On 25 June 2003, a fire broke out at the Al-Mishraq sulphur plant, about 25 kilometres south of the city of Mosul, and a thick sulphur smoke dominated the sky in the area.
23 March 2022
25 June 2003
The fire had been caused by rocket-propelled grenades fired by unknown persons.
The toxic smoke affected the cities of Qayyarah, Al Shurah and Makhmur, along with approximately 25 surrounding villages. The major health concern associated with exposure to high concentrations of sulphur dioxide includes effects on breathing, respiratory illnesses and alterations in pulmonary defenses. It causes eye, nose, throat, and skin irritations especially for people with allergies.
The environmental impact that sulphur dioxide inflicts on the surrounding area causes even greater concern. More than 40 percent of the trees lost their leaves in a radius of 100km from the plant. The fire was finally extinguished one month later, after releasing millions of metric tonnes of sulphur dioxide into the air.
The area covered by the sulphur dioxide concentrations has been large enough to detect with Meteosat Second Generation (MSG). There are two SO2 absorption bands in the infrared region: one stronger band at around 7.3µm and a weaker band at around 8.6µm.
In this extreme case, the IR8.7 channel on Meteosat-8 easily detected the plume (see image above), while the WV7.3 channel failed to detect it. The reason for this is probably that, due to a strong temperature inversion, the SO2 cloud was limited to the Planetary Boundary Layer (PBL) and not detectable by the WV7.3 channel, which has the peak of the weighting function in the layer from about 700 to 400hPa (depending on the humidity content). The SO2 cloud is even better depicted in the brightness temperature difference between the IR10.8 and the IR8.7 channels (see image and animation above).
During day-time, the IR8.7 channel was up to 21K colder than the IR10.8 channel due to the strong absorption of the radiation from the very hot surface. During night-time, the IR8.7 channel was up to 4K warmer than the IR10.8 channel, indicating the presence of a low-level temperature inversion (the SO2 absorbs the radiation from the surface, which is then re-emitted at a higher temperature).
The images below show the smoke plume from the fire (MODIS RGB composite image) and the monthly averaged SO2 concentration in the area (from SCIAMACHY data). As can be seen from the latter, most of the SO2 plume went in easterly direction, towards the Caspian Sea, indicating prevailing winds from the west during the week(s) that followed the accident.