scholarly journals Long term measurements of optical properties and their hygroscopic enhancement

2014 ◽  
Vol 14 (20) ◽  
pp. 27731-27767 ◽  
Author(s):  
M. Hervo ◽  
K. Sellegri ◽  
J. M. Pichon ◽  
J. C. Roger ◽  
P. Laj
Keyword(s):  
Optical Properties ◽  
Diurnal Variation ◽  
Asymmetry Factor ◽  
Optical Parameters ◽  
Strong Impact ◽  
Aerosol Optical Properties ◽  
Diurnal Variability ◽  
Air Mass ◽  
The Impact

Abstract. Optical properties of aerosols were measured from the GAW Puy de Dôme station (1465 m) over a seven year period (2006–2012). The impact of hygroscopicity on aerosol optical properties was calculated over a two year period (2010–2011). The analysis of the spatial and temporal variability of the optical properties showed that while no long term trend was found, a clear seasonal and diurnal variation was observed on the extensive parameters (scattering, absorption). Scattering and absorption coefficients were highest during the warm season and daytime, in concordance with the seasonality and diurnal variation of the PBL height reaching the site. Intensive parameters (single scattering albedo, asymmetry factor, refractive index) did not show such a strong diurnal variability, but still indicated different values depending on the season. Both extensive and intensive optical parameters were sensitive to the air mass origin. A strong impact of hygroscopicity on aerosol optical properties was calculated, mainly on aerosol scattering, with a dependence on the aerosol type. At 90% humidity, the scattering factor enhancement (fσsca) was more than 4.4 for oceanic aerosol that have mixed with a pollution plume. Consequently, the aerosol radiative forcing was estimated to be 2.8 times higher at RH = 90% and 1.75 times higher at ambient RH when hygroscopic growth of the aerosol was considered. The hygroscopicity enhancement factor of the scattering coefficient was parameterized as a function of humidity and air mass type.

scholarly journals Aerosol effects on the photochemistry in Mexico City during MCMA-2006/MILAGRO campaign

2011 ◽  
Vol 11 (3) ◽  
pp. 8625-8664 ◽  
Author(s):  
G. Li ◽  
N. Bei ◽  
X. Tie ◽  
L. T. Molina
Keyword(s):  
Optical Properties ◽  
Mexico City ◽  
Uv Radiation ◽  
Surface Ozone ◽  
Organic Aerosols ◽  
Asymmetry Factor ◽  
Aerosol Optical Properties ◽  
Enhanced Absorption ◽  
Photolysis Rates ◽  
The Impact

Abstract. In the present study, the impact of aerosols on the photochemistry in Mexico City is evaluated using the WRF-CHEM model for the period from 24 to 29 March during the MCMA-2006/MILAGRO campaign. An aerosol radiative module has been developed with detailed consideration of aerosol size, composition, and mixture. The module has been coupled into the WRF-CHEM model to calculate the aerosol optical properties, including optical depth, single scattering albedo, and asymmetry factor. Calculated aerosol optical properties are in good agreement with the surface observations and aircraft and satellite measurements during daytime. In general, the photolysis rates are reduced due to the absorption by carbonaceous aerosols, particularly in the early morning and late afternoon with a long aerosol optical path. However, with the growth of aerosol particles and the decrease of the solar zenith angle around noontime, aerosols can slightly enhance photolysis rates when ultraviolet (UV) radiation scattering dominates UV absorption by aerosols. The changes in photolysis rates due to aerosols lead to about 2–17% surface ozone reduction during daytime in the urban area in Mexico City, resulting in a decrease of OH level by about 9%, as well as a decrease in the daytime concentrations of nitrate and secondary organic aerosols by 5–6% on average. In addition, the rapid aging of black carbon aerosols and the enhanced absorption of UV radiation by organic aerosols contribute substantially to the reduction of photolysis rates, resulting in a further decrease of other chemical species.

The impact of air mass advection on aerosol optical properties over Gotland (Baltic Sea)

2016 ◽  
Vol 182 ◽  
pp. 142-155 ◽  
Author(s):  
Agnieszka Zdun ◽  
Anna Rozwadowska ◽  
Susanne Kratzer
Keyword(s):  
Optical Properties ◽  
Baltic Sea ◽  
Aerosol Optical Properties ◽  
Air Mass ◽  
The Impact

scholarly journals Aerosol effects on the photochemistry in Mexico City during MCMA-2006/MILAGRO campaign

2011 ◽  
Vol 11 (11) ◽  
pp. 5169-5182 ◽  
Author(s):  
G. Li ◽  
N. Bei ◽  
X. Tie ◽  
L. T. Molina
Keyword(s):  
Optical Properties ◽  
Mexico City ◽  
Uv Radiation ◽  
Organic Aerosols ◽  
Early Morning ◽  
Asymmetry Factor ◽  
Aerosol Optical Properties ◽  
Enhanced Absorption ◽  
Photolysis Rates ◽  
The Impact

Abstract. In the present study, the impact of aerosols on the photochemistry in Mexico City is evaluated using the WRF-CHEM model for the period from 24 to 29 March during the MCMA-2006/MILAGRO campaign. An aerosol radiative module has been developed with detailed consideration of aerosol size, composition, and mixing. The module has been coupled into the WRF-CHEM model to calculate the aerosol optical properties, including optical depth, single scattering albedo, and asymmetry factor. Calculated aerosol optical properties are in good agreement with the surface observations and aircraft and satellite measurements during daytime. In general, the photolysis rates are reduced due to the absorption by carbonaceous aerosols, particularly in the early morning and late afternoon hours with a long aerosol optical path. However, with the growth of aerosol particles and the decrease of the solar zenith angle around noontime, aerosols can slightly enhance photolysis rates when ultraviolet (UV) radiation scattering dominates UV absorption by aerosols at the lower-most model layer. The changes in photolysis rates due to aerosols lead to about 2–17 % surface ozone reduction during daytime in the urban area in Mexico City with generally larger reductions during early morning hours near the city center, resulting in a decrease of OH level by about 9 %, as well as a decrease in the daytime concentrations of nitrate and secondary organic aerosols by 5–6 % on average. In addition, the rapid aging of black carbon aerosols and the enhanced absorption of UV radiation by organic aerosols contribute substantially to the reduction of photolysis rates.

scholarly journals Synthesis of PVA/CeO2 Based Nanocomposites with Tuned Refractive Index and Reduced Absorption Edge: Structural and Optical Studies

Materials ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1570
Author(s):  
Shujahadeen B. Aziz ◽  
Elham M. A. Dannoun ◽  
Dana A. Tahir ◽  
Sarkawt A. Hussen ◽  
Rebar T. Abdulwahid ◽  
...  
Keyword(s):  
Refractive Index ◽  
Optical Properties ◽  
Absorption Edge ◽  
Ceo2 Nanoparticles ◽  
Poly Vinyl Alcohol ◽  
Optical Parameters ◽  
Single Oscillator Model ◽  
Vis Spectroscopy ◽  
The Impact ◽  
Host Polymer

In the current study, polymer nanocomposites (NCPs) based on poly (vinyl alcohol) (PVA) with altered refractive index and absorption edge were synthesized by means of a solution cast technique. The characterization techniques of UV–Vis spectroscopy and XRD were used to inspect the structural and optical properties of the prepared films. The XRD patterns of the doped samples have shown clear amendments in the structural properties of the PVA host polymer. Various optical parameters were studied to get more insights about the influence of CeO2 on optical properties of PVA. On the insertion of CeO2 nanoparticles (NPs) into the PVA matrix, the absorption edge was found to move to reduced photon energy sides. It was concluded that the CeO2 nanoparticles can be used to tune the refractive index (n) of the host polymer, and it reached up to 1.93 for 7 wt.% of CeO2 content. A detailed study of the bandgap (BG) was conducted using two approaches. The outcomes have confirmed the impact of the nanofiller on the BG reduction of the host polymer. The results of the optical BG study highlighted that it is crucial to address the ɛ” parameter during the BG analysis, and it is considered as a useful tool to specify the type of electronic transitions. Finally, the dispersion region of n is conferred in terms of the Wemple–DiDomenico single oscillator model.

scholarly journals Expansions in Maternity Leave Coverage and Children's Long-Term Outcomes

2012 ◽  
Vol 4 (3) ◽  
pp. 190-224 ◽  
Author(s):  
Christian Dustmann ◽  
Uta Schönberg
Keyword(s):  
Return To Work ◽  
Maternity Leave ◽  
Work Behavior ◽  
Strong Impact ◽  
Policy Changes ◽  
Long Term Outcomes ◽  
Long Run ◽  
Causal Impact ◽  
The Impact

This paper evaluates the impact of three major expansions in maternity leave coverage in Germany on children's long-run outcomes. To identify the causal impact of the reforms, we use a difference-indifference design that compares outcomes of children born shortly before and shortly after a change in maternity leave legislation in years of policy changes, and in years when no changes have taken place. We find no support for the hypothesis that the expansions in leave coverage improved children's outcomes, despite a strong impact on mothers' return to work behavior after childbirth. (JEL J13, J16, J22, J32)

scholarly journals Lalinet status - station expansion and lidar ratio systematic measurements

2018 ◽  
Vol 176 ◽  
pp. 09002
Author(s):  
Eduardo Landulfo ◽  
Fabio Lopes ◽  
Gregori Arruda Moreira ◽  
Jonatan da Silva ◽  
Pablo Ristori ◽  
...  
Keyword(s):  
Optical Properties ◽  
Radiation Transfer ◽  
Optical Parameters ◽  
Aerosol Optical Properties ◽  
The North ◽  
Circulation Patterns ◽  
Spatial Coverage ◽  
Ratio Data ◽  
Lidar Ratio ◽  
Transfer Models

LALINET is expanding regionally to guarantee spatial coverage over South and Central Americas. One of the network goals is to obtain a set of regional representative aerosol optical properties such as particle backscatter, extinction and lidar ratio. Given the North-South extension and influence of distinct airmass circulation patterns it is paramount to distinguish these optical parameters in order to gain better perfomance in radiation transfer models. A set of lidar ratio data is presented.

scholarly journals Aerosol optical properties and radiative forcing in the high Himalaya based on measurements at the Nepal Climate Observatory – pyramid site (5100 m a.s.l)

2010 ◽  
Vol 10 (2) ◽  
pp. 5627-5663 ◽  
Author(s):  
S. Marcq ◽  
P. Laj ◽  
J. C. Roger ◽  
P. Villani ◽  
K. Sellegri ◽  
...  
Keyword(s):  
Optical Properties ◽  
Radiative Forcing ◽  
Large Scale ◽  
Aerosol Particles ◽  
Small Scale ◽  
Atmospheric Layer ◽  
Aerosol Optical Properties ◽  
Diurnal Variability ◽  
Regional Pollution ◽  
Pollution Events

Abstract. Intense anthropogenic emissions over the Indian sub-continent lead to the formation of layers of particulate pollution that can be transported to the high altitude regions of the Himalaya-Hindu-Kush (HKH). Aerosol particles contain a substantial fraction of strongly absorbing material, including black carbon (BC), organic compounds (OC), and dust all of which can contribute to atmospheric warming, in addition to greenhouse gases. Using a 3-year record of continuous measurements of aerosol optical properties, we present a time series of key climate relevant aerosol properties including the aerosol absorption (σap) and scattering (σsp) coefficients as well as the single-scattering albedo (w). Results of this investigation show substantial seasonal variability of these properties, with long range transport during the pre- and post-monsoon seasons and efficient precipitation scavenging of aerosol particles during the monsoon season. The monthly averaged scattering coefficients range from 0.1 Mm−1 (monsoon) to 20 Mm−1 while the average absorption coefficients range from 0.5 Mm−1 to 3.5 Mm−1. Both have their maximum values during the pre-monsoon period (April) and reach a minimum during Monsoon (July–August). This leads to w values from 0.86 (pre-monsoon) to 0.79 (monsoon) seasons. Significant diurnal variability due to valley wind circulation is also reported. Using typical air mass trajectories encountered at the station, and aerosol optical depth (aod) measurements, we calculated the resulting direct local radiative forcing due to aerosols. We found that the presence of absorbing particulate material can locally induce an additional top of the atmosphere (TOA) forcing of 10 to 20 W m−2 for the first atmospheric layer (500 m above surface). The TOA positive forcing depends on the presence of snow at the surface, and takes place preferentially during episodes of regional pollution occurring on a very regular basis in the Himalayan valleys. Warming of the first atmospheric layer is paralleled by a substantial decrease of the amount of radiation reaching the surface. The surface forcing is estimated to range from −4 to −20 W m−2 for small-scale regional pollution events and large-scale pollution events, respectively. The calculated surface forcing is also very dependent on surface albedo, with maximum values occurring over a snow-covered surface. Overall, this work presents the first estimates of aerosol direct radiative forcing over the high Himalaya based on in-situ aerosol measurements, and results suggest a TOA forcing significantly greater than the IPCC reported values for green house gases.

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