Search results for "CONDENSATION NUCLEI"

Growth of nucleation mode particles in the summertime Arctic: a case study

2016

Abstract. The summertime Arctic lower troposphere is a relatively pristine background aerosol environment dominated by nucleation and Aitken mode particles. Understanding the mechanisms that control the formation and growth of aerosol is crucial for our ability to predict cloud properties and therefore radiative balance and climate. We present an analysis of an aerosol growth event observed in the Canadian Arctic Archipelago during summer as part of the NETCARE project. Under stable and clean atmospheric conditions, with low inversion heights, carbon monoxide less than 80 ppbv, and black carbon less than 5 ng m−3, we observe growth of small particles,  <  20 nm in diameter, into sizes ab…

Comparison of aircraft measurements during GoAmazon2014/5 and ACRIDICON-CHUVA

2019

Abstract. The indirect effect of atmospheric aerosol particles on the Earth's radiation balance remains one of the most uncertain components affecting climate change throughout the industrial period. The large uncertainty is partly due to the incomplete understanding of aerosol–cloud interactions. One objective of the GoAmazon2014/5 and the ACRIDICON (Aerosol, Cloud, Precipitation, and Radiation Interactions and Dynamics of Convective Cloud Systems)-CHUVA (Cloud Processes of the Main Precipitation Systems in Brazil) projects was to understand the influence of emissions from the tropical megacity of Manaus (Brazil) on the surrounding atmospheric environment of the rainforest and to investiga…

Linear relationship between effective radius and precipitation water content near the top of convective clouds: measurement results from ACRIDICON–CH…

2021

Quantifying the precipitation within clouds is a crucial challenge to improve our current understanding of the Earth's hydrological cycle. We have investigated the relationship between the effective radius of droplets and ice particles (re) and precipitation water content (PWC) measured by cloud probes near the top of growing convective cumuli. The data for this study were collected during the ACRIDICON–CHUVA campaign on the HALO research aircraft in clean and polluted conditions over the Amazon Basin and over the western tropical Atlantic in September 2014. Our results indicate a threshold of re∼13 µm for warm rain initiation in convective clouds, which is in agreement with previous studie…

A numerical model of the cloud-topped planetary boundary-layer: cloud processing of aerosol particles in marine stratus

1999

Abstract In a numerical study with the one-dimensional chemical microphysical stratus model CHEMISTRA the effect of stratiform clouds on aerosol particles is investigated. The microphysical part of CHEMISTRA consists of a detailed description of cloud microphysical processes by means of a joint two-dimensional particle distribution for aerosols and cloud droplets. In the chemical part of the model the particle spectrum is subdivided into three categories referring to inactivated aerosols, small and large cloud droplets. Aqueous phase chemical reactions are separately treated in the two droplet size classes. Numerical results are presented demonstrating that the uptake of trace gases by clou…

Condensation nuclei measurements at theGeorg von Neumayer-Station (F.R.G.), Coastal Antarctica

1991

The analysis of nearly continuous records of surface-based atmospheric condensation nucleiconcentration (CNC) since 1984 up to the present at the Georg von Neumayer-Station (GvN) shows clearly: u - an annual cycle of CNC with low values in winter time; - a significantly increasing frequency of CNC of more than 1000 particles per cm3 over the years.

Measurements of atmospheric condensation nuclei size distributions in Siberia

1992

Abstract The least investigated atmospheric aerosol is the one in remote continental areas. In this study, measurements of condensation nuclei size distributions near Lake Baikal, Siberia, were performed. Data for total aerosol number concentration and aerosol size distribution were obtained. The measurement equipment consisted of a TSI screen diffusion battery (SDB) Model 3040 and a TSI condensational nuclei counter (CNC) Model 3020. The average aerosol number concentration was about 104 cm−3. The evolution of aerosol number concentration during the day is correlated with the solar radiation. The inversion problem was solved using Tihonov's regularisation procedure. The possibility of appl…

Determination in situ of the size distribution of the atmospheric aerosol

1975

Abstract The aim of the present study was the investigation of the in situ number/size distribution of the atmospheric aerosol in the size range between 0·05 and 2 μm radius. The experimental system consisted of a 4-channel integrating nephelometer, a 2-channel optical particle counter and a condensation nucleus counter. With a new inversion method, which had been tested previously by model computations and by measurements with artificial aerosols, the in situ size distribution was computed from the data of the experimental system.

The vertical profile of condensation nuclei on cloudy days

2008

Performance of a Focused Cavity Aerosol Spectrometer for Measurements in the Stratosphere of Particle Size in the 0.06–2.0-µm-Diameter Range

1995

A focused cavity aerosol spectrometer aboard a NASA ER-2 high-altitude aircraft provided high-resolution measurements of the size of the stratospheric particles in the 0.06-2.0-micrometer-diameter range in flights following the eruption of Mount Pinatubo in 1991. Effects of anisokinetic sampling and evaporation in the sampling system were accounted for by means adapted and specifically developed for this instrument. Calibrations with monodisperse aerosol particles provided the instrument's response matrix, which upon inversion during data reduction yielded the particle size distributions. The resultant dataset is internally consistent and generally shows agreement to within a factor of 2 wi…

2014

Abstract. Dynamical and microphysical processes in pyroconvective clouds in mid-latitude conditions are investigated using idealized three-dimensional simulations with the Active Tracer High resolution Atmospheric Model (ATHAM). A state-of-the-art two-moment microphysical scheme building upon a realistic parameterization of cloud condensation nuclei (CCN) activation has been implemented in order to study the influence of aerosol concentration on cloud development. The results show that aerosol concentration influences the formation of precipitation. For low aerosol concentrations (NCN = 200 cm−3), rain droplets are rapidly formed by autoconversion of cloud droplets. This also triggers the f…