Global distribution of sea salt aerosols: new constraints from in situ and remote sensing observations

Atmospheric Chemistry and Physics (ACP), Vol. 11. N° 7. Jaeglé L.; Quinn P.K.; Bates T.S.; et al. - Copernicus GmbH, 2011

We combine in situ measurements of sea salt aerosols (SS) from open ocean cruises and ground-based stations together with aerosol optical depth (AOD) observations from MODIS and AERONET, and the GEOS-Chem global chemical transport model to provide new constraints on SS emissions over the world's oceans. We find that the GEOS-Chem model using the Gong (2003) source function overestimates cruise observations of coarse mode SS mass concentrations by factors of 2–3 at high wind speeds over the cold waters of the Southern, North Pacific and North Atlantic Oceans. Furthermore, the model systematical ...

English

[article] 

Global distribution of sea salt aerosols: new constraints from in situ and remote sensing observations

  Available online: http://dx.doi.org/10.5194/acp-11-3137-2011

L. Jaeglé ; P.K. Quinn ; T.S. Bates ; B. Alexander ; J.-T. Lin

in Atmospheric Chemistry and Physics (ACP) > Vol. 11. N° 7 [04/01/2011] . - p.3137-3157

We combine in situ measurements of sea salt aerosols (SS) from open ocean cruises and ground-based stations together with aerosol optical depth (AOD) observations from MODIS and AERONET, and the GEOS-Chem global chemical transport model to provide new constraints on SS emissions over the world's oceans. We find that the GEOS-Chem model using the Gong (2003) source function overestimates cruise observations of coarse mode SS mass concentrations by factors of 2–3 at high wind speeds over the cold waters of the Southern, North Pacific and North Atlantic Oceans. Furthermore, the model systematically underestimates SS over the warm tropical waters of the Central Pacific, Atlantic, and Indian Oceans. This pattern is confirmed by SS measurements from a global network of 15 island and coastal stations. The model discrepancy at high wind speeds (>6 m s −1) has a clear dependence on sea surface temperature (SST). We use the cruise observations to derive an empirical SS source function depending on both wind speed and SST. Implementing this new source function in GEOS-Chem results in improved agreement with in situ observations, with a decrease in the model bias from +64% to +33% for the cruises and from +32% to −5% for the ground-based sites. We also show that the wind speed-SST source function significantly improves agreement with MODIS and AERONET AOD, and provides an explanation for the high AOD observed over the tropical oceans. With the wind speed-SST formulation, global SS emissions show a small decrease from 5200 Mg yr−1 to 4600 Mg yr−1, while the SS burden decreases from 9.1 to 8.5 mg m−2. The spatial distribution of SS, however, is greatly affected, with the SS burden increasing by 50% in the tropics and decreasing by 40% at mid- and high-latitudes. Our results imply a stronger than expected halogen source from SS in the tropical marine boundary layer. They also imply stronger radiative forcing of SS in the tropics and a larger response of SS emissions to climate change than previously thought.

Language(s): English

Format: Digital (Free)

Tags: Aerosols ; Methodology ; Observations Add tag

[article] 

No review, please log in to add yours !

Characteristics, sources, and transport of aerosols measured in spring 2008 during the aerosol, radiation, and cloud processes affecting Arctic Climate (ARCPAC) Project

Atmospheric Chemistry and Physics (ACP), Vol. 11. N° 3. Brock C.A.; Cozic J.; Bahreini R.; et al. - Copernicus GmbH, 2011

We present an overview of the background, scientific goals, and execution of the Aerosol, Radiation, and Cloud Processes affecting Arctic Climate (ARCPAC) project of April 2008. We then summarize airborne measurements, made in the troposphere of the Alaskan Arctic, of aerosol particle size distributions, composition, and optical properties and discuss the sources and transport of the aerosols. The aerosol data were grouped into four categories based on gas-phase composition. First, the background troposphere contained a relatively diffuse, sulfate-rich aerosol extending from the top of the sea ...

English

[article] 

Characteristics, sources, and transport of aerosols measured in spring 2008 during the aerosol, radiation, and cloud processes affecting Arctic Climate (ARCPAC) Project

  Available online: http://dx.doi.org/10.5194/acp-11-2423-2011

C.A. Brock ; J. Cozic ; R. Bahreini ; K.D. Froyd ; A.M. Middlebrook ; A. McComiskey ; J. Brioude ; O.R. Cooper ; A. Stohl ; K.C. Aikin ; J.A. de Gouw ; D.W. Fahey ; R.A. Ferrare ; R.-S. Gao ; W. Gore ; J.S. Holloway ; G. Hübler ; A. Jefferson ; D.A. Lack ; S. Lance ; R.H. Moore ; D.M. Murphy ; A. Nenes ; P.C. Novelli ; J.B. Nowak ; J.A. Ogren ; J. Peischl ; R.B. Pierce ; P. Pilewskie ; P.K. Quinn ; T.B. Ryerson ; K.S. Schmidt ; J.P. Schwarz ; H. Sodemann ; J.R. Spackman ; H. Stark ; D.S. Thomson ; T. Thornberry ; P. Veres ; L.A. Watts ; C. Warneke ; A.G. Wollny

in Atmospheric Chemistry and Physics (ACP) > Vol. 11. N° 3 [03/01/2011] . - p.2423-2453

We present an overview of the background, scientific goals, and execution of the Aerosol, Radiation, and Cloud Processes affecting Arctic Climate (ARCPAC) project of April 2008. We then summarize airborne measurements, made in the troposphere of the Alaskan Arctic, of aerosol particle size distributions, composition, and optical properties and discuss the sources and transport of the aerosols. The aerosol data were grouped into four categories based on gas-phase composition. First, the background troposphere contained a relatively diffuse, sulfate-rich aerosol extending from the top of the sea-ice inversion layer to 7.4 km altitude. Second, a region of depleted (relative to the background) aerosol was present within the surface inversion layer over sea-ice. Third, layers of dense, organic-rich smoke from open biomass fires in southern Russia and southeastern Siberia were frequently encountered at all altitudes from the top of the inversion layer to 7.1 km. Finally, some aerosol layers were dominated by components originating from fossil fuel combustion.
Of these four categories measured during ARCPAC, the diffuse background aerosol was most similar to the average springtime aerosol properties observed at a long-term monitoring site at Barrow, Alaska. The biomass burning (BB) and fossil fuel layers were present above the sea-ice inversion layer and did not reach the sea-ice surface during the course of the ARCPAC measurements. The BB aerosol layers were highly scattering and were moderately hygroscopic. On average, the layers produced a noontime net heating of ~0.1 K day−1 between 3 and 7 km and a slight cooling at the surface. The ratios of particle mass to carbon monoxide (CO) in the BB plumes, which had been transported over distances >5000 km, were comparable to the high end of literature values derived from previous measurements in wildfire smoke. These ratios suggest minimal precipitation scavenging and removal of the BB particles between the time they were emitted and the time they were observed in dense layers above the sea-ice inversion layer.

Language(s): English

Format: Digital (Free)

Tags: Aerosols ; Atmospheric circulation ; Climate ; Impact studies ; Cloud formation ; Research ; Arctic Add tag

[article] 

No review, please log in to add yours !