Water Vapour Imagery Pallet

• Chapter III: Cyclogenesis in WV imagery - Baroclinic Leaf
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• Baroclinic Leaf
• The formation of a baroclinic leaf
• Leaf variations
• Baroclinic Leaf 15/16 October 2012
• Exercises

Baroclinic Leaf

Baroclinic leaves are cloud or moisture patterns that can be found on the front sides of high level troughs, most often located downstream of PV anomalies. They are associated with surface baroclinic zones or cold fronts. A baroclinic leaf of this kind can be the first phase of a baroclinic disturbance and is therefore often described as a pre-cyclogenetic cloud band. Cyclogenesis occurs with 75% of baroclinic leaves.

The features of baroclinic leaves can be seen in VIS, IR and WV images. The advantage of using WV channels for observing baroclinic leaves is the possibility to detect early stages of development. This can be seen best when comparing a VIS image of a baroclinic leaf with a WV image (figure 1a and 1b).

Figure 1a: WV 6.2 µm image from 20 May 2012, 12:00 UTC – a baroclinic leaf (red square) develops over the Atlantic.