Found 9985 publications. Showing page 63 of 400:
As the leading climate mode of wintertime climate variability over Europe, the North Atlantic Oscillation (NAO) has been extensively studied over the last decades. Recently, studies highlighted the state of the Eurasian cryosphere as a possible predictor for the wintertime NAO. However, missing correlation between snow cover and wintertime NAO in climate model experiments and strong non-stationarity of this link in reanalysis data are questioning the causality of this relationship.
Here we use the large ensemble of Atmospheric Seasonal Forecasts of the 20th Century (ASF-20C) with the European Centre for Medium-Range Weather Forecasts model, focusing on the winter season. Besides the main 110-year ensemble of 51 members, we investigate a second, perturbed ensemble of 21 members where initial (November) land conditions over the Northern Hemisphere are swapped from neighboring years. The Eurasian snow–NAO linkage is examined in terms of a longitudinal snow depth dipole across Eurasia. Subsampling the perturbed forecast ensemble and contrasting members with high and low initial snow dipole conditions, we found that their composite difference indicates more negative NAO states in the following winter (DJF) after positive west-to-east snow depth gradients at the beginning of November. Surface and atmospheric forecast anomalies through the troposphere and stratosphere associated with the anomalous positive snow dipole consist of colder early winter surface temperatures over eastern Eurasia, an enhanced Ural ridge and increased vertical energy fluxes into the stratosphere, with a subsequent negative NAO-like signature in the troposphere. We thus confirm the existence of a causal connection between autumn snow patterns and subsequent winter circulation in the ASF-20C forecasting system.
2021
Svalbard Integrated Arctic Earth Observing System (SIOS) is an international partnership of research institutions studying the environment and climate in and around Svalbard. SIOS is developing an efficient observing system, where researchers share technology, experience, and data, work together to close knowledge gaps, and decrease the environmental footprint of science. SIOS maintains and facilitates various scientific activities such as the State of the Environmental Science in Svalbard (SESS) report, international access to research infrastructure in Svalbard, Earth observation and remote sensing services, training courses for the Arctic science community, and open access to data. This perspective paper highlights the activities of SIOS Knowledge Centre, the central hub of SIOS, and the SIOS Remote Sensing Working Group (RSWG) in response to the unprecedented situation imposed by the global pandemic coronavirus (SARS-CoV-2) disease 2019 (COVID-19). The pandemic has affected Svalbard research in several ways. When Norway declared a nationwide lockdown to decrease the rate of spread of the COVID-19 in the community, even more strict measures were taken to protect the Svalbard community from the potential spread of the disease. Due to the lockdown, travel restrictions, and quarantine regulations declared by many nations, most physical meetings, training courses, conferences, and workshops worldwide were cancelled by the first week of March 2020. The resumption of physical scientific meetings is still uncertain in the foreseeable future. Additionally, field campaigns to polar regions, including Svalbard, were and remain severely affected. In response to this changing situation, SIOS initiated several operational activities suitable to mitigate the new challenges resulting from the pandemic. This article provides an extensive overview of SIOS’s Earth observation (EO), remote sensing (RS) and other operational activities strengthened and developed in response to COVID-19 to support the Svalbard scientific community in times of cancelled/postponed field campaigns in Svalbard. These include (1) an initiative to patch up field data (in situ) with RS observations, (2) a logistics sharing notice board for effective coordinating field activities in the pandemic times, (3) a monthly webinar series and panel discussion on EO talks, (4) an online conference on EO and RS, (5) the SIOS’s special issue in the Remote Sensing (MDPI) journal, (6) the conversion of a terrestrial remote sensing training course into an online edition, and (7) the announcement of opportunity (AO) in airborne remote sensing for filling the data gaps using aerial imagery and hyperspectral data. As SIOS is a consortium of 24 research institutions from 9 nations, this paper also presents an extensive overview of the activities from a few research institutes in pandemic times and highlights our upcoming activities for the next year 2021. Finally, we provide a critical perspective on our overall response, possible broader impacts, relevance to other observing systems, and future directions. We hope that our practical services, experiences, and activities implemented in these difficult times will motivate other similar monitoring programs and observing systems when responding to future challenging situations. With a broad scientific audience in mind, we present our perspective paper on activities in Svalbard as a case study.
Earth observation; Remote sensing; COVID-19; Svalbard; Earth System Science; SIOS
2021
2021
2021
Microfibers (MF) are one of the major classes of microplastic found in the marine environment on a global scale. Very little is known about how they move and distribute from point sources such as wastewater effluents into the ocean. We chose Adventfjorden near the settlement of Longyearbyen on the Arctic Svalbard archipelago as a case study to investigate how microfibers emitted with untreated wastewater will distribute in the fjord, both on a spatial and temporal scale. Fiber abundance in the effluent was estimated from wastewater samples taken during two one-week periods in June and September 2017. Large emissions of MFs were detected, similar in scale to a modern WWTP serving 1.3 million people and providing evidence of the importance of untreated wastewater from small settlements as major local sources for MF emissions in the Arctic. Fiber movement and distribution in the fjord mapped using an online-coupled hydrodynamic-drift model (FVCOM-FABM). For parameterizing a wider spectrum of fibers from synthetic to wool, four different density classes of MFs, i.e., buoyant, neutral, sinking, and fast sinking fibers are introduced to the modeling framework. The results clearly show that fiber class has a large impact on the fiber distributions. Light fibers remained in the surface layers and left the fjord quickly with outgoing currents, while heavy fibers mostly sank to the bottom and deposited in the inner parts of the fjord and along the northern shore. A number of accumulation sites were identified within the fjord. The southern shore, in contrast, was much less affected, with low fiber concentrations throughout the modeling period. Fiber distributions were then compared with published pelagic and benthic fauna distributions in different seasons at selected stations around the fjord. The ratios of fibers to organisms showed a very wide range, indicating hot spots of encounter risk for pelagic and benthic biota. This approach, in combination with in-situ ground-truthing, can be instrumental in understanding microplastic pathways and fate in fjord systems and coastal areas and help authorities develop monitoring and mitigation strategies for microfiber and microplastic pollution in their local waters.
2021
The Monitoring Nitrous Oxide Sources (MIN
The Monitoring Nitrous Oxide Sources (MIN2OS) satellite project aims at monitoring global-scale nitrous oxide (N2O) sources by retrieving N2O surface fluxes from the inversion of space-borne N2O measurements that are sensitive to the lowermost atmospheric layers under favorable conditions. MIN2OS will provide emission estimates of N2O at a horizontal resolution of 1° × 1° on the global scale and 10 × 10 km2 on the regional scale on a weekly to monthly basis depending on the application (e.g., agriculture, national inventories, policy, scientific research). Our novel approach is based on the development of: 1) a space-borne instrument operating in the Thermal InfraRed domain providing, in clear sky conditions, N2O mixing ratio in the lowermost atmosphere (900 hPa) under favorable conditions (summer daytime) over land and under favorable and unfavorable (winter nighttime) conditions over the ocean and 2) an atmospheric inversion framework to estimate N2O surface fluxes from the atmospheric satellite observations. After studying three N2O spectral bands (B1 at 1240–1350 cm−1, B2 at 2150–2260 cm−1 and B3 at 2400–2600 cm−1), a new TIR instrument will be developed, centered at 1250–1330 cm−1, with a resolution of 0.125 cm−1, a Full Width at Half Maximum of 0.25 cm−1 and a swath of 300 km. To optimally constrain the retrieval of N2O vertical profiles, the instrument will be on-board a platform at ~830 km altitude in a sun-synchronous orbit crossing the Equator in descending node at 09:30 local time in synergy with two other platforms (Metop-SG and Sentinel-2 NG) expected to fly in 2031–32 aiming at detecting surface properties, agricultural information on the field scale and vertical profiles of atmospheric constituents and temperature. The lifetime of the MIN2OS project would be 4–5 years to study the interannual variability of N2O surface fluxes. The spectral noise can be decreased by at least a factor of 5 compared to the lowest noise accessible to date with the Infrared Atmospheric Sounding Interferometer-New Generation (IASI-NG) mission. The N2O total error is expected to be less than ~1% (~3 ppbv) along the vertical. The preliminary design of the MIN2OS project results in a small instrument (payload of 90 kg, volume of 1200 × 600 × 300 mm3) with, in addition to the spectrometer, a wide field and 1-km resolution imager for cloud detection. The instruments could be hosted on a small platform, the whole satellite being largely compatible with a dual launch on VEGA-C. The MIN2OS project has been submitted to the European Space Agency Earth Explorer 11 mission ideas.
2021
2021
Dimethyl Sulfide-Induced Increase in Cloud Condensation Nuclei in the Arctic Atmosphere
Oceanic dimethyl sulfide (DMS) emissions have been recognized as a biological regulator of climate by contributing to cloud formation. Despite decades of research, the climatic role of DMS remains ambiguous largely because of limited observational evidence for DMS-induced cloud condensation nuclei (CCN) enhancement. Here, we report concurrent measurement of DMS, physiochemical properties of aerosol particles, and CCN in the Arctic atmosphere during the phytoplankton bloom period of 2010. We encountered multiple episodes of new particle formation (NPF) and particle growth when DMS mixing ratios were both low and high. The growth of particles to sizes at which they can act as CCN accelerated in response to an increase in atmospheric DMS. Explicitly, the sequential increase in all relevant parameters (including the source rate of condensable vapor, the growth rate of particles, Aitken mode particles, hygroscopicity, and CCN) was pronounced at the DMS-derived NPF and particle growth events. This field study unequivocally demonstrates the previously unconfirmed roles of DMS in the growth of particles into climate-relevant size and eventual CCN activation.
2021
Integrated water vapor during rain and rain-free conditions above the Swiss Plateau
Water vapor column density, or vertically-integrated water vapor (IWV), is monitored by ground-based microwave radiometers (MWR) and ground-based receivers of the Global Navigation Satellite System (GNSS). For rain periods, the retrieval of IWV from GNSS Zenith Wet Delay (ZWD) neglects the atmospheric propagation delay of the GNSS signal by rain droplets. Similarly, it is difficult for ground-based dual-frequency single-polarisation microwave radiometers to separate the microwave emission of water vapor and cloud droplets from the rather strong microwave emission of rain. For ground-based microwave radiometry at Bern (Switzerland), we take the approach that IWV during rain is derived from linearly interpolated opacities before and after the rain period. The intermittent rain periods often appear as spikes in the time series of integrated liquid water (ILW) and are indicated by ILW ≥ 0.4 mm. In the present study, we assume that IWV measurements from radiosondes are not affected by rain. We intercompare the climatologies of IWV(rain), IWV(no rain), and IWV(all) obtained by radiosonde, ground-based GNSS atmosphere sounding, ground-based MWR, and ECMWF reanalysis (ERA5) at Payerne and Bern in Switzerland. In all seasons, IWV(rain) is 3.75 to 5.94 mm greater than IWV(no rain). The mean IWV differences between GNSS and radiosonde at Payerne are less than 0.26 mm. The datasets at Payerne show a better agreement than the datasets at Bern. However, the MWR at Bern agrees with the radiosonde at Payerne within 0.41 mm for IWV(rain) and 0.02 mm for IWV(no rain). Using the GNSS and rain gauge measurements at Payerne, we find that IWV(rain) increases with increase of the precipitation rate during summer as well as during winter. IWV(rain) above the Swiss Plateau is quite well estimated by GNSS and MWR though the standard retrievals are limited or hampered during rain periods.
2021
Fate of Springtime Atmospheric Reactive Mercury: Concentrations and Deposition at Zeppelin, Svalbard
Mid-latitude atmospheric elemental mercury (Hg) emissions undergo extensive oxidation to reactive Hg (RM) compounds during Arctic polar sunrise, resulting in enhanced atmospheric deposition that impacts Arctic marine wildlife and humans. It has been difficult to estimate RM dry deposition, because RM concentrations, compounds, and their deposition velocities are ill-defined. Here, we investigate RM concentrations sampled with membrane-based methods and find these to exceed denuder-based RM detection by 5 times at the Zeppelin Observatory on Svalbard (March 26–July 24, 2019). Measured dry deposition of gaseous oxidized Hg was about half of the modeled RM deposition, demonstrating that particulate-bound Hg was an important component of dry deposition. Using thermal membrane desorption, RM chemistry was found to be dominated by Hg–Cl/Br (51%) and Hg–N (45%) compounds. Back-trajectory analysis indicated that Hg–Br/Cl compounds were predominantly advected from within the marine boundary layer (sea ice exposure), while Hg–N originated from the free troposphere. Weekly average RM compound-specific dry deposition velocities ranged from 0.12 to 0.49 cm s–1, with a net RM dry deposition of 1.9 μg m–2 (1.5–2.5 μg m–2; 95% confidence interval) that exceeds the mean annual Hg wet deposition flux in Svalbard. Overall, we find that springtime atmospheric RM deposition has been underestimated in the Arctic marine environment.
2021
Black Carbon Emission Reduction Due to COVID-19 Lockdown in China
During the Lunar New Year Holiday of 2020, China implemented an unprecedented lockdown to fight the COVID-19 outbreak, which strongly affected the anthropogenic emissions. We utilized elemental carbon observations (equivalent to black carbon, BC) from 42 sites and performed inverse modeling to determine the impact of the lockdown on the weekly BC emissions and quantify the effect of the stagnant conditions on BC observations in densely populated eastern and northern China. BC emissions declined 70% (eastern China) and 48% (northern China) compared to the first half of January. In northern China, under the stagnant conditions of the first week of the lockdown, the observed BC concentrations rose unexpectedly (29%) even though the BC emissions fell. The emissions declined substantially thereafter until a week after the lockdown ended. On the contrary, in eastern China, BC emissions dropped sharply in the first week and recovered synchronously with the end of the lockdown.
2021
Black Carbon (BC) aerosol is a major climate forcer in the Arctic. Here, we present 15 years (2001–2015) of surface observations of the aerosol absorption coefficient babs (corresponding to Equivalent BC), obtained at the Zeppelin Observatory, Ny Ålesund, Svalbard, coupled with backward transport modeling with Flexpart in order to calculate the Potential Source Contribution Function (PSCF) for BC. The observed long-term variability superimposed on a strong annual cycle is studied as a function of large-scale circulation patterns represented by monthly index values for the North Atlantic Oscillation (NAO) and the Scandinavian pattern (SCAN). We find a 35% increase of babs values at Zeppelin during the SCAN+ phase in the winter half-year compared to the SCAN+ phase but no significant difference in babs values between the NAO index phases. Both NAO and SCAN induce significant regional variability on the areas of origin of babs, mainly Siberia, Europe, and North America.
2021
2021
The Tibetan Plateau (TP), referred to as the “Asian water tower,” contains one of the largest land ice masses on Earth. The local glacier shrinkage and frozen-water storage are strongly affected by variations in surface air temperature over the TP (TPSAT), especially in springtime. This study reveals that the relationship between the February North Atlantic Oscillation (NAO) and March TPSAT is unstable with time and regulated by the phase of the Atlantic multidecadal variability (AMV). The significant out-of-phase connection occurs only during the warm phase of AMV (AMV+). The results show that during the AMV+, the negative phase of the NAO persists from February to March, and is accompanied by a quasi-stationary Rossby wave train trapped along a northward-shifted subtropical westerly jet stream across Eurasia, inducing an anomalous adiabatic descent that warms the TP. However, during the cold phase of the AMV, the negative NAO cannot persist into March. The Rossby wave train propagates along the well-separated polar and subtropical westerly jets, and the NAO–TPSAT connection is broken. Further investigation suggests that the enhanced synoptic eddy and low-frequency flow (SELF) interaction over the North Atlantic in February and March during the AMV+, caused by the southward-shifted storm track, helps maintain the NAO pattern via positive eddy feedback. This study provides a new detailed perspective on the decadal variability of the North Atlantic–TP connection in late winter to early spring.
2021
The role of nature-based solutions for improving environmental quality, health and well-being
Nature-based solutions (NbS) have been positioned and implemented in urban areas as solutions for enhancing urban resilience in the face of a wide range of urban challenges. However, there is a lack of recommendations of optimal NbS and appropriate typologies fitting to different contexts and urban design. The analytical frameworks for NbS implementation and impact evaluation, that integrate NbS into local policy frameworks, socio-economic transition pathways, and spatial planning, remain fragmented. In this article, the NbS concept and its related terminologies are first discussed. Second, the types of NbS implemented in Europe are reviewed and their benefits over time are explored, prior to categorizing them and highlighting the key methods, criteria, and indicators to identify and assess the NbS’s impacts, co-benefits, and trade-offs. The latter involved a review of the websites of 52 projects and some relevant publications funded by EU Research and Innovation programs and other relevant publications. The results show that there is a shared understanding that the NbS concept encompasses benefits of restoration and rehabilitation of ecosystems, carbon neutrality, improved environmental quality, health and well-being, and evidence for such benefits. This study also shows that most NbS-related projects and activities in Europe use hybrid approaches, with NbS typically developed, tested, or implemented to target specific types of environmental–social–economic challenges. The results of this study indicate that NbS as a holistic concept would be beneficial in the context of climate action and sustainable solutions to enhance ecosystem resilience and adaptive capacity within cities. As such, this article provides a snapshot of the role of NbS in urban sustainability development, a guide to the state-of-the-art, and key messages and recommendations of this rapidly emerging and evolving field.
2021
Knowledge architecture for the wise governance of sustainability transitions
The need for sustainability transitions is widely recognised, along with a concurrent need for the evolution of knowledge systems to inform more effective policy action. Although there are many new policy targets relating to net zero emissions and other sustainability challenges, cities, regional and national governments are struggling to rapidly develop transformational policies to achieve them. As academics and practitioners who work at the science-policy interface, we identify specific knowledge and competency needs for governing sustainability transitions related to the interlinked phases of envisioning, implementing and evaluating. In short, coordinated reforms of both policy and knowledge systems are urgently needed to address the speed and scale of sustainability challenges. These include embedding systems thinking literacy, mainstreaming participatory policy making, expanding the capacity to undertake transdisciplinary research, more adaptive governance and continuous organisational learning. These processes must guide further knowledge development, uptake and use as part of an iterative and holistic process. Such deep-seated change in policy-knowledge systems will be disruptive and presents challenges for traditional organisational models of knowledge delivery, but is essential for successful sustainability transformations.
2021
2021
Målinger av PM10 i Lohavn. April og mai 2020.
NILU – Norsk institutt for luftforskning har på oppdrag fra HAV Eiendom utført målinger av svevestøv (PM10) i Lohavn i Oslo. Området skal utvikles til et nytt byområde med boliger, skole, utearealer og næring. PM-konsentrasjonen ble målt på tre steder i Lohavn for å kartlegge svevestøvkonsentrasjonen og mulige kilder. Måleprosjektet pågikk våren 2020. Mulige effekter av Covid-nedstengning, variasjoner i trafikkmengden i området og variasjoner av meteorologiske parametere på PM-konsentrasjonen er diskutert.
Måleresultatene viser lavere PM-konsentrasjon enn i måleperioden 2016/17. Årsaken var trolig bortfall av midlertidige kilder som førte til periodevis høye konsentrasjoner i 2016/17. De høyeste PM10-konsentrasjonene ble observert ved vind fra sør-sørvest (som dominerer på dagtid).
NILU
2021