In 2014, the united states defined poverty as the state in which anyone is surviving on less than9/19/2023 ![]() ![]() The ability of dust particles to serve as such depends on their size, shape and composition, which in turn depend on the nature of parent soils, emissions and transport processes. Interaction with weather and climateĪerosols, particularly mineral dusts, impact weather as well as global and regional climate. Dust particles, especially if coated by pollution, act as condensation nuclei for warm cloud formation and as efficient ice nuclei agents for cold cloud generation. The average lifetime of dust particles in the atmosphere ranges from a few hours for particles with a diameter larger than 10 μm, to more than 10 days for the sub-micrometric ones. Dust is also washed out of the atmosphere by precipitation. They can then be transported by winds for lengths of time, depending on their size and meteorological conditions, before being pulled back down to the surface again. As larger particles sediment more quickly than smaller ones, there is a shift toward smaller particle sizes during transport. Once released from the surface, dust particles are raised to higher levels of the troposphere by turbulent mixing and convective updrafts. Global estimates of dust emissions, mainly derived from simulation models, vary between one and three Gigatons per year. Comparatively, Australia, America and South Africa make minor, but still important, contributions. The main sources of these mineral dusts are the arid regions of Northern Africa, the Arabian Peninsula, Central Asia and China. They are usually caused by thunderstorms – or strong pressure gradients associated with cyclones – which increase wind speed over a wide area. These strong winds lift large amounts of sand and dust from bare, dry soils into the atmosphere, transporting them hundreds to thousands of kilometres away. Some 40% of aerosols in the troposphere (the lowest layer of Earth’s atmosphere) are dust particles from wind erosion. Sand and dust storms are common meteorological hazards in arid and semi-arid regions. ![]()
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