Contrails, low-level wave clouds, pre-frontal cirrus clouds.

This timelapse movie nicely documents large temporal and spatial variations of the conditions favorable for the formation of contrails (condensation trails behind jet planes) and for their persistence. To better understand the weather conditions for this case, attached below are three movies, based on multispectral imagery from the MSG (Meteosat Second Generation) weather satellite:

• general situation above Europe in pseudo-real colors (RGB combination of the MSG bands VIS0.6, VIS0.8 and IR10.8; MOV file, 9 MB);

• detailed view of the Czech Republic in a similar combination (RGB combination of bands HRV, HRV and IR10.8; MOV, 8 MB);

• and the same area shown in the 24-hour microphysical product (RGB combination of R=IR12.0-IR10.8, G=IR10.8-IR8.7 and B=IR10.8 bands; MOV, 9 MB), where the pinkish to light violet represent cloud-free terrain, yellow-green corresponds to low and middle clouds, dark red shows optically thick high clouds, and dark blue to black indicate very thin cirrus clouds or contrails.

These MSG movies show a large shield of cirrus clouds moving slowly eastward, while the individual cirrus clouds within it stream southward, partially and irregularly dissipating above the Czech Republic for most of the day. Besides the high cirrus clouds, we can also see low-level clouds, partially organized in small-scale waves. The entire area was covered by snow.

Similar to the variable conditions affecting the natural cirrus clouds formation and dissipation, the local conditions affecting the contrails also change rapidly in space and time. Besides the horizontal variability of these conditions, the actual flight level may also have a big impact on the appearance of the contrail. While some of the flight levels are located within the moist cirrus layer (where distinct contrails are likely to form), other flight levels are above or under it, in a dryer air - much less favorable for contrail formation. This explains why we can simultaneously watch various forms of contrails in the timelapse movie. Those contrails which persist longer are carried southward (to the left in the time-lapse movie) by the ambient high-level winds.

During the later part of the timelapse movie, shallow convective clouds begin to form, and become partially arranged in low-level waves. The time-lapse movie ends shortly before the dense cirrus clouds entirely cover the area. The red dot in the detailed satellite loops indicates the location from which the Ricoh timelapse movie was taken (Praha-Libus) and its time. The camera was aimed toward the southwest.

Satellite data sources: CHMI and EUMETSAT. Information on the MSG RGB composite products is available here (brief) or here (detailed), and references to scientific publications on contrails are here.

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Similar cases:  [2009-11-25], [2009-11-30]

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