SEA SALT AEROSOLS ON THE REGIONAL SCALE TFMM

SEA SALT AEROSOLS ON THE REGIONAL SCALE TFMM Meeting, Zagreb, April 2005 Valentin Foltescu, Sara Pryor, Cecilia Bennet ” All I ask is a windy day with the white clouds flying, And the flung spray and the blown spume, and the sea-gulls crying. ” John Masefield, SEA-FEVER

SEA SALT AEROSOLS: GENERATION WIND WAVES BUBBLES

SEA SALT AEROSOLS: GENERATION Radius Film drops: 0. 1 - 50 �m Jet drops: 1 - 300 �m Spume drops: 20 �m till > 500 �m BUBBLES FILM DROPS and JET DROPS

SEA SALT AEROSOLS: GENERATION FILM DROPS AND JET DROPS SEA (SALT) AEROSOLS Drops mean radius Particles mean radius Film drops: 1 �m 0. 2 �m Jet drops: 10 �m 2 �m Spume drops: 100 �m 20 �m

SEA SALT AEROSOLS: HISTORY (John Aitken, 1839 -1919)

SEA SALT AEROSOLS: RELEVANCE ON THE REGIONAL SCALE dominant aerosol component in the remote marine surface air and occasionally a significant one over the continent controls the radiative properties of the clean marine background atmosphere influence cloud cover, cloud properties and lifetime provide media for chemical reactions contribute to the sea surface-atmosphere exchange plays a role for plant stress contributes to corrosion in coastal regions

SEA SALT AEROSOL MODELLING: AIM OF RESEARCH ACHIEVE A REALISTIC DESCRIPTION OF THE SEA SALT AEROSOL FRACTION, FOCUSING ON THE PM 10 - FRACTION

SEA SALT AEROSOL : MODEL DESCRIPTION Transport model: MATCH (Multi-scale Atmospheric Transport and Chemistry) - meteorological input from HIRLAM (High Resolution Limited Area Model), 3 h - horizontal scale 44 km - 22 lowest layers up to 11600 m Particle bins used for the sea salt modelling Class: 1 2 3 4 rdry min ( m)0. 03 0. 06 0. 13 0. 25 0. 5 rdry max ( m) 0. 06 0. 13 0. 25 0. 50 rdry geom ( m) 0. 04 0. 09 0. 18 0. 35 5 1 1. 0 0. 71 6 2 2 1. 4 7 5 5 2. 8 8 8 5. 6 The dry particle classes are treated as individual tracers with no dynamics between the particle bins.

SEA SALT AEROSOL : SOURCE FORMULATION Mårtensson et al. (2003) Size class: 1 2 3 4 rdry min ( m)0. 03 0. 06 0. 13 0. 25 0. 5 rdry max ( m) 0. 06 0. 13 0. 25 0. 50 F = particle flow (m-2 s-1) U 10= 10 m-wind (m s-1) Tw = water temperature (K), Dp = dry particle diameter ( m) Ak and Bk = polynomials for three particle size intervals Monahan et al. (1986) 5 6 7 8 1 2 5 1. 0 2 5 8 F = particle flow (m-2 s-1) U 10= 10 m-wind (m s-1) r = radius at 80% relative humidity ( m)

SEA SALT AEROSOL : SOURCE FORMULATION Size dependency of sea salt number flux

SEA SALT AEROSOL : DRY DEPOSITION Dry deposition over land includes: turbulent transfer, Brownian diffusion, impaction, interception, settling and particle rebound. (Zhang et al. , 2001). Dry deposition over sea includes: the effect of increased downward movement of particles as a result of bubble burst activity. (Prior and Barthelmie, 2000).

SEA SALT AEROSOL : WET DEPOSITION In-cloud scavenging: - nucleation scavenging of particles larger than 0. 1 m diameter. - collection of non-activated fraction of particles by coagulation with hydrometeors. (Svenningsson et al. , 1997) Below-cloud scavenging: Washout coefficient taking into account Brownian diffusion, interception and inertial impaction. (Dana & Hales, 1976).

SEA SALT AEROSOL : CONCENTRATION FIELDS Fine particles Fine and coarse particles

SEA SALT AEROSOL : DEPOSITION FIELDS Dry deposition Wet deposition

SEA SALT AEROSOL : EVALUATION WITH AIRBORNE CONCENTRATION MEASUREMENTS EMEP-DK 03 thin line: MATCH thick line: measurements EMEP-NO 01

SEA SALT AEROSOL : EVALUATION WITH AIRBORNE CONCENTRATION MEAS.

SEA SALT AEROSOL : EVALUATION WITH WET DEPOSITION MEASUREMENTS Comparison at 28 EMEP stations: EMEP-NO 01 - modelled mean concentration in precipitation: 0. 73 mg Na+ l-1 vs. 1. 21 mg Na+ l-1 measured - station-wise correlations for monthly values: 0. 11 and 0. 92 (mean 0. 62). highest correlations (R>0. 8) for the Dutch and Norwegian locations.

SEA SALT AEROSOL : APPLICATIONS Size distribution Complex index of refraction for different aerosols Atmospheric transmission

SEA SALT AEROSOL : APPLICATIONS (c) Free. Foto. com

SEA SALT AEROSOL : APPLICATIONS Diurnal means for lat: 51. 10 N, lon: 3. 75 E (Gent) simulated using MATCH with RCA 3 met. data for 1980 -2003