Analysis of fog and stratus cloudiness over the Pannonian Basin

Synoptic field

From 18th to 20th November 2011, central and eastern parts of Europe, including the Balkan Peninsula, were under the influence of an anticyclone and a weak gradient flow at higher atmospheric levels. This was an ideal synoptic situation for the formation of fog over the Pannonian Basin.

Fig. 2.1. 19th November 2011 06 UTC 500hPa Geopotential (black line), Mean Sea Level Pressure (white line).

Further maintenance of this pressure field and deposition of cold air in the anticyclone caused an increase in the fog thickness and its gradual transition to the stratus cloudiness. This is confirmed by METAR reports showing the visibility observations and current weather at Belgrade Nikola Tesla airport on 18-20 November, 2011:

LYBE 180600Z 19003KT 0100 R12/0125N R30/0100N FZFG VV001 M04/M05 Q1027 NOSIG

LYBE 190600Z 05002KT 0200 R12/0250N R30/0250N FZFG VV001 M02/M04 Q1027 NOSIG

LYBE 200600Z VRB02KT 1800 BR BKN003 M01/M02 Q1028 TEMPO 1000

Sounding

For an analysis of the vertical profile of the atmosphere, soundings from two locations were used: Belgrade (203m) and Szeged (83m). Low-level temperature inversion formed by cooling of the surface by intensive overnight Earth's radiation can be seen in Figure 2.2 (left). It should be stressed that the Belgrade sounding station's location is not representative for the city parts with lower altitudes, Figure 2.2 (right). Also, it can be noticed that humidity at the surface is too low for fog formation.

Fig. 2.2. 18th November, 2011 00 UTC sounding for Szeged (left) and Belgrade (right).

The next day when the fog lifted, stratus formed (Fig. 2.3 and 2.4).

Fig. 2.3. 19th November, 2011 00 UTC sounding for Szeged (left) and Belgrade (right).

Fig. 2.4. 20th November, 2011 00 UTC sounding for Szeged (left) and Belgrade (right).