72b1205e-d036-4221-bf87-621ac63ebdfb eng 2f8f7474-e97d-4ba4-bb6a-424b05b23adb Ev-K2-CNR +39 035 3230511 +39 035 3230551 Via San Bernardino 145 Bergamo BG 24126 Italy metadata@evk2cnr.org http://www.evk2cnr.org/ 2012-04-02T09:08:34 ISO 19115:2003/19139 1.0 Seasonal variations of aerosol size distributions based on long-term measurements at the high altitude Himalayan site of Nepal Climate Observatory-Pyramid (5079 m), Nepal ACP - Special Issue 2010-11-12T00:00:00 Atmospheric Chemistry and Physics, 10 Special Issue"Atmospheric brown cloud in the Himalayas." 10679-10690 Atmospheric Chemistry and Physics, 10, 10679-10690, 2010 Special Issue :"Atmospheric brown cloud in the Himalayas." 1680-7316 The present paper investigates the diurnal and seasonal variability of the aerosol total number concentration, number and volume size distribution between 10 nm and 10 µm, from a combination of a scanning mobility particle sizer (SMPS) and an optical counter (OPC), performed over a two-year period (January 2006–February 2008) at the Nepal Climate Observatory-Pyramid (NCO-P) research station, (5079 m a.s.l.). The annual average number concentration measured over the two-year period at the NCO-P is 860 cm-3. Total concentrations show a strong seasonality with maxima during pre-monsoon and post-monsoon seasons and minima during the dry and monsoon seasons. A diurnal variation is also clearly observed, with maxima between 09:00 and 12:00 UTC. The aerosol concentration maxima are mainly due to nucleation processes during the postmonsoon season, as witnessed by high nucleation mode integrated number concentrations, and to transport of high levels of pollution from the plains by valley breezes during the pre-monsoon season, as demonstrated by high accumulation mode integrated number concentrations. Night-time number concentration of particles (from 03:00 to 08:00 NST) are relatively low throughout the year (from 450 cm-3 during the monsoon season to 675 cm-3 during the pre-monsoon season), indicating the of high altitudes background level, as a result of downslope winds during this part of the day. However, it was found that these background concentrations are strongly influenced by the daytime concentrations, as theyshow the same seasonal variability. If nighttime concentrations were presumed to be representative of free troposphere (FT)/residual layer concentrations, they would be found to be two times higher than at other lower altitudes European sites, such as the Jungfraujoch. However, BL intrusions might contaminate the free troposphere/residual layer even at this altitude, especially during regional air masses influence. Nighttime measurements were subsequently selected to study the FT composition according to different air masses, and the effect of long range transport to the station. Copernicus GmbH (Copernicus Publications) +49 5519003390 +49 55190033970 Bahnhofsallee 1e Göttingen 37081 Germany info@copernicus.org http://www.copernicus.org/ WWW:LINK-1.0-http--related Karine Sellegri Blaise Pascal University, CNRS +33 473407394 +33 473405136 24 avenue des Landais Aubière Cedex 63177 France K.Sellegri@opgc.univ-bpclermont.fr wwwobs.univ-bpclermont.fr Paolo Laj CNRS Laboratory of Meteorology Physics - Laboratory of Glaciology +33 685628874 +33 473405132 Avenue des Landais Aubiere Cedex 63177 France aj@lgge.obs.ujf-grenoble.fr http://wwwobs.univ-bpclermont.fr/ WWW:LINK-1.0-http--partners Paolo Bonasoni Institute of Atmospheric Sciences and Climate (ISAC) - CNR +39 0516399590 +39 0516399652 Via Gobetti,101 Bologna BO 40129 Italy p.bonasoni@isac.cnr.it http://www.isac.cnr.it/ WWW:LINK-1.0-http--partners Angela Marinoni Institute of Atmospheric Sciences and Climate (ISAC) - CNR +39 0516399597 +39 0516399652 Via Gobetti,101 Bologna BO 40129 Italy a.marinoni@isac.cnr.it http://www.isac.cnr.it/ WWW:LINK-1.0-http--partners Paolo Cristofanelli Institute of Atmospheric Sciences and Climate (ISAC) - CNR +39 0516399597 +39 0516399652 Via Gobetti,101 Bologna BO 40129 Italy p.cristofanelli@isac.cnr.it http://www.isac.cnr.it/ WWW:LINK-1.0-http--partners Elisa Vuillermoz Ev-K2-CNR +39 0353230513 +39 0353230551 Via San Bernardino, 145 Bergamo BG 24126 Italy elisa.vuillermoz@evk2cnr.org http://www.evk2cnr.org/ H.Venzac Blaise Pascal University,CNRS +33 473407678 +33 473405136 Aubières 63177 France h.venzac@opgc.univ-bpclermont.fr Julien Boulon Physical Laboratory of Meteorology, University Blaise Pascal,CNRS +33 473405278 24,avenue des Landais Aubière 63177 France j.boulon@opgc.univ-bpclermont.fr http://wwwobs.univ-bpclermont.fr Jean Picard CNRS/University of Clermont-Ferrand +33 0473407061 +33 0473407064 Aubière Cedex 63177 France Jean.Picard@math.univ-bpclermont.fr http://math.univ-bpclermont.fr/~picard/ WWW:LINK-1.0-http--related Paolo Villani Blaise Pascal University,CNRS +33 473405136 +33 473407678 Aubières 63177 France p.villani@opgc.univ-bpclermont.fr www.univ-bpclermont.fr/ https://geoportal.mountaingenius.org/geonetwork/srv/eng/resources.get?uuid=72b1205e-d036-4221-bf87-621ac63ebdfb&fname=mountain_witness__s.png thumbnail png Atmospheric Brown Clouds Himalayas Nepal Climate Observatory-Pyramid Nepal aerosol size distributions aerosol SHARE GAW ABC eng climatologyMeteorologyAtmosphere environment geoscientificInformation 80.0522 88.1946 26.3684 30.4247 http://www.atmos-chem-phys.net/special_issue162.html WWW:LINK-1.0-http--link The book contains the scientific papers published by EvK2Cnr researchers in a special issue of Atmospheric Chemistry and Physics, entitled "Atmospheric brown clouds in the Himalayas " https://geoportal.mountaingenius.org/webapp/srv/en/resources.get?id=1670&fname=acp-10-10679-2010.pdf&access=private WWW:DOWNLOAD-1.0-http--download acp-10-10679-2010.pdf Full Text(pdf):"Seasonal variations of aerosol size distributions based on long-term measurements at the high altitude Himalayan site of Nepal Climate Observatory-Pyramid (5079 m), Nepal" http://www.atmos-chem-phys.net/10/10679/2010/acp-10-10679-2010.html WWW:LINK-1.0-http--partners Abstract:"Seasonal variations of aerosol size distributions based on long-term measurements at the high altitude Himalayan site of Nepal Climate Observatory-Pyramid (5079 m), Nepal" The book contains the scientific papers by EvK2Cnr researchers in a special issue of Atmospheric Chemistry and Physics, entitled "Atmospheric brown clouds in the Himalayas " "Seasonal variations of aerosol size distributions based on long-term measurements at the high altitude Himalayan site of Nepal Climate Observatory-Pyramid (5079 m), Nepal " K. Sellegri, P. Laj, H. Venzac, J. Boulon, D. Picard, P. Villani, P. Bonasoni, A. Marinoni, P. Cristofanelli, and E. Vuillermoz. Atmos. Chem. Phys., 10, 10679-10690, 2010.