’s microclimate, I sought scientific input to validate and explain the picture I was building. I contacted researchers at universities in Sheffield, Manchester, and Leeds to interview and film their interpretations of what was happening in the skies above our cities. Bringing a level of scrutiny I hadn’t yet encountered was a scientist based in Manchester.
David Schultz, a Professor in Synoptic Meteorology at the University of Manchester, was born in Pittsburgh and has an academic record reading like the smartest storm chaser you’ll ever meet. David challenged my assumptions. He questioned whether a rain shadow was the main reason why the city he worked in was often so wet. He didn’t believe the Peaks were big enough to create a characteristic rain shadow, and suspected that rain would fizzle out generally as it travelled east across the British Isles.
Professor Schultz proposed we put the rain shadow theory to the test with help from his long-time collaborator, Dr Jonathan Fairman, another North American calling Manchester their home at the time. We inspected wind and rainfall records from 54 weather stations around Sheffield, Manchester and the Peaks from 1981 to 2010, searching for signals of a rain shadow under both westerly and easterly winds. The results of our research, ‘Quantifying the Rain-Shadow Effect: Results from the Peak District, British Isles’, were published in 2018, in the April edition of the Bulletin of the American Meteorological Society.
We started by confirming that the prevailing wind in the region is westerly. On 207 days each year, the weather moves across us from the west. Only on 28 days per year does it come from the east.
Then, we looked at the volume of rain falling across the region. On an average day, under a westerly, we found that Manchester receives 3.9 mm of rain; the Manchester side of the Peak District gets 4.5 mm; and Sheffield 1.7 mm. Putting the wind to one side, this levels out around 1200 mm of rain in Manchester and 700 mm in Sheffield each year in total.
Finally, we tried identifying the number of days showing a characteristic rain shadow pattern: throughout a day with a westerly wind, rain falling in Manchester but none at all in Sheffield. We found, on average across the thirty years, 34 occasions each year when this happens. That’s just over an extra month of rainy days in Manchester under a westerly wind each year. Further research from a collaborator of David and Jonathan’s, found that these rain/no rain days tend to happen more often in warmer seasons and peak during the summer.
Although we found increased rainfall in Manchester and the Peaks compared to Sheffield, it doesn’t follow that they were all due to rain shadow effects. As David summed it up in the paper: “An explanation for the rain shadow is easily demonstrated and intellectually satisfying… upon deeper reflection, however, such an explanation may not be so obvious.”
The Peaks are fairly modest, not dissimilar to the people of Sheffield. Most of the land across the 56 kilometres or so between Sheffield and Manchester rises above and around 300 m. At its highest, in the north of the national park, the terrain pushes 600m. I have felt the effects of this terrain on the weather, but there are always larger-scale forces at play.
Our data and research spoke purely about rainfall and wind direction. They’re indicative rather than explanatory. We’d have needed to involve computational modelling of the weather to account more conclusively for the patterns we found.
Speaking from experience, it’s hard for me not to believe that the contours, a persistent westerly, and a clear difference in rainfall across the Peaks paint the picture that a rain shadow has something to do with leaving Sheffield drier than its neighbours to the west.
I spent the summer of 2014 filming the weather, and whenever I’m in the city I often see it in the forecast and skies. I managed to capture with timelapse photography what appears to me to be the Peaks holding up clouds on a few occasions. As for the cloudless rain from my skylight in Crookes, it could have been ‘spillover precipitation’ drifting over, with the Peaks holding up the bulk of the rainfall. I’d go as far as to suggest it’s why, until recently, Sheffield held the crown of the world’s longest-lasting rainbow.
I wouldn’t have been able to make the documentary or pursue the project without help from friends, family and collaborators. The scientists I interviewed in Sheffield, Manchester, and Leeds all had a different take on the rain shadow but generously gave their time to help shape and inform the project, particularly Professor David Schultz. Crucially, making the deadline to present the documentary for my thesis came down to collaboration and support from friends who helped me film, edit and soundtrack the final cut, on occasion getting up before dawn to shoot the weather at sunrise.