Short-lived contrails may also form without ambient water vapor if ambient temperatures are sufficiently low. Water vapor partial pressure and temperature measurements and calculations from various contrail studies. Contrails become visible within roughly a wingspan distance behind the aircraft, implying that the ice particles form and grow large enough to become visible within the first tenths of a second of plume age. However, the resulting contrails would have fewer and larger particles. These particles would be thermodynamically stable and longer lived and would cause a different chemical perturbation than would short-lived stratospheric contrails composed of water ice.
Acidic solutions freeze at lower temperatures than pure water.
If homogeneous and heterogeneous freezing processes are possible, the most efficient freezing mode takes up available H 2 O and may prevent the growth of other particle modes. This critical size hence freezing probability depends on maximum supercooling reached in the expanding plume. Particle growth rates hence freezing rates are larger in cooler and more humid ambient air, so volatile particles may contribute considerably to ice crystal nucleation at temperatures below the contrail threshold value. Volatile droplets will be prevented from freezing if rapid freezing of soot-containing particles occurs. Hence, more fuel sulfur leads to a greater number of ice particles.