Webinar: Micro Pulse Lidar -​ Measuring Atmospheric Aerosols

May 24, 2021

Suspended particulate matter in the atmosphere, commonly known as aerosol plays an important role in climate change, air quality/ human health, sand and dust storms, ozone depletion and the long-range transport and deposition of toxics and nutrients. Aerosols have many sources ranging from sea spray and mineral dust that are mechanically generated by wind at the Earth’s surface to sulphates, nitrates and organics produced primarily by chemical reaction of gases in the atmosphere producing non-volatile products that condense to form particulate mass. Because most effects of aerosols on climate occur at elevated layers, e.g., the direct modification of the radiation field through scattering and absorption or the indirect effect through modification of the cloud condensation nuclei, the long-term climatology needs to cover the vertical as well as the horizontal properties of the aerosol field. The aerosol vertical distribution depends on the distributions of the emissions, on chemical production for secondary aerosols (secondary particulate matter and sulphate), on the distribution of clouds and precipitation (that determine aqueous chemistry aerosol production and wet deposition), on the parameterization of wet deposition processes, and on the transport characteristics determined by the flow field.

Aerosol properties can be derived from lidar observations using the different instrument types. Main parameters defining the instrument performance are operating wavelength, laser power or pulse energy, receiver collecting area, optical throughput, out-of-band rejection ratio, as well as detector efficiency, linearity and dynamic range.

Several factors influence the choice of wavelength for an aerosol lidar. The micro pulse lidar (MPL) is a ground-based, autonomous, eye-safe lidar operating at 532 nm. A short pulse of laser light is transmitted from the telescope. As the pulse travels along, part of it is scattered by molecules, water droplets, or other objects in the atmosphere. The greater the number of scatterers, the greater the part scattered. A small portion of the scattered light is scattered back, collected by the telescope, and detected. The detected signal is stored in bins according to how long it has been since the pulse was transmitted, which is directly related to how far away the backscatter occurred. The collection of bins for each pulse is called a profile. A cloud would be evident as an increase or spike in the backscattered signal profile, since the water droplets that make up the cloud will produce a lot of backscatter.

The webinar discussed the technology covering basics of operation of MPL, possible application areas, and relevant case studies. We hoped you enjoyed our webinar “Micro Pulse Lidar -​ Measuring Atmospheric Aerosols” as much as we did! If you weren’t able to make it, catch our replay.


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