scholarly journals Properties of Cirrus Clouds over the European Arctic (Ny-Ålesund, Svalbard)

2021 ◽  
Vol 13 (22) ◽  
pp. 4555
Author(s):  
Konstantina Nakoudi ◽  
Christoph Ritter ◽  
Iwona S. Stachlewska
Keyword(s):  
Optical Properties ◽  
Particle Surface ◽  
Visible Spectral Region ◽  
Cirrus Clouds ◽  
The Arctic ◽  
Specular Reflections ◽  
Ice Particles ◽  
Westerly Flow ◽  
European Arctic ◽  
Winter Time

Cirrus is the only cloud type capable of inducing daytime cooling or heating at the top of the atmosphere (TOA) and the sign of its radiative effect highly depends on its optical depth. However, the investigation of its geometrical and optical properties over the Arctic is limited. In this work the long-term properties of cirrus clouds are explored for the first time over an Arctic site (Ny-Ålesund, Svalbard) using lidar and radiosonde measurements from 2011 to 2020. The optical properties were quality assured, taking into account the effects of specular reflections and multiple-scattering. Cirrus clouds were generally associated with colder and calmer wind conditions compared to the 2011–2020 climatology. However, the dependence of cirrus properties on temperature and wind speed was not strong. Even though the seasonal cycle was not pronounced, the winter-time cirrus appeared under lower temperatures and stronger wind conditions. Moreover, in winter, geometrically- and optically-thicker cirrus were found and their ice particles tended to be more spherical. The majority of cirrus was associated with westerly flow and westerly cirrus tended to be geometrically-thicker. Overall, optically-thinner layers tended to comprise smaller and less spherical ice crystals, most likely due to reduced water vapor deposition on the particle surface. Compared to lower latitudes, the cirrus layers over Ny-Ålesund were more absorbing in the visible spectral region and they consisted of more spherical ice particles.

scholarly journals Regional aerosol optical properties and radiative impact of the extreme smoke event in the European Arctic in spring 2006

2007 ◽  
Vol 7 (4) ◽  
pp. 9519-9559 ◽  
Author(s):  
C. Lund Myhre ◽  
C. Toledano ◽  
G. Myhre ◽  
K. Stebel ◽  
K. E. Yttri ◽  
...  
Keyword(s):  
Air Pollution ◽  
Optical Properties ◽  
Eastern Europe ◽  
Radiative Forcing ◽  
Arctic Region ◽  
The Arctic ◽  
Synoptic Situation ◽  
Aerosol Optical Properties ◽  
Modis Aod ◽  
European Arctic

Abstract. In spring 2006 a special meteorological situation occurred in the European Arctic region giving record high levels of air pollution. The synoptic situation resulted in extensive transport of pollution predominantly from agricultural fires in Eastern Europe into the Arctic region and record high air-pollution levels were measured at the Zeppelin observatory at Ny-Ålesund (78°54' N, 11°53' E) in the period from 25 April to 12 May. In the present study we investigate the optical properties of the aerosols from this extreme event and we estimate the radiative forcing of this episode. We examine the aerosol optical properties from the source region and into the European Arctic and explore the evolution of the episode and the changes in the optical properties. A number of sites in Eastern Europe, Northern Scandinavia and Svalbard are included in the study. In addition to AOD measurements, we explored lidar measurements from Minsk, ALOMAR (Arctic Lidar Observatory for Middle Atmosphere Research at Andenes) and Ny-Ålesund. For the AERONET sites included (Minsk, Toravere, Hornsund) we have further studied the evolution of the aerosol size. Importantly, at Svalbard it is consistency between the AERONET measurements and calculations of single scattering albedo based on aerosol chemical composition. We have found strong agreement between the satellite daily MODIS AOD and the ground-based AOD observations. This agreement is crucial for the radiative forcing calculations. We calculate a strong negative radiative forcing for the most polluted days employing the analysed ground based data, MODIS AOD and a multi-stream model for radiative transfer of solar radiation.

scholarly journals Regional aerosol optical properties and radiative impact of the extreme smoke event in the European Arctic in spring 2006

2007 ◽  
Vol 7 (22) ◽  
pp. 5899-5915 ◽  
Author(s):  
C. Lund Myhre ◽  
C. Toledano ◽  
G. Myhre ◽  
K. Stebel ◽  
K. E. Yttri ◽  
...  
Keyword(s):  
Optical Properties ◽  
Radiative Forcing ◽  
Source Region ◽  
Arctic Region ◽  
Single Scattering ◽  
The Arctic ◽  
Aerosol Layer ◽  
Aerosol Optical Properties ◽  
Modis Aod ◽  
European Arctic

Abstract. In spring 2006 a special meteorological situation occurred in the European Arctic region giving record high levels of air pollution. The synoptic situation resulted in extensive transport of pollution predominantly from agricultural fires in Eastern Europe into the Arctic region and record high air-pollution levels were measured at the Zeppelin observatory at Ny-Ålesund (78°54' N, 11°53' E) in the period from 25 April to 12 May. In the present study we investigate the optical properties of the aerosols from this extreme event and we estimate the radiative forcing of this episode. We examine the aerosol optical properties from the source region and into the European Arctic and explore the evolution of the episode and the changes in the optical properties. A number of sites in Eastern Europe, Northern Scandinavia and Svalbard are included in the study. The observations show that the maximum AOD was from 2–3 May at all sites and varies from 0.52 to 0.87, and the corresponding Ångstrøm exponent was relatively large. Lidar measurements from Minsk, ALOMAR (Arctic Lidar Observatory for Middle Atmosphere Research at Andenes) and Ny-Ålesund show that the aerosol layer was below 3 km at all sites the height is decreasing from the source region and into the Arctic. For the AERONET sites included (Minsk, Toravere, Hornsund) we have further studied the evolution of the aerosol size. The single scattering albedo at Svalbard is provided for two sites; Ny-Ålesund and Hornsund. Importantly the calculated single scattering albedo based on the aerosol chemical composition and size distribution from Ny-Ålesund and the AERONET measurements at Hornsund are consistent. We have found strong agreement between the satellite daily MODIS AOD and the ground-based AOD observations. This agreement is crucial for accurate radiative forcing calculations. We calculate a strong negative radiative forcing for the most polluted days employing the analysed ground based data, MODIS AOD and a multi-stream model for radiative transfer of solar radiation. During this specific pollution event the forcing reached values as low as −35 W m−2 in the region. For comparison, the direct forcing of a corresponding aerosol layer with a typical AOD of 0.05 for the season is around −5 W m−2.

scholarly journals A New Parameterization of an Asymmetry Factor of Cirrus Clouds for Climate Models

2007 ◽  
Vol 64 (11) ◽  
pp. 4140-4150 ◽  
Author(s):  
Qiang Fu
Keyword(s):  
Surface Roughness ◽  
Solar Radiation ◽  
Climate Models ◽  
Particle Surface ◽  
Visible Spectrum ◽  
Cirrus Clouds ◽  
Asymmetry Factor ◽  
Hexagonal Ice ◽  
Ice Particles ◽  
The Asymmetry

Abstract The aspect ratio (AR) of a nonspherical ice particle is identified as the key microphysical parameter to determine its asymmetry factor for solar radiation. The mean effective AR is defined for cirrus clouds containing various nonspherical ice particles. A new parameterization of the asymmetry factor of cirrus clouds in terms of AR and mean effective size, Dge, is developed for solar radiation. It is based on geometric ray-tracing calculations for hexagonal ice crystals with a simple representation of particle surface roughness. The present parameterization well reproduces the asymmetry factors of complicated ice particles such as bullet rosettes, aggregates with rough surfaces, and fractal crystals and agrees well with observations. It thus can be properly applied to cirrus clouds containing various nonspherical ice particles. The asymmetry factor from this parameterization in the visible spectrum ranges from about 0.73 to more than 0.85. Radiative transfer calculations show that for a cirrus cloud with an optical depth of 4 and a solar zenith angle of 60°, changes in AR from 1.0 to 0.5 or from 1.0 to 0.1 result in differences in reflected solar fluxes of about −30 or −70 W m−2, respectively. For the same cloudy conditions, the effect of ice particle surface roughness on the reflected solar flux is found to be about 20 W m−2.

scholarly journals Seasonal patterns in Arctic planktonic metabolism (Fram Strait – Svalbard region)

2013 ◽  
Vol 10 (3) ◽  
pp. 1451-1469 ◽  
Author(s):  
R. Vaquer-Sunyer ◽  
C. M. Duarte ◽  
J. Holding ◽  
A. Regaudie-de-Gioux ◽  
L. S. García-Corral ◽  
...  
Keyword(s):  
Arctic Ocean ◽  
Early Spring ◽  
The Arctic ◽  
Fram Strait ◽  
Metabolic Rates ◽  
Net Community Production ◽  
Western Sector ◽  
The Arctic Ocean ◽  
European Arctic ◽  
Community Production

Abstract. The metabolism of the Arctic Ocean is marked by extremely pronounced seasonality and spatial heterogeneity associated with light conditions, ice cover, water masses and nutrient availability. Here we report the marine planktonic metabolic rates (net community production, gross primary production and community respiration) along three different seasons of the year, for a total of eight cruises along the western sector of the European Arctic (Fram Strait – Svalbard region) in the Arctic Ocean margin: one at the end of 2006 (fall/winter), two in 2007 (early spring and summer), two in 2008 (early spring and summer), one in 2009 (late spring–early summer), one in 2010 (spring) and one in 2011 (spring). The results show that the metabolism of the western sector of the European Arctic varies throughout the year, depending mostly on the stage of bloom and water temperature. Here we report metabolic rates for the different periods, including the spring bloom, summer and the dark period, increasing considerably the empirical basis of metabolic rates in the Arctic Ocean, and especially in the European Arctic corridor. Additionally, a rough annual metabolic estimate for this area of the Arctic Ocean was calculated, resulting in a net community production of 108 g C m−2 yr−1.

scholarly journals The importance of Asia as a source of black carbon to the European Arctic during springtime 2013

2015 ◽  
Vol 15 (20) ◽  
pp. 11537-11555 ◽  
Author(s):  
D. Liu ◽  
B. Quennehen ◽  
E. Darbyshire ◽  
J. D. Allan ◽  
P. I. Williams ◽  
...  
Keyword(s):  
Black Carbon ◽  
Arctic Sea Ice ◽  
Anthropogenic Sources ◽  
The Arctic ◽  
Geometric Standard Deviation ◽  
Free Troposphere ◽  
Aerosol Composition ◽  
Upper Troposphere ◽  
European Arctic ◽  
Mean Concentration

Abstract. Black carbon aerosol (BC) deposited to the Arctic sea ice or present in the free troposphere can significantly affect the Earth's radiation budget at high latitudes yet the BC burden in these regions and the regional source contributions are poorly constrained. Aircraft measurements of aerosol composition in the European Arctic were conducted during the Aerosol–Cloud Coupling And Climate Interactions in the Arctic (ACCACIA) campaign in March 2013. Pollutant plumes were encountered throughout the lower to upper Arctic troposphere featuring enhancements in CO and aerosol mass loadings, which were chemically speciated into BC and non-refractory sulphate and organic matter. FLEXPART-WRF simulations have been performed to evaluate the likely contribution to the pollutants from regional ground sources. By combining up-to-date anthropogenic and open fire biomass burning (OBB) inventories, we have been able to compare the contributions made to the observed pollution layers from the sources of eastern/northern Asia (AS), Europe (EU) and North America (NA). Over 90 % of the contribution to the BC was shown to arise from non-OBB anthropogenic sources. AS sources were found to be the major contributor to the BC burden, increasing background BC loadings by a factor of 3–5 to 100.8 ± 48.4 ng sm−3 (in standard air m3 at 273.15 K and 1013.25 mbar) and 55.8 ± 22.4 ng sm−3 in the middle and upper troposphere respectively. AS plumes close to the tropopause (about 7.5–8 km) were also observed, with BC concentrations ranging from 55 to 73 ng sm−3, which will potentially have a significant radiative impact. EU sources influenced the middle troposphere with a BC mean concentration of 70.8 ± 39.1 ng sm−3 but made a minor contribution to the upper troposphere due to the relatively high latitude of the source region. The contribution of NA was shown to be much lower at all altitudes with BC mean concentration of 20 ng sm−3. The BC transported to the Arctic is mixed with a non-BC volume fraction representing between 90–95 % of the mass, and has a relatively uniform core size distribution with mass median diameter 190–210 nm and geometric standard deviation σg = 1.55–1.65 and this varied little across all source regions. It is estimated that 60–95 % of BC is scavenged between emission and receptor based on BC / ΔCO comparisons between source inventories and measurement. We show that during the springtime of 2013, the anthropogenic pollution particularly from sources in Asia, contributed significantly to BC across the European Arctic free troposphere. In contrast to previous studies, the contribution from open wildfires was minimal. Given that Asian pollution is likely to continue to rise over the coming years, it is likely that the radiative forcing in the Arctic will also continue to increase.

scholarly journals Spectral albedo of seasonal snow during intensive melt period at Sodankylä, beyond the Arctic Circle

2013 ◽  
Vol 13 (7) ◽  
pp. 3793-3810 ◽  
Author(s):  
O. Meinander ◽  
S. Kazadzis ◽  
A. Arola ◽  
A. Riihelä ◽  
P. Räisänen ◽  
...  
Keyword(s):  
Spectral Irradiance ◽  
The Arctic ◽  
Visible Range ◽  
Air Masses ◽  
Clear Sky ◽  
Effective Grain Size ◽  
European Arctic ◽  
Small Absorption ◽  
High Concentrations ◽  
Double Monochromator

Abstract. We have measured spectral albedo, as well as ancillary parameters, of seasonal European Arctic snow at Sodankylä, Finland (67°22' N, 26°39' E). The springtime intensive melt period was observed during the Snow Reflectance Transition Experiment (SNORTEX) in April 2009. The upwelling and downwelling spectral irradiance, measured at 290–550 nm with a double monochromator spectroradiometer, revealed albedo values of ~0.5–0.7 for the ultraviolet and visible range, both under clear sky and variable cloudiness. During the most intensive snowmelt period of four days, albedo decreased from 0.65 to 0.45 at 330 nm, and from 0.72 to 0.53 at 450 nm. In the literature, the UV and VIS albedo for clean snow are ~0.97–0.99, consistent with the extremely small absorption coefficient of ice in this spectral region. Our low albedo values were supported by two independent simultaneous broadband albedo measurements, and simulated albedo data. We explain the low albedo values to be due to (i) large snow grain sizes up to ~3 mm in diameter; (ii) meltwater surrounding the grains and increasing the effective grain size; (iii) absorption caused by impurities in the snow, with concentration of elemental carbon (black carbon) in snow of 87 ppb, and organic carbon 2894 ppb, at the time of albedo measurements. The high concentrations of carbon, detected by the thermal–optical method, were due to air masses originating from the Kola Peninsula, Russia, where mining and refining industries are located.

scholarly journals Effect of gas-transfer-velocity parameterization choice on CO<sub>2</sub> air–sea fluxes in the North Atlantic and European Arctic

2015 ◽  
Vol 12 (6) ◽  
pp. 2591-2616
Author(s):  
I. Wróbel ◽  
J. Piskozub
Keyword(s):  
North Atlantic ◽  
World Ocean ◽  
Software Tool ◽  
The Arctic ◽  
Gas Transfer ◽  
Transfer Velocity ◽  
Gas Transfer Velocity ◽  
The North ◽  
European Arctic ◽  
The North Atlantic

Abstract. The ocean sink is an important part of the anthropogenic CO2 budget. Because the terrestrial biosphere is usually treated as a residual, understanding the uncertainties the net flux into the ocean sink is crucial for understanding the global carbon cycle. One of the sources of uncertainty is the parameterization of CO2 gas transfer velocity. We used a recently developed software tool, FluxEngine, to calculate monthly net carbon air–sea flux for the extratropical North Atlantic, European Arctic as well as global values (or comparison) using several available parameterizations of gas transfer velocity of different dependence of wind speed, both quadratic and cubic. The aim of the study is to constrain the uncertainty caused by the choice of parameterization in the North Atlantic, a large sink of CO2 and a region with good measurement coverage, characterized by strong winds. We show that this uncertainty is smaller in the North Atlantic and in the Arctic than globally, within 5 % in the North Atlantic and 4 % in the European Arctic, comparing to 9 % for the World Ocean when restricted to functions with quadratic wind dependence and respectively 42, 40 and 67 % for all studied parameterizations. We propose an explanation of this smaller uncertainty due to the combination of higher than global average wind speeds in the North Atlantic and lack of seasonal changes in the flux direction in most of the region. We also compare the available pCO2 climatologies (Takahashi and SOCAT) pCO2 discrepancy in annual flux values of 8 % in the North Atlantic and 19 % in the European Arctic. The seasonal flux changes in the Arctic have inverse seasonal change in both climatologies, caused most probably by insufficient data coverage, especially in winter.

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