Aerosol Flux Measurements Above the Ocean Surface Using Unmanned Aerial Systems
Abstract
Oceans cover nearly three quarters of the Earth's surface, yet marine aerosol emissions are still poorly quantified. As a result, the ocean is one of the key regions for performing energy and aerosol surface flux measurements to improve weather and climate models. The relative importance of local sources of aerosol generation at the sea surface (from wave surges, white cap cover) relative to background concentration remains an important unresolved issue.
Deploying aerosol and flux instruments within a few meters of the surface to study particle emissions is, however, technically difficult. Measurements from instruments fixed on scientific vessels or buoys are at a single altitude and often perturbed by interactions with the platform structure. In addition, traditional research aircraft cannot fly within a few meters above the sea surface for obvious safety reasons. To this end, unmanned aerial systems (UAS) are able to perform autonomous flights safely at low altitude over the sea to characterize the air-sea exchanges at this interface. Research campaigns have been carried out in the framework of the MIRIAD project (Mesures scIentifiques de flux de suRface en mIlieu mAritime par Drone; funded by the European Union and Région Midi-Pyrénées) and have revealed strong gradients related to aerosol concentrations and size in the first tens of meters above the above the surf zone. An aerosol sensor measures the particle size distribution and used to estimate the mass (and flux) of aerosols emitted from the sea surface. UAS flights have been made above a surf zone to perform in-situ aerosol measurements between 7 and 150 m.asl. Based on the gradient in aerosol number size distribution between the surface layer and the marine layer (z 20 to 60 m.asl), the mass flux of aerosols over the surf zone was estimated. Mean vertical profiles suggest that aerosols are well mixed in the surface layer, yet a large variability of aerosol number and mass concentration was also observed, related to spatial gradients between the crests of the waves. The results presented here illustrate the ability of UAS to fill this niche.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.A41N3184R
- Keywords:
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- 3305 Climate change and variability;
- ATMOSPHERIC PROCESSESDE: 3307 Boundary layer processes;
- ATMOSPHERIC PROCESSESDE: 3311 Clouds and aerosols;
- ATMOSPHERIC PROCESSESDE: 3394 Instruments and techniques;
- ATMOSPHERIC PROCESSES