Alatroposfäärin tuulimaksimit Suomessa ja niiden yhteys syvään kosteaan konvektioon

Alatroposfäärissä havaittava tuulimaksimi on maailmanlaajuinen ja melko tavanomainen ilmiö. Kuitenkin lämmön ja kosteuden tehokkaina kuljettajina voimakkaat alatroposfäärin tuulimaksimit voivat suotuisissa olosuhteissa olla sään kannalta merkittäviä.Voimakkailla alatroposfäärin tuulimaksimeilla on havaittu yhteys mm. syvän kostean konvektion esiintymiseen. Suomessa edellinen alatroposfäärin tuulimaksimien klimatologiaa käsittelevä tutkimus tehtiin 1970-luvulla. Nyt vuosikymmeniä myöhemmin nykyaikaisempien menetelmien, havaintolaitteiden, sekä uudempien tutkimustulosten avulla on mahdollista tarkentaa tietämystä alatroposfäärin tuulimaksimien esiintymisestä ja ominaisuuksista Suomen alueella. Tämän tutkimuksen päätavoite onkin päivittää ilmiön klimatologista tuntemusta, mutta lisäksi palvella Ilmatieteen laitoksen sää- ja turvallisuuskeskuksen päivystäviä meteorologeja. Tämän lisäksi osoitettiin, että alatroposfäärin tuulimaksimeilla on vaikutusta syvän kostean konvektion esiintymiseen myös Suomen alueella. Tässä tutkimuksessa Suomessa esiintyviä alatroposfäärin tuulimaksimeja tarkasteltiin 12 vuoden ajalta, vuosilta 1998-2009. Tarkastelu tehtiin kaikilta Suomen luotausasemilta, eli Jokioisista, Jyväskylästä sekä Sodankylästä. Mielenkiintoiset tapaukset etsittiin yli 26000 luotauksen joukosta tietokoneavusteisesti Ilmatieteen laitoksen sähköisestä luotausarkistosta. Haku perustui aiemmissa klimatologisissa tutkimuksissa käytettyihin kriteereihin. Kuhunkin alatroposfäärin tuulimaksimitapaukseen liittyen kerättiin keskeisiä tietoja ilmakehäluotauksista sekä luotausasemalla tehdyistä havainnoista. Tietojen avulla tutkittiin erityisesti alatroposfäärin tuulimaksimien esiintymistä, korkeutta, voimakkuutta, tuulen suuntaa sekä näihin liittyviä vuodenaikais- ja vuorokausivaihteluja. Lisäksi tarkasteltiin ilmiön syntytapoja mm. globaalin säteilyn, painegradientin, vuorokauden lämpötilavaihteluiden, lämpötilainversion korkeuden, ilmankosteuden sekä luotausasemilla havaitun pilvisyyden avulla. Alatroposfäärin tuulimaksimeja esiintyi vuosina 1998-2009 Suomessa kaiken kaikkiaan noin 30%:ssa havaituista luotauksista. Tapauksia havaittiin kaikkina vuodenaikoina, mutta suurin osa, noin 60% tapauksista, esiintyi talvella. Vuorokausivaihtelu oli suurinta kesällä, jolloin 70% tapauksista havaittiin yöaikaan. Talvella vuorokausivaihtelu ei ollut merkittävää. Talven ja kesän välillä esiintyvät voimakkaat vaihtelut tekevät välivuodenajoista erityisen mielenkiintoisia. Esimerkiksi keväällä ja alkukesällä havaittiin varsinkin Jokioisissa yöajan tuulimaksimien sekundäärinen esiintymismaksimi, johon liittyi myös vähän voimakkaampia tuulen nopeuksia. Alatroposfäärin tuulimaksimeihin liittyvät tuulennopeudet olivat talvella keskimäärin selvästi voimakkaampia kuin kesällä. Tuulen nopeudessa suurin frekvenssi havaittiin luokassa 10-11 m/s, mutta voimakkaimmat tuulimaksimit olivat selvästi yli 30 m/s. Voimakkaimmassa tapauksessa tuulen nopeudeksi mitattiin 43 m/s. Mielenkiintoista on, että tuulimaksimien korkeuden havaittiin olevan lähes suoraan verrannollinen tuulimaksimin nopeuteen. Talvella alatroposfäärin tuulimaksimit esiintyivät sekä yöllä että päivällä n. 500-600 m korkeudella maanpinnasta. Sitä vastoin varsinkin selkeinä kesäöinä esiintymisessä havaittiin talven korkeusjakaumaan verrattuna terävämpi maksimi n. 300 m korkeudella maanpinnasta. Kesäöinä alatroposfäärin tuulimaksimit esiintyivät lisäksi lähellä inversion huippua. Kesäpäivinä alatroposfäärin tuulimaksimien korkeusjakauma oli huomattavan tasainen ja selvää esiintymishuippua ei ollut havaittavissa, mikä johtui voimakkaasta turbulenttisesta sekoittumisesta. Tuulimaksimeihin liittyvä tuulen suunta oli lähellä pitkän ajan keskiarvoja. Tuloksista voidaan päätellä Suomessa esiintyvien alatroposfäärin tuulimaksimien tärkeimmät syntymekanismit. Talvella auringonsäteily on vähäistä ja alatroposfäärin tuulimaksimit syntyvät suurimmaksi osaksi synoptisten häiriöiden ja niihin liittyvien syöttövirtausten, rintamavyöhykkeiden, sekä termisen tuulen vaikutuksista. Kesällä auringonsäteily sekä lämpötilan vuorokausivaihtelu on voimakasta, mikä suosii inertiaalioskillaation esiintymistä ja tuulimaksimin muodostumista auringon laskun jälkeen. Maanpinnan ja rajakerroksen väliset turbulenttiset vuot ovat myös tärkeitä vuorokausivaihtelussa. Havaittavan ja latentin lämmönvuon suhde (Bowenin suhde) vaikuttaa voimakkaasti 2m lämpötilan vuorokausivaihtelun voimakkuuteen ja on siksi merkityksellinen inertiaalioskillaation kannalta. Tulosten mukaan havaittavan lämmönvuon hallitsevuus on auringonsäteilyn sekä painegradientin keskimääräisen vuotuisen vaihtelun rinnalla osasyy kevään sekundäärimaksimin syntyyn. Tapaustutkimuksissa tarkasteltiin mm. matalapaineiden syöttövirtauksiin liittyviä alatroposfäärin tuulimaksimeja. Lisäksi inertiaalioskillaatiolla havaittiin sopivissa olosuhteissa olevan merkittävä vaikutus alatroposfäärin tuulimaksimien syntymiseen. Syvään kosteaan konvektioon liittyvät tapaustutkimukset osoittivat, että voimakkailla alatroposfäärin tuulimaksimeilla voi myös Suomen alueella olla suosiollinen tai jopa merkittävä vaikutus syvän kostean konvektion kehitykseen

Vegetation controls of water and energy balance of a drained peatland forest: Responses to alternative harvesting practices

We quantified the response of peatland water table level (WTL) and energy fluxes to harvesting of a drained peatland forest. Two alternative harvests (clear-cut and partial harvest) were carried out in a mixed-species ditch-drained peatland forest in southern Finland, where water and energy balance components were monitored for six pre-treatment and three post-treatment growing seasons. To explore the responses caused by harvestings, we applied a mechanistic multi-layer soil-plant-atmosphere transfer model. At the clear-cut site, the mean growing season WTL rose by 0.18 +/- 0.02 m (error estimate based on measurement uncertainty), while net radiation, and sensible and latent heat fluxes decreased after harvest. On the contrary, we observed only minor changes in energy fluxes and mean WTL (0.05 +/- 0.03 m increase) at the partial harvest site, although as much as 70% of the stand basal area was removed and leaf-area index was reduced to half. The small changes were mainly explained by increased water use of spruce undergrowth and field layer vegetation, as well as increased forest floor evaporation. The rapid establishment of field layer vegetation had a significant role in energy balance recovery at the clear-cut site. At partial harvest, chlorophyll fluorescence measurements and model-data comparison suggested the shade-adapted spruce undergrowth was suffering from light stress during the first post-harvest growing season. We conclude that in addition to stand basal area, species composition and stand structure need to be considered when controlling WTL in peatland forests with partial harvesting. Our results have important implications on the operational use of continuous cover forestry on drained peatlands. A continuously maintained tree cover with significant evapotranspiration capacity could enable optimizing WTL from both tree growth and environmental perspectives.Peer reviewe

Set-up and instrumentation of the greenhouse gas measurements on experimental sites of continuous cover forestry

A set of experimental study sites was established to monitor greenhouse gas (GHG) emissions from drained peatland forests under different harvesting regimes in Finland. The purpose of these experimental sites is to study the effects of continuous cover forestry (CCF) and clear-cutting (CC) on ecosystem processes including GHG emissions and stand development on drained peatland forests. The sites represent fertile Norway spruce dominated peatland forests, where soil GHG emissions are high due to drainage that has exposed peat to decomposition in aerobic conditions. Two “flagship” sites for greenhouse gas (GHG) monitoring have been established and instrumented by the Natural Resources Institute Finland (Luke), University of Helsinki (UH) and the Finnish Meteorological Institute (FMI). The sites host continuous GHG monitoring with Eddy Covariance (EC) towers and with automatic chambers. In addition, greenhouse gas (CO2, CH4, and N2O) emissions are monitored with manually operated chambers at four sites, where effects of selection (CCF) harvests are studied with replicated treatments. These data will be used to calculate the ecosystem and soil GHG balances of the sites by using methodologies standardized earlier and compatible with the IPCC guidelines. On all experimental sites, ground water table (WT), tree growth and regeneration are monitored in different management trials. These data will form the basic data needed for designing and demonstrating optimal harvesting cycles and evaluating and generalizing the climate impacts. The results including the biological drainage capacity (evapotranspiration) of different-sized tree stands as well as the soil GHG balance of different tree stand – WT combinations will be incorporated into existing models that can be used to estimate the mitigation obtained with different management options and in different site and climatic conditions. The study sites are actively used for training and demonstration of alternative peatland management practices by host projects and by multiple stakeholders. The host projects and organizations also promote further extensions for the measurements and all complementary research activities are welcome to these study sites

Association of genetic variation with systolic and diastolic blood pressure among African Americans: the Candidate Gene Association Resource study

The prevalence of hypertension in African Americans (AAs) is higher than in other US groups; yet, few have performed genome-wide association studies (GWASs) in AA. Among people of European descent, GWASs have identified genetic variants at 13 loci that are associated with blood pressure. It is unknown if these variants confer susceptibility in people of African ancestry. Here, we examined genome-wide and candidate gene associations with systolic blood pressure (SBP) and diastolic blood pressure (DBP) using the Candidate Gene Association Resource (CARe) consortium consisting of 8591 AAs. Genotypes included genome-wide single-nucleotide polymorphism (SNP) data utilizing the Affymetrix 6.0 array with imputation to 2.5 million HapMap SNPs and candidate gene SNP data utilizing a 50K cardiovascular gene-centric array (ITMAT-Broad-CARe [IBC] array). For Affymetrix data, the strongest signal for DBP was rs10474346 (P= 3.6 × 10−8) located near GPR98 and ARRDC3. For SBP, the strongest signal was rs2258119 in C21orf91 (P= 4.7 × 10−8). The top IBC association for SBP was rs2012318 (P= 6.4 × 10−6) near SLC25A42 and for DBP was rs2523586 (P= 1.3 × 10−6) near HLA-B. None of the top variants replicated in additional AA (n = 11 882) or European-American (n = 69 899) cohorts. We replicated previously reported European-American blood pressure SNPs in our AA samples (SH2B3, P= 0.009; TBX3-TBX5, P= 0.03; and CSK-ULK3, P= 0.0004). These genetic loci represent the best evidence of genetic influences on SBP and DBP in AAs to date. More broadly, this work supports that notion that blood pressure among AAs is a trait with genetic underpinnings but also with significant complexit

A Meta-analysis of Gene Expression Signatures of Blood Pressure and Hypertension

Genome-wide association studies (GWAS) have uncovered numerous genetic variants (SNPs) that are associated with blood pressure (BP). Genetic variants may lead to BP changes by acting on intermediate molecular phenotypes such as coded protein sequence or gene expression, which in turn affect BP variability. Therefore, characterizing genes whose expression is associated with BP may reveal cellular processes involved in BP regulation and uncover how transcripts mediate genetic and environmental effects on BP variability. A meta-analysis of results from six studies of global gene expression profiles of BP and hypertension in whole blood was performed in 7017 individuals who were not receiving antihypertensive drug treatment. We identified 34 genes that were differentially expressed in relation to BP (Bonferroni-corrected p<0.05). Among these genes, FOS and PTGS2 have been previously reported to be involved in BP-related processes; the others are novel. The top BP signature genes in aggregate explain 5%–9% of inter-individual variance in BP. Of note, rs3184504 in SH2B3, which was also reported in GWAS to be associated with BP, was found to be a trans regulator of the expression of 6 of the transcripts we found to be associated with BP (FOS, MYADM, PP1R15A, TAGAP, S100A10, and FGBP2). Gene set enrichment analysis suggested that the BP-related global gene expression changes include genes involved in inflammatory response and apoptosis pathways. Our study provides new insights into molecular mechanisms underlying BP regulation, and suggests novel transcriptomic markers for the treatment and prevention of hypertension

Association of genetic variation with systolic and diastolic blood pressure among African Americans: the Candidate Gene Association Resource study.

The prevalence of hypertension in African Americans (AAs) is higher than in other US groups; yet, few have performed genome-wide association studies (GWASs) in AA. Among people of European descent, GWASs have identified genetic variants at 13 loci that are associated with blood pressure. It is unknown if these variants confer susceptibility in people of African ancestry. Here, we examined genome-wide and candidate gene associations with systolic blood pressure (SBP) and diastolic blood pressure (DBP) using the Candidate Gene Association Resource (CARe) consortium consisting of 8591 AAs. Genotypes included genome-wide single-nucleotide polymorphism (SNP) data utilizing the Affymetrix 6.0 array with imputation to 2.5 million HapMap SNPs and candidate gene SNP data utilizing a 50K cardiovascular gene-centric array (ITMAT-Broad-CARe [IBC] array). For Affymetrix data, the strongest signal for DBP was rs10474346 (P= 3.6 × 10(-8)) located near GPR98 and ARRDC3. For SBP, the strongest signal was rs2258119 in C21orf91 (P= 4.7 × 10(-8)). The top IBC association for SBP was rs2012318 (P= 6.4 × 10(-6)) near SLC25A42 and for DBP was rs2523586 (P= 1.3 × 10(-6)) near HLA-B. None of the top variants replicated in additional AA (n = 11 882) or European-American (n = 69 899) cohorts. We replicated previously reported European-American blood pressure SNPs in our AA samples (SH2B3, P= 0.009; TBX3-TBX5, P= 0.03; and CSK-ULK3, P= 0.0004). These genetic loci represent the best evidence of genetic influences on SBP and DBP in AAs to date. More broadly, this work supports that notion that blood pressure among AAs is a trait with genetic underpinnings but also with significant complexity

Genetic variants in novel pathways influence blood pressure and cardiovascular disease risk.

Blood pressure is a heritable trait influenced by several biological pathways and responsive to environmental stimuli. Over one billion people worldwide have hypertension (≥140 mm Hg systolic blood pressure or  ≥90 mm Hg diastolic blood pressure). Even small increments in blood pressure are associated with an increased risk of cardiovascular events. This genome-wide association study of systolic and diastolic blood pressure, which used a multi-stage design in 200,000 individuals of European descent, identified sixteen novel loci: six of these loci contain genes previously known or suspected to regulate blood pressure (GUCY1A3-GUCY1B3, NPR3-C5orf23, ADM, FURIN-FES, GOSR2, GNAS-EDN3); the other ten provide new clues to blood pressure physiology. A genetic risk score based on 29 genome-wide significant variants was associated with hypertension, left ventricular wall thickness, stroke and coronary artery disease, but not kidney disease or kidney function. We also observed associations with blood pressure in East Asian, South Asian and African ancestry individuals. Our findings provide new insights into the genetics and biology of blood pressure, and suggest potential novel therapeutic pathways for cardiovascular disease prevention

Causal effect of plasminogen activator inhibitor type 1 on coronary heart disease

Background--Plasminogen activator inhibitor type 1 (PAI-1) plays an essential role in the fibrinolysis system and thrombosis. Population studies have reported that blood PAI-1 levels are associated with increased risk of coronary heart disease (CHD). However, it is unclear whether the association reflects a causal influence of PAI-1 on CHD risk. Methods and Results--To evaluate the association between PAI-1 and CHD, we applied a 3-step strategy. First, we investigated the observational association between PAI-1 and CHD incidence using a systematic review based on a literature search for PAI-1 and CHD studies. Second, we explored the causal association between PAI-1 and CHD using a Mendelian randomization approach using summary statistics from large genome-wide association studies. Finally, we explored the causal effect of PAI-1 on cardiovascular risk factors including metabolic and subclinical atherosclerosis measures. In the systematic meta-analysis, the highest quantile of blood PAI-1 level was associated with higher CHD risk comparing with the lowest quantile (odds ratio=2.17; 95% CI: 1.53, 3.07) in an age- and sex-adjusted model. The effect size was reduced in studies using a multivariable-adjusted model (odds ratio=1.46; 95% CI: 1.13, 1.88). The Mendelian randomization analyses suggested a causal effect of increased PAI-1 level on CHD risk (odds ratio=1.22 per unit increase of log-transformed PAI-1; 95% CI: 1.01, 1.47). In addition, we also detected a causal effect of PAI-1 on elevating blood glucose and high-density lipoprotein cholesterol. Conclusions--Our study indicates a causal effect of elevated PAI-1 level on CHD risk, which may be mediated by glucose dysfunction

New genetic loci link adipose and insulin biology to body fat distribution.

Body fat distribution is a heritable trait and a well-established predictor of adverse metabolic outcomes, independent of overall adiposity. To increase our understanding of the genetic basis of body fat distribution and its molecular links to cardiometabolic traits, here we conduct genome-wide association meta-analyses of traits related to waist and hip circumferences in up to 224,459 individuals. We identify 49 loci (33 new) associated with waist-to-hip ratio adjusted for body mass index (BMI), and an additional 19 loci newly associated with related waist and hip circumference measures (P < 5 × 10(-8)). In total, 20 of the 49 waist-to-hip ratio adjusted for BMI loci show significant sexual dimorphism, 19 of which display a stronger effect in women. The identified loci were enriched for genes expressed in adipose tissue and for putative regulatory elements in adipocytes. Pathway analyses implicated adipogenesis, angiogenesis, transcriptional regulation and insulin resistance as processes affecting fat distribution, providing insight into potential pathophysiological mechanisms