EUMeTrain: CAL Module on Dust Cloud

Author

Jarno Schipper - ZAMG
Nuno Moreira - Meteorological Institute Portugal
Jochen Kerkmann - EUMETSAT

Introduction

Dust storms over the Mediterranean and the Atlantic are phenomena mostly seen throughout the whole year with peaks in springtime because of reduced vegetation coverage and increased differential heating. The effect it has on public life, namely in health and aviation, can be devastating. In this module several dust storms that were observed over Europe over the past few years will be discussed. The events are described With the help of satellite imagery.

Meteosat 8 RGB (HRVis; HRVis; IR10.8i): 2005-09-16 1200UTC	Meteosat 8 Dust-RGB (IR12.0-IR10.8; IR10.8-IR8.7; IR10.8)

In the two above images a dust storm is pictured over the island of Sardinia. The event took place on July 28th 2005 and was well tracked by several channels of Meteosat 8. The left image shows the combination of the high resolution visible channel (around 0.7 μm) and IR10.8μm. To the right an (artificial) RGB build from several IR channels. More details on this latter RGB will follow in the course of this CAL module.
During the CAL Module it will be shown that satellite images can prove to be a powerful tool to detect and forecast dust. However, there are some downfalls to it:

• High clouds may obscure dust. Just because clouds are pictured in satellite imagery, it does not mean that dust is not affecting the surface.
• It is difficult to estimate surface visibilities based on dust observed in satellite images
• It is not easy to determine the altitude of dust from images. It could be near the surface, causing visibility restrictions, or it could be high up in the troposphere with relatively good visibilities underneath.
• Since dust is optically thin, it may not be seen in Visible or IR Images.

---

The aim of this case study is to understand how:

• Satellite imagery can help to nowcast atmospheric dust
• Dust appears on Meteosat IR images
• To interpret and use the "Dust-RGB"
• The "Dust Flag" from the NWCSAF can help to detect atmospheric dust

The effects of dust on public life and the forecasting of dust has also been the theme of a CAL Module produced by COMET. It is highly adviceable to study this CAL module at Forecasting Dust Storms.