High frequency new particle formation in the Himalayas

Venzac, H.; Sellegri, Karine; Laj, Paolo; Villani, Paolo; Bonasoni, Paolo; Marinoni, Angela; Cristofanelli, Paolo; Calzolari, F.; Fuzzi, S.; Decesari, Stefano; Facchini, M. C.; Vuillermoz, Elisa; Verza, G. P.

doi:10.1073/pnas.0801355105

Cited by 166 publications

(179 citation statements)

References 24 publications

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“…4). During pre-Monsoon periods, w 0 shows a maximum (0.87) in the morning hours in correspondence with the nucleation peak seen by Venzac et al (2008). Although scattering intensity by small particle is limited, presence of elevated levels of non-absorbing 20-40 nm particles might explain the w 0 increase.…”

Section: Diurnal Variations Of Measured Propertiesmentioning

confidence: 84%

“…In particular, the diurnal variation of anthropogenic species such as BC regularly exhibits very low night-time concentrations and daytime values peaking in the middle of the afternoon. Consequences of local circulation on aerosol dynamics are discussed by Venzac et al (2008) and Panday et al (2009). Local circulation is not considered in the cluster analysis of Bonasoni et al (2010).…”

Section: Synoptic and Local Meteorology And Air Mass Classificationmentioning

confidence: 99%

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Aerosol optical properties and radiative forcing in the high Himalaya based on measurements at the Nepal Climate Observatory-Pyramid site (5079 m a.s.l.)

et al. 2010

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Abstract. Intense anthropogenic emissions over the Indian sub-continent lead to the formation of layers of particulate pollution that can be transported to the high altitude regions of the Himalaya-Hindu-Kush (HKH). Aerosol particles contain a substantial fraction of strongly absorbing material, including black carbon (BC), organic compounds (OC), and dust all of which can contribute to atmospheric warming, in addition to greenhouse gases. Using a 3-year record of continuous measurements of aerosol optical properties, we present a time series of key climate relevant aerosol properties including the aerosol absorption (σ ap ) and scattering (σ sp ) coefficients as well as the single-scattering albedo (w 0 ). Results of this investigation show substantial seasonal variability of these properties, with long range transport during the pre-and post-monsoon seasons and efficient precipitation scavenging of aerosol particles during the monsoon season. The monthly averaged scattering coefficients range from 0.1 Mm −1 (monsoon) to 20 Mm −1 while the average absorption coefficients range from 0.5 Mm −1 to 3.5 Mm −1 . Both have their maximum values during the premonsoon period (April) and reach a minimum during Monsoon (July-August). This leads to dry w 0 values from 0.86 (pre-monsoon) to 0.79 (monsoon) seasons. Significant diurnal variability due to valley wind circulation is also reported. Using aerosol optical depth (AOD) measurements, Correspondence to: P. Laj (laj@lgge.obs.ujf-grenoble.fr) we calculated the resulting direct local radiative forcing due to aerosols for selected air mass cases. We found that the presence of absorbing particulate material can locally induce an additional top of the atmosphere (TOA) forcing of 10 to 20 W m −2 for the first atmospheric layer (500 m above surface). The TOA positive forcing depends on the presence of snow at the surface, and takes place preferentially during episodes of regional pollution occurring on a very regular basis in the Himalayan valleys. Warming of the first atmospheric layer is paralleled by a substantial decrease of the amount of radiation reaching the surface. The surface forcing is estimated to range from −4 to −20 W m −2 for small-scale regional pollution events and large-scale pollution events, respectively. The calculated surface forcing is also very dependent on surface albedo, with maximum values occurring over a snow-covered surface. Overall, this work presents the first estimates of aerosol direct radiative forcing over the high Himalaya based on in-situ aerosol measurements, and results suggest a TOA forcing significantly greater than the IPCC reported values for green house gases.

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Section: Diurnal Variations Of Measured Propertiesmentioning

confidence: 84%

Section: Synoptic and Local Meteorology And Air Mass Classificationmentioning

confidence: 99%

Aerosol optical properties and radiative forcing in the high Himalaya based on measurements at the Nepal Climate Observatory-Pyramid site (5079 m a.s.l.)

et al. 2010

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“…Clusters are considered as embryos for new particle formation and growth, they are found to be ubiquitous in the atmosphere (Kulmala and Kerminen, 2008), intermediate ions concentrations usually increase only when a NPF is occurring (see Venzac et al, 2007Venzac et al, , 2008, lastly large ions can be disconnected from the new particle formation events and be linked to external incoming of polluted air parcels. Total ion concentrations are dominated by the cluster ions concentrations, which drive the observed diurnal variations.…”

Section: Ultrafine Charged Aerosol Climatologymentioning

confidence: 99%

“…CO) is made by thermally driven vertical transport which occurs during daytime. Finally, night time measurements from 03:00 to 09:00 were considered representative of FT conditions for Jungfraujoch (Weingartner et al, 1999) but also for other high altitude sites in Europe (puy de Dôme, Venzac et al, 2007, and high altitude Himalaya, Venzac et al, 2008). Here, we calculated the diurnal variation of CO, CS, neutron flux and wind direction and speed averaged over the measurement period (Fig.…”

Section: Ultrafine Charged Aerosol Climatologymentioning

confidence: 99%

New particle formation and ultrafine charged aerosol climatology at a high altitude site in the Alps (Jungfraujoch, 3580 m a.s.l., Switzerland)

et al. 2010

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Atmospheric Chemistry and PhysicsNew particle formation and ultrafine charged aerosol climatology at a high altitude site in the Alps (Jungfraujoch, 3580 m a.s.l., Switzerland) Abstract. We investigate the formation and growth of charged aerosols clusters at Jungfraujoch, in the Swiss Alps (3580 m a.s.l.), the highest altitude site of the European EU-CAARI project intensive campaign. Charged particles and clusters (0.5 − 1.8 nm) were measured from April 2008 to April 2009 and allowed the detection of nucleation events in this very specific environment (presence of free tropospheric air and clouds). We found that the naturally charged aerosol concentrations, which are dominated by the cluster size class, shows a strong diurnal pattern likely linked to valley breezes transporting surface layer ion precursors, presumably radon. Cosmic rays were found not to be the major ion source at the measurement site. However, at night, when air masses are more representative of free tropospheric conditions, we found that the cluster concentrations are still high. The charged aerosol size distribution and concentration are strongly influenced by the presence of clouds at the station. Clouds should be taken into account when deriving high altitude nucleation statistics. New particle formation occurs on average 17.5% of the measurement period and shows a weak seasonality with a minimum of frequency during winter, but this seasonality is enhanced when the data set is screened forCorrespondence to: J. Boulon (j.boulon@opgc.univ-bpclermont.fr) periods when the atmospheric station is out of clouds. The role of ions in the nucleation process was investigated and we found that the ion-mediated nucleation explains 22.3% of the particle formation. The NPF events frequency is correlated with UV radiation but not with calculated H 2 SO 4 concentrations, suggesting that other compounds such as organic vapors are involved in the nucleation and subsequently growth process. In fact, NPF events frequency also surprisingly increases with the condensational sink (CS), suggesting that at Jungfraujoch, the presence of condensing vapours probably coupled with high CS are driving the occurrence of NPF events. A strong link to the air mass path was also pointed out and events were observed to be frequently occurring in Eastern European air masses, which present the highest condensational sink. In these air masses, pre-existing cluster concentrations are more than three time larger than in other air masses during event days, and no new clusters formation is observed, contrarily to what is happening in other air mass types.

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“…New particle formation was also observed during prior studies at high altitude observation sites and aircraft studies within different climatic regions (e.g. Weingartner et al, 1999;Venzac et al, 2008;Kivekäs et al, 2009;Hallar et al, 2011b). However, a detailed analysis of new particle formation observed at the Pico Espejo would be beyond the scope of this paper and has to be accomplished in further work.…”

Section: Diurnal Cyclementioning

confidence: 65%

Long-term in situ observations of biomass burning aerosol at a high altitude station in Venezuela – sources, impacts and interannual variability

et al. 2013

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Abstract. First long-term observations of South American biomass burning aerosol within the tropical lower free troposphere are presented. The observations were conducted between 2007 and 2009 at a high altitude station (4765 m a.s.l.) on the Pico Espejo, Venezuela. Sub-micron particle volume, number concentrations of primary particles and particle absorption were observed. Orographic lifting and shallow convection leads to a distinct diurnal cycle at the station. It enables measurements within the lower free troposphere during night-time and observations of boundary layer air masses during daytime and at their transitional regions. The seasonal cycle is defined by a wet rainy season and a dry biomass burning season. The particle load of biomass burning aerosol is dominated by fires in the Venezuelan savannah. Increases of aerosol concentrations could not be linked to long-range transport of biomass burning plumes from the Amazon basin or Africa due to effective wet scavenging of particles. Highest particle concentrations were observed within boundary layer air masses during the dry season. Ambient sub-micron particle volume reached 1.4 ± 1.3 µm 3 cm −3 , refractory particle number concentrations (at 300 • C) 510 ± 420 cm −3 and the absorption coefficient 0.91 ± 1.2 Mm −1 . The respective concentrations were lowest within the lower free troposphere during the wet season and averaged at 0.19±0.25 µm 3 cm −3 , 150±94 cm −3 and 0.15±0.26 Mm −1 . A decrease of particle concentrations during the dry seasons from 2007-2009 could be connected to a decrease in fire activity in the wider region of Venezuela using MODIS satellite observations. The variability of biomass burning is most likely linked to the El Niño-Southern Oscillation (ENSO). Low biomass burning activity in the Venezuelan savannah was observed to follow La Niña conditions, high biomass burning activity followed El Niño conditions.

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High frequency new particle formation in the Himalayas

Cited by 166 publications

References 24 publications

Aerosol optical properties and radiative forcing in the high Himalaya based on measurements at the Nepal Climate Observatory-Pyramid site (5079 m a.s.l.)

Aerosol optical properties and radiative forcing in the high Himalaya based on measurements at the Nepal Climate Observatory-Pyramid site (5079 m a.s.l.)

New particle formation and ultrafine charged aerosol climatology at a high altitude site in the Alps (Jungfraujoch, 3580 m a.s.l., Switzerland)

Long-term in situ observations of biomass burning aerosol at a high altitude station in Venezuela – sources, impacts and interannual variability

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