ok i'll try to explain it. temperature of the track is higher than the temperature of the air. since everything that is happening with the temperature is based with the fact that everything wants to come to a state of termical balance, track releases temperature in the surrounding air, and since it receives teperature from the sun it doesn't neccesarily lose any temperaure it has(quite different often it raises cause sun gives more energy to the track than track gives to surrounding air) and the closer you are to track temperature is higher cause you are closer to the sourse of temperature(and temperture has a tendancy to fall with distance from thermical source). i hope i cleared it up some