scholarly journals Investigation of the effective peak supersaturation for liquid-phase clouds at the high-alpine site Jungfraujoch, Switzerland (3580 m a.s.l.)

2014 ◽  
Vol 14 (2) ◽  
pp. 1123-1139 ◽  
Author(s):  
E. Hammer ◽  
N. Bukowiecki ◽  
M. Gysel ◽  
Z. Jurányi ◽  
C. R. Hoyle ◽  
...  
Keyword(s):  
Climate Models ◽  
Cloud Condensation Nuclei ◽  
Radiation Budget ◽  
Minor Role ◽  
Research Station ◽  
Cumulus Clouds ◽  
Air Masses ◽  
The Difference ◽  
Aerosol Cloud Interactions ◽  
A Minor

Abstract. Aerosols influence the Earth's radiation budget directly through absorption and scattering of solar radiation in the atmosphere but also indirectly by modifying the properties of clouds. However, climate models still suffer from large uncertainties as a result of insufficient understanding of aerosol-cloud interactions. At the high altitude research station Jungfraujoch (JFJ; 3580 m a.s.l., Switzerland) cloud condensation nuclei (CCN) number concentrations at eight different supersaturations (SS) from 0.24% to 1.18% were measured using a CCN counter during Summer 2011. Simultaneously, in-situ aerosol activation properties of the prevailing ambient clouds were investigated by measuring the total and interstitial (non-activated) dry particle number size distributions behind two different inlet systems. Combining all experimental data, a new method was developed to retrieve the so-called effective peak supersaturation SSpeak, as a measure of the SS at which ambient clouds are formed. A 17-month CCN climatology was then used to retrieve the SSpeak values also for four earlier summer campaigns (2000, 2002, 2004 and 2010) where no direct CCN data were available. The SSpeak values varied between 0.01% and 2.0% during all campaigns. An overall median SSpeak of 0.35% and dry activation diameter of 87 nm was observed. It was found that the difference in topography between northwest and southeast plays an important role for the effective peak supersaturation in clouds formed in the vicinity of the JFJ, while differences in the number concentration of potential CCN only play a minor role. Results show that air masses coming from the southeast (with the slowly rising terrain of the Aletsch Glacier) generally experience lower SSpeak values than air masses coming from the northwest (steep slope). The observed overall median values were 0.41% and 0.22% for northwest and southeast wind conditions, respectively, corresponding to literature values for cumulus clouds and shallow-layer clouds. These cloud types are consistent with weather observations routinely performed at the JFJ.

scholarly journals Investigation of the effective peak supersaturation for liquid-phase clouds at the high-alpine site Jungfraujoch, Switzerland (3580 m a.s.l.)

2013 ◽  
Vol 13 (8) ◽  
pp. 20419-20462 ◽  
Author(s):  
E. Hammer ◽  
N. Bukowiecki ◽  
M. Gysel ◽  
Z. Jurányi ◽  
C. R. Hoyle ◽  
...  
Keyword(s):  
Climate Models ◽  
Cloud Condensation Nuclei ◽  
Radiation Budget ◽  
Minor Role ◽  
Research Station ◽  
Cumulus Clouds ◽  
Air Masses ◽  
The Difference ◽  
Aerosol Cloud Interactions ◽  
A Minor

Abstract. Aerosols influence the Earth's radiation budget directly through absorption and scattering of solar radiation in the atmosphere but also indirectly by modifying the properties of clouds. However, climate models still suffer from large uncertainties as a result of insufficient understanding of aerosol-cloud interactions. At the high altitude research station Jungfraujoch (JFJ; 3580 m a.s.l., Switzerland) cloud condensation nuclei (CCN) number concentrations at eight different supersaturations (SS) from 0.24% to 1.18% were measured using a CCN counter during Summer 2011. Simultaneously, in-situ aerosol activation properties of the prevailing ambient clouds were investigated by measuring the total and interstitial (non-activated) dry particle number size distributions behind two different inlet systems. Combining all experimental data, a new method was developed to retrieve the so-called effective peak supersaturation SSpeak, as a measure of the SS at which ambient clouds are formed. A 17 month CCN climatology was then used to retrieve the SSpeak values also for four earlier summer campaigns (2000, 2002, 2004 and 2010) where no direct CCN data were available. The SSpeak values varied between 0.01% and 2.0% during all campaigns. An overall median SSpeak of 0.35% and dry activation diameter of 87 nm was observed. It was found that the difference in topography between northwest and southeast plays an important role for the effective peak supersaturation in clouds formed in the vicinity of the JFJ, while differences in the number concentration of potential CCN only play a minor role. Results show that air masses coming from the southeast (with the slowly rising terrain of the Aletsch Glacier) generally experience lower SSpeak values than air masses coming from the northwest (steep slope). The observed overall median values were 0.41% and 0.22% for northwest and southeast wind conditions, respectively, corresponding to literature values for cumulus clouds and shallow-layer clouds. These cloud types are consistent with weather observations routinely performed at the JFJ.

scholarly journals Observations of fluorescent aerosol–cloud interactions in the free troposphere at the High-Altitude Research Station Jungfraujoch

2016 ◽  
Vol 16 (4) ◽  
pp. 2273-2284 ◽  
Author(s):  
I. Crawford ◽  
G. Lloyd ◽  
E. Herrmann ◽  
C. R. Hoyle ◽  
K. N. Bower ◽  
...  
Keyword(s):  
High Altitude ◽  
Pseudomonas Syringae ◽  
Wide Band ◽  
Cloud Microphysics ◽  
Research Station ◽  
Air Masses ◽  
Hierarchical Agglomerative Cluster ◽  
Aerosol Fraction ◽  
Aerosol Cloud Interactions ◽  
A Minor

Abstract. The fluorescent nature of aerosol at a high-altitude Alpine site was studied using a wide-band integrated bioaerosol (WIBS-4) single particle multi-channel ultraviolet – light-induced fluorescence (UV-LIF) spectrometer. This was supported by comprehensive cloud microphysics and meteorological measurements with the aims of cataloguing concentrations of bio-fluorescent aerosols at this high-altitude site and also investigating possible influences of UV–fluorescent particle types on cloud–aerosol processes. Analysis of background free tropospheric air masses, using a total aerosol inlet, showed there to be a minor increase in the fluorescent aerosol fraction during in-cloud cases compared to out-of-cloud cases. The size dependence of the fluorescent aerosol fraction showed the larger aerosol to be more likely to be fluorescent with 80 % of 10 μm particles being fluorescent. Whilst the fluorescent particles were in the minority (NFl∕NAll  =  0.27 ± 0.19), a new hierarchical agglomerative cluster analysis approach, Crawford et al. (2015) revealed the majority of the fluorescent aerosols were likely to be representative of fluorescent mineral dust. A minor episodic contribution from a cluster likely to be representative of primary biological aerosol particles (PBAP) was also observed with a wintertime baseline concentration of 0.1 ± 0.4 L−1. Given the low concentration of this cluster and the typically low ice-active fraction of studied PBAP (e.g. pseudomonas syringae), we suggest that the contribution to the observed ice crystal concentration at this location is not significant during the wintertime.

scholarly journals Size-resolved cloud condensation nuclei concentration measurements in the Arctic: two case studies from the summer of 2008

2015 ◽  
Vol 15 (23) ◽  
pp. 13803-13817 ◽  
Author(s):  
J. Zábori ◽  
N. Rastak ◽  
Y. J. Yoon ◽  
I. Riipinen ◽  
J. Ström
Keyword(s):  
Cloud Condensation Nuclei ◽  
Measurement Data ◽  
Particle Diameter ◽  
Cloud Formation ◽  
The Arctic ◽  
Research Station ◽  
Condensation Nuclei ◽  
Air Masses ◽  
The Difference ◽  
Measurement Period

Abstract. The Arctic is one of the most vulnerable regions affected by climate change. Extensive measurement data are needed to understand the atmospheric processes governing this vulnerability. Among these, data describing cloud formation potential are of particular interest, since the indirect effect of aerosols on the climate system is still poorly understood. In this paper we present, for the first time, size-resolved cloud condensation nuclei (CCN) data obtained in the Arctic. The measurements were conducted during two periods in the summer of 2008: one in June and one in August, at the Zeppelin research station (78°54´ N, 11°53´ E) in Svalbard. Trajectory analysis indicates that during the measurement period in June 2008, air masses predominantly originated from the Arctic, whereas the measurements from August 2008 were influenced by mid-latitude air masses. CCN supersaturation (SS) spectra obtained on the 27 June, before size-resolved measurements were begun, and spectra from the 21 and 24 August, conducted before and after the measurement period, revealed similarities between the 2 months. From the ratio between CCN concentration and the total particle number concentration (CN) as a function of dry particle diameter (Dp) at a SS of 0.4 %, the activation diameter (D50), corresponding to CCN / CN = 0.50, was estimated. D50 was found to be 60 and 67 nm for the examined periods in June and August 2008, respectively. Corresponding D50 hygroscopicity parameter (κ) values were estimated to be 0.4 and 0.3 for June and August 2008, respectively. These values can be compared to hygroscopicity values estimated from bulk chemical composition, where κ was calculated to be 0.5 for both June and August 2008. While the agreement between the 2 months is reasonable, the difference in κ between the different methods indicates a size dependence in the particle composition, which is likely explained by a higher fraction of inorganics in the bulk aerosol samples.

scholarly journals Size-resolved cloud condensation nuclei concentration measurements in the Arctic: two case studies from the summer of 2008

2015 ◽  
Vol 15 (4) ◽  
pp. 5079-5128 ◽  
Author(s):  
J. Zábori ◽  
N. Rastak ◽  
Y. J. Yoon ◽  
I. Riipinen ◽  
J. Ström
Keyword(s):  
Cloud Condensation Nuclei ◽  
Measurement Data ◽  
Particle Diameter ◽  
Cloud Formation ◽  
The Arctic ◽  
Research Station ◽  
Condensation Nuclei ◽  
Air Masses ◽  
The Difference ◽  
Measurement Period

Abstract. The Arctic is one of the most vulnerable regions affected by climate change. Extensive measurement data are needed to understand the atmospheric processes governing this vulnerability. Among these, data describing cloud formation potential are of particular interest, since the indirect effect of aerosols on the climate system is still poorly understood. In this paper we present, for the first time, size-resolved cloud condensation nuclei (CCN) data obtained in the Arctic. The measurements were conducted during two periods in the summer of 2008: one in June, and one in August, at the Zeppelin research station (78°54' N, 11°53' E) in Svalbard. Trajectory analysis indicates that during the measurement period in June 2008, air masses predominantly originated from the Arctic, whereas the measurements from August 2008 were characteristic of mid-latitude air masses. CCN supersaturation (SS) spectra obtained on the 27 June, before size-resolved measurements were begun, and spectra from the 21 and 24 August, conducted before and after the measurement period, revealed similarities between the two months. From the ratio between CCN concentration and the total particle number concentration (CN) as a function of dry particle diameter (Dp) at a SS of 0.4%, the activation diameter (D50), corresponding to CCN / CN = 0.50, was estimated. D50 was found to be 60 and 67 nm for the examined periods in June and August 2008, respectively. Corresponding D50 hygroscopicity parameter (κ) values were estimated to be 0.4 and 0.3 for June and August 2008, respectively. These values can be compared to hygroscopicity values estimated from bulk chemical composition, where κ was calculated to be 0.5 for both June and August 2008. While the agreement between the two months is reasonable, the difference in κ between the different methods indicates a size-dependence in the particle composition, which is likely explained by a higher fraction of sea salt in the bulk aerosol samples.

scholarly journals The aerosol-cyclone indirect effect in observations and high-resolution simulations

2017 ◽  
Author(s):  
Daniel T. McCoy ◽  
Paul R. Field ◽  
Anja Schmidt ◽  
Daniel P. Grosvenor ◽  
Frida A.-M. Bender ◽  
...  
Keyword(s):  
High Resolution ◽  
Indirect Effect ◽  
Climate Models ◽  
Climate Model ◽  
Cloud Condensation Nuclei ◽  
Cloud Droplet ◽  
2014 Eruption ◽  
Cloud Droplet Number Concentration ◽  
Aerosol Cloud Interactions ◽  
First Time

Abstract. Aerosol-cloud interactions are a major source of uncertainty in predicting 21st century climate change. Using high-resolution, convection-permitting global simulations we predict that increased cloud condensation nuclei (CCN) interacting with midlatitude cyclones will increase their cloud droplet number concentration (CDNC), liquid water (CLWP), and albedo. For the first time this effect is shown with 13 years of satellite observations. Causality between enhanced CCN and enhanced cyclone liquid content is supported by the 2014 eruption of Holuhraun. The change in midlatitude cyclone albedo due to enhanced CCN in a surrogate climate model is around 70 % of the change in a high-resolution convection-permitting model, indicating that climate models may underestimate this indirect effect.

scholarly journals Machine learning uncovers aerosol size information from chemistry and meteorology to quantify potential cloud-forming particles

2021 ◽  
Author(s):  
Arshad Nair ◽  
Fangqun Yu ◽  
Pedro Campuzano Jost ◽  
Paul DeMott ◽  
Ezra Levin ◽  
...  
Keyword(s):  
Climate Change ◽  
Machine Learning ◽  
Radiative Forcing ◽  
Climate Models ◽  
Cloud Condensation Nuclei ◽  
Global Climate Models ◽  
Aerosol Composition ◽  
Airborne Measurements ◽  
Aerosol Cloud ◽  
Aerosol Cloud Interactions

Abstract Cloud condensation nuclei (CCN) are mediators of aerosol–cloud interactions, which contribute to the largest uncertainty in climate change prediction. Here, we present a machine learning/artificial intelligence model that quantifies CCN from variables of aerosol composition, atmospheric trace gases, and meteorology. Comprehensive multi-campaign airborne measurements, covering varied physicochemical regimes in the troposphere, confirm the validity of and help probe the inner workings of this machine learning model: revealing for the first time that different ranges of atmospheric aerosol composition and mass correspond to distinct aerosol number size distributions. Machine learning extracts this information, important for accurate quantification of CCN, additionally from both chemistry and meteorology. This can provide a physicochemically explainable, computationally efficient, robust machine learning pathway in global climate models that only resolve aerosol composition; potentially mitigating the uncertainty of effective radiative forcing due to aerosol–cloud interactions (ERFaci) and improving confidence in assessment of anthropogenic contributions and climate change projections.

Aerosols and Their Impact on Radiation, Clouds, Precipitation, and Severe Weather Events

2017 ◽  
Author(s):  
Zhanqing Li ◽  
Daniel Rosenfeld ◽  
Jiwen Fan
Keyword(s):  
Cloud Condensation Nuclei ◽  
Severe Weather ◽  
Radiation Budget ◽  
Atmospheric Pollutant ◽  
Complex Interactions ◽  
Weather Events ◽  
Aerosol Scattering ◽  
Weather And Climate ◽  
Aerosol Cloud Interactions ◽  
A Chain

Aerosols (tiny solid or liquid particles suspended in the atmosphere) have been in the forefront of environmental and climate change sciences as the primary atmospheric pollutant and external force affecting Earth’s weather and climate. There are two dominant mechanisms by which aerosols affect weather and climate: aerosol-radiation interactions (ARIs) and aerosol-cloud interactions (ACIs). ARIs arise from aerosol scattering and absorption, which alter the radiation budgets of the atmosphere and surface, while ACIs are connected to the fact that aerosols serve as cloud condensation nuclei and ice nuclei. Both ARIs and ACIs are coupled with atmospheric dynamics to produce a chain of complex interactions with a large range of meteorological variables that influence both weather and climate. Elaborated here are the impacts of aerosols on the radiation budget, clouds (microphysics, structure, and lifetime), precipitation, and severe weather events (lightning, thunderstorms, hail, and tornadoes). Depending on environmental variables and aerosol properties, the effects can be both positive and negative, posing the largest uncertainties in the external forcing of the climate system. This has considerably hindered the ability to project future climate changes and make accurate numerical weather predictions.

scholarly journals The impacts of biomass burning activities on convective systems over the Maritime Continent

2020 ◽  
Vol 20 (4) ◽  
pp. 2533-2548
Author(s):  
Hsiang-He Lee ◽  
Chien Wang
Keyword(s):  
Biomass Burning ◽  
Cloud Condensation Nuclei ◽  
Radiation Budget ◽  
Convective Precipitation ◽  
Fire Season ◽  
Maritime Continent ◽  
Near Surface ◽  
Anticyclonic Circulation ◽  
Convective Systems ◽  
Aerosol Cloud Interactions

Abstract. Convective precipitation associated with Sumatra squall lines and diurnal rainfall over Borneo is an important weather feature of the Maritime Continent in Southeast Asia. Over the past few decades, biomass burning activities have been widespread during summertime over this region, producing massive fire aerosols. These additional aerosols, when brought into the atmosphere, besides influencing the local radiation budget through directly scattering and absorbing sunlight, can also act as cloud condensation nuclei or ice nuclei to alter convective clouds and precipitation over the Maritime Continent via so-called aerosol indirect effects. Based on 4-month simulations with or without biomass burning aerosols, conducted using the Weather Research and Forecasting model coupled with a chemistry module (WRF-Chem), we have investigated the aerosol–cloud interactions associated with biomass burning aerosols over the Maritime Continent. Results from selected cases of convective events have specifically shown the significant impact of fire aerosols on weak convections by their increasing of the quantities of hydrometeors and rainfall in both the Sumatra and Borneo regions. Statistical analysis over the fire season also suggests that fire aerosols have impacts on the nocturnal convections associated with the local anticyclonic circulation in western Borneo and weaken nocturnal rainfall intensity by about 9 %. Such an effect is likely to have come from the near-surface heating due to absorbing aerosols emitted from fires, which could weaken land breezes and thus the convergence of anticyclonic circulation.

scholarly journals Uptake Study in Lysosome-Enriched Fraction: Critical Involvement of Lysosomal Trapping in Quinacrine Uptake but Not Fluorescence-Labeled Verapamil Transport at Blood-Retinal Barrier

Pharmaceutics ◽  
2020 ◽  
Vol 12 (8) ◽  
pp. 747 ◽  
Author(s):  
Yoshiyuki Kubo ◽  
Miki Yamada ◽  
Saki Konakawa ◽  
Shin-ichi Akanuma ◽  
Ken-ichi Hosoya
Keyword(s):  
Retinal Pigment ◽  
Transport Processes ◽  
Minor Role ◽  
Bafilomycin A1 ◽  
Blood Retinal Barrier ◽  
Retinal Capillary ◽  
Intracellular Compartments ◽  
The Difference ◽  
A Minor

Lysosomal trapping at the blood–retinal barrier (BRB) was investigated through quinacrine and fluorescence-labeled verapamil (EFV) uptake. Quinacrine uptake by conditionally immortalized rat retinal capillary endothelial (TR-iBRB2) cells suggested saturable and non-saturable transport processes in the inner BRB. The reduction of quinacrine uptake by bafilomycin A1 suggested quinacrine distribution to the acidic intracellular compartments of the inner BRB, and this notion was also supported in confocal microscopy. In the study using the lysosome-enriched fraction of TR-iBRB2 cells, quinacrine uptake was inhibited by bafilomycin A1, suggesting the lysosomal trapping of quinacrine in the inner BRB. Pyrilamine, clonidine, and nicotine had no effect on quinacrine uptake, suggesting the minor role of lysosomal trapping in their transport across the inner BRB. Bafilomycin A1 had no effect on EFV uptake, and lysosomal trapping driven by the acidic interior pH was suggested as a minor mechanism for EFV transport in the inner BRB. The minor contribution of lysosomal trapping was supported by the difference in inhibitory profiles between EFV and quinacrine uptakes. Similar findings were observed in the outer BRB study with the fraction of conditionally immortalized rat retinal pigment epithelial (RPE-J) cells. These results suggest the usefulness of lysosome-enriched fractions in studying lysosomal trapping at the BRB.

The German Labour Market Miracle

2010 ◽  
Vol 214 ◽  
pp. R38-R50 ◽  
Author(s):  
Jens Boysen-Hogrefe ◽  
Dominik Groll
Keyword(s):  
Labour Market ◽  
Minor Role ◽  
Dynamic Simulations ◽  
The Great Recession ◽  
Wage Moderation ◽  
Time Work ◽  
The Difference ◽  
A Minor ◽  
Short Time ◽  
Minor Reaction

This paper lays out the various reasons for the exceptional performance of the German labour market during and after the Great Recession of 2008/9. The reference point of our analysis is provided by an empirical model of both total hours worked and employment. We conduct dynamic simulations of the crisis period to assess how surprising the reaction of the labour market really was. We argue that the most important precondition for the minor reaction of employment during this crisis was the pronounced wage moderation observed in the years before, which constitutes a distinct difference to all other recessions in Germany. Beyond that, the flexibility of adjusting working time, which has increased considerably during the past ten years, facilitated a tendency to labour hoarding. In contrast, short-time work plays a minor role in explaining the difference from previous recessions, since this instrument has always been available to firms in Germany and its use has not been extraordinary compared with earlier recessions.

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