The frequency of stability classes is either determined from the
radiation balance and the wind speed at Kittsee (Fig. 2a) or the OSP
with a roughness length of 0.02 m derived from on-site wind
measurements (Fig. 2b) following Beljaars (1987), cit. in Kobmann
and Namyslo (2007). With both schemes, neutral conditions are
most abundant at Kittsee, class 4 (AODM) and class III/1 (LASAT)
showing frequencies of 35 to more than 50%. This is due to the high
wind speeds and/or cloudy conditions. The Klug-Manier and the
LASAT schemes deliver less unstable cases than the Reuter (1970)
and the Golder (1972) schemes. The large differences for classes 4and 5 compared to III/2 and III/1 is due to the different stability
concepts of the Reuter and Klug/Manier schemes. For the OSPderived
percentages in Fig. 2b, the differences are also an effect of
the different limit values to attribute OSP to atmospheric stability
(see Table 1): Instability starts at a much lower negative value,
strong stability at a much lower positive value with the Golder
(1972) compared to the LASAT scheme. Neutral conditions are
more frequent with the LASAT scheme because of the much larger
window for classes III/1 and III/2 compared to the Golder (1972)
scheme for class 4. Golder's class 5 has no appropriate counterpart
in the LASAT scheme.