Gases and particles emitted into the atmosphere by natural or anthropogenic processes are subject to atmosphere transport. This can occur over short and also long distances – between different places within a country, between countries, or even across and between continents. The distance travelled is strongly influenced by the height and type of emission (gas or particle), its physical and chemical characteristics (e.g. particle size or type of gas), wind direction and speed, and the amount of precipitation encountered.

With aerosols for example, whilst the largest will settle out of the atmosphere onto surfaces quite quickly after their formation, smaller aerosols can sometimes be transported over very long distances. This maybe particularly the case if they are injected into the atmosphere at higher altitudes, such as may occur in a large explosive volcanic eruption that can place material directly into the stratosphere. Small aerosol particles at higher altitudes can also act as condensation nuclei for meteorological clouds, which means they have a role in rainfall and Earth's radiative budget for example, and are also a major concern for human health if they are present in high concentrations close to Earth’s surface. It is therefore generally considered important that we monitor the sources, transport and impact of this type of fine particulate air pollution.

Large diameter atmospheric aerosols such as dust, as well as smaller aerosols such as those present in the smoke emitted from wildfires, can all be monitored from space. Combined with models of atmospheric transport, this ability can be very useful for helping forecast the movement of these aerosols more accurately, and for the first time ever the Aeolus satellite is allowing global wind speeds across multiple layers of the atmosphere to be measured from space aswell. Previously, most atmospheric winds were measured using equipment on weather balloons or aircraft which only provided data over limited geographic areas.

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Featured Educators

• Dr Pepijn Veefkind, Senior Scientist, KNMI
• Professor Martin Wooster, Professor of Earth Observation Science, KCL
• Dr Anne Grete Straume, Aeolus Mission Scientist, ESA