SVP = saturated vapour pressure. I understand that the SVP over ice is less than that over water for temperatures less than 0C. I'm doing an exam question which asks 'what is the significance of this difference?'. My first guess is that in clouds with both ice and water present, this difference results in growth of ice crystals at the expense of droplets. Not sure if this is the only significance, and whether anyone could point me to some others.