Measurements of size resolved marine aerosol fluxes
Primary marine aerosols from the bursting of air bubbles produced by breaking waves is the largest global aerosol source and influences the properties of the atmosphere and the climate over the Oceans and a large part of the continental landmasses. The marine aerosols both act as cloud condensation nuclei and reflect the incoming solar radiation.
Production of primary marine aerosols is expected to change when the climate change affects the water temperature, one of the key physical factors driving the sea spray emissions. The size resolved emissions of marine aerosols from Oceans with different salinity and temperatures measured with the eddy covariance method are important for validations and/or improvements of parameterizations used in both regional chemical transport models and global climate models. In co-operation with Stockholm University the marine aerosol fluxes are measured continually at the field station at Östergarnsholm at the 10 meter tower next to the mast. The project also includes shorter campaigns at different locations for example one at Svalbard, close to Ny Ålesund and a cruise from Boston to Bermuda passing the Saragasso Sea, see figures. The instrumentation consists of optical particle counters for the aerosol size distributions from 0.25 to 2.5 micrometer diameter and condensation particle counters for the total number of particles from 10 nanometer to 3.0 micrometer diameter. An ultrasonic anemometer measures the vertical and horizontal wind speed, everything is logged at 20 Hz. The fluctuations in vertical wind (w’), horizontal wind (u’) and aerosol (N’) are sampled in parallel and processed so that the covariance is calculated using a 30 minutes average, where <u’w’> and <N’w’> equals the momentum and aerosol fluxes.
Monica Mårtensson and Anna Rutgersson Uppsala University and Douglas Nilsson Stockholm University