Observations of aerosols in the free troposphere and marine boundary layer of the subtropical Northeast Atlantic: Discussion of processes determining their size distribution

Raes, Frank; Dingenen, Rita Van; Cuevas, E.; Velthoven, P. F. J. van; Prospero, Joseph M.

doi:10.1029/97jd01122

Cited by 123 publications

(105 citation statements)

References 33 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Hence most of the non-sea salt sulfate aerosol in the MBL must originate from other locations. Indeed, model studies Raes, 1995) and observations (Clarke et al, 1996;Raes et al, 1997;Bates et al, 1998) have explained MBL aerosol concentrations with entrainment from the free troposphere. Katoshevski et al (1999) even concluded that MBL aerosol number concentration is dominated by aerosol from the free troposphere under virtually all conditions.…”

Section: Sources Of Marine Boundary Layer Aerosolmentioning

confidence: 99%

Aerosol nucleation over oceans and the role of galactic cosmic rays

et al. 2006

View full text Add to dashboard Cite

Abstract. We investigate formation of sulfate aerosol in the marine troposphere from neutral and charged nucleation of H 2 SO 4 and H 2 O. A box model of neutral and charged aerosol processes is run on a grid covering the oceans. Input data are taken from a model of galactic cosmic rays in the atmosphere, and from global chemistry and transport models. We find a weak aerosol production over the tropical oceans in the lower and middle troposphere, and a stronger production at higher latitudes, most notably downwind of industrial regions. The strongest aerosol production however occurs in the upper troposphere over areas with frequent convective activity, in particular in the tropics. This finding supports the proposition by which non-sea salt marine boundary layer aerosol in tropical regions does not form in situ, but nucleates in the upper troposphere from convectively lifted and cloud processed boundary layer air rich in aerosol precursor gases, from where it descends in subsiding air masses compensating convection. Convection of boundary layer air also appears to drive the formation of condensation nuclei in the tropical upper troposphere which maintains the stratospheric aerosol layer in the absence of volcanic activity. Neutral nucleation contributes only marginally to aerosol production in our simulations. This highlights the importance of other mechanisms, including charged binary and ternary, and neutral ternary nucleation for aerosol formation. Our analysis indicates that the variation of ionization by galactic cosmic rays over the decadal solar cycle does not entail a response in aerosol production and cloud cover via the second indirect aerosol effect that would explain observed variations in global cloud cover. We estimate that the variation in radiative forcing resulting from a response of clouds to the change in galactic cosmic ray ionization and subsequent aerosol production over the decadal solar cycle is smaller than the concurrent variation of total solar irradiance.

show abstract

Section: Sources Of Marine Boundary Layer Aerosolmentioning

confidence: 99%

Aerosol nucleation over oceans and the role of galactic cosmic rays

et al. 2006

View full text Add to dashboard Cite

show abstract

“…2,000 Clarke et al [1997] midlat free trop (Atl) 6,000 O'Dowd et al [1997] Weddell Sea MBL (Antarctic) 4,300 Raes et al [1997] subtropical free trop, cloud free 4,000 Schröder and Ström [1997] midlat cont UT 10,000 Thornton et al [1997] tropical UT, near convection 18,000 Weber et al [1997] and Eisele and McMurry [1997] midlat clean cont, free trop air 600…”

Section: Observationsmentioning

confidence: 99%

Deep convection as a source of new particles in the midlatitude upper troposphere

et al. 2002

View full text Add to dashboard Cite

[1] A case study of new particle formation in the region downwind of a mesoscale convective system stretching across much of the central United States is presented. Airborne measurements were made of condensation nuclei (CN), cloud particle surface area, water vapor, and other gases. CN concentrations were greatly enhanced above and downwind of the cirrus anvil, with maximum concentrations of 45,000 per standard cm 3 . Volatility and electron microscope measurements indicated that most of the particles were likely to be small sulfate particles. The enhancement extended over at least a 600-km region. Multivariate statistical analysis revealed that high CN concentrations were associated with surface tracers, as well as convective elements. Convection apparently brings gas-phase particle precursors from the surface to the storm outflow region, where particle nucleation is favored by the extremely low temperatures. Simple calculations showed that deep convective systems may contribute to a substantial portion of the background aerosol in the upper troposphere at midlatitudes.

show abstract

“…Concerns related to the potential effects of these small aerosols on human health, visibility, and climate have initiated studies on the formation an evolution of ultrafine particles (UFP), which in this work denote aerosol particles with d p < 100 nm. Using instruments that can detect particles with diameters as low as 3 nm, UFP have been documented in the free troposphere [Clarke et al, 1998;Raes et al, 1997;Schröder and Ström, 1997] and in the vicinity of clouds [Hegg et al, 1991]. Significant evidence of nucleation of new particles was found at continental boundary layer sites [Birmili and Wiedensohler, 2000;Verheggen and Mozurkewich, 2002;Birmili et al, 2003], including boreal forests [Mäkelä et al, 1997;Kulmala et al, 1998Kulmala et al, , 2001aKulmala et al, , 2001bKomppula et al, 2003] and Arctic regions [Wiedensohler et al, 1996;Pirjola et al, 1998].…”

Section: Introductionmentioning

confidence: 99%

Precipitation removal of ultrafine aerosol particles from the atmospheric boundary layer

Andronache

2004

J. Geophys. Res.

View full text Add to dashboard Cite

[1] Ultrafine particles (UFP) formed in the boundary layer (BL) by nucleation processes need to grow up to a diameter d p $ 100 nm to become activated as cloud droplets (CD). The time required to reach d p = 100 nm is about 2-3 days for a typical growth rate of 5 nm h À1 . If precipitation occurs, most UFP are too small to become CD, and some particles are removed by scavenging processes. A model to estimate the UFP wet removal from the BL by rainfall and coagulation is presented. The scavenging coefficient that describes the decay of aerosol mass in various size bins is a function of aerosol size (d p ), rainfall rate (R), and BL background aerosol. The model is applied to determine the UFP 0.5-folding time (t 05 ) during rain events and results show that t 05 $ 1 hour for R $ 1 mm h À1 for newly created particles (d p < 10 nm) and t 05 $ 1 day for larger UFP (d p $ 10-100 nm). To infer the likelihood of UFP removal at a given location, the average time interval (Dt) between rain events with rainfall rate R = 1 mm h À1 at stations with different precipitation regimes was determined. Results show that on average, UFP are very effectively removed from the BL by below-cloud scavenging in tropical regions (Dt $ 1 day), removed to a significant extent in eastern U.S. regions (Dt $ 3 days), and are less likely to be removed in southwest U.S. regions (Dt $ 6-8 days), where the frequency of dry periods is high and UFP have sufficient time to grow.

show abstract

Observations of aerosols in the free troposphere and marine boundary layer of the subtropical Northeast Atlantic: Discussion of processes determining their size distribution

Cited by 123 publications

References 33 publications

Aerosol nucleation over oceans and the role of galactic cosmic rays

Aerosol nucleation over oceans and the role of galactic cosmic rays

Deep convection as a source of new particles in the midlatitude upper troposphere

Precipitation removal of ultrafine aerosol particles from the atmospheric boundary layer

Contact Info

Product

Resources

About