Foehn - Typical Appearance In Vertical Cross Sections

by ZAMG


The typical appearance in vertical cross sections is somewhat false, because of the fact that the effect of mountains is not treated realistically within cross sections, neither from radio soundings nor from numerical models. Radio Sonde stations have too big a spatial resolution while numerical models usually do not contain the fine structure and real height of mountainous areas. Nevertheless some interesting features can be derived.

The example below, used to demonstrate general Foehn dynamics, is from the Alpine region. Therefore the following relation between vertical cross section, frontal cloud and mountains exists.

27 January 2008/00.00 UTC - Meteosat 9 IR10.8 image

Equivalent potential temperature: vertical cross sections from radiosonde stations compared with the output from numerical models

27 January 2008/00.00 UTC - Vertical cross section; black: isentropes (ThetaE)

Relative humidity: vertical cross section from radio sounding stations

27 January 2008/00.00 UTC - Vertical cross section; blue: relative humidity, black: isentropes (ThetaE)

Convergence: vertical cross sections from numerical model

27 January 2008/00.00 UTC - Vertical cross section; magenta: divergence, black: isentropes (ThetaE)

Vertical motion: vertical cross sections from numerical model

27 January 2008/00.00 UTC - Vertical cross section; cyan: vertical motion, black: isentropes (ThetaE)


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