Article
Extended Data Fig. 7 | Saturation ratio as a function of temperature.
At constant nitric acid and ammonia, a decline in temperature leads to an
exponential increase in the saturation ratio of ammonium nitrate, shown as the
product of nitric acid and ammonia vapour concentration. With an adiabatic
lapse rate of −9 °C km−1 during adiabatic vertical mixing, upward transport of a
few hundred metres alone is enough for a saturated nitric acid and ammonia air
parcel to reach the saturation ratio capable of triggering rapid growth at a few
nanometres.