Journal ArticleDOI
Flood or drought: How do aerosols affect precipitation?
Daniel Rosenfeld,Ulrike Lohmann,Graciela B. Raga,Colin D. O'Dowd,Markku Kulmala,Sandro Fuzzi,Anni Reissell,Meinrat O. Andreae +7 more
TLDR
A conceptual model is proposed that explains this apparent dichotomy of pristine tropical clouds with low CCN concentrations rain out too quickly to mature into long-lived clouds and heavily polluted clouds evaporate much of their water before precipitation can occur.Abstract:
Aerosols serve as cloud condensation nuclei (CCN) and thus have a substantial effect on cloud properties and the initiation of precipitation. Large concentrations of human-made aerosols have been reported to both decrease and increase rainfall as a result of their radiative and CCN activities. At one extreme, pristine tropical clouds with low CCN concentrations rain out too quickly to mature into long-lived clouds. On the other hand, heavily polluted clouds evaporate much of their water before precipitation can occur, if they can form at all given the reduced surface heating resulting from the aerosol haze layer. We propose a conceptual model that explains this apparent dichotomy.read more
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Long-term volatility measurements of submicron atmospheric aerosol in Hyytiälä, Finland
S. A. K. Hakkinen,Mikko Äijälä,Katrianne Lehtipalo,Heikki Junninen,John Backman,Aki Virkkula,Aki Virkkula,Tuomo Nieminen,Mika Vestenius,Hannele Hakola,Mikael Ehn,D. R. Worsnop,Markku Kulmala,Tuukka Petäjä,Ilona Riipinen,Ilona Riipinen +15 more
Abstract: . The volatility of submicron atmospheric aerosol particles was investigated at a boreal forest site in Hyytiala, Finland from January 2008 to May 2010. These long-term observations allowed for studying the seasonal behavior of aerosol evaporation with a special focus on compounds that remained in the aerosol phase at 280 °C. The temperature-response of evaporation was also studied by heating the aerosol sample step-wise to six temperatures ranging from 80 °C to 280 °C. The mass fraction remaining after heating (MFR) was determined from the measured particle number size distributions before and after heating assuming a constant particle density (1.6 g cm−3). On average 19% of the total aerosol mass remained in the particulate phase at 280 °C. The particles evaporated less at low ambient temperatures during winter as compared with the warmer months. Black carbon (BC) fraction of aerosol mass correlated positively with the MFR at 280 °C, but could not explain it completely: most of the time a notable fraction of this non-volatile residual was something other than BC. Using additional information on ambient meteorological conditions and results from an Aerodyne aerosol mass spectrometer (AMS), the chemical composition of MFR at 280 °C and its seasonal behavior was further examined. Correlation analysis with ambient temperature and mass fractions of polycyclic aromatic hydrocarbons (PAHs) indicated that MFR at 280 °C is probably affected by anthropogenic emissions. On the other hand, results from the AMS analysis suggested that there may be very low-volatile organics, possibly organonitrates, in the non-volatile (at 280 °C) fraction of aerosol mass.
Journal ArticleDOI
Hygroscopic growth and cloud activation of pollen: a laboratory and modelling study
Paul T. Griffiths,J.-S. Borlace,Peter J. Gallimore,Markus Kalberer,Michael Herzog,Francis D. Pope +5 more
TL;DR: In this article, an electrodynamic balance was used to measure the water uptake on pollen and an environmental scanning electron microscope is used to visualize the response of the pollen to subsaturated humidities.
Journal ArticleDOI
Evaluating aerosol direct radiative effects on global terrestrial ecosystem carbon dynamics from 2003 to 2010
Min Chen,Min Chen,Qianlai Zhuang +2 more
TL;DR: In this article, an integrated terrestrial ecosystem model and an atmospheric radiative transfer module are developed and applied to evaluate aerosol direct radiative effects on carbon dynamics of global terrestrial ecosystems during 2003-2010.
Journal ArticleDOI
Spatio-temporal variations in aerosol optical and cloud parameters over Southern India retrieved from MODIS satellite data
G. Balakrishnaiah,K. Raghavendra Kumar,B. Suresh Kumar Reddy,K. Rama Gopal,R. Ramakrishna Reddy,L. S. S. Reddy,C. Swamulu,Y. Nazeer Ahammed,K. Narasimhulu,K. KrishnaMoorthy,S. Suresh Babu +10 more
TL;DR: In this article, the spatial and temporal variations in aerosol particles over Southern India were described and the impact of these variations on various optical properties of clouds, using Moderate Resolution Imaging Spectroradiometer (MODIS) data retrieved from the Terra satellite.
Journal ArticleDOI
Seasonal inhomogeneity in cloud precursors over Gangetic Himalayan region during GVAX campaign
Umesh Chandra Dumka,Deepika Bhattu,Sachchida Nand Tripathi,Dimitris G. Kaskaoutis,B. L. Madhavan +4 more
TL;DR: In this article, simultaneous measurements of number concentration of condensation nuclei (NCCN) and NCCN activation were obtained at Nainital, in the Gangetic-Himalayan (GH) region, during the frameworks of Ganges Valley Aerosol Experiment (GVAX), June 2011 to March 2012.
References
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TL;DR: PfPMP1)与感染红细胞、树突状组胞以及胎盘的单个或多个受体作用,在黏附及免疫逃避中起关键的作�ly.
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Aerosols, climate, and the hydrological cycle
TL;DR: Human activities are releasing tiny particles (aerosols) into the atmosphere that enhance scattering and absorption of solar radiation, which can lead to a weaker hydrological cycle, which connects directly to availability and quality of fresh water, a major environmental issue of the 21st century.
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Global indirect aerosol effects: a review
Ulrike Lohmann,Johann Feichter +1 more
TL;DR: In this article, the effects of aerosols on the climate system are discussed and different approaches how the climatic implications of these effects can be estimated globally as well as improvements that are needed in global climate models in order to better represent indirect aerosol effects are discussed.
Journal ArticleDOI
Climate Effects of Black Carbon Aerosols in China and India
TL;DR: A global climate model used to investigate possible aerosol contributions to trends in China and India found precipitation and temperature changes in the model that were comparable to those observed if the aerosols included a large proportion of absorbing black carbon (“soot”), similar to observed amounts.
Journal ArticleDOI
Inaugural Article by a Recently Elected Academy Member
Jian Xu,Jeffrey I. Gordon +1 more