Seasonality: The anthropogenic Middle East Plume (MEP) exists in the northern summer typically from May to September each year at varying levels of intensity.
Sources Anthropogenic: The anthropogenic MEP is nearly exclusively derived from gas flares in the oil production industry identified by the World Bank Global Gas Flaring Reduction Partnership and NOAA. Oil production in the Middle East was almost zero at the end of the second World War and rose continuously until 1967 when production topped 10 million barrels of oil per day for the first time, a figure below which it has never fallen. Associated gas produced with the oil was originally vented and is now flared if no market is available for the gas.
Sources Natural: Natural aerosols from volcanoes around the Red Sea may contribute to the plume.
Trajectory: The anthropogenic MEP originates in the oilfields of the Arabian Peninsula and Iran where the prevailing winds blow from the east to north north east. These winds drive the aerosols either directly south west to Darfur and the Sahel or south to the Gulf of Aden where, constrained by the high ground to the west in Somalia and Ethiopia, the aerosols are forced north along the Red Sea until they round the northern tip of the high ground and resume their south westerly trajectory to Darfur and the Sahel.
Most Extreme: 1991 was the most extreme apparition of the MEP driven by the Kuwaiti oil fields which burned for much of the year after the first Gulf War. The NASA image s from the Nimbus 7 satellite. This may well be the largest and most extreme anthropogeic aerosol plume humanity has ever created!!
Effects: My paper presented at the AGU Fall Meeting in 2015 shows how the MEP caused and is causing drought in Darfur and the eastern Sahel.