Origin, evolution and dynamics of ISSRs

Abstract

Ice supersaturation in the upper troposphere is mostly confined to regions where the air flow is upward, divergent, and anticyclonic. However, these characteristics alone do not suffice to predict ice supersaturation. Whether an air parcel in a region with upwind, divergence and anticyclonic flow is supersaturated or not depends on its origin and history. In the mid-latitudes, ice supersaturation often occurs in the upper tropospheric outflow regions of warm conveyor belts where the flow turns anticyclonically. In this talk, I will compare climatologies of ice supersaturated regions and of warm conveyor belts. Then I will present a special case and will show that the temperature profile along an air parcel’s trajectory is crucial to make the parcel part of an ice supersaturated region or not. A bit surprisingly, the moisture transport does not differ much between ice supersaturated and subsaturated regions.