Wind-blown dust is among the most common aerosol types in the Earth's atmosphere. These particles can affect climate by reflecting and absorbing solar radiation, but also by influencing cloud formation. Dust can be transported over long distances in air, thereby spreading nutrients to terrestrial and marine ecosystems. High levels of dust particles can degrade air quality, cause adverse health effects, and affect aviation safety.
The main source regions of airborne dust particles are the great desert areas. Emissions of dust particles are driven by the wind, which causes medium-sized sand grains near the ground to be lifted up and travel short distances through the air in a bouncing motion. As these sand grains fall to the ground, they rebound and splash small dust particles off the surface, which can remain suspended in air for days and be transported over long distances. This emission process, known as saltation, is physically complex and difficult to describe in air quality and climate models. The uncertainties can be reduced with information on particle quantities that can be obtained from radiation measurements with satellite-based remote sensing instruments.
The main problem when studying desert aerosol emissions from satellites is that the dust particles are often mixed with other types of aerosols, mainly anthropogenic air pollution or sea salt particles. This makes the measurements very difficult to interpret.
Method
This project analyses the problem in two steps:
In the first step, measurements of wind-driven dust emissions are analysed in a very large 'laboratory', namely the planet Mars. The entire planet is a vast desert landscape, and there are no people or ocean surfaces that give rise to other types of aerosol emissions. We will use lidar observations from the Phoenix lander. This is an instrument that emits laser pulses and measures the light signal that is backscattered by suspended dust particles. There are also weather measurement instruments at Phoenix, including wind observations. An analysis of these data will highlight the relationship between wind speed and particle emission, which will be used to evaluate a numerical model to calculate the emission process.
In the second step, measurements from the lidar instruments on the CALIPSO and EarthCARE satellites are used to study wind-driven dust emissions on Earth. We will select and use data that are minimally affected by other emission sources. The measurements will be compared with the numerical model.
About the project
Projekt name: Interplanetary assessment of dust-emission processes using active remote sensing on Earth and Mars
Funded by: Swedish National Space Agency
Project duration: 2023-2025
Project manager: Michael Kahnert