Found 9849 publications. Showing page 284 of 394:
Pergamon Press
2018
Warm Arctic–cold Siberia: comparing the recent and the early 20th century Arctic warmings
The Warm Arctic–cold Siberia surface temperature pattern during recent boreal winter is suggested to be triggered by the ongoing decrease of Arctic autumn sea ice concentration and has been observed together with an increase in mid-latitude extreme events and a meridionalization of tropospheric circulation. However, the exact mechanism behind this dipole temperature pattern is still under debate, since model experiments with reduced sea ice show conflicting results. We use the early twentieth-century Arctic warming (ETCAW) as a case study to investigate the link between September sea ice in the Barents–Kara Sea (BKS) and the Siberian temperature evolution. Analyzing a variety of long-term climate reanalyses, we find that the overall winter temperature and heat flux trend occurs with the reduction of September BKS sea ice. Tropospheric conditions show a strengthened atmospheric blocking over the BKS, strengthening the advection of cold air from the Arctic to central Siberia on its eastern flank, together with a reduction of warm air advection by the westerlies. This setup is valid for both the ETCAW and the current Arctic warming period.
2018
2018
2018
Air quality in Norwegian cities in 2015. Evaluation Report for NBV Main Results.
This report documents the final deliveries of the first phase of development of the Norwegian Air Quality Planning Tool,
also called “Nasjonalt Beregningsverktøy” or NBV. The main purpose of NBV is to provide a common methodological and
information platform for local air quality modelling applications. The system is addressed to local and regional
environmental authorities, air quality experts and consulting companies. It is intended to help them meet the requirements
of current air quality legislation, to support local air quality planning and facilitate air quality good practices where people live.
The report constitutes a comprehensive user guide for the NBV services available at http://www.luftkvalitet-nbv.no. It
presents each of the different products developed at NBV, documents how the product has been calculated, provides
recommendations on how best to use it for planning purposes and explains the main strengths and limitations of each
product. The report also includes an extensive validation of the air quality information currently available at NBV.
NILU
2018
Equinors miljøovervåkingsprogram for Snøhvit. Overvåking av vegetasjon og jord – reanalyser i 2018
Petroleumsanlegget på Melkøya utenfor Hammerfest ble startet opp i 2007 og slipper ut karbon-dioksid (CO2), nitrogenoksider (NOx), metan (CH4), flyktige organiske forbindelser utenom metan (nmVOC), svoveldioksid (SO2) og hydrogensulfid (H2S) fra energiproduksjon og prosessanlegg. Utslipp av nitrogen og svovelholdige gasser kan generelt påvirke terrestriske økosystemer ved forsuring og gjødsling av jordsmonn og vegetasjon. Petroleumsanlegget på Melkøya tar imot naturgass fra feltene Snøhvit og Albatross i Barentshavet. Her prosesseres og nedkjøles natur-gassen til flytende gass (LNG) for videre distribuering. Utslippene fra LNG-anlegget er beregnet til å ligge under gjeldene kritiske tålegrenseverdier for terrestriske naturtyper, men tålegrense-verdiene i arktisk/alpine naturtyper er imidlertid usikre. For å kunne dokumentere eventuelle ef-fekter av utslipp til luft, ble det i 2006 (før utslipp) etablert et overvåkingsprogram for vegetasjon og jord i influensområdet fra LNG-anlegget på Melkøya. Grunnlagsundersøkelsen ble utført samme år, og det ble utført analyser i 2008, 2013 og 2018 etter samme metodikk som i 2006.
To overvåkingsområder ble opprettet i 2006, ett med estimert relativt høy avsetning av nitrogen, nordøst på Kvaløya ved Forsøl og ett område med relativt lav avsetning sør på Kvaløya ved Stangnes. Områdene er samkjørt med Norsk institutt for luftforskning (NILU) sine overvåkings-stasjoner for luft- og nedbørskvalitet. Innen hvert område utføres det en integrert overvåking av vegetasjonens artssammensetning og kjemisk innhold av planter og jord i to atskilte naturtyper (næringsfattig kreklinghei og litt kalkfattig og svakt intermediær jordvannsmyr).
Vegetasjonen overvåkes i permanent oppmerkede ruter (1m × 1m i arktisk hei og 0,5m × 0,5m på myr). I hver rute registreres mengde av karplanter, moser og lav, samt vegetasjonssjiktenes høyde og dekning. Lys reinlav/fjellreinlav (reinlav) og rusttorvmose analyseres for kjemisk inn-hold, Kjeldahl-nitrogen, tungmetallene bly (Pb), nikkel (Ni) og sink (Zn) og polyaromatiske hydro-karboner (PAH). Jordprøver fra hver av naturtypene analyseres for pH, Kjeldahl-nitrogen, ekstraherbare kationer, utbyttingskapasitet, basemetning, Pb, Ni, Zn og PAH. De kjemiske analysene av planter og jord utføres av Norsk institutt for bioøkonomi og NILU.
Analysene av vegetasjonens artssammensetning viste få endringer i mengdeforhold mellom artene fra 2006 til 2018. De små endringene vi fant skyldes trolig årlige variasjoner. Det ble funnet noen få endringer av arter som normalt responderer positivt på nitrogengjødsling, slik som gress. Lav har gått noe tilbake mest sannsynlig pga. økt beitepress fra rein. Det er således ingen indikasjon på at en eventuell forurensing fra LNG-anlegget på Melkøya har påvirket vegetasjonens artssammensetning og mengdeforholdet mellom arter.
NØKKELORD : Hammerfest, Melkøya, Kvaløya, LNG-anlegg, forurensing, forsuring, gjødsling, nitrogen, arktisk/ alpin vegetasjon, kreklinghei, myr, plantekjemi, jordkjemi, polyaromatiske hydrokarboner,
KEY WORDS : Hammerfest, Melkøya, Kvaløya, LNG plant, pollution, acidification, fertilization, nitrogen, arctic/ alpine vegetation, mire, plant chemistry, soil chemistry, polynuclear aromatic hydrocarbons
Norsk institutt for naturforskning
2018
2018
Based on observations of the chlorofluorocarbons CFC-13 (chlorotrifluoromethane), ΣCFC-114 (combined measurement of both isomers of dichlorotetrafluoroethane), and CFC-115 (chloropentafluoroethane) in atmospheric and firn samples, we reconstruct records of their tropospheric histories spanning nearly 8 decades. These compounds were measured in polar firn air samples, in ambient air archived in canisters, and in situ at the AGAGE (Advanced Global Atmospheric Gases Experiment) network and affiliated sites. Global emissions to the atmosphere are derived from these observations using an inversion based on a 12-box atmospheric transport model. For CFC-13, we provide the first comprehensive global analysis. This compound increased monotonically from its first appearance in the atmosphere in the late 1950s to a mean global abundance of 3.18 ppt (dry-air mole fraction in parts per trillion, pmol mol−1) in 2016. Its growth rate has decreased since the mid-1980s but has remained at a surprisingly high mean level of 0.02 ppt yr−1 since 2000, resulting in a continuing growth of CFC-13 in the atmosphere. ΣCFC-114 increased from its appearance in the 1950s to a maximum of 16.6 ppt in the early 2000s and has since slightly declined to 16.3 ppt in 2016. CFC-115 increased monotonically from its first appearance in the 1960s and reached a global mean mole fraction of 8.49 ppt in 2016. Growth rates of all three compounds over the past years are significantly larger than would be expected from zero emissions. Under the assumption of unchanging lifetimes and atmospheric transport patterns, we derive global emissions from our measurements, which have remained unexpectedly high in recent years: mean yearly emissions for the last decade (2007–2016) of CFC-13 are at 0.48 ± 0.15 kt yr−1 (> 15 % of past peak emissions), of ΣCFC-114 at 1.90 ± 0.84 kt yr−1 (∼ 10 % of peak emissions), and of CFC-115 at 0.80 ± 0.50 kt yr−1 (> 5 % of peak emissions). Mean yearly emissions of CFC-115 for 2015–2016 are 1.14 ± 0.50 kt yr−1 and have doubled compared to the 2007–2010 minimum. We find CFC-13 emissions from aluminum smelters but if extrapolated to global emissions, they cannot account for the lingering global emissions determined from the atmospheric observations. We find impurities of CFC-115 in the refrigerant HFC-125 (CHF2CF3) but if extrapolated to global emissions, they can neither account for the lingering global CFC-115 emissions determined from the atmospheric observations nor for their recent increases. We also conduct regional inversions for the years 2012–2016 for the northeastern Asian area using observations from the Korean AGAGE site at Gosan and find significant emissions for ΣCFC-114 and CFC-115, suggesting that a large fraction of their global emissions currently occur in northeastern Asia and more specifically on the Chinese mainland.
2018
2018
2018
2018
Coordinated numerical ensemble experiments with six different state-of-the-art atmosphere models have been used in order to evaluate the respective impact of the observed Arctic sea ice and sea surface temperature (SST) variations on air temperature variations in mid and high latitude land areas. Two sets of experiments have been designed; in the first set (EXP1), observed daily sea ice concentration and SST variations are used as lower boundary forcing over 1982–2014 while in the second set (EXP2) the SST variations are replaced by the daily SST climatology. The observed winter 2 m air temperature (T2m) variations are relatively well reproduced in a number of mid and high latitude land areas in EXP1, with best agreement in southwestern North America and northern Europe. Sea ice variations are important for the interannual T2m variations in northern Europe but have limited impact on all other mid and high latitude land regions. In particular, sea ice variations do not contribute to the observed opposite variations in the Arctic and mid latitude in our model experiments. The spread across ensemble members is large and many ensemble members are required to reproduce the observed T2m variations over northern Europe in our models. The amplitude of T2m anomalies in the coldest observed winters over northern Europe is not reproduced by our multi-model ensemble means. However, the sea ice conditions in these respective winters and mainly the thermodynamic response to the ice anomalies lead to an enhanced likelihood for occurrence of colder than normal winters and extremely cold winters. Still, the main reason for the observed extreme cold winters is internal atmospheric dynamics. The coldest simulated northern European winters in EXP1 and EXP2 between 1982 and 2014 show the same large scale T2m and atmospheric circulation anomaly patterns as the observed coldest winters, indicating that the models are well able to reproduce the processes, which cause these cold anomalies. The results are robust across all six models used in this study.
Springer
2018
Low concentrations of persistent organic pollutants (POPs) in air at Cape Verde
Ambient air is a core medium for monitoring of persistent organic pollutants (POPs) under the Stockholm Convention
and is used in studies of global transports of POPs and their atmospheric sources and source regions. Still,
data based on active air sampling remain scarce in many regions. The primary objectives of this study were to
(i) monitor concentrations of selected POPs in air outside West Africa, and (ii) to evaluate potential atmospheric
processes and source regions affecting measured concentrations. For this purpose, an active high-volume air
sampler was installed on the Cape Verde Atmospheric Observatory at Cape Verde outside the coast of West
Africa. Sampling commenced in May 2012 and 43 samples (24 h sampling) were collected until June 2013. The samples were analyzed for selected polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), hexachlorobenzene (HCB) and chlordanes. The concentrations of these POPs at Cape Verde were generally low and comparable to remote sites in the Arctic for several compounds. Seasonal trends varied between compounds and concentrations exhibited strong temperature dependence for chlordanes. Our results indicate
net volatilization fromthe Atlantic Ocean north of Cape Verde as sources of these POPs. Air mass back trajectories
demonstrated that air masses measured at Cape Verdewere generally transported fromthe Atlantic Ocean or the North African continent. Overall, the low concentrations in air at Cape Verde were likely explained by absence of major emissions in areas from which the air masses originated combined with depletion during long-range atmospheric
transport due to enhanced degradation under tropical conditions (high temperatures and concentrations of hydroxyl radicals).
Elsevier
2018
2018