MID-TROPOSPHERIC DRY LAYERS AND THEIR RELATIONSHIP TO PRECIPITATION TYPE IN A SUB-FREEZING TROPOSPHERE

• Main Author: Gregory Smith
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Arctic
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.664.1606; http://nwas.org/digest/papers/1995/Vol20-Issue2-Dec1995/Pg34-Smith.pdf

The effect of mid-tropospheric dry layers on precipitation type is examinedfor cases in which freezing (vs.frozen) precipi-tation fell when the entire depth of the troposphere was well below freezing. Aggressive mid-level dry slotting associated with a mature cyclone is examined. The depth of the mid-level dry layer and associated ice crystal sublimation, and subsequent disruption of ice nucleation and diffusional ice Clystal growth in the lower tropospheric moist layer, is studied. The lack of lower tropospheric warm layers (above freezing) suggest that ice crystal sublimation in the mid-level dry layer was the primary atmospheric process responsible for freezing, rather than frozen, precipitation. A shallow arctic air mass case is also presented, in which the lower tropospheric moist layer was confined to an environment warmer than-15°C and bounded by a deep mid-tropospheric dlY layer. A forecaster checklist is presented based on the study findings. 1.