Original scientific paper
COLD AIR DAMMING OVER PO VALLEY AND ADRIATIC COAST
Teodoro La Rocca
; Italian Met Service, C.N.M.C.A. Aeroporto M.De Bernardi, Pratica di Mare 00040 Pomezia Italy
Abstract
The “ Cold Air Damming” consists in a weak cold air mass flux blocked by a mountain chain on the upward side, at low levels; is is not able to scavalcare the mountains in the lee side and is trapped topographically. This event develops extended low-middle level cloudness, low temperatures, generally weak precipitations and
sometimes, freezing or frozen rain. In terms of thermodynamics, the cold air mass is generated by weak advection, adiabatic cooling as air ascends the mountain slopes and finally diabatic cooling by melting or evaporation. In this presentation, we consider two CAD cases reported in Italy: trapped cold air on the east side of Appenninian mountainous terrain (Adriatic coast) and into Po Valley. Primary diagnostic features are a weak easterly flux coming
from the Balcan region and a thermal inversion at low level (Met 8 elaborated images, soundings). In terms of prognosis, Local Models frequently capture the CAD features well ( low cloud cover, wind precipitation); some errors depend on parametrizations at low levels as thermal ad humidity lapse rate structures, as water phase into the
cloud ( liquid, iced, snow, supercooled water) and finally the intensity of the wind.
Keywords
Hrčak ID:
64612
URI
Publication date:
15.12.2005.
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