beelsebob wrote:godlameroso wrote:Wind doesn't blow in a direction it circulates from a direction, the difference is subtle, keep that in mind. What might be a tailwind through 3/4ths of the back straight may be a side wind before the breaking zone.
The size of the circulations you're talking about are so large that for the purpose of a race track, it blows from a direction. Circles thousands of miles across are effectively straight lines on the 1-2 mile scale.
Note – of course small variations, (or even large local variations) occur, due to the wind being funneled through or sheered around buildings, but that does not mean that the general trend is for a circular pattern over the circuit.
All the data I'm privy to says otherwise, there is always localized eddy and vortex formation in air masses that can cause partial shearing forces in the overall flow direction in even unobstructed flow(thus a tail wind can become a side or even head wind temporarily). The statistically relevant flow of air can remain constant for hundreds of miles, but there will always be localized shifts. This is even observed in laboratory conditions in essentially closed loop air tunnels and can throw air tunnel data off. We noticed the effect was even greater when the pressure distribution in the tunnel wasn't uniform(the nature of a wind tunnel makes completely uniform pressure impossible). Once the tunnel pressure was stabilized to the maximum we could muster the effects were mitigated somewhat, but I digress, that is whole 'nother can-o-worms.
For one, China's mountainous topography easily causes pressure gradients that can affect overall wind patterns. Also to some small but important effect is the increased air density caused by pollution, and the way the sun interacts with the track as the haze changes the refraction of the sun and the way it interacts with the track. Typically the China race has a very minimal delta with ambient to track temperature compared to say Barcelona, or Germany.