How climate science is key to going fast in Olympic Velodrome
When a storm brews over London's Olympic Park this summer, expect it to be raining world records inside the Velodrome.
Britain's track stars were full of praise for the new venue at last week's World Cup test event as they topped the medals table while records tumbled.
"I was expecting some good performances but this is the best I've been since Beijing, no question," said Sir Chris Hoy, while Victoria Pendleton added: "It's been a wonderful track to ride. On the whole it's been a huge success."
Hard work and raw speed were clearly the main factors behind their success, but the British elements could yet provide home riders with that crucial edge come Games time.
Thunder and lightning might offer the quickest-possible conditions for track cycling in an arena where speed is influenced by a vast range of factors, many derived from the weather outside.
For performances indoors to be governed partly by meteorology might seem odd, if your time is not spent immersed in the data which now drives elite sport.
But the waking hours of Esme Taylor, an English Institute of Sport physiologist, are consumed harvesting the tiniest details about how Britain's finest are performing and what affects them.
Taylor worked with British Cycling during last week's Track World Cup - the first event to be held inside the new Olympic Velodrome. Armed with laptops, small boxes affixed to bikes and other sensors, she and her colleagues amassed an arsenal of information.
"We're using this event as a dry-run for the Olympics, trying to learn from it," she says.
"We collect information on temperature, pressure and humidity in the velodrome throughout the racing so we can get an idea of what to expect. That's affected by the weather outside.
"A lot of people have talked about this being a world record-breaking track. Some of that is related to track geometry, but a lot is related to the weather."
There is no air-conditioning at the velodrome, which prides itself on a system of "natural ventilation" to create a constant track temperature of around 28 degrees Celsius.
"It's not so hot that it would affect club cyclists negatively, and we don't want it too cold either," Taylor explains.
"You generally find, standing in the centre of the track, that it feels a lot warmer than it does if you're riding around. You get a cooling effect when competing from the air rushing around you, so while it may sound quite warm, it isn't for them."
Organisers encountered some difficulty in maintaining that fixed temperature during the World Cup, which doubled as an Olympic test event. Taylor and the British Cycling team noticed the temperature fluctuate, including a drop in Friday's evening session, later ascribed in reports to stewards accidentally opening the wrong doors to let people leave early.
Temperature, though, is not the only influence. Humidity plays a part in determining the outcome of endurance events as it affects riders' ability to thermoregulate, or control their body temperature.
"The longer the event, the more effect that has," says Taylor. "If you look at the omnium, where you have the points race, scratch race and elimination race, those are events in which it is quite hard to control your temperature. You become more fatigued by an increase in body temperature than by anything else.
"During this competition the humidity has been quite low, but it depends on what's going on outside. You can't control humidity, even if you can control temperature."
World records may come down to a third factor, air pressure, characterised by Taylor as "the force of mass of the atmosphere pushing down on the earth". As she explains, velodromes at high altitude - such as La Paz in Bolivia - quite often play host to world-record rides because the air pressure is lower.
All three - temperature, humidity and pressure - help to control a fourth and vital component of the velodrome's climate: air density.
"The higher the air density, the harder it is to push through the air," says Taylor. In a sport where medals are often decided by hundredths of a second, even the slightest change in air density can lower times noticeably. "Temperature and humidity have an effect on air density and, when you're cycling in a velodrome, if the atmospheric pressure goes down then the air density goes down as well, so riding is easier.
"Again, that's affected by weather systems. Cold weather from the north means low air pressure whereas, around the equator, you can expect the pressure to be high. When those meet, that's what changes the pressure.
"Really low pressure outside with a high temperature will create the fastest conditions inside, and we could get that in a British summer.
"If it's quite stormy then you tend to have quite low pressure. It wouldn't be nice for everyone outside, but we'd quite like it stormy."
What can any of the riders do about any of this? Although conditions could feasibly change during an extended qualifying session, benefiting some more than others, most major races will be head-to-head finals with all competitors facing the same temperature, humidity, air pressure and air density.
Is there a point, then, to monitoring that data if the playing field essentially stays the same for everyone?
The answer is that if you know how conditions will affect the way your riders operate, you can plan their preparation around the predicted velodrome climate. Exactly what form that preparation will take is kept a mystery by British Cycling but, if it shaves a few hundredths of a second off a lap time, it might be worth a medal.
"The data gives us an idea of what we can expect," says Taylor, "but more importantly there are things you can do, related to these variables, that might help you.
"Nothing you can do will have a dramatic effect - you still need all the training and hard work - but there are things that I can't go into, and that's why we monitor it."