[1] Eddy covariance aerosol flux measurements were conducted at the Mace Head coastal station in the North East Atlantic. Footprint and micrometeorological analysis under clean marine air mass conditions indicated that fluxes representative of open ocean conditions could be derived during high tide conditions and an oceanic fetch. Sea-spray fluxes were derived for total particle sizes larger than 10 nm and total particle sizes larger than 100 nm (i.e. covering the Aitken and Accumulation mode). The source fluxes (F ) were found to be strongly correlated with both wind speed (U) and friction velocity (u*), following, by convention, an exponential relationship (Log F = a U + c) relationship. Comparison of source fluxes at sizes larger than 10 nm and larger than 100 nm demonstrates that approximately 50% of the number flux can be attributed to the accumulation mode and 50% to the Aitken mode. At 10 ms À1 wind speeds, the total primary marine aerosol flux is of the order of 2 Â 10 6 m À2 s À1, increasing to 20 Â 10 6 m À2 s À1 at 20 ms À1 . Citation: Geever, M

Abstract. Nucleation of new, ultra-fine, aerosol particles has been observed in the clean marine coastal atmosphere under a variety of conditions. These nucleation events were observed to occur frequently over spatial scales of 10's-100's of metres and temporal scales of seconds to minutes. Two conditions appeared to be necessary for nucleation event to occur: low tide and solar irradiation. The requirement of low tide conditions suggests that the exposed shore area provides the source of new particle precursors. It is speculated that VOC and/or alkyl halide derivatives contribute to nucleation under these conditions. Nucleation rates were calculated to be --10 3 -10 4 cm '3 $-1, suggesting that the coastal zone is an important source of atmospheric nuclei.

We adapt general statistical methods to estimate the optimal error covariance matrices in a regional inversion system inferring methane surface emissions from atmospheric concentrations. Using a minimal set of physical hypotheses on the patterns of errors, we compute a guess of the error statistics that is optimal in regard to objective statistical criteria for the specific inversion system. With this very general approach applied to a real-data case, we recover sources of errors in the observations and in the prior state of the system that are consistent with expert knowledge while inferred from objective criteria and with affordable computation costs. By not assuming any specific error patterns, our results depict the variability and the inter-dependency of errors induced by complex factors such as the misrepresentation of the observations in the transport model or the inability of the model to reproduce well the situations of steep gradients of concentrations. Situations with probable significant biases (e.g., during the night when vertical mixing is ill-represented by the transport model) can also be diagnosed by our methods in order to point at necessary improvement in a model. By additionally analysing the sensitivity of the inversion to each observation, guidelines to enhance data selection in regional inversions are also proposed. We applied our method to a recent significant accidental methane release from an offshore platform in the North Sea and found methane fluxes of the same magnitude than what was officially declared

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Environmental Context.The formation of new secondary aerosol particles in the natural atmosphere is important in terms of controlling the background aerosol population, which significantly impacts on climate. The coastal zone is perhaps the strongest natural source of new secondary aerosol particles, driven by the release of biogenic vapours, which, after undergoing photochemical reactions, lead to the massive production of nucleation mode aerosols, with concentrations often reaching in excess of 106 cm−3. Quantification of this source strength is important, particularly on a regional scale, in terms of estimating the impact of aerosols on climate. Abstract.Measurements of the flux of new secondary aerosol particles during nucleation events in the coastal environment using an eddy-correlation technique are reported for the first time. Events are divided into two types based on the prevailing wind direction. During tidal-related nucleation events, new-particle upward fluxes are typically of the order of 109–1010 particles m−2 s−1. A close correlation (r2 = 0.86) was found between total particle concentration and total (positive) flux when air masses were not affected by multiple sources. This would suggest that continuous measurements of particle number concentration at Mace Head can be translated into a flux using the resulting parameterization. It is expected that parameterizations obtained from similar data and analysis would be equally feasible at other coastal locations.