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Are there specific weather patterns that would make these massive sand storms we keep hearing about on the news about Iraq? If so, does it have something to do with the weather coming off the Mediterranean Sea?
Question Date: 2003-03-25
Answer 1:

This tectonic environment sets the stage for the hydrology of Iraq which is at least partly related to the major dust storms that we are seeing in the news. The trough of the overall syncline of Iraq is occupied by the twin rivers, the Tigris and Euphrates, the lower reaches of which gave birth to some of the earliest civilizations. These rivers (along with some smaller rivers) historically fed the Mesopotamian marshlands which used to occupy the plain which dominates much of south-eastern Iraq. In the last decade or few, major hydro-engineering structures have held back this water in reservoirs, diverted it for irrigation, or simply re-routed it so that it wouldn't supply the marshlands and, as a result, about 90% of the marshlands have become dry.

Fine sediments tend to settle out of stream water when it slows in marsh or lake systems so the soil exposed by drying the marshes is composed of readily erodible fine particles. Add strong winds (which I'll talk about in a moment) and a lot of vehicles driving over these surfaces, and you get a lot of fine material getting into the atmosphere and making very severe dust storms.

During spring and autumn months, atmospheric low pressure systems can develop over Iraq which bring with them the Sharqi, a gusty and dusty wind from the southeast that comes with serious dust storms and sometimes thunderstorms.

As temperatures warm during the summer, a high pressure system develops and the winds (called the Shamal) become more steady from the north and northwest and are very dry.

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