scholarly journals Pan-Arctic seasonal cycles and long-term trends of aerosol properties from ten observatories

2021 ◽  
Author(s):  
Julia Schmale ◽  
Sangeeta Sharma ◽  
Stefano Decesari ◽  
Jakob Pernov ◽  
Andreas Massling ◽  
...  
Keyword(s):  
Black Carbon ◽  
Methanesulfonic Acid ◽  
The Arctic ◽  
Anthropogenic Emissions ◽  
Natural Sources ◽  
Arctic Haze ◽  
Long Term Trends ◽  
Aerosol Properties ◽  
Natural Aerosol

Abstract. Even though the Arctic is remote, aerosol properties observed there are strongly influenced by anthropogenic emissions from outside the Arctic. This is particularly true for the so-called Arctic haze season (January through April). In summer (June through September), when atmospheric transport patterns change, and precipitation is more frequent, local Arctic, i.e. natural sources of aerosols and precursors, play an important role. Over the last decades, significant reductions in anthropogenic emissions have taken place. At the same time a large body of literature shows evidence that the Arctic is undergoing fundamental environmental changes due to climate forcing, leading to enhanced emissions by natural processes that may impact aerosol properties. In this study, we analyze nine aerosol chemical species and four particle optical properties from ten Arctic observatories (Alert, Gruvebadet, Kevo, Pallas, Summit, Thule, Tiksi, Barrow, Villum, Zeppelin) to understand changes in anthropogenic and natural aerosol contributions. Variables include equivalent black carbon, particulate sulfate, nitrate, ammonium, methanesulfonic acid, sodium, iron, calcium and potassium, as well as scattering and absorption coefficients, single scattering albedo and scattering Ångström exponent. First, annual cycles are investigated, which despite anthropogenic emission reductions still show the Arctic haze phenomenon. Second, long-term trends are studied using the Mann-Kendall Theil-Sen slope method. We find in total 28 significant trends over full station records, i.e. spanning more than a decade, compared to 17 significant decadal trends. The majority of significantly declining trends is from anthropogenic tracers and occurred during the haze period, driven by emission changes between 1990 and 2000. For the summer period, no uniform picture of trends has emerged. Twenty-one percent of trends, i.e. eleven out of 57, are significant, and of those five are positive and six are negative. Negative trends include not only anthropogenic tracers such as equivalent black carbon at Kevo, but also natural indicators such as methanesulfonic acid and non-sea salt calcium at Alert. Positive trends are observed for sulfate at Zeppelin and Gruvebadet. No clear evidence of a significant change in the natural aerosol contribution can be observed yet. However, testing the sensitivity of the Mann-Kendall Theil-Sen method, we find that monotonic changes of around 5 % per year in an aerosol property are needed to detect a significant trend within one decade. This highlights that long-term efforts well beyond a decade are needed to capture smaller changes. It is particularly important to understand the ongoing natural changes in the Arctic, where interannual variability can be high, such as with forest fire emissions and their influence on the aerosol population. To investigate the climate-change induced influence on the aerosol population and the resulting climate feedback, long-term observations of tracers more specific to natural sources are needed, as well as of particle microphysical properties such as size distributions, which can be used to identify changes in particle populations which are not well captured by mass-oriented methods such as bulk chemical composition.

scholarly journals Long-term trends of black carbon and sulphate aerosol in the Arctic: changes in atmospheric transport and source region emissions

2010 ◽  
Vol 10 (5) ◽  
pp. 12133-12184 ◽  
Author(s):  
D. Hirdman ◽  
J. F. Burkhart ◽  
H. Sodemann ◽  
S. Eckhardt ◽  
A. Jefferson ◽  
...  
Keyword(s):  
Black Carbon ◽  
Atmospheric Circulation ◽  
Atmospheric Transport ◽  
Particle Dispersion ◽  
Downward Trend ◽  
The Arctic ◽  
Northern Eurasia ◽  
Source Regions ◽  
Long Term Trends

Abstract. As a part of the IPY project POLARCAT (Polar Study using Aircraft, Remote Sensing, Surface Measurements and Models, of Climate, Chemistry, Aerosols and Transport) and building on previous work (Hirdman et al., 2010), this paper studies the long-term trends of both atmospheric transport as well as equivalent black carbon (EBC) and sulphate for the three Arctic stations Alert, Barrow and Zeppelin. We find a general downward trend in the measured EBC concentrations at all three stations, with a decrease of −2.1±0.4 ng m−3 yr−1 (for the years 1989–2008) and −1.4±0.8 ng m−3 yr−1 (2002–2009) at Alert and Zeppelin respectively. The decrease at Barrow is, however, not statistically significant. The measured sulphate concentrations show a decreasing trend at Alert and Zeppelin of −15±3 ng m−3 yr−1 (1985–2006) and −1.3±1.2 ng m−3 yr−1 (1990–2008) respectively, while the trend at Barrow is unclear. To reveal the influence of different source regions on these trends, we used a cluster analysis of the output of the Lagrangian particle dispersion model FLEXPART run backward in time from the measurement stations. We have investigated to what extent variations in the atmospheric circulation, expressed as variations in the frequencies of the transport from four source regions with different emission rates, can explain the long-term trends in EBC and sulphate measured at these stations. We find that the long-term trend in the atmospheric circulation can only explain a minor fraction of the overall downward trend seen in the measurements of EBC (0.3–7.2%) and sulphate (0.3–5.3%) at the Arctic stations. The changes in emissions are dominant in explaining the trends. We find that the highest EBC and sulphate concentrations are associated with transport from Northern Eurasia and decreasing emissions in this region drive the downward trends. Northern Eurasia (cluster: NE, WNE and ENE) is the dominant emission source at all Arctic stations for both EBC and sulphate during most seasons. In wintertime, there are indications that the EBC emissions from the eastern parts of Northern Eurasia (ENE cluster) have increased over the last decade.

scholarly journals Long-term trends of black carbon and sulphate aerosol in the Arctic: changes in atmospheric transport and source region emissions

2010 ◽  
Vol 10 (19) ◽  
pp. 9351-9368 ◽  
Author(s):  
D. Hirdman ◽  
J. F. Burkhart ◽  
H. Sodemann ◽  
S. Eckhardt ◽  
A. Jefferson ◽  
...  
Keyword(s):  
Black Carbon ◽  
Atmospheric Circulation ◽  
Atmospheric Transport ◽  
Particle Dispersion ◽  
Downward Trend ◽  
The Arctic ◽  
Northern Eurasia ◽  
Source Regions ◽  
Long Term Trends

Abstract. As a part of the IPY project POLARCAT (Polar Study using Aircraft, Remote Sensing, Surface Measurements and Models, of Climate, Chemistry, Aerosols and Transport) and building on previous work (Hirdman et al., 2010), this paper studies the long-term trends of both atmospheric transport as well as equivalent black carbon (EBC) and sulphate for the three Arctic stations Alert, Barrow and Zeppelin. We find a general downward trend in the measured EBC concentrations at all three stations, with a decrease of −2.1±0.4 ng m−3 yr−1 (for the years 1989–2008) and −1.4±0.8 ng m−3 yr−1 (2002–2009) at Alert and Zeppelin respectively. The decrease at Barrow is, however, not statistically significant. The measured sulphate concentrations show a decreasing trend at Alert and Zeppelin of −15±3 ng m−3 yr−1 (1985–2006) and −1.3±1.2 ng m−3 yr−1 (1990–2008) respectively, while there is no trend detectable at Barrow. To reveal the contribution of different source regions on these trends, we used a cluster analysis of the output of the Lagrangian particle dispersion model FLEXPART run backward in time from the measurement stations. We have investigated to what extent variations in the atmospheric circulation, expressed as variations in the frequencies of the transport from four source regions with different emission rates, can explain the long-term trends in EBC and sulphate measured at these stations. We find that the long-term trend in the atmospheric circulation can only explain a minor fraction of the overall downward trend seen in the measurements of EBC (0.3–7.2%) and sulphate (0.3–5.3%) at the Arctic stations. The changes in emissions are dominant in explaining the trends. We find that the highest EBC and sulphate concentrations are associated with transport from Northern Eurasia and decreasing emissions in this region drive the downward trends. Northern Eurasia (cluster: NE, WNE and ENE) is the dominant emission source at all Arctic stations for both EBC and sulphate during most seasons. In wintertime, there are indications that the EBC emissions from the eastern parts of Northern Eurasia (ENE cluster) have increased over the last decade.

Aerosol black carbon measurements in the Arctic haze during AGASP-II

1989 ◽  
Vol 9 (1-3) ◽  
pp. 347-361 ◽  
Author(s):  
A. D. A. Hansen ◽  
T. Novakov
Keyword(s):  
Black Carbon ◽  
The Arctic ◽  
Arctic Haze

Comparison of the Long-Term Trends of the Largest Waves in the Ice-Free Arctic Waters From Different Reanalysis Products

2018 ◽  
Author(s):  
Takuji Waseda ◽  
Takehiko Nose ◽  
Adrean Webb
Keyword(s):  
Arctic Ocean ◽  
The Arctic ◽  
Extreme Value Analysis ◽  
Positive Trend ◽  
Value Analysis ◽  
The Arctic Ocean ◽  
Ship Route ◽  
Long Term Trends ◽  
Horizontal Grid

The long-term trends of the expected largest waves in the ice-free Arctic waters from Laptev to Beaufort Seas was studied analyzing the ERA-interim reanalysis from 1979 to 2016. The analysis showed that the positive trend is largest in October and increased almost 70 cm in 38 years. For ships navigating the Northern Ship Route, it is important to know what the possible largest waves to expect during its cruise. In view of conducting the extreme value analysis, the uncertainty of the largest wave needs to be validated. However, the observation in the Arctic Ocean is limited. We, therefore, rely on the reanalysis wave products in the Arctic Ocean, whose uncertainty is yet to be determined. ERA-Interim and ERA-5 are compared in the Laptev, the East Siberian, Chukchi and Beaufort Seas. The comparison is relevant as the two products differ in its horizontal grid resolution and availability of the satellite altimeter significant wave height data assimilation. During 2010–2016 when the ERA5 is available, only a small difference from ERA-Interim was detected in the mean. However, the expected largest waves in the domain tended to be large for the ERA-5, 8% normalized bias. The tendency was quite similar with a high correlation of 0.98.

scholarly journals Wave Climate from Spectra and Its Connections with Local and Remote Wind Climate

2019 ◽  
Vol 49 (2) ◽  
pp. 543-559 ◽  
Author(s):  
Haoyu Jiang ◽  
Lin Mu
Keyword(s):  
Wind Field ◽  
Wave Climate ◽  
The Arctic ◽  
Target Point ◽  
Wave Spectra ◽  
Basin Scale ◽  
Long Term Trends ◽  
Wind Climate ◽  
Climate Systems

AbstractWind-generated waves can propagate over large distances. Therefore, wave spectra from a fixed point can record information about air–sea interactions in distant areas. In this study, the spectral wave climate for a point in the tropical eastern Pacific Ocean is computed. Several well-defined wave climate systems are observed in the mean wave spectrum. Significant seasonal cycling, long-term trends, and correlations with the Southern Oscillation, the Arctic Oscillation, and the Antarctic Oscillation are observed in the local wave spectra, showing abundant climatic information. Projections of wind vectors on the directions pointing to the target location are used to connect the spectral wave climate and basin-scale wind climate, because significant correlations are observed between the wave spectra and the wind projections of both local and remote wind systems. The origins of all the identified wave climate systems, including the westerlies and the trade winds in both hemispheres, are clearly shown in wind projection maps. Some of these origins are thousands of kilometers away from the target point, demonstrating the validity of this connection. Comparisons are made between wave spectra and the corresponding local and remote wind fields with respect to seasonal and interannual variability and long-term trends. The results show that each frequency and direction of ocean wave spectra at a certain location can be approximately linked to the wind field for a geographical area, implying that it is feasible to reconstruct spectral wave climates from observational wind field data and monitor wind climates from observational wave spectra geographically far away.

STRATEGIC OPPORTUNITIES OF DEVELOPMENT OF INTERNATIONAL RELATIONS IN THE ARCTIC

2016 ◽  
Vol 11 (1) ◽  
pp. 114-119
Author(s):  
Медведев ◽  
Dmitriy Medvedev
Keyword(s):  
International Relations ◽  
Political Development ◽  
The Arctic ◽  
Security Dilemma ◽  
Security Environment ◽  
Political Cooperation ◽  
Long Term Trends ◽  
Development Prospects ◽  
Foreign Policy Strategies

The article describes the long-term trends in the development of international relations in the Arctic, the strategic importance of the region in modern international relations is proved. By analyzing the foreign policy strategies of the polar states the possible directions of international cooperation are formulated, threats to the development of constructive cooperation in the region are identified. The trends and key integration structures of military and political cooperation in the region are described, for the study of development prospects of the situation the concept of «security dilemma» is applied. The author describes the conditions necessary to reduce the tension in the region and the establishment of a non-confrontational model of world political development in the Arctic. In particular, the recognition of insolvency of isolation policy, as well as the rejection of the fragmentation of international security environment in the Arctic will allow to overcome the destructive tendencies of development and increase the possibility to maintain a mutually acceptable dialogue.

scholarly journals Current model capabilities for simulating black carbon and sulfate concentrations in the Arctic atmosphere: a multi-model evaluation using a comprehensive measurement data set

2015 ◽  
Vol 15 (16) ◽  
pp. 9413-9433 ◽  
Author(s):  
S. Eckhardt ◽  
B. Quennehen ◽  
D. J. L. Olivié ◽  
T. K. Berntsen ◽  
R. Cherian ◽  
...  
Keyword(s):  
Black Carbon ◽  
Atmospheric Chemistry ◽  
Emission Inventory ◽  
Dispersion Model ◽  
Measurement Data ◽  
Particle Dispersion ◽  
The Arctic ◽  
Late Winter ◽  
Data Set ◽  
Arctic Haze

Abstract. The concentrations of sulfate, black carbon (BC) and other aerosols in the Arctic are characterized by high values in late winter and spring (so-called Arctic Haze) and low values in summer. Models have long been struggling to capture this seasonality and especially the high concentrations associated with Arctic Haze. In this study, we evaluate sulfate and BC concentrations from eleven different models driven with the same emission inventory against a comprehensive pan-Arctic measurement data set over a time period of 2 years (2008–2009). The set of models consisted of one Lagrangian particle dispersion model, four chemistry transport models (CTMs), one atmospheric chemistry-weather forecast model and five chemistry climate models (CCMs), of which two were nudged to meteorological analyses and three were running freely. The measurement data set consisted of surface measurements of equivalent BC (eBC) from five stations (Alert, Barrow, Pallas, Tiksi and Zeppelin), elemental carbon (EC) from Station Nord and Alert and aircraft measurements of refractory BC (rBC) from six different campaigns. We find that the models generally captured the measured eBC or rBC and sulfate concentrations quite well, compared to previous comparisons. However, the aerosol seasonality at the surface is still too weak in most models. Concentrations of eBC and sulfate averaged over three surface sites are underestimated in winter/spring in all but one model (model means for January–March underestimated by 59 and 37 % for BC and sulfate, respectively), whereas concentrations in summer are overestimated in the model mean (by 88 and 44 % for July–September), but with overestimates as well as underestimates present in individual models. The most pronounced eBC underestimates, not included in the above multi-site average, are found for the station Tiksi in Siberia where the measured annual mean eBC concentration is 3 times higher than the average annual mean for all other stations. This suggests an underestimate of BC sources in Russia in the emission inventory used. Based on the campaign data, biomass burning was identified as another cause of the modeling problems. For sulfate, very large differences were found in the model ensemble, with an apparent anti-correlation between modeled surface concentrations and total atmospheric columns. There is a strong correlation between observed sulfate and eBC concentrations with consistent sulfate/eBC slopes found for all Arctic stations, indicating that the sources contributing to sulfate and BC are similar throughout the Arctic and that the aerosols are internally mixed and undergo similar removal. However, only three models reproduced this finding, whereas sulfate and BC are weakly correlated in the other models. Overall, no class of models (e.g., CTMs, CCMs) performed better than the others and differences are independent of model resolution.

scholarly journals Long-term trends of surface ozone and its influencing factors at the Mt. Waliguan GAW station, China, Part 2: Variation mechanism and links to some climate indices

2017 ◽  
Author(s):  
Wanyun Xu ◽  
Xiaobin Xu ◽  
Meiyun Lin ◽  
Weili Lin ◽  
Jie Tang ◽  
...  
Keyword(s):  
Southeast Asia ◽  
Trajectory Analysis ◽  
Surface Ozone ◽  
Eastern China ◽  
Sunspot Cycle ◽  
Anthropogenic Emissions ◽  
Climate Indices ◽  
Air Masses ◽  
Long Term Trends

Abstract. Interannual variability and long-term trends of tropospheric ozone are both of environmental and climate concerns. Ozone measured at Mt. Waliguan Observatory (WLG, 3816 m asl) on the Tibetan Plateau over the period 19947ndash;2013 has increased significantly by 0.2–0.3 ppbv year-1 during spring and autumn, but shows a much smaller trend in winter and no significant trend in summer. Here we explore the factors driving the observed ozone changes at WLG using backward trajectory analysis, chemistry-climate model hindcast simulations (GFDL-AM3), a trajectory-mapped ozonesonde dataset and various climate indices. A stratospheric ozone tracer implemented in GFDL-AM3 indicates that stratosphere-to-troposphere transport (STT) can explain ~ 70 % of the observed springtime ozone increase at WLG, consistent with an increase in the NW air mass frequency inferred from the trajectory analysis. Enhanced STT associated with the strengthening of the mid-latitude jet stream contributes to the observed high-ozone anomalies at WLG during the springs of 1999 and 2012. During autumn, observations at WLG are more heavily influenced by polluted air masses originated from Southeast Asia than in the other seasons. Rising Asian anthropogenic emissions of ozone precursors is the key driver of increasing autumnal ozone observed at WLG, as supported by the GFDL-AM3 model with time-varying emissions, which captures the observed ozone increase (0.26 ± 0.11 ppbv year-1). AM3 simulates a greater ozone increase of 0.38 ± 0.11 ppbv year-1 at WLG in autumn under conditions with strong transport from Southeast Asia and shows no significant ozone trend in autumn when anthropogenic emissions are held constant in time. During summer, WLG is mostly influenced by easterly air masses but these trajectories do not extend to the polluted regions of eastern China and have decreased significantly over the last two decades, which likely explains why summertime ozone measured at WLG shows no significant trend despite ozone increases in Eastern China. Analysis of the Trajectory-mapped Ozonesonde dataset for the Stratosphere and Troposphere (TOST) and trajectory residence time reveals increases in direct ozone transport from the eastern sector during autumn, which adds to the autumnal ozone increase. We further examine the links of ozone variability at WLG to the QBO, the North Atlantic Oscillation (NAO), the East Asian summer monsoon (EASM) and the sunspot cycle. Our results suggest that the 2–3 year, 3–7 year and 11 year periodicities are linked to QBO, EASMI and NAO and the sunspot cycle, respectively. A multivariate regression analysis is performed to quantify the relative contributions of various factors to surface ozone concentrations at WLG. Through an observational and modelling analysis, this study demonstrates the complex relationships between surface ozone at remote locations and its dynamical and chemical influencing factors.

scholarly journals Effect of changing NO<sub><i>x</i></sub> lifetime on the seasonality and long-term trends of satellite-observed tropospheric NO<sub>2</sub> columns over China

2019 ◽  
Author(s):  
Viral Shah ◽  
Daniel J. Jacob ◽  
Ke Li ◽  
Rachel F. Silvern ◽  
Shixian Zhai ◽  
...  
Keyword(s):  
Transport Model ◽  
Eastern China ◽  
Anthropogenic Emissions ◽  
Organic Nitrates ◽  
Nox Emissions ◽  
Chemical Transport Model ◽  
Volatile Organic ◽  
Tropospheric No2 ◽  
Long Term Trends

Abstract. Satellite observations of tropospheric NO2 columns are extensively used to infer trends in anthropogenic emissions of nitrogen oxides (NOx ≡ NO + NO2), but this may be complicated by trends in NOx lifetime. Here we use 2004–2018 observations from the OMI satellite-based instrument (QA4ECV and POMINO v2 retrievals) to examine the seasonality and trends of tropospheric NO2 columns over central-eastern China, and we interpret the results with the GEOS-Chem chemical transport model. The observations show a factor of 3 increase in NO2 columns from summer to winter, which we explain in GEOS-Chem as reflecting a longer NOx lifetime in winter than in summer (21 h versus 5.9 h in 2017). The 2005–2018 summer trends of OMI NO2 closely follow the trends in the Multi-resolution Emission Inventory for China (MEIC), with a rise over the 2005–2011 period and a 25 % decrease since. We find in GEOS-Chem no significant trend of the NOx lifetime in summer, supporting the emission trend reported by MEIC. The winter trend of OMI NO2 is steeper than in summer over the entire period, which we attribute to a decrease in NOx lifetime at lower NOx emissions. Half of the NOx sink in winter is from N2O5 hydrolysis, which counterintuitively becomes more efficient as NOx emissions decrease due to less titration of ozone at night. Formation of organic nitrates also becomes an increasing sink of NOx as NOx emissions decrease but emissions of volatile organic compounds (VOCs) do not.

scholarly journals Long-term trends of the Polar and Arctic cells influencing the Arctic climate since 1989

2016 ◽  
Vol 121 (6) ◽  
pp. 2679-2690 ◽  
Author(s):  
Weihong Qian ◽  
Kaijun Wu ◽  
Jeremy Cheuk-Hin Leung ◽  
Jian Shi
Keyword(s):  
Arctic Climate ◽  
The Arctic ◽  
Long Term Trends
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