scholarly journals In situ observations of black carbon in snow and the corresponding spectral surface albedo reduction

2015 ◽  
Vol 120 (4) ◽  
pp. 1476-1489 ◽  
Author(s):  
C. A. Pedersen ◽  
J.-C. Gallet ◽  
J. Ström ◽  
S. Gerland ◽  
S. R. Hudson ◽  
...  
Keyword(s):  
Black Carbon ◽  
Surface Albedo ◽  
In Situ Observations

scholarly journals CLARA-SAL: a global 28-yr timeseries of Earth's black-sky surface albedo

2012 ◽  
Vol 12 (9) ◽  
pp. 25573-25615 ◽  
Author(s):  
A. Riihelä ◽  
T. Manninen ◽  
V. Laine ◽  
K. Andersson ◽  
F. Kaspar
Keyword(s):  
Sea Ice ◽  
Surface Albedo ◽  
Greenland Ice Sheet ◽  
Open Water ◽  
Atmospheric Effect ◽  
Clear Sky ◽  
Product Features ◽  
In Situ Observations

Abstract. We present a novel 28-yr dataset of Earth's black-sky surface albedo, derived from AVHRR instruments. The dataset is created using algorithms to separately derive the surface albedo for different land use areas globally. Snow, sea ice, open water and vegetation are all treated independently. The product features corrections for the atmospheric effect in satellite-observed surface radiances, a BRDF correction for the anisotropic reflectance properties of natural surfaces, and a novel topography correction of geolocation and radiometric accuracy of surface reflectance observations over mountainous areas. The dataset is based on a homogenized AVHRR radiance timeseries. The product is validated against quality-controlled in situ observations of clear-sky surface albedo at various BSRN sites around the world. Snow and ice albedo retrieval validation is given particular attention using BSRN sites over Antarctica, Greenland Climate Network stations on the Greenland Ice Sheet (GrIS), as well as sea ice albedo data from the SHEBA and Tara expeditions. The product quality is found to be comparable to other previous long-term surface albedo datasets from AVHRR.

scholarly journals Comparison of different methods to retrieve effective snow grain size in central Antarctica

2017 ◽  
Author(s):  
Tim Carlsen ◽  
Gerit Birnbaum ◽  
André Ehrlich ◽  
Johannes Freitag ◽  
Georg Heygster ◽  
...  
Keyword(s):  
Grain Size ◽  
Measurement System ◽  
Surface Albedo ◽  
Austral Summer ◽  
Surface Energy Budget ◽  
Research Station ◽  
Polar Regions ◽  
Radiation Measurement ◽  
In Situ Observations

Abstract. The effective size of snow grains (reff) affects the reflectivity of snow surfaces and thus the local surface energy budget in particular in polar regions. Therefore, the specific surface area (SSA) was monitored for a two-month period in central Antarctica (Kohnen research station) during austral summer 2013/14. The data were retrieved on the basis of spectral surface albedo measurements collected by the COmpact RAdiation measurement System (CORAS, ground-based) and the Spectral Modular Airborne Radiation measurement sysTem (SMART, airborne). The Snow Grain Size and Pollution amount (SGSP) algorithm, originally developed to analyze spaceborne reflectance measurements by the MODerate Resolution Imaging Spectroradiometer (MODIS), was modified and applied to the ground-based and airborne observations collected in this study. Furthermore, spectral ratios of surface albedo at 1280 nm and 1100 nm wavelength were used to reduce the retrieval uncertainty. Additionally, the algorithm originally developed for cloudless conditions was adapted to handle overcast conditions. Optical in situ observations of SSA utilizing an IceCube device were used to validate the retrieval results. The SSA retrieved from CORAS observations varied between 27 m2 kg-1 and 86 m2 kg-1. Snowfall events caused distinct SSA maxima which were often followed by a gradual decrease in SSA due to snow metamorphism and wind-induced transport of fresh fallen ice crystals (vice versa for reff). SSA retrieved by data from CORAS and MODIS agree with the in situ observations within the ranges given by the measurement uncertainties. However, SSA retrieved by the airborne SMART observations underestimated the ground-based observations by a factor of 2.1 (overestimation of reff).

scholarly journals Assessing spatio-temporal variability and trends in modelled and measured Greenland Ice Sheet albedo (2000–2013)

2014 ◽  
Vol 8 (6) ◽  
pp. 2293-2312 ◽  
Author(s):  
P. M. Alexander ◽  
M. Tedesco ◽  
X. Fettweis ◽  
R. S. W. van de Wal ◽  
C. J. P. P. Smeets ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Temporal Variability ◽  
Surface Albedo ◽  
Climate Model ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
High Elevation ◽  
In Situ Observations ◽  
Spatio Temporal

Abstract. Accurate measurements and simulations of Greenland Ice Sheet (GrIS) surface albedo are essential, given the role of surface albedo in modulating the amount of absorbed solar radiation and meltwater production. In this study, we assess the spatio-temporal variability of GrIS albedo during June, July, and August (JJA) for the period 2000–2013. We use two remote sensing products derived from data collected by the Moderate Resolution Imaging Spectroradiometer (MODIS), as well as outputs from the Modèle Atmosphérique Régionale (MAR) regional climate model (RCM) and data from in situ automatic weather stations. Our results point to an overall consistency in spatio-temporal variability between remote sensing and RCM albedo, but reveal a difference in mean albedo of up to ~0.08 between the two remote sensing products north of 70° N. At low elevations, albedo values simulated by the RCM are positively biased with respect to remote sensing products by up to ~0.1 and exhibit low variability compared with observations. We infer that these differences are the result of a positive bias in simulated bare ice albedo. MODIS albedo, RCM outputs, and in situ observations consistently indicate a decrease in albedo of −0.03 to −0.06 per decade over the period 2003–2013 for the GrIS ablation area. Nevertheless, satellite products show a decline in JJA albedo of −0.03 to −0.04 per decade for regions within the accumulation area that is not confirmed by either the model or in situ observations. These findings appear to contradict a previous study that found an agreement between in situ and MODIS trends for individual months. The results indicate a need for further evaluation of high elevation albedo trends, a reconciliation of MODIS mean albedo at high latitudes, and the importance of accurately simulating bare ice albedo in RCMs.

scholarly journals In situ observations and model calculations of black carbon emission by aircraft at cruise altitude

1999 ◽  
Vol 104 (D18) ◽  
pp. 22171-22181 ◽  
Author(s):  
A. Petzold ◽  
A. Döpelheuer ◽  
C. A. Brock ◽  
F. Schröder
Keyword(s):  
Black Carbon ◽  
Carbon Emission ◽  
Model Calculations ◽  
In Situ Observations

scholarly journals CLARA-SAL: a global 28 yr timeseries of Earth's black-sky surface albedo

2013 ◽  
Vol 13 (7) ◽  
pp. 3743-3762 ◽  
Author(s):  
A. Riihelä ◽  
T. Manninen ◽  
V. Laine ◽  
K. Andersson ◽  
F. Kaspar
Keyword(s):  
Sea Ice ◽  
Surface Albedo ◽  
Greenland Ice Sheet ◽  
Open Water ◽  
Atmospheric Effect ◽  
Clear Sky ◽  
Product Features ◽  
In Situ Observations

Abstract. We present a novel 28 yr dataset of Earth's black-sky surface albedo, derived from AVHRR instruments. The dataset is created using algorithms to separately derive the surface albedo for different land use areas globally. Snow, sea ice, open water and vegetation are all treated independently. The product features corrections for the atmospheric effect in satellite-observed surface radiances, a BRDF correction for the anisotropic reflectance properties of natural surfaces, and a novel topography correction of geolocation and radiometric accuracy of surface reflectance observations over mountainous areas. The dataset is based on a homogenized AVHRR radiance timeseries. The product is validated against quality-controlled in situ observations of clear-sky surface albedo at various BSRN sites around the world. Snow and ice albedo retrieval validation is given particular attention using BSRN sites over Antarctica, Greenland Climate Network stations on the Greenland Ice Sheet (GrIS), as well as sea ice albedo data from the SHEBA and Tara expeditions. The product quality is found to be comparable to other previous long-term surface albedo datasets from AVHRR.

scholarly journals Assessing spatio-temporal variability and trends (2000–2013) of modelled and measured Greenland ice sheet albedo

2014 ◽  
Vol 8 (4) ◽  
pp. 3733-3783 ◽  
Author(s):  
P. M. Alexander ◽  
M. Tedesco ◽  
X. Fettweis ◽  
R. S. W. van de Wal ◽  
C. J. P. P. Smeets ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Temporal Variability ◽  
Surface Albedo ◽  
Climate Model ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Spatiotemporal Variability ◽  
In Situ Observations ◽  
Spatio Temporal

Abstract. Accurate measurements and simulations of Greenland Ice Sheet (GrIS) surface albedo are essential, given the crucial role of surface albedo in modulating the amount of absorbed solar radiation and meltwater production. In this study, we assess the spatio-temporal variability of GrIS albedo (during June, July, and August) for the period 2000–2013. We use two remote sensing products derived from data collected by the Moderate Resolution Imaging Spectroradiometer (MODIS), as well as outputs from the Modèle Atmosphérique Régionale (MAR) regional climate model (RCM) and data from in situ automatic weather stations. Our results point to an overall consistency in spatiotemporal variability between remote sensing and RCM albedo, but reveal a difference in mean albedo of up to ~0.08 between the two remote sensing products north of 70° N. At low elevations, albedo values simulated by the RCM are positively biased with respect to remote sensing products and in situ measurements by up to ~0.1 and exhibit low variability compared with observations. We infer that these differences are the result of a positive bias in simulated bare-ice albedo. MODIS albedo, RCM outputs and in situ observations consistently point to a~decrease in albedo of −0.03 to −0.06 per decade over the period 2003–2013 for the GrIS ablation zone (where there is a net loss of mass at the GrIS surface). Nevertheless, satellite products show a~decline in albedo of −0.03 to −0.04 per decade for regions within the accumulation zone (where there is a net gain of mass at the surface) that is not confirmed by either the model or in situ observations.

scholarly journals Comparison of different methods to retrieve optical-equivalent snow grain size in central Antarctica

2017 ◽  
Vol 11 (6) ◽  
pp. 2727-2741 ◽  
Author(s):  
Tim Carlsen ◽  
Gerit Birnbaum ◽  
André Ehrlich ◽  
Johannes Freitag ◽  
Georg Heygster ◽  
...  
Keyword(s):  
Grain Size ◽  
Measurement System ◽  
Surface Albedo ◽  
Surface Energy Budget ◽  
Research Station ◽  
Polar Regions ◽  
Radiation Measurement ◽  
In Situ Observations ◽  
The Impact

Abstract. The optical-equivalent snow grain size affects the reflectivity of snow surfaces and, thus, the local surface energy budget in particular in polar regions. Therefore, the specific surface area (SSA), from which the optical snow grain size is derived, was observed for a 2-month period in central Antarctica (Kohnen research station) during austral summer 2013/14. The data were retrieved on the basis of ground-based spectral surface albedo measurements collected by the COmpact RAdiation measurement System (CORAS) and airborne observations with the Spectral Modular Airborne Radiation measurement sysTem (SMART). The snow grain size and pollution amount (SGSP) algorithm, originally developed to analyze spaceborne reflectance measurements by the MODerate Resolution Imaging Spectroradiometer (MODIS), was modified in order to reduce the impact of the solar zenith angle on the retrieval results and to cover measurements in overcast conditions. Spectral ratios of surface albedo at 1280 and 1100 nm wavelength were used to reduce the retrieval uncertainty. The retrieval was applied to the ground-based and airborne observations and validated against optical in situ observations of SSA utilizing an IceCube device. The SSA retrieved from CORAS observations varied between 27 and 89 m2 kg−1. Snowfall events caused distinct relative maxima of the SSA which were followed by a gradual decrease in SSA due to snow metamorphism and wind-induced transport of freshly fallen ice crystals. The ability of the modified algorithm to include measurements in overcast conditions improved the data coverage, in particular at times when precipitation events occurred and the SSA changed quickly. SSA retrieved from measurements with CORAS and MODIS agree with the in situ observations within the ranges given by the measurement uncertainties. However, SSA retrieved from the airborne SMART data slightly underestimated the ground-based results.

scholarly journals Changes in black carbon emissions over Europe due to COVID-19 lockdowns

2020 ◽  
Author(s):  
Nikolaos Evangeliou ◽  
Stephen M. Platt ◽  
Sabine Eckhardt ◽  
Cathrine Lund Myhre ◽  
Paolo Laj ◽  
...  
Keyword(s):  
Black Carbon ◽  
Remote Sensing Data ◽  
Pollutant Emissions ◽  
World Health ◽  
Socioeconomic Impacts ◽  
Global Pandemic ◽  
The World ◽  
In Situ Observations ◽  
Health Organization

Abstract. Following the emergence of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) responsible for COVID-19 in December 2019 in Wuhan (China) and its spread to the rest of the world, the World Health Organization declared a global pandemic in March 2020. Without effective treatment in the initial pandemic phase, social distancing and mandatory quarantines were introduced as the only available preventative measure. Despite the socioeconomic impacts, air quality improved due to lower pollutant emissions. Here we investigate the effects of the COVID-19 lockdowns on ambient black carbon (BC), which affects climate and damages health, using in-situ observations from 17 European stations in a Bayesian inversion framework. BC emissions declined by 11 % in Europe (20 % in Italy, 32 % in Germany, 20 % in Spain) during lockdown compared to the same period in the previous five years. BC temporal variation in the countries enduring the most drastic restrictions showed the most distinct lockdown impacts. Increased particle light absorption in at the beginning of the lockdown, confirmed by assimilated satellite and remote sensing data, suggests residential combustion was the dominant BC source. Accordingly, in Central and Eastern Europe, which experienced lower than average temperatures, BC was elevated compared to the previous five years. Except for the comparison of BC emissions in the lockdown with the previous five years, an immediate decrease was also seen, as compared with the period before the lockdown, which averaged about 10 % over Europe. Such a decrease was not seen in the previous years, which also confirms an impact on BC emissions from COVID-19.

In situ observations of electromigration induced void behavior

1995 ◽  
Vol 53 ◽  
pp. 244-245
Author(s):  
T. Marieb ◽  
J. C. Bravman ◽  
P. Flinn ◽  
D. Gardner ◽  
M. Madden
Keyword(s):  
Electron Microscopy ◽  
Void Nucleation ◽  
Plan View ◽  
Transmission Electron ◽  
Nucleation Sites ◽  
Microelectronics Industry ◽  
In Situ Observations ◽  
Backscatter Electron Detector ◽  
Voltage Scanning

Electromigration and stress voiding have been active areas of research in the microelectronics industry for many years. While accelerated testing of these phenomena has been performed for the last 25 years[1-2], only recently has the introduction of high voltage scanning electron microscopy (HVSEM) made possible in situ testing of realistic, passivated, full thickness samples at high resolution.With a combination of in situ HVSEM and post-testing transmission electron microscopy (TEM) , electromigration void nucleation sites in both normal polycrystalline and near-bamboo pure Al were investigated. The effect of the microstructure of the lines on the void motion was also studied.The HVSEM used was a slightly modified JEOL 1200 EX II scanning TEM with a backscatter electron detector placed above the sample[3]. To observe electromigration in situ the sample was heated and the line had current supplied to it to accelerate the voiding process. After testing lines were prepared for TEM by employing the plan-view wedge technique [6].

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