| 1. |
- Aamaas, Borgar, et al.
(författare)
-
Elemental carbon deposition to Svalbard snow from Norwegian settlements and long-range transport
- 2011
-
Ingår i: Tellus. Series B, Chemical and physical meteorology. - : Stockholm University Press. - 0280-6509 .- 1600-0889. ; 63:3, s. 340-351
-
Tidskriftsartikel (refereegranskat)abstract
- The impact on snow pack albedo from local elemental carbon (EC) sources in Svalbard has been investigated for the winter of 2008. Highly elevated EC concentrations in the snow are observed around the settlements of Longyearbyen and Svea (locally > 1000 ng g(-1), about 200 times over the background level), while EC concentrations similar to the background level are seen around Ny-Alesund. Near Longyearbyen and Svea, darkened snow influenced by wind transported coal dust from open coal stockpiles is clearly visible from satellite images and by eye at the ground. As a first estimate, the reduction in snow albedo caused by local EC pollution from the Norwegian settlements has been compared to the estimated reduction caused by long-range transported EC for entire Svalbard. The effect of local EC from Longyearbyen, Svea and all Norwegian settlements are estimated to 2.1%, 7.9% and 10% of the total impact of EC, respectively. The EC particles tend to stay on the surface during melting, and elevated EC concentrations due to the spring melt was observed. This accumulation of EC enhances the positive albedo feedbacks. The EC concentrations were observed to be larger in metamorphosed snow than in fresh snow, and especially around ice lenses.
|
|
| 2. |
- Björkman, Mats P., et al.
(författare)
-
Nitrate dry deposition in svalbard
- 2013
-
Ingår i: Tellus. Series B, Chemical and physical meteorology. - : Stockholm University Press. - 0280-6509 .- 1600-0889. ; 65, s. 19071-
-
Tidskriftsartikel (refereegranskat)abstract
- Arctic regions are generally nutrient limited, receiving an extensive part of their bio-available nitrogen from the deposition of atmospheric reactive nitrogen. Reactive nitrogen oxides, as nitric acid (HNO3) and nitrate aerosols (p-NO3), can either be washed out from the atmosphere by precipitation or dry deposited, dissolving to nitrate (NO3-). During winter, NO3- is accumulated in the snowpack and released as a pulse during spring melt. Quantification of NO3- deposition is essential to assess impacts on Arctic terrestrial ecology and for ice core interpretations. However, the individual importance of wet and dry deposition is poorly quantified in the high Arctic regions where in-situ measurements are demanding. In this study, three different methods are employed to quantify NO3- dry deposition around the atmospheric and ecosystem monitoring site, Ny-Alesund, Svalbard, for the winter season (September 2009 to May 2010): (1) A snow tray sampling approach indicates a dry deposition of -10.27 +/- 3.84 mg m(-2) (+/- S.E.); (2) A glacial sampling approach yielded somewhat higher values -30.68 +/- 12.00 mg m(-2); and (3) Dry deposition was also modelled for HNO3 and p-NO3 using atmospheric concentrations and stability observations, resulting in a total combined nitrate dry deposition of -10.76 +/- 1.26 mg m(-2). The model indicates that deposition primarily occurs via HNO3 with only a minor contribution by p-NO3. Modelled median deposition velocities largely explain this difference: 0.63 cm s(-1) for HNO3 while p-NO3 was 0.0025 and 0.16 cm s(-1) for particle sizes 0.7 and 7 mm, respectively. Overall, the three methods are within two standard errors agreement, attributing an average 14% (total range of 2-44%) of the total nitrate deposition to dry deposition. Dry deposition events were identified in association with elevated atmospheric concentrations, corroborating recent studies that identified episodes of rapid pollution transport and deposition to the Arctic.
|
|
| 3. |
- Coz Diego, Esther, et al.
(författare)
-
Morphology and state of mixture of atmospheric soot aggregates during the winter season over Southern Asia-a quantitative approach
- 2011
-
Ingår i: Tellus. Series B, Chemical and physical meteorology. - : Stockholm University Press. - 0280-6509 .- 1600-0889. ; 63:1, s. 107-116
-
Tidskriftsartikel (refereegranskat)abstract
- The atmospheric brown cloud phenomena characterized by a high content of soot and a large impact on the solar radiative heating especially affects the tropical Indian Ocean during the winter season. The present study focuses on morphological characteristics and state of mixture of soot aggregates during the winter season over India. Given are quantitative measures of size, morphology and texture on aggregates collected in air at two different sites: Sinhagad near Pune in India and Hanimaadhoo in Maldives. For the latter site two different synoptic patterns prevailed: advection of air from the Arabian region and from the Indian subcontinent, respectively. Aggregates collected at Sinhagad, were associated with open branched structures, characteristic of fresh emission and diameters between 220 and 460 nm. The Hanimaadhoo aggregates were associated with aged closed structures, smaller sizes (130-360 nm) and frequently contained inorganic inclusions. Those arriving from the Indian subcontinent were characterized by the presence of an additional organic layer that covered the aggregate structure. These organic coatings might be a reasonable explanation of the low average wash-out ratios of soot two to seven times lower than that of nss-SO(4)2- that have been reported for air flow arriving at Hanimaadhoo from the Indian subcontinent in winter.
|
|
| 4. |
|
|
| 5. |
- Devasthale, Abhay, et al.
(författare)
-
The vertical distribution of thin features over the Arctic analysed from CALIPSO observations : Part 1: Optically thin clouds
- 2011
-
Ingår i: Tellus. Series B, Chemical and physical meteorology. - : Stockholm University Press. - 0280-6509 .- 1600-0889. ; 63:1, s. 77-85
-
Tidskriftsartikel (refereegranskat)abstract
- Clouds play a crucial role in the Arctic climate system. Therefore, it is essential to accurately and reliably quantify and understand cloud properties over the Arctic. It is also important to monitor and attribute changes in Arctic clouds. Here, we exploit the capability of the CALIPSO-CALIOP instrument and provide comprehensive statistics of tropospheric thin clouds, otherwise extremely difficult to monitor from passive satellite sensors. We use 4 yr of data (June 2006-May 2010) over the circumpolar Arctic, here defined as 67-82 degrees N, and characterize probability density functions of cloud base and top heights, geometrical thickness and zonal distribution of such cloud layers, separately for water and ice phases, and discuss seasonal variability of these properties. When computed for the entire study area, probability density functions of cloud base and top heights and geometrical thickness peak at 200-400, 1000-2000 and 400-800 m, respectively, for thin water clouds, while for ice clouds they peak at 6-8, 7-9 and 400-1000 m, respectively. In general, liquid clouds were often identified below 2 km during all seasons, whereas ice clouds were sensed throughout the majority of the upper troposphere and also, but to a smaller extent, below 2 km for all seasons.
|
|
| 6. |
- Fleischer, Siegfried, 1938-, et al.
(författare)
-
Dark oxidation of water in soils
- 2013
-
Ingår i: Tellus. Series B, Chemical and physical meteorology. - Hoboken, NJ : Wiley-Blackwell. - 0280-6509 .- 1600-0889. ; 65:1
-
Tidskriftsartikel (refereegranskat)abstract
- We report the release of oxygen (O2) under dark conditions in aerobic soils. This unexpected process is hidden by respiration which constitutes the dominating reversal O2 flux. By using H218O in different soils, we confirmed that 16O18O and 18O2 released under dark soil conditions originated from added H218O. Water is the only large-scale source of electrons for reduction of CO2 in soils, but it has not been considered as an electron donor because of the very strong oxidation system needed. A high share of soil inorganic material seems to favor the release of O2. © 2013 S. Fleischer et al.
|
|
| 7. |
- Friberg, Johan, et al.
(författare)
-
Sources of increase in lowermost stratospheric sulphurous and carbonaceous aerosol background concentrations during 1999-2008 derived from CARIBIC flights
- 2014
-
Ingår i: Tellus. Series B: Chemical and Physical Meteorology. - : Stockholm University Press. - 0280-6509 .- 1600-0889.
-
Tidskriftsartikel (refereegranskat)abstract
- This study focuses on sulphurous and carbonaceous aerosol, the major constituents of particulate matter in the lowermost stratosphere (LMS), based on in situ measurements from 1999 to 2008. Aerosol particles in the size range of 0.082 mm were collected monthly during intercontinental flights with the CARIBIC passenger aircraft, presenting the first long-term study on carbonaceous aerosol in the LMS. Elemental concentrations were derived via subsequent laboratory-based ion beam analysis. The stoichiometry indicates that the sulphurous fraction is sulphate, while an O/C ratio of 0.2 indicates that the carbonaceous aerosol is organic. The concentration of the carbonaceous component corresponded on average to approximately 25% of that of the sulphurous, and could not be explained by forest fires or biomass burning, since the average mass ratio of Fe to K was 16 times higher than typical ratios in effluents from biomass burning. The data reveal increasing concentrations of particulate sulphur and carbon with a doubling of particulate sulphur from 1999 to 2008 in the northern hemisphere LMS. Periods of elevated concentrations of particulate sulphur in the LMS are linked to downward transport of aerosol from higher altitudes, using ozone as a tracer for stratospheric air. Tropical volcanic eruptions penetrating the tropical tropopause are identified as the likely cause of the particulate sulphur and carbon increase in the LMS, where entrainment of lower tropospheric air into volcanic jets and plumes could be the cause of the carbon increase.
|
|
| 8. |
- Hegg, Dean A., et al.
(författare)
-
Measurements of black carbon aerosol washout ratio on Svalbard
- 2011
-
Ingår i: Tellus. Series B, Chemical and physical meteorology. - : Stockholm University Press. - 0280-6509 .- 1600-0889. ; 63:5, s. 891-900
-
Tidskriftsartikel (refereegranskat)abstract
- Simultaneous measurements of aerosol black carbon (BC) in both fresh snow and in air on Svalbard are presented. From these, washout ratios for BC are calculated and compared to sparse previous measurements of this metric in the arctic. The current ratios are significantly higher than previously found measured values. We argue that the degree of snow riming within the accretion zone can explain most of this difference. Using an analytical model of the scavenging process, BC scavenging efficiencies are estimated to lie in the range 0.25-0.5, comparable to measured values.
|
|
| 9. |
- Hieronymus, Jenny, 1981-, et al.
(författare)
-
Unravelling the land source : an investigation of the processes contributing to the oceanic input of DIC and alkalinity
- 2013
-
Ingår i: Tellus. Series B, Chemical and physical meteorology. - : Stockholm University Press. - 0280-6509 .- 1600-0889. ; 65, s. 19683-
-
Tidskriftsartikel (refereegranskat)abstract
- In models of the marine carbon system, it is important to correctly represent riverine and aerial inputs of dissolved inorganic carbon (DIC) and alkalinity. We have examined the different processes contributing to this exchange. In terms of DIC, we have divided the fluxes into their internal component, constituting the carbon ultimately derived from the atmosphere, and their external component originating from rocks. We find that the only process contributing to external DIC input is carbonate and fossil carbon weathering and that erosion of organic matter ultimately constitutes a DIC sink. A number of both riverine and aerial inputs affect the alkalinity. Beside carbonate and silicate weathering, we examine processes of pyrite weathering, aerial input of sulphuric acid, and riverine and aerial inputs of various nitrogen species. Using the observation that, in the ocean, the nitrate concentration follows that of phosphate, we assume a steady state in nitrate. This leads to the surprising result that the only processes affecting the alkalinity is riverine input of nitrate, constituting an alkalinity source and input of ammonia, constituting an alkalinity sink. Furthermore, we compare the flux sizes. As expected, carbonate and silicate weathering has the largest effect on alkalinity, though we note that burial of pyrite might be of importance during periods of large-scale anoxia.
|
|
| 10. |
- Horst, Axel, et al.
(författare)
-
Stable bromine isotopic composition of atmospheric CH3Br
- 2013
-
Ingår i: Tellus. Series B, Chemical and physical meteorology. - : Stockholm University Press. - 0280-6509 .- 1600-0889. ; 65, s. 21040-
-
Tidskriftsartikel (refereegranskat)abstract
- Tropospheric methyl bromide (CH3Br) is the largest source of bromine to the stratosphere and plays an important role in ozone depletion. Here, the first stable bromine isotope composition (delta Br-81) of atmospheric CH3Br is presented. The delta Br-81 of higher concentration Stockholm samples and free air subarctic Abisko samples suggest a source/background value of -0.04 +/- 0.28 parts per thousand ranging up to +1.75 +/- 0.12 parts per thousand. The Stockholm delta Br-81 versus concentration relationship corresponds to an apparent isotope enrichment factor of -4.7 +/- 3.7 parts per thousand, representing the combined reaction sink. This study demonstrates the scientific potential of atmospheric delta Br-81 measurements, which in the future may be combined with other isotope systems in a top-down inverse approach to further understand key source and sink processes of methyl bromide.
|
|
