| 1. |
- Reddington, C. L., et al.
(författare)
-
THE GLOBAL AEROSOL SYNTHESIS AND SCIENCE PROJECT (GASSP) : Measurements and Modeling to Reduce Uncertainty
- 2017
-
Ingår i: Bulletin of The American Meteorological Society - (BAMS). - 0003-0007 .- 1520-0477. ; 98:9, s. 1857-1877
-
Tidskriftsartikel (refereegranskat)abstract
- The largest uncertainty in the historical radiative forcing of climate is caused by changes in aerosol particles due to anthropogenic activity. Sophisticated aerosol microphysics processes have been included in many climate models in an effort to reduce the uncertainty. However, the models are very challenging to evaluate and constrain because they require extensive in situ measurements of the particle size distribution, number concentration, and chemical composition that are not available from global satellite observations. The Global Aerosol Synthesis and Science Project (GASSP) aims to improve the robustness of global aerosol models by combining new methodologies for quantifying model uncertainty, to create an extensive global dataset of aerosol in situ microphysical and chemical measurements, and to develop new ways to assess the uncertainty associated with comparing sparse point measurements with low-resolution models. GASSP has assembled over 45,000 hours of measurements from ships and aircraft as well as data from over 350 ground stations. The measurements have been harmonized into a standardized format that is easily used by modelers and nonspecialist users. Available measurements are extensive, but they are biased to polluted regions of the Northern Hemisphere, leaving large pristine regions and many continental areas poorly sampled. The aerosol radiative forcing uncertainty can be reduced using a rigorous model-data synthesis approach. Nevertheless, our research highlights significant remaining challenges because of the difficulty of constraining many interwoven model uncertainties simultaneously. Although the physical realism of global aerosol models still needs to be improved, the uncertainty in aerosol radiative forcing will be reduced most effectively by systematically and rigorously constraining the models using extensive syntheses of measurements.
|
|
| 2. |
- Fuzzi, Sandro, et al.
(författare)
-
Overview of the inorganic and organic composition of size-segregated aerosol in Rondonia, Brazil, from the biomass-burning period to the onset of the wet season
- 2007
-
Ingår i: Journal of Geophysical Research. - 2156-2202. ; 112:D1
-
Tidskriftsartikel (refereegranskat)abstract
- The aerosol characterization experiment performed within the Large-Scale Biosphere-Atmosphere Experiment in Amazonia-Smoke, Aerosols, Clouds, Rainfall and Climate (LBA-SMOCC) field experiment carried out in Rondonia, Brazil, in the period from September to November 2002 provides a unique data set of size-resolved chemical composition of boundary layer aerosol over the Amazon Basin from the intense biomass-burning period to the onset of the wet season. Three main periods were clearly distinguished on the basis of the PM10 concentration trend during the experiment: (1) dry period, with average PM10 well above 50 mu g m(-3); (2) transition period, during which the 24-hour-averaged PM10 never exceeded 40 mu g m(-3) and never dropped below 10 mg m(-3); (3) and wet period, characterized by 48-hour-averaged concentrations of PM10 below 12 mu g m(-3) and sometimes as low as 2 mu g m(-3). The trend of PM10 reflects that of CO concentration and can be directly linked to the decreasing intensity of the biomass- burning activities from September through November, because of the progressive onset of the wet season. Two prominent aerosol modes, in the submicron and supermicron size ranges, were detected throughout the experiment. Dry period size distributions are dominated by the fine mode, while the fine and coarse modes show almost the same concentrations during the wet period. The supermicron fraction of the aerosol is composed mainly of primary particles of crustal or biological origin, whereas submicron particles are produced in high concentrations only during the biomass-burning periods and are mainly composed of organic material, mostly water-soluble, and similar to 10% of soluble inorganic salts, with sulphate as the major anion. Size-resolved average aerosol chemical compositions are reported for the dry, transition, and wet periods. However, significant variations in the aerosol composition and concentrations were observed within each period, which can be classified into two categories: (1) diurnal oscillations, caused by the diurnal cycle of the boundary layer and the different combustion phase active during day (flaming) or night (smouldering); and (2) day-to-day variations, due to alternating phases of relatively wet and dry conditions. In a second part of the study, three subperiods representative of the conditions occurring in the dry, transition, and wet periods were isolated to follow the evolution of the aerosol chemical composition as a function of changes in rainfall rate and in the strength of the sources of particulate matter. The chemical data set provided by the SMOCC field experiment will be useful to characterize the aerosol hygroscopic properties and the ability of the particles to act as cloud condensation nuclei.
|
|
| 3. |
- Martin, S. T., et al.
(författare)
-
An overview of the Amazonian Aerosol Characterization Experiment 2008 (AMAZE-08)
- 2010
-
Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7324. ; 10:23, s. 11415-11438
-
Tidskriftsartikel (refereegranskat)abstract
- The Amazon Basin provides an excellent environment for studying the sources, transformations, and properties of natural aerosol particles and the resulting links between biological processes and climate. With this framework in mind, the Amazonian Aerosol Characterization Experiment (AMAZE-08), carried out from 7 February to 14 March 2008 during the wet season in the central Amazon Basin, sought to understand the formation, transformations, and cloud-forming properties of fine-and coarse-mode biogenic aerosol particles, especially as related to their effects on cloud activation and regional climate. Special foci included (1) the production mechanisms of secondary organic components at a pristine continental site, including the factors regulating their temporal variability, and (2) predicting and understanding the cloud-forming properties of biogenic particles at such a site. In this overview paper, the field site and the instrumentation employed during the campaign are introduced. Observations and findings are reported, including the large-scale context for the campaign, especially as provided by satellite observations. New findings presented include: (i) a particle number-diameter distribution from 10 nm to 10 mu m that is representative of the pristine tropical rain forest and recommended for model use; (ii) the absence of substantial quantities of primary biological particles in the submicron mode as evidenced by mass spectral characterization; (iii) the large-scale production of secondary organic material; (iv) insights into the chemical and physical properties of the particles as revealed by thermodenuder-induced changes in the particle number-diameter distributions and mass spectra; and (v) comparisons of ground-based predictions and satellite-based observations of hydrometeor phase in clouds. A main finding of AMAZE-08 is the dominance of secondary organic material as particle components. The results presented here provide mechanistic insight and quantitative parameters that can serve to increase the accuracy of models of the formation, transformations, and cloud-forming properties of biogenic natural aerosol particles, especially as related to their effects on cloud activation and regional climate.
|
|
| 4. |
- Martin, Scot T., et al.
(författare)
-
Sources and properties of Amazonian aerosol particles
- 2010
-
Ingår i: Reviews of Geophysics. - 8755-1209. ; 48, s. 2002-2002
-
Forskningsöversikt (refereegranskat)abstract
- This review provides a comprehensive account of what is known presently about Amazonian aerosol particles and concludes by formulating outlook and priorities for further research. The review is organized to follow the life cycle of Amazonian aerosol particles. It begins with a discussion of the primary and secondary sources relevant to the Amazonian particle burden, followed by a presentation of the particle properties that characterize the mixed populations present over the Amazon Basin at different times and places. These properties include number and mass concentrations and distributions, chemical composition, hygroscopicity, and cloud nucleation ability. The review presents Amazonian aerosol particles in the context of natural compared to anthropogenic sources as well as variability with season and meteorology. This review is intended to facilitate an understanding of the current state of knowledge on Amazonian aerosol particles specifically and tropical continental aerosol particles in general and thereby to enhance future research in this area.
|
|
| 5. |
|
|
| 6. |
- Andreae, Christina, 1969-, et al.
(författare)
-
Changes in Appetite During the Heart Failure Trajectory and Association With Fatigue, Depressive Symptoms, and Quality of Life
- 2021
-
Ingår i: Journal of Cardiovascular Nursing. - : Lippincott Williams & Wilkins. - 0889-4655 .- 1550-5049. ; 36:6, s. 539-545
-
Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Decreased appetite can contribute to malnutrition in patients with heart failure (HF). Little is known about the trajectory of appetite over time in patients with HF and the factors associated with decreased appetite after discharge from the hospital.OBJECTIVE: The aims of this study were to investigate changes in appetite over time and explore how fatigue, depressive symptoms, and quality of life are associated with decreased appetite.METHODS: Data from the multicenter randomized Coordinating study evaluating Outcomes of Advising and Counseling in Heart Failure were used. Logistic regression and mixed-effects logistic regression were used to investigate changes in appetite over time and to explore the relationship between appetite and fatigue, depressive symptoms, and quality of life.RESULTS: A total of 734 patients with HF (mean age, 69 years) were included. Decreased appetite was present at all follow-up measurements; however, decreased appetite was significantly lower at the 1-month (odds ratio [OR], 0.43; confidence interval [CI], 0.29-0.63), 6-month (OR, 0.31; CI, 0.20-0.47), 12-month (OR, 0.22; CI, 0.14-0.34), and 18-month (OR, 0.24; CI, 0.15-0.37) follow-ups compared with baseline. Decreased appetite was associated with fatigue (OR, 3.09; CI, 1.98-4.84), depressive symptoms (OR, 1.76; CI, 1.35-2.29), and low quality of life (OR, 1.01; CI, 1.01-1.02) across all measurement points adjusted for covariates.CONCLUSIONS: Appetite improved after discharge; however, at all time points, at least 22% of patients reported decreased appetite. Fatigue, depressive symptoms, and low quality of life are factors associated with decreased appetite. Decreased appetite is a long-standing problem in that it does not disappear spontaneously after an acute HF deterioration.
|
|
| 7. |
- Andreae, Christina, 1969-, et al.
(författare)
-
Depressive Symptoms Moderate the Association Between Appetite and Health Status in Patients With Heart Failure
- 2018
-
Ingår i: Journal of Cardiovascular Nursing. - : Lippincott Williams & Wilkins. - 0889-4655 .- 1550-5049. ; 33:2, s. E15-E20
-
Tidskriftsartikel (refereegranskat)abstract
- Background: Decreased appetite and depressive symptoms are clinical problems in patients with heart failure. Both may result in impaired health status. Objective: The aims of this study were to investigate the association between appetite and health status in patients with heart failure and to explore whether depressive symptoms moderate this association. Methods: In this cross-sectional study, patients with heart failure (n = 186; mean age, 71 years), New York Heart Association class II to IV, participated. Data on appetite (Council of Nutrition Appetite Questionnaire), depressive symptoms (Patient Health Questionnaire-9), and health status (EQ-5D 3-level scale [EQ-5D-3L] descriptive system, EQ-5D-3L index, and EQ Visual Analog Scale) were collected by self-rating questionnaires. Pearson correlation was used to investigate the association between appetite and health status. Multiple regression was performed to examine whether depressive symptoms moderate the association between appetite and health status. Results: There was a significant association between appetite and health status for EQ-5D-3L descriptive system, mobility (P < .001), pain/discomfort (P < .001), and anxiety/depression (P < .001). This association was also shown in EQ-5D-3L index (P < .001) and EQ Visual Analog Scale (P < .001). Simple slope analysis showed that the association between appetite and health status was only significant for patients without depressive symptoms (B = 0.32, t = 4.66, P < .001). Conclusions: Higher level of appetite was associated with better health status. In moderation analysis, the association was presented for patients without depressive symptoms. Decreased appetite is an important sign of poor health status. To improve health status, health professionals should have greater attention on appetite, as well on signs of depressive symptoms.
|
|
| 8. |
- Andreae, Christina, et al.
(författare)
-
Diet variety mediates the relationship between appetite and micronutrient intake in patients with heart failure
- 2022
-
Ingår i: European Journal of Cardiovascular Nursing. - : Oxford University Press. - 1474-5151 .- 1873-1953. ; 22:5, s. 537-543
-
Tidskriftsartikel (refereegranskat)abstract
- AIMS: Eating a varied diet promotes adequate micronutrient intake. Poor appetite could decrease desire to eat a varied diet leading to dietary micronutrient insufficiencies. The interrelationships among appetite, diet variety, and dietary micronutrient intake has not been investigated in patients with heart failure. The purpose with the study was to determine whether the relationship between appetite and micronutrient insufficiency was mediated through diet variety.METHODS AND RESULTS: A total of 238 patients with heart failure, mean age 61 ± 12.1; 68% male and 45% NYHA class III/IV were included in this secondary analysis. Data collection consisted of a four-day food diary and self-reported appetite on a 10-point visual analog scale. Micronutrient insufficiency was defined as the total number of 17 minerals and vitamins that were insufficient in the diet. Diet variety was calculated as the number of 23 food types consumed over the 4 days. Mediation analysis, controlling for co-variates age, gender, NYHA-class and body mass index showed that diet variety mediated the relationship between appetite and micronutrient insufficiencies (indirect effect = -.0828, 95% CI: -.1585 to -.0150). There was no direct effect of appetite on micronutrient insufficiency (c´ = -.1802; 95% CI = -.3715 to.0111).CONCLUSIONS: Diet variety played a previously unrecognized role in the relationship between appetite and dietary micronutrient intake in patients with heart failure. More research is needed to validate these associations in patients with heart failure.
|
|
| 9. |
|
|
| 10. |
- Andreae, Christina, et al.
(författare)
-
The relationship between physical activity and appetite in heart failure – A cross sectional study
- 2017
-
Ingår i: European Journal of Heart Failure. - : John Wiley & Sons. - 1388-9842 .- 1879-0844. ; 19:S1, s. 135-135
-
Tidskriftsartikel (refereegranskat)abstract
- Background: Physical activity and appetite are important for maintaining physical health. Yet, sedentary lifestyle and poor appetite are frequently observed in the heart failure (HF) population. However, the relationships between these phenomena are not yet clearly understood. Purpose: To investigate the relationship between physical activity and appetite in patients with stable HF.Methods: In this cross sectional study, a consecutive sample of 186 patients with confirmed HF with NYHA class II-IV (median age 72y, 70% men, NYHA class II 61%) participated in the study. Patients were recruited from three HF outpatient clinics in central Sweden. Physical activity measures included total energy expenditure (TEE), active energy expenditure (AEE) above 3 METs, average daily METs and number of steps per day during four days using a validated multi-sensor wearable armband (SenseWear®, Body Monitoring System). Patients also self-reported their physical activity on a ten point numeric rating scale, from extremely low (1) to extremely high (10). Self-reported appetite was measured by Council on Nutrition Appetite Questionnaire (CNAQ), an 8-item instrument (score range 8-40) where CNAQ ≤28 indicate poor appetite. Associations between physical activity and appetite were analyzed by Spearman correlation while differences in physical activity between poor vs good appetite were analyzed using Mann Whitney U test.Results: There was a significant positive relationship between physical activity and appetite assessed by TEE (rs=.184, p=.012), AEE of moderate intensity >3 METs (rs=.262, p=.000), number of steps (rs=.292, p=.000), average METs intensity (rs=.249, p=.001), and self- reported physical activity (rs=.191, p =.009). Levels of physical activity in the low appetite group differed significantly from the group with better appetite, this was seen in all physical dimensions, TEE (U=3225, z=-2.26, p=.024), AEE (U=2902, z=-3.178, p=.001), number of steps (U=2706, z=-3.734, p=.000), average METs intensity (U=3128, z=-2.541, p=.011), levels of self-reported physical activity (U=3185, z=-2.47, p=.013).Conclusion: This study shows that physical activity is associated with appetite and that levels of physical activity differs between patients with poor and good appetite. These findings has implications for both research and practice and underlines the importance in monitoring both physical activity and appetite. Further research is needed to determine whether interventions targeting physical activity also improve appetite and vice versa in the HF population.
|
|
| 11. |
- Artaxo, Paulo, et al.
(författare)
-
Tropical and Boreal Forest – Atmosphere Interactions : A Review
- 2022
-
Ingår i: Tellus. Series B, Chemical and physical meteorology. - : Stockholm University Press. - 0280-6509 .- 1600-0889. ; 74:1, s. 24-163
-
Forskningsöversikt (refereegranskat)abstract
- This review presents how the boreal and the tropical forests affect the atmosphere, its chemical composition, its function, and further how that affects the climate and, in return, the ecosystems through feedback processes. Observations from key tower sites standing out due to their long-term comprehensive observations: The Amazon Tall Tower Observatory in Central Amazonia, the Zotino Tall Tower Observatory in Siberia, and the Station to Measure Ecosystem-Atmosphere Relations at Hyytiäla in Finland. The review is complemented by short-term observations from networks and large experiments.The review discusses atmospheric chemistry observations, aerosol formation and processing, physiochemical aerosol, and cloud condensation nuclei properties and finds surprising similarities and important differences in the two ecosystems. The aerosol concentrations and chemistry are similar, particularly concerning the main chemical components, both dominated by an organic fraction, while the boreal ecosystem has generally higher concentrations of inorganics, due to higher influence of long-range transported air pollution. The emissions of biogenic volatile organic compounds are dominated by isoprene and monoterpene in the tropical and boreal regions, respectively, being the main precursors of the organic aerosol fraction.Observations and modeling studies show that climate change and deforestation affect the ecosystems such that the carbon and hydrological cycles in Amazonia are changing to carbon neutrality and affect precipitation downwind. In Africa, the tropical forests are so far maintaining their carbon sink.It is urgent to better understand the interaction between these major ecosystems, the atmosphere, and climate, which calls for more observation sites, providing long-term data on water, carbon, and other biogeochemical cycles. This is essential in finding a sustainable balance between forest preservation and reforestation versus a potential increase in food production and biofuels, which are critical in maintaining ecosystem services and global climate stability. Reducing global warming and deforestation is vital for tropical forests.
|
|
| 12. |
- Gunthe, S. S., et al.
(författare)
-
Cloud condensation nuclei in pristine tropical rainforest air of Amazonia: size-resolved measurements and modeling of atmospheric aerosol composition and CCN activity
- 2009
-
Ingår i: Atmospheric Chemistry and Physics. - 1680-7324. ; 9:19, s. 7551-7575
-
Tidskriftsartikel (refereegranskat)abstract
- Atmospheric aerosol particles serving as cloud condensation nuclei (CCN) are key elements of the hydrological cycle and climate. We have measured and characterized CCN at water vapor supersaturations in the range of S=0.10-0.82% in pristine tropical rainforest air during the AMAZE-08 campaign in central Amazonia. The effective hygroscopicity parameters describing the influence of chemical composition on the CCN activity of aerosol particles varied in the range of kappa approximate to 0.1-0.4 (0.16+/-0.06 arithmetic mean and standard deviation). The overall median value of kappa approximate to 0.15 was by a factor of two lower than the values typically observed for continental aerosols in other regions of the world. Aitken mode particles were less hygroscopic than accumulation mode particles (kappa approximate to 0.1 at D approximate to 50 nm; kappa approximate to 0.2 at D approximate to 200 nm), which is in agreement with earlier hygroscopicity tandem differential mobility analyzer (H-TDMA) studies. The CCN measurement results are consistent with aerosol mass spectrometry (AMS) data, showing that the organic mass fraction (f(org)) was on average as high as similar to 90% in the Aitken mode (D <= 100 nm) and decreased with increasing particle diameter in the accumulation mode (similar to 80% at D approximate to 200 nm). The kappa values exhibited a negative linear correlation with f(org) (R-2=0.81), and extrapolation yielded the following effective hygroscopicity parameters for organic and inorganic particle components: kappa(org)approximate to 0.1 which can be regarded as the effective hygroscopicity of biogenic secondary organic aerosol (SOA) and kappa(inorg)approximate to 0.6 which is characteristic for ammonium sulfate and related salts. Both the size dependence and the temporal variability of effective particle hygroscopicity could be parameterized as a function of AMS-based organic and inorganic mass fractions (kappa(p)=kappa(org) x f(org)+kappa(inorg) x f(inorg)). The CCN number concentrations predicted with kappa(p) were in fair agreement with the measurement results (similar to 20% average deviation). The median CCN number concentrations at S=0.1-0.82% ranged from N-CCN,N-0.10 approximate to 35 cm(-3) to N-CCN,N-0.82 approximate to 160 cm(-3), the median concentration of aerosol particles larger than 30 nm was N-CN,N-30 approximate to 200 cm(-3), and the corresponding integral CCN efficiencies were in the range of N-CCN,N-0.10/NCN,N-30 approximate to 0.1 to N-CCN,N-0.82/NCN,N-30 approximate to 0.8. Although the number concentrations and hygroscopicity parameters were much lower in pristine rainforest air, the integral CCN efficiencies observed were similar to those in highly polluted megacity air. Moreover, model calculations of N-CCN,N-S assuming an approximate global average value of kappa approximate to 0.3 for continental aerosols led to systematic overpredictions, but the average deviations exceeded similar to 50% only at low water vapor supersaturation (0.1%) and low particle number concentrations (<= 100 cm(-3)). Model calculations assuming aconstant aerosol size distribution led to higher average deviations at all investigated levels of supersaturation: similar to 60% for the campaign average distribution and similar to 1600% for a generic remote continental size distribution. These findings confirm earlier studies suggesting that aerosol particle number and size are the major predictors for the variability of the CCN concentration in continental boundary layer air, followed by particle composition and hygroscopicity as relatively minor modulators. Depending on the required and applicable level of detail, the information and parameterizations presented in this paper should enable efficient description of the CCN properties of pristine tropical rainforest aerosols of Amazonia in detailed process models as well as in large-scale atmospheric and climate models.
|
|
| 13. |
- Lumsden, A, et al.
(författare)
-
Neurobiology.
- 2001
-
Ingår i: Current Opinion in Neurobiology. - 0959-4388 .- 1873-6882. ; 11:3, s. 259-66
-
Forskningsöversikt (refereegranskat)
|
|
| 14. |
- Mircea, M, et al.
(författare)
-
Importance of the organic aerosol fraction for modeling aerosol hygroscopic growth and activation: a case study in the Amazon Basin
- 2005
-
Ingår i: Atmospheric Chemistry and Physics. - 1680-7324. ; 5, s. 3111-3126
-
Tidskriftsartikel (refereegranskat)abstract
- The aerosol in the Amazon basin is dominated throughout the year by organic matter, for the most part soluble in water. In this modeling study, we show how the knowledge of water-soluble organic compounds (WSOC) and the associated physical and chemical properties (e.g. solubility, surface tension, dissociation into ions) affect the hygroscopic growth and activation of the aerosol in this area. The study is based on data obtained during the SMOCC field experiment carried out in Rondonia, Brazil, over a period encompassing the dry (biomass burning) season to the onset of the wet season (September to mid-November, 2002). The comparison of predicted and measured cloud condensation nuclei (CCN) number concentration shows that the knowledge of aerosol WSOC composition in terms of classes of compounds and of their relative molecular weights and acidic properties may be sufficient to predict aerosol activation, without any information on solubility. Conversely, the lack of knowledge on WSOC solubility leads to a high overestimation of the observed diameter growth factors (DGF) by the theory. Moreover, the aerosol water soluble inorganic species fail to predict both DGFs and CCN number concentration. In fact, this study shows that a good reproduction of the measured DGF and CCN concentration is obtained if the chemical composition of aerosol, especially that of WSOC, is appropriately taken into account in the calculations. New parameterizations for the computed CCN spectra are also derived which take into account the variability caused by chemical effects (surface tension, molecular composition, solubility, degree of dissociation of WSOC).
|
|
| 15. |
- Paramonov, M., et al.
(författare)
-
A synthesis of cloud condensation nuclei counter (CCNC) measurements within the EUCAARI network
- 2015
-
Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7324. ; 15:21, s. 12211-12229
-
Tidskriftsartikel (refereegranskat)abstract
- Cloud condensation nuclei counter (CCNC) measurements performed at 14 locations around the world within the European Integrated project on Aerosol Cloud Climate and Air Quality interactions (EUCAARI) framework have been analysed and discussed with respect to the cloud condensation nuclei (CCN) activation and hygroscopic properties of the atmospheric aerosol. The annual mean ratio of activated cloud condensation nuclei (N-CCN) to the total number concentration of particles (N-CN), known as the activated fraction A, shows a similar functional dependence on supersaturation S at many locations - exceptions to this being certain marine locations, a free troposphere site and background sites in south-west Germany and northern Finland. The use of total number concentration of particles above 50 and 100 nm diameter when calculating the activated fractions (A(50) and A(100), respectively) renders a much more stable dependence of A on S; A(50) and A(100) also reveal the effect of the size distribution on CCN activation. With respect to chemical composition, it was found that the hygroscopicity of aerosol particles as a function of size differs among locations. The hygroscopicity parameter kappa decreased with an increasing size at a continental site in south-west Germany and fluctuated without any particular size dependence across the observed size range in the remote tropical North Atlantic and rural central Hungary. At all other locations kappa increased with size. In fact, in Hyytiala, Vavihill, Jungfraujoch and Pallas the difference in hygroscopicity between Aitken and accumulation mode aerosol was statistically significant at the 5% significance level. In a boreal environment the assumption of a size-independent kappa can lead to a potentially substantial overestimation of N-CCN at S levels above 0.6 %. The same is true for other locations where kappa was found to increase with size. While detailed information about aerosol hygroscopicity can significantly improve the prediction of N-CCN, total aerosol number concentration and aerosol size distribution remain more important parameters. The seasonal and diurnal patterns of CCN activation and hygroscopic properties vary among three long-term locations, highlighting the spatial and temporal variability of potential aerosol-cloud interactions in various environments.
|
|
| 16. |
- Poeschl, U., et al.
(författare)
-
Rainforest Aerosols as Biogenic Nuclei of Clouds and Precipitation in the Amazon
- 2010
-
Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 1095-9203 .- 0036-8075. ; 329:5998, s. 1513-1516
-
Tidskriftsartikel (refereegranskat)abstract
- The Amazon is one of the few continental regions where atmospheric aerosol particles and their effects on climate are not dominated by anthropogenic sources. During the wet season, the ambient conditions approach those of the pristine pre-industrial era. We show that the fine submicrometer particles accounting for most cloud condensation nuclei are predominantly composed of secondary organic material formed by oxidation of gaseous biogenic precursors. Supermicrometer particles, which are relevant as ice nuclei, consist mostly of primary biological material directly released from rainforest biota. The Amazon Basin appears to be a biogeochemical reactor, in which the biosphere and atmospheric photochemistry produce nuclei for clouds and precipitation sustaining the hydrological cycle. The prevailing regime of aerosol-cloud interactions in this natural environment is distinctly different from polluted regions.
|
|
| 17. |
- Suni, T., et al.
(författare)
-
The significance of land-atmosphere interactions in the Earth system-iLEAPS achievements and perspectives
- 2015
-
Ingår i: Anthropocene. - : Elsevier BV. - 2213-3054. ; 12, s. 69-84
-
Tidskriftsartikel (refereegranskat)abstract
- The integrated land ecosystem-atmosphere processes study (iLEAPS) is an international research project focussing on the fundamental processes that link land-atmosphere exchange, climate, the water cycle, and tropospheric chemistry. The project, iLEAPS, was established 2004 within the International Geosphere-Biosphere Programme (IGBP). During its first decade, iLEAPS has proven to be a vital project, well equipped to build a community to address the challenges involved in understanding the complex Earth system: multidisciplinary, integrative approaches for both observations and modeling. The iLEAPS community has made major advances in process understanding, land-surface modeling, and observation techniques and networks. The modes of iLEAPS operation include elucidating specific iLEAPS scientific questions through networks of process studies, field campaigns, modeling, long-term integrated field studies, international interdisciplinary mega-campaigns, synthesis studies, databases, as well as conferences on specific scientific questions and synthesis meetings. Another essential component of iLEAPS is knowledge transfer and it also encourages community-and policy-related outreach activities associated with the regional integrative projects. As a result of its first decade of work, iLEAPS is now setting the agenda for its next phase (2014-2024) under the new international initiative, future Earth. Human influence has always been an important part of land-atmosphere science but in order to respond to the new challenges of global sustainability, closer ties with social science and economics groups will be necessary to produce realistic estimates of land use and anthropogenic emissions by analysing future population increase, migration patterns, food production allocation, land management practices, energy production, industrial development, and urbanization.
|
|
| 18. |
- Wang, Jian, et al.
(författare)
-
Amazon boundary layer aerosol concentration sustained by vertical transport during rainfall
- 2016
-
Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 539:7629, s. 416-419
-
Tidskriftsartikel (refereegranskat)abstract
- The nucleation of atmospheric vapours is an important source of new aerosol particles that can subsequently grow to form cloud condensation nuclei in the atmosphere(1). Most field studies of atmospheric aerosols over continents are influenced by atmospheric vapours of anthropogenic origin (for example, ref. 2) and, in consequence, aerosol processes in pristine, terrestrial environments remain poorly understood. The Amazon rainforest is one of the few continental regions where aerosol particles and their precursors can be studied under near-natural conditions(3-5), but the origin of small aerosol particles that grow into cloud condensation nuclei in the Amazon boundary layer remains unclear(6-8). Here we present aircraft- and ground-based measurements under clean conditions during the wet season in the central Amazon basin. We find that high concentrations of small aerosol particles (with diameters of less than 50 nanometres) in the lower free troposphere are transported from the free troposphere into the boundary layer during precipitation events by strong convective downdrafts and weaker downward motions in the trailing stratiform region. This rapid vertical transport can help to maintain the population of particles in the pristine Amazon boundary layer, and may therefore influence cloud properties and climate under natural conditions.
|
|
