Analysis of fog and stratus cloudiness over the Pannonian Basin

The following animation of the infrared spectrum (IR 10.8 µm) shows the 6-hourly development of the weather conditions within a large anticyclonic area from the 18th to 20th November 2011.

Anim. 3.1. Infrared IR10.8 satellite imagery, 18th to 20th November 2011.

Because of the daily warming of the soil, the greatest contrast between the areas under the fog and cloud-free areas is observed at 12 UTC. The lower mountain peaks, such as the top of the Fruška Gora (538 m, Crveni Cot), can be observed on the first day of the period (18 November 2011, 12 UTC - indicated by the green arrow). On the next day (19 November 2011, 12 UTC), due to the formation of stratus cloudiness, only the peaks reaching 1000 m are visible (Papuk 953 m and Psunj 984 m, Croatia - indicated by the red arrow). From these pictures the characteristics of weather conditions cannot be accurately observed because there is no significant difference in the temperature of the fog layer and ground temperature. Because of that, a combination of different channels of radiation spectrum is recommended for satellite fog monitoring.

At night-time or during the winter months the following combination of the channels is recommended (Night Microphysics RGB): Red: Difference IR12.0 - IR10.8; Green: Difference IR10.8 - IR3.9; Blue: Channel IR10.8. During daytime, the natural color RGB is the recommended RGB combination that exploits best the channels of the visible spectrum of radiation. Red: NIR1.6, Green: VIS0.8 and Blue: VIS0.6 can be used. See the following animation.

Anim. 3.2. Night microphysics and natural color RGB imagery, 18th to 21st November 2011.

Fog and low clouds are shown in yellowish-orange colors in the night-time images (00 UTC and 06 UTC), and in the daytime images (12 UTC) in white tones. In the night images, the pink color represents cloud-free areas.

At 19th November 06 UTC dark grey clouds can be observed over the Czech Republic and Poland. These clouds are high Cirrus clouds superimposed to the Stratus shield. In the natural color RGB these clouds are less visible during daytime. The cyan clouds located over Slovakia and Hungary at 12 UTC on the same day result from the a strong signal from the green and the blue channel. MSG channel 3 shows little contribution due to the presence of ice crystals.