From nanoclusters to climate forcers : global modeling of aerosol climate effects

Atmospheric aerosol particles influence everyday life through their adverse health effects. Aerosols also affect the Earth's climate, directly by scattering and absorbing radiation and indirectly by acting as cloud condensation nuclei (CCN) and modifying cloud properties. The net effect of aerosols on climate is cooling. Although only a small fraction of atmospheric aerosol mass is of direct human origin, the anthropogenic aerosol climate forcing can be of same magnitude, but opposite in sign, as the anthropogenic forcing via CO2. As aerosols are short-lived and respond rapidly to changes in emissions, they are an important factor in determining the future climate change. Aerosols are either emitted as primary particles or they are formed from gas-phase precursors. Atmospheric new particle formation is observed around the world. In this thesis, new particle formation is studied with a global aerosol-climate model. Several thermodynamic and semi-empirical parameterizations of nucleation are investigated. It is shown that in addition to the thermodynamic models, semi-empirical parameterizations are needed to explain the observed aerosol number concentrations. Volatile organic compounds (VOCs) can contribute to particle number, particle growth, and total aerosol mass. It was shown that biogenic VOCs have an important role in growing the freshly-nucleated particles to sizes capable of acting as CCN. It was also shown that the current atmospheric concentrations of nitric acid can greatly affect cloud droplet activation and increase the number of cloud droplets, making a large contribution to the indirect aerosols effect. With current scenarios for anthropogenic SO2 emissions, the formation of new particles will diminish significantly by the year 2100. Together with the predicted reductions in primary particles, the future cloud droplet number concentrations were shown to decrease close to pre-industrial levels. As a result, the anthropogenic aerosol forcing decreased close to zero. Several possible counteracting processes were studied. It was shown that an increase in either oceanic dimethyl sulfide (DMS) or biogenic VOC emission could provide more CCN and cooling in the future. Also, the differences in the predicted future trend of NOx and SO2 emissions indicate an increasingly important role for the indirect effects via nitric acid.Ilmakehän pienhiukkaset vaikuttavat sekä ihmisten terveyteen että ilmastoon. Hiukkaset voivat muun muassa heijastaa Auringon säteilyä takaisin avaruuteen tai lämmittää ilmakehää. Hiukkaset voivat myös toimia pilvipisaroiden tiivistymisytiminä, vaikuttaen siten pilvien heijastavuuteen, elinikään ja sateisuuteen. Pienhiukkasten kokonaisvaikutus on ilmastoa viilentävä. Vaikka ihmisperäisten hiukkaspäästöjen vaikutus ilmakehän hiukkasten kokonaismassaan on pieni, antropogeenisten hiukkasten viilentävä vaikutus saattaa oleellisesti kompensoida ihmisperäisten kasvihuonekaasujen aiheuttamaa lämpenemistä. Hiukkasten ilmastovaikutus on kuitenkin edelleen yksi suurimmista epävarmuustekijöistä ilmastomalleissa. Hiukkasia pääsee ilmakehään primäärisinä päästöinä, kuten merisuola- ja pölyhiukkasina. Hiukkasia muodostuu ilmakehässä myös kaasu-hiukkas -muuntuman kautta, jossa rikkihappo on oleellisessa asemassa. Muodostuneita hiukkasia kasvattavat erityisesti biogeeniset orgaaniset kaasut. Tässä väitöskirjassa on kehitetty ilmakehän hiukkasmuodostuksen kuvausta globaalissa ilmastomallissa. Sisällyttämällä hiukkasmuodostus ilmastomalliin saatiin pienennettyä eroa mittauksissa havaittujen hiukkaslukumäärien ja mallitulosten välillä. Hiukkasmuodostuksen todettiin lisäävän merkittävästi pilvipisaroiden lukumäärää ja vaikuttavan sitä kautta pilvien ominaisuuksiin, kuten heijastavuuteen. Tulevaisuuden ennusteet osoittavat huomattavia vähenemisiä antropogeenisissa hiukkaspäästöissä, mikä saattaa johtaa hiukkasten viilentävän vaikutuksen heikentymiseen. Tässä tutkimuksessa kehitettyä mallia käyttämällä on osoitettu, että erityisesti rikkidioksidiemissioiden leikkaamisesta johtuva hiukkasmuodostuksen väheneminen heikentää hiukkasten säteilyvaikutusta vuoteen 2100 mennessä. Typpioksidipäästöjen leikkaukset ovat ennusteiden mukaan hitaampia kuin rikkidioksidin. Väitöskirjassa tutkittiin myös typpioksidien vaikutusta pilvipisaroiden muodostukseen, ja todettiin typpioksidien olevan merkittävässä roolissa pilvien säteilyvaikutuksessa. Lukuisat maajärjestelmän takaisinkytkennät voivat joko heikentää tai vahvistaa ilmastonmuutosta. Tässä tutkimuksessa todettiin, että ilmaston lämpenemisen seurauksena mahdollisesti kasvavat biogeeniset kaasupäästöt voivat viilentää ilmastoa lisääntyneen hiukkasmuodostuksen ja hiukkasten kasvun seurauksena

Effects of snow grain shape on climate simulations : sensitivity tests with the Norwegian Earth System Model

Snow consists of non-spherical grains of various shapes and sizes. Still, in radiative transfer calculations, snow grains are often treated as spherical. This also applies to the computation of snow albedo in the Snow, Ice, and Aerosol Radiation (SNICAR) model and in the Los Alamos sea ice model, version 4 (CICE4), both of which are employed in the Community Earth System Model and in the Norwegian Earth System Model (NorESM). In this study, we evaluate the effect of snow grain shape on climate simulated by NorESM in a slab ocean configuration of the model. An experiment with spherical snow grains (SPH) is compared with another (NONSPH) in which the snow shortwave single-scattering properties are based on a combination of three non-spherical snow grain shapes optimized using measurements of angular scattering by blowing snow. The key difference between these treatments is that the asymmetry parameter is smaller in the non-spherical case (0.77-0.78 in the visible region) than in the spherical case (similar to 0.89). Therefore, for the same effective snow grain size (or equivalently, the same specific projected area), the snow broadband albedo is higher when assuming non-spherical rather than spherical snow grains, typically by 0.02-0.03. Considering the spherical case as the baseline, this results in an instantaneous negative change in net shortwave radiation with a global-mean top-of-the-model value of ca. -0.22Wm(-2). Although this global-mean radiative effect is rather modest, the impacts on the climate simulated by NorESM are substantial. The global annual-mean 2m air temperature in NONSPH is 1.17K lower than in SPH, with substantially larger differences at high latitudes. The climatic response is amplified by strong snow and sea ice feedbacks. It is further demonstrated that the effect of snow grain shape could be largely offset by adjusting the snow grain size. When assuming non-spherical snow grains with the parameterized grain size increased by ca. 70 %, the climatic differences to the SPH experiment become very small. Finally, the impact of assumed snow grain shape on the radiative effects of absorbing aerosols in snow is discussed.Peer reviewe

Self-Conscious Affect Is Modulated by Rapid Eye Movement Sleep but Not by Targeted Memory Reactivation–A Pilot Study

The neurophysiological properties of rapid eye movement sleep (REMS) are believed to tune down stressor-related emotional responses. While prior experimental findings are controversial, evidence suggests that affective habituation is hindered if REMS is fragmented. To elucidate the topic, we evoked self-conscious negative affect in the participants (N = 32) by exposing them to their own out-of-tune singing in the evening. Affective response to the stressor was measured with skin conductance response and subjectively reported embarrassment. To address possible inter-individual variance toward the stressor, we measured the shame-proneness of participants with an established questionnaire. The stressor was paired with a sound cue to pilot a targeted memory reactivation (TMR) protocol during the subsequent night's sleep. The sample was divided into three conditions: control (no TMR), TMR during slow-wave sleep, and TMR during REMS. We found that pre- to post-sleep change in affective response was not influenced by TMR. However, REMS percentage was associated negatively with overnight skin conductance response habituation, especially in those individuals whose REMS was fragmented. Moreover, shame-proneness interacted with REM fragmentation such that the higher the shame-proneness, the more the affective habituation was dependent on non-fragmented REMS. In summary, the potential of REMS in affective processing may depend on the quality of REMS as well as on individual vulnerability toward the stressor type.Peer reviewe

Implementing a sectional scheme for early aerosol growth from new particle formation in the Norwegian Earth System Model v2 : comparison to observations and climate impacts

Aerosol-cloud interactions contribute to a large portion of the spread in estimates of climate forcing, climate sensitivity and future projections. An important part of this uncertainty is how much new particle formation (NPF) contributes to cloud condensation nuclei (CCN) and, furthermore, how this changes with changes in anthropogenic emissions. Incorporating NPF and early growth in Earth system models (ESMs) is, however, challenging due to uncertain parameters (e.g. participating vapours), structural issues (numerical description of growth from similar to 1 to similar to 100 nm) and the large scale of an ESM grid compared to the NPF scale. A common approach in ESMs is to represent the particle size distribution by a certain number of log-normal modes. Sectional schemes, on the other hand, in which the size distribution is represented by bins, are considered closer to first principles because they do not make an a priori assumption about the size distribution. In order to improve the representation of early growth, we have implemented a sectional scheme for the smallest particles (5-39.6 nm diameter) in the Norwegian Earth System Model (NorESM), feeding particles into the original aerosol scheme. This is, to our knowledge, the first time such an approach has been tried. We find that including the sectional scheme for early growth improves the aerosol number concentration in the model when comparing against observations, particularly in the 50-100 nm diameter range. Furthermore, we find that the model with the sectional scheme produces much fewer particles than the original scheme in polluted regions, while it produces more in remote regions and the free troposphere, indicating a potential impact on the estimated aerosol forcing. Finally, we analyse the effect on cloud-aerosol interactions and find that the effect of changes in NPF efficiency on clouds is highly heterogeneous in space. While in remote regions, more efficient NPF leads to higher cloud droplet number concentration (CDNC), in polluted regions the opposite is in fact the case.Peer reviewe

Presleep physiological stress is associated with a higher cortical arousal in sleep and more consolidated REM sleep

How sleep regulates physiological stress in healthy individuals is not well understood. We explored the associations between naturally occurring pre-sleep physiological arousal and EEG power spectral density together with rapid eye movement sleep (REMS) continuity. One hundred and fifty-four individuals (mean age 16.9, SD 0.1 years) collected five samples of saliva between the evening (mean time 18:20) and bedtime (mean 23:00) by using swabs, and underwent an overnight in-home polysomnography. We calculated spectral density for REMS and non-rapid eye movement sleep (non-REMS), and the number and duration of REMS arousals (Peer reviewe

BDNF Val66Met polymorphism moderates the association between sleep spindles and overnight visual recognition

A common single nucleotide polymorphism (SNP) of the brain-derived neurotrophic factor (BDNF) gene, Val66Met, has been reported to impair BDNF secretion and memory function. However, few studies have investigated the interaction of BDNF genotype and sleep characteristics, such as sleep spindles, that promote long-term potentiation during sleep. In this study we compared overnight visual memory between the carriers of BDNF Met and non-carriers (Val homozygotes), and examined how sleep spindle density associated with memory performance. The sample constituted of 151 adolescents (mean age 16.9 years; 69% Val homozygotes, 31% Met carriers). The learning task contained high and low arousal pictures from Interactive Affective Picture System. The learning task and all-night polysomnography were conducted at the homes of the adolescents. Slow (10–13 Hz) and fast (13–16 Hz) spindles were detected with automated algorithm. Neither post-sleep recognition accuracy nor spindle density differed between Val homozygotes and Met carriers. While frontal slow and fast spindle densities associated with better recognition accuracy in the entire sample, examining the allelic groups separately indicated paralleling associations in Val homozygotes only. Interaction analyses revealed a significant genotype-moderated difference in the associations between frontal fast sleep spindles and high arousal pictures. In sum, sleep spindles promote or indicate visual learning in Val homozygote adolescents but not in Met carriers. The result suggests that the role of sleep spindles in visual recognition memory is not equal across individuals but moderated by a common gene variant.Peer reviewe

A simulation of aerosols over Green Sahara in Mid-Holocene period with prescribed vegetation covers

Non peer reviewe

Yhteisopettajuus ja joustavat oppimisryhmät yläkoulun matematiikan opetuksen tukena

Tässä artikkelissa raportoidaan kolmivuotisen tutkimusprojektin tuloksia, jossa oppilaiden matematiikan osaamista seurattiin yläkoulun ajan seurannan pääpainon ollessa kymmenjärjestelmän perusteiden hallinnassa. Koekoulussa oppilaiden (n=153) opetus toteutettiin painotetun opetuksen luokkia lukuun ottamatta oppilaiden oppimistarpeen pohjalta muodostetuissa joustavissa oppimisryhmissä, ja erityisopetuksen työmuotona oli matematiikan aineenopettajan ja erityisopettajan yhteisopetus. Kontrolliryhmän muodosti toisen yläkoulun oppilaat (n = 58). Toistomittauksissa käytettiin Kymppi 2-kartoitusta, ja aineistoa analysoitiin sekä parametrisesti että epäparametrisesti. Peruskoulun lopussa oppilaiden osaamista arvioitiin parametrisesti matematiikan opetussuunnitelman keskeisiä sisältöjä mittaavalla KTLT-testillä. Oppilaan oppimistarpeen pohjalta muodostetuissa oppimisryhmissä, joissa erityisopetuksen tuki toteutui pääosin yhteisopettajuutena, matematiikassa heikosti menestyvien oppilaiden kymmenjärjestelmän hallinta ja peruskoulun matematiikan opetussuunnitelman tavoitteet saavutettiin paremmin kuin kiinteissä perusopetusryhmissä erityisopetuksen tuen toteutuessa pelkästään osa-aikaisen erityisopetuksen tukemana. Merkittävänä tuloksena voi pitää sitä, että koekoulun joustavissa oppimisryhmissä opiskelleiden suoriutumisen ero kymmenjärjestelmän hallinnassa ei kasvanut verrattuna parhaiten menestyneisiin painotetun opetuksen oppilaisiin toisin kuin kontrollikoulussa. Tutkimusprojektin aikana tuli esille, että osa oppilaista tarvitsi vielä pienempää oppimisryhmää kuin yhteisopettajuusryhmissä oli mahdollista tarjota: Erityisopetuksen työmuotojen tulee olla joustavia ja monipuolisia.Peer reviewe

A preliminary simulation of dust load over Green Sahara in Mid-Holocene period with prescribed vegetation covers

Non peer reviewe

BVOC-aerosol-climate feedbacks investigated using NorESM

Both higher temperatures and increased CO2 concentrations are (separately) expected to increase the emissions of biogenic volatile organic compounds (BVOCs). This has been proposed to initiate negative climate feedback mechanisms through increased formation of secondary organic aerosol (SOA). More SOA can make the clouds more reflective, which can provide a cooling. Furthermore, the increase in SOA formation has also been proposed to lead to increased aerosol scattering, resulting in an increase in diffuse radiation. This could boost gross primary production (GPP) and further increase BVOC emissions. In this study, we have used the Norwegian Earth System Model (NorESM) to investigate both these feedback mechanisms. Three sets of experiments were set up to quantify the feedback with respect to (1) doubling the CO2, (2) increasing temperatures corresponding to a doubling of CO2 and (3) the combined effect of both doubling CO2 and a warmer climate. For each of these experiments, we ran two simulations, with identical setups, except for the BVOC emissions. One simulation was run with interactive BVOC emissions, allowing the BVOC emissions to respond to changes in CO2 and/or climate. In the other simulation, the BVOC emissions were fixed at present-day conditions, essentially turning the feedback off. The comparison of these two simulations enables us to investigate each step along the feedback as well as estimate their overall relevance for the future climate. We find that the BVOC feedback can have a significant impact on the climate. The annual global BVOC emissions are up to 63 % higher when the feedback is turned on compared to when the feedback is turned off, with the largest response when both CO2 and climate are changed. The higher BVOC levels lead to the formation of more SOA mass (max 53 %) and result in more particles through increased new particle formation as well as larger particles through increased condensation. The corresponding changes in the cloud properties lead to a -0.43 W m(-2) stronger net cloud forcing. This effect becomes about 50 % stronger when the model is run with reduced anthropogenic aerosol emissions, indicating that the feedback will become even more important as we decrease aerosol and precursor emissions. We do not find a boost in GPP due to increased aerosol scattering on a global scale. Instead, the fate of the GPP seems to be controlled by the BVOC effects on the clouds. However, the higher aerosol scattering associated with the higher BVOC emissions is found to also contribute with a potentially important enhanced negative direct forcing (-0.06 W m(-2)). The global total aerosol forcing associated with the feedback is -0.49 W m(-2), indicating that it has the potential to offset about 13 % of the forcing associated with a doubling of CO2.Peer reviewe