Persistent cloud patch moving along the Norwegian coast.
More information and detailed analysis of the feature can be found in the In Depth section.
by HansPeter Roesli, Jochen Kerkmann (EUMETSAT) and Daniel Rosenfeld (HUJI)
After the advection of polluted air over the Norwegian Sea from Scandinavia and the Russia-Ukraine region (see Smoke/pollen plume over Europe and the Northern Atlantic), an extended cloud patch formed off the Norwegian coast during the night of 7–8 May 2006 and remained intact until the night of 9–10 May (see Animation, 7 May 19:00–10 May 00:00 UTC, MPG, 15 MB).
In its early stage the form of the patch suggests the presence of shallow cyclonic circulation. There is no satellite data available (Meteosat-8, MODIS on Terra and MODIS/AIRS on Aqua) to confirm the hypotheses explicitly. Some evidence may be gained however, on two specially enhanced Meteosat-8 Dust RGB images.
One of them (see enhanced Dust RGB image, 7 May 17:00 UTC, PNG, 598 KB) shows a hazy whirl a couple of hours before cloud formation set in. Some hours afterwards the second one suggests cyclonic circulation in the cloud system (see enhanced Dust RGB image, 8 May 00:30 UTC, PNG, 599 KB). The relative motion field during the mature stage of the cloud patch (see Animation, 8 May 2006, 04:00–23:00 UTC, MPG, 4 MB) gives further insight into its dynamics. Again cyclonic circulation cannot be excluded.
Using highly enhanced 'natural colour' images from Meteosat-8 and MODIS (see enhanced Terra MODIS image, 8 May 11:20 UTC, PNG, 57 KB and enhanced Aqua MODIS image, 8 May 11:35 UTC, PNG, 64 KB) at 1 km spatial resolution the cloud patch appears to have cleaned the surrounding air.
The relatively high reflectivity in solar light points to cloud droplet spectra with many small drops, an indication of cloud formation in heavily polluted air that in turn might be one of the ingredients that maintained this cloud patch in such a stable form over an extended period of time (e.g. no dissolution through rain-out). In fact, the cloud patch survived for over two days, moving steadily along the Norwegian coast, before becoming distorted in a divergent flow off the Scottish coast during the night of 9/10 May.
During its mature stage on 8 May MODIS imagery at 250 m spatial resolution (see Aqua MODIS image at 250 m resolution, 8 May 11:35 UTC, PNG, 944 KB) shows the presence of closed Bénard cells in a large part of the patch. Open Bénard cells appear towards the fringes.
VIS0.6, NIR1.6, IR3.9r
Full Area (605 KB)
NIR1.6, VIS0.8, VIS0.6
Full Area (545 KB)
Smoke/pollen plume over Europe and the Northern Atlantic (9 May 2006)
cells in response to the suppression of precipitation by aerosols
(D. Rosenfeld ,Y. J. Kaufman and I. Koren, 2006 (in print), PDF, 2 MB)
VIS0.8, IR3.9r, IR10.8
Full Area (598 KB)
IR12.0–-IR10.8, IR10.8–IR8.7, IR10.8
Full Area (693 KB)