The Impact of Scattering Clouds when Studying Exoplanet Emission Spectra with JWST

2020 ◽  
Author(s):  
Jake Taylor ◽  
Vivien Parmentier ◽  
Michael Line ◽  
Graham Lee ◽  
Patrick Irwin ◽  
...  
Keyword(s):  
Prior Knowledge ◽  
Emission Spectra ◽  
Single Scattering ◽  
Single Scattering Albedo ◽  
Spectral Signatures ◽  
Modelling Techniques ◽  
Novel Method ◽  
Cloud Modelling ◽  
The Impact ◽  
Current Modelling

<p>Observational studies of exoplanets show that many of them contain some form of cloud coverage. The current modelling techniques used in emission to account for the clouds tend to require prior knowledge of the cloud condensing species as well as not considering the scattering caused by the clouds. We explore the effects that scattering has on the emission spectra by modelling a suite of hot Jupiter atmospheres with varying cloud single scattering albedos and temperature profiles. We examine from simple isothermal cases to more complex thermal structures and physically driven cloud modelling. We show that scattering can produce spectral signatures in the emission spectrum even for isothermal atmospheres. We identify the problems that arise from fitting JWST spectra when the spectral shape is dominated by the scattering from the clouds. Finally, we propose a novel method of fitting the single scattering albedo of the cloud in emission retrievals, this technique does not require any prior knowledge of the cloud chemical or physical properties. We show that this technique can retrieve the wavelength dependent shape of the single scattering albedo while accurately modelling the chemistry in the atmosphere.  </p> <p> </p> <p> </p> <p> </p> <p> </p> <p> </p>

Global OMI Aerosol Single Scattering Albedo evaluation using ground-based AERONET

2020 ◽  
Author(s):  
Periklis Drakousis ◽  
Marios-Bruno Korras-Carraca ◽  
Hiren Jethva ◽  
Omar Torres ◽  
Nikos Hatzianastassiou
Keyword(s):  
Optical Properties ◽  
Climate Models ◽  
Spatial Scales ◽  
Single Scattering ◽  
Single Scattering Albedo ◽  
Absolute Difference ◽  
Ozone Monitoring Instrument ◽  
Seasonal Basis ◽  
Radiance Data ◽  
The Impact

<p>Aerosol measurements are carried out worldwide in order to reduce the uncertainties about the impact of aerosols on climate. Over the past two decades, different methods (ground- or satellite-based) for measuring aerosol properties have been developed, covering a variety of approaches with different temporal and spatial scales, which can be considered complementary. Aerosol optical properties are essential for assessing the effects of aerosols on radiation and climate. Aerosol single scattering albedo (SSA), along with optical depth and asymmetry parameter, is one of the three key optical properties that are necessary for radiation transfer and climate models. At the same time, SSA strongly depends on different aerosol types, thus enabling the identification of these different aerosol particles. However, despite the strong need for aerosol SSA products with global and climatological coverage, and the significant progress in retrieving SSA from satellite measurements, the satellite SSA retrievals are still subjected to uncertainties.</p><p>In this study, we perform an evaluation of the OMAERUVd (PGE Version V1.8.9.1) daily L3 (1° x 1° latitude-longitude) aerosol SSA data, which are based on the enhanced two-channel OMAERUV algorithm that essentially uses the ultraviolet radiance data from Aura/Ozone Monitoring Instrument (OMI), through comparisons against daily SSA products from 541 globally distributed Aerosol Robotic Network (AERONET) stations for a 15-year period (2005-2019). The comparison is performed between the available OMAERUVd SSA data at 354 nm, 388 nm, and 500 nm, and the AERONET SSA data at 440 nm (or 443 nm). The comparison is made on an annual and seasonal basis in order to reveal possible seasonally dependent patterns, as well as on a climatological and a year-to-year basis. The statistical metrics, such as Coefficient of Correlation (R) and Bias, are computed for individual AERONET stations as well as for all stations. The effect of availability of common OMI and AERONET data pairs on the comparison is assessed by making comparisons when at least 10, 50 and 100 common pairs are available.</p><p>The results show that about 50% (75%) of OMI-AERONET matchups agree within the absolute difference of ±0.03 (±0.05) for the 500 nm OMI SSA and the 440 nm (or 443 nm) AERONET SSA. The corresponding percentage for the 388 nm OMI SSA and the 440 nm (or 443 nm) AERONET SSA increases to 58% (81%), while the corresponding numbers for the 354 nm SSA OMI and the 440 nm (or 443 nm) AERONET are 43% (67%). It is found that in overall, OMI tends mainly to overestimate (underestimate) SSA for the 500 nm (354 nm) products in comparison to AERONET 440 nm (or 443 nm) with a total bias of 0.025 (-0.024), or 2.7% (2.6%) in relative percentage terms with respect to AERONET (mean AERONET value equal to 0.908), and an overall R value of 0.399 (0.386). At 388 nm, OMI tends to retrieve higher SSA over regions where biomass burning occurs, against lower SSA values elsewhere, with overall bias and R values equal to -0.002 (0.22%) and 0.395, respectively.</p>

scholarly journals The impact of aerosol hygroscopic growth on the single-scattering albedo and its application on the NO<sub>2</sub> photolysis rate coefficient

2014 ◽  
Vol 14 (11) ◽  
pp. 16351-16386
Author(s):  
J. C. Tao ◽  
C. S. Zhao ◽  
N. Ma ◽  
P. F. Liu
Keyword(s):  
Boundary Layer ◽  
Aerosol Particle ◽  
Rate Coefficient ◽  
Aerosol Particles ◽  
Single Scattering ◽  
Single Scattering Albedo ◽  
Hygroscopic Growth ◽  
Particle Population ◽  
The Impact ◽  
Upper Boundary

Abstract. Hygroscopic growth of aerosol particles can significantly affect their single-scattering albedo (ω), and consequently alters the aerosol effect on tropospheric photochemistry. In this study, the impact of aerosol hygroscopic growth on the ω and its application on NO2 photolysis rate coefficient (JNO2) are investigated for a typical aerosol particle population in the North China Plain (NCP). The variations of aerosol optical properties with relative humidity (RH) are calculated using a Mie-theory aerosol optical model, on the basis of field measurements of number size distribution and hygroscopic growth factor from 2009 HaChi (Haze in China) project. Results demonstrate that ambient ω has pronounced diurnal patterns and is highly sensitive to the ambient RHs. Ambient ω in the NCP can be described by a dry state ω value of 0.863, increasing with the RH following a characteristic RH dependence curve. The Monte Carlo simulation shows that the uncertainty of ω from the propagation of uncertainties in the input parameters decreases from 0.03 (at dry state) to 0.01 (RHs > 90%). The impact of hygroscopic growth on ω is further applied in the calculation of the radiative transfer process. Hygroscopic growth of the studied aerosol particle population generally inhibits the photolysis of NO2 at the ground level, whereas accelerates it above the upper boundary layer. Compared with dry state, the calculated JNO2 at RH of 98% at the height of 1 km increases by 30.4%, because of the enhancement of ultraviolet radiation by the humidified scattering-dominant aerosol particles. The increase of JNO2 due to the aerosol hygroscopic growth above the upper boundary layer may affect the tropospheric photochemical processes and this needs to be taken into account in the atmospheric chemical models.

Global variability of aerosol optical properties retrieved from the network of GAW near-surface observatories

2020 ◽  
Author(s):  
Alessandro Bigi ◽  
Martine Collaud Coen ◽  
Elisabeth J. Andrews ◽  
Clémence Rose ◽  
Cathrine Lund Myhre ◽  
...  
Keyword(s):  
Optical Properties ◽  
Single Scattering ◽  
Single Scattering Albedo ◽  
Scattering Coefficient ◽  
Near Surface ◽  
World Data ◽  
Data Centre ◽  
The Impact ◽  
Urban Sites ◽  
Aerosol Properties

&lt;p&gt;Atmospheric aerosols are known to play a key role in Earth&amp;#8217;s radiative budget, although the quantification of their climate forcing is still highly uncertain. In order to improve the scientific understanding of their climatic effect, in-situ ground-based aerosol properties observations are needed by the research community. Such data would also allow the global assessment of the effect of environmental policies over both the short and the long term.&lt;/p&gt;&lt;p&gt;To develop a robust and consistent view over time of the worldwide variability of aerosol properties, data resulting from a fully-characterized value chain, including uncertainty estimation, is needed.&lt;/p&gt;&lt;p&gt;The present work is part of a wider project, having among its goals the investigation of the variability of climate-relevant aerosol properties observed at all sites connected to the Global Atmospheric Watch network, whose data are publicly available from the World Data Centre for Aerosols and follow the aforementioned specifications.&lt;/p&gt;&lt;p&gt;This work focuses on aerosol optical proprieties, i.e. the aerosol light scattering coefficient (&amp;#963;&lt;sub&gt;sp&lt;/sub&gt;), the aerosol light absorption coefficient (&amp;#963;&lt;sub&gt;ap&lt;/sub&gt;), single scattering albedo (&amp;#969;&lt;sub&gt;o&lt;/sub&gt;) and both scattering and absorption &amp;#197;ngstr&amp;#246;m exponents (&amp;#229;&lt;sub&gt;sp&lt;/sub&gt; and &amp;#229;&lt;sub&gt;ap&lt;/sub&gt;).&lt;/p&gt;&lt;p&gt;The analysis includes 108 yearly datasets collected either during 2016 or 2017 at different sites: 53 for absorption and 55 for scattering coefficient datasets, respectively. For 29 of these sites it was also possible to compute single scattering albedo.&lt;/p&gt;&lt;p&gt;The spatial variability in extensive and intensive optical properties was analysed in terms of each site&amp;#8217;s geographical location (either polar, continental, coastal or mountain) and its footprint (from pristine to urban, representing increasing levels of anthropogenic influence).&lt;/p&gt;&lt;p&gt;The results highlight the impact of anthropogenic emissions and biomass burning on absolute levels and annual variability. The effect of sea spray or long range transport of dust is also evident for several sites, along with the influence of regional emissions. The largest seasonality in aerosol loading was observed at mountain sites under mixed footprint conditions, while the lowest seasonality occurred at urban sites. Urban sites also exhibited the highest &amp;#963;sp and &amp;#963;ap values. The lowest levels in &amp;#963;&lt;sub&gt;sp&lt;/sub&gt; and &amp;#963;&lt;sub&gt;ap&lt;/sub&gt; were observed at some polar sites, along with few coastal and mountain sites, despite their typically mixed footprint.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Acknowledgements&lt;/strong&gt;&lt;/p&gt;&lt;p&gt;The authors acknowledge WMO-GAW World Data Centre on Aerosol for providing data available at http://ebas.nilu.no&lt;/p&gt;

scholarly journals A global study of hygroscopicity-driven light-scattering enhancement in the context of other in situ aerosol optical properties

2021 ◽  
Vol 21 (17) ◽  
pp. 13031-13050
Author(s):  
Gloria Titos ◽  
María A. Burgos ◽  
Paul Zieger ◽  
Lucas Alados-Arboledas ◽  
Urs Baltensperger ◽  
...  
Keyword(s):  
Light Scattering ◽  
Radiative Forcing ◽  
Incident Light ◽  
Single Scattering ◽  
Single Scattering Albedo ◽  
Clear Pattern ◽  
Opposite Pattern ◽  
Aerosol Radiative Forcing ◽  
Dry Conditions ◽  
The Impact

Abstract. The scattering and backscattering enhancement factors (f(RH) and fb(RH)) describe how aerosol particle light scattering and backscattering, respectively, change with relative humidity (RH). They are important parameters in estimating direct aerosol radiative forcing (DARF). In this study we use the dataset presented in Burgos et al. (2019) that compiles f(RH) and fb(RH) measurements at three wavelengths (i.e., 450, 550 and 700 nm) performed with tandem nephelometer systems at multiple sites around the world. We present an overview of f(RH) and fb(RH) based on both long-term and campaign observations from 23 sites representing a range of aerosol types. The scattering enhancement shows a strong variability from site to site, with no clear pattern with respect to the total scattering coefficient. In general, higher f(RH) is observed at Arctic and marine sites, while lower values are found at urban and desert sites, although a consistent pattern as a function of site type is not observed. The backscattering enhancement fb(RH) is consistently lower than f(RH) at all sites, with the difference between f(RH) and fb(RH) increasing for aerosol with higher f(RH). This is consistent with Mie theory, which predicts higher enhancement of the light scattering in the forward than in the backward direction as the particle takes up water. Our results show that the scattering enhancement is higher for PM1 than PM10 at most sites, which is also supported by theory due to the change in scattering efficiency with the size parameter that relates particle size and the wavelength of incident light. At marine-influenced sites this difference is enhanced when coarse particles (likely sea salt) predominate. For most sites, f(RH) is observed to increase with increasing wavelength, except at sites with a known dust influence where the spectral dependence of f(RH) is found to be low or even exhibit the opposite pattern. The impact of RH on aerosol properties used to calculate radiative forcing (e.g., single-scattering albedo, ω0, and backscattered fraction, b) is evaluated. The single-scattering albedo generally increases with RH, while b decreases. The net effect of aerosol hygroscopicity on radiative forcing efficiency (RFE) is an increase in the absolute forcing effect (negative sign) by a factor of up to 4 at RH = 90 % compared to dry conditions (RH < 40 %). Because of the scarcity of scattering enhancement measurements, an attempt was made to use other more commonly available aerosol parameters (i.e., ω0 and scattering Ångström exponent, αsp) to parameterize f(RH). The majority of sites (75 %) showed a consistent trend with ω0 (higher f(RH = 85 %) for higher ω0), while no clear pattern was observed between f(RH = 85 %) and αsp. This suggests that aerosol ω0 is more promising than αsp as a surrogate for the scattering enhancement factor, although neither parameter is ideal. Nonetheless, the qualitative relationship observed between ω0 and f(RH) could serve as a constraint on global model simulations.

scholarly journals Comparison of Columnar, Surface, and UAS Profiles of Absorbing Aerosol Optical Depth and Single-Scattering Albedo in South-East Poland

Atmosphere ◽  
2019 ◽  
Vol 10 (8) ◽  
pp. 446 ◽  
Author(s):  
Michał T. Chiliński ◽  
Krzysztof M. Markowicz ◽  
Olga Zawadzka ◽  
Iwona S. Stachlewska ◽  
Justyna Lisok ◽  
...  
Keyword(s):  
Absorption Coefficient ◽  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Measurement Data ◽  
Single Scattering ◽  
Single Scattering Albedo ◽  
Height Distribution ◽  
Vertical Profiles ◽  
Absorbing Aerosols ◽  
The Impact

The impact of absorbing aerosols on climate is complex, with their potential positive or negative forcing, depending on many factors, including their height distribution and reflective properties of the underlying background. Measurement data is very limited, due to insufficient remote sensing methods dedicated to the retrieval of their vertical distribution. Columnar values of absorbing aerosol optical depth (AAOD) and single scattering albedo (SSA) are retrieved by the Aerosol Robotic Network (AERONET). However, the number of available results is low due to sky condition and aerosol optical depth (AOD) limitation. Presented research describes results of field campaigns in Strzyżów (South-East Poland, Eastern Europe) dedicated to the comparison of the absorption coefficient and SSA measurements performed with on-ground in-situ devices (aethalomter, nephelometer), small unmanned aerial system (UAS) carrying micro-aethalometer, as well as with lidar/ceilometer. An important aspect is the comparison of measurement results with those delivered by AERONET. Correlation of absorption to scattering coefficients measured on ground (0.79) and correlation of extinction on ground to AOD measured by AERONET (0.77) was visibly higher than correlation between AOD and AAOD retrieved by AERONET (0.56). Columnar SSA was weakly correlated with ground SSA (higher values of columnar SSA), which were mainly explained by hygroscopic effects, increasing scattering coefficient in ambient (wet conditions), and partly high uncertainty of SSA retrieval. AAOD derived with the use of profiles from UAS up to PBL height, was estimated to contribute in average to 37% of the total AAOD. A method of AAOD estimation, in the whole troposphere, with use of measured vertical profiles of absorption coefficient and extinction coefficient profiles from lidars was proposed. AAOD measured with this method has poor correlation with AERONET data, however for some measurements, within PBL, AAOD was higher than reported by AERONET, suggesting potential underestimation in photometric measurement under particular conditions. Correlation of absorption coefficient in profile to on ground measurements decrease with altitude. Measurements of SSA from drones agree well with ground measurements and are lower than results from AERONET, which suggests a larger contribution of absorbing aerosols. As an alternative for AAOD estimation in case of lack of AERONET AAOD data simple models are proposed, which base on AOD scaling with SSA measured with different methods. Proposed solution increase potential of absorption coefficient measurements in vertical profiles and columns of the atmosphere. Presented solutions make measurements of absorption coefficients in vertical profiles more affordable and allow rough estimation of columnar values for the whole atmosphere.

scholarly journals The impact of aerosol hygroscopic growth on the single-scattering albedo and its application on the NO<sub>2</sub> photolysis rate coefficient

2014 ◽  
Vol 14 (22) ◽  
pp. 12055-12067 ◽  
Author(s):  
J. C. Tao ◽  
C. S. Zhao ◽  
N. Ma ◽  
P. F. Liu
Keyword(s):  
Boundary Layer ◽  
Aerosol Particle ◽  
Rate Coefficient ◽  
Aerosol Particles ◽  
Single Scattering ◽  
Single Scattering Albedo ◽  
Hygroscopic Growth ◽  
Particle Population ◽  
Photolysis Rate ◽  
The Impact

Abstract. Hygroscopic growth of aerosol particles can significantly affect their single-scattering albedo (ω), and consequently alters the aerosol effect on tropospheric photochemistry. In this study, the impact of aerosol hygroscopic growth on ω and its application to the NO2 photolysis rate coefficient (JNO2) are investigated for a typical aerosol particle population in the North China Plain (NCP). The variations of aerosol optical properties with relative humidity (RH) are calculated using a Mie theory aerosol optical model, on the basis of field measurements of number–size distribution and hygroscopic growth factor (at RH values above 90%) from the 2009 HaChi (Haze in China) project. Results demonstrate that ambient ω has pronouncedly different diurnal patterns from ω measured at dry state, and is highly sensitive to the ambient RHs. Ambient ω in the NCP can be described by a dry state ω value of 0.863, increasing with the RH following a characteristic RH dependence curve. A Monte Carlo simulation shows that the uncertainty of ω from the propagation of uncertainties in the input parameters decreases from 0.03 (at dry state) to 0.015 (RHs > 90%). The impact of hygroscopic growth on ω is further applied in the calculation of the radiative transfer process. Hygroscopic growth of the studied aerosol particle population generally inhibits the photolysis of NO2 at the ground level, whereas accelerates it above the moist planetary boundary layer. Compared with dry state, the calculated JNO2 at RH of 98% at the height of 1 km increases by 30.4%, because of the enhancement of ultraviolet radiation by the humidified scattering-dominant aerosol particles. The increase of JNO2 due to the aerosol hygroscopic growth above the upper boundary layer may affect the tropospheric photochemical processes and this needs to be taken into account in the atmospheric chemical models.

scholarly journals A global study of hygroscopicity-driven light scattering enhancement in the context of other in-situ aerosol optical properties

2020 ◽  
Author(s):  
Gloria Titos ◽  
María A. Burgos ◽  
Paul Zieger ◽  
Lucas Alados-Arboledas ◽  
Urs Baltensperger ◽  
...  
Keyword(s):  
Light Scattering ◽  
Radiative Forcing ◽  
Incident Light ◽  
Single Scattering ◽  
Single Scattering Albedo ◽  
Opposite Pattern ◽  
Aerosol Radiative Forcing ◽  
Dry Conditions ◽  
The Difference ◽  
The Impact

Abstract. The scattering and backscattering enhancement factors (f(RH) and fb(RH)) describe how aerosol particle light scattering and backscattering, respectively, change with relative humidity (RH). They are important parameters in estimating direct aerosol radiative forcing (DARF). In this study we use a dataset presented in Burgos et al. (2019) that compiles f(RH) and fb(RH) measurements at three wavelengths (i.e. 450, 550 and 700 nm) performed with tandem nephelometer systems at multiple sites around the world. We present an overview of f(RH) and fb(RH) based on both long-term and campaign observations from 23 sites representing a range of aerosol types. The scattering enhancement shows a strong variability from site to site, with no clear pattern with respect to total scattering coefficient. In general, higher f(RH) is observed at Arctic and marine sites while lower values are found at urban and desert sites, although a consistent pattern as a function of site type is not observed. The backscattering enhancement fb(RH) is consistently lower tan f(RH) at all sites, with the difference between f(RH) and fb(RH) increasing for aerosol with higher f(RH). This is consistent with Mie theory which predicts higher enhancement of the light-scattering in the forward than in the backward direction as the particle takes up water. Our results show that the scattering enhancement is higher for PM1 than PM10 at most sites, which is also supported by theory due to the change in scattering efficiency with the size parameter that relates particle size and wavelength of incident light. At marine-influenced sites this difference is enhanced when coarse particles (likely sea salt) predominate. For most sites, f(RH) is observed to increase with increasing wavelength, except at sites with a known dust influence where the spectral dependence of f(RH) is found to be low or even exhibit the opposite pattern. The impact of RH on aerosol properties used to calculate radiative forcing (e.g., single scattering albedo, ω0, and backscattered fraction, b) is evaluated. The single scattering albedo generally increases with RH while b decreases. The net effect of aerosol hygroscopicity on radiative forcing efficiency (RFE) is an increase in the absolute forcing effect (negative sign) by a factor of up to 4 at RH = 90 % compared to dry conditions (RH 

scholarly journals Quantifying the single scattering albedo for the January 2017 Chile wildfires from simulations of the OMI absorbing aerosol index

2018 ◽  
Author(s):  
Jiyunting Sun ◽  
J. Pepijn Veefkind ◽  
Peter van Velthoven ◽  
Pieternel F. Levelt
Keyword(s):  
Radiative Transfer ◽  
Single Scattering ◽  
Single Scattering Albedo ◽  
Orthogonal Polarization ◽  
Satellite Measurement ◽  
Physical Parameters ◽  
Transfer Model ◽  
Small Data ◽  
The Impact ◽  
Aerosol Index

Abstract. The absorbing aerosol index (AAI) based on the near Ultra-Violet (near-UV) remote sensing techniques is a qualitative parameter that allows to retrieve aerosol optical properties with confidence. In the first part of this study, a series of AAI sensitivity analysis is presented exclusively on biomass burning aerosols. Later on, this study applies a radiative transfer model (DISAMAR) to simulate the AAI measured by the Ozone Monitoring Instrument (OMI) and to derive the aerosol single scattering albedo (ω0). The inputs for the radiative transfer calculations are satellite measurement geometry and surface conditions from OMI, aerosol optical thickness (τ) from the MODerate-resolution Imaging Spectroradiometer (MODIS), and aerosol micro-physical parameters from the AErosol RObotic NETwork (AERONET), respectively. This approach is applied to the Chile wildfires for the period from 26 to 30 January 2017, when the OMI observed AAI of this event reached its peak. The Cloud and Aerosol Lidar with Orthogonal Polarization (CALIOP) failed to capture the evolution of the smoke plume, therefore the aerosol profile is parameterized. The simulated plume ascends to an altitude of 4.5–4.9 km, which is in good agreement with measurements. Due to the relatively small data size of this case, an outlier detection criterion has to be applied. The results show that the AAI simulated by DISAMAR is consistent with observations. The correlation coefficients are over 0.85. The retrieved mean ω0 at 550 nm is approximately 0.84, slightly smaller than the value of 0.90 measured independently by the AERONET instrument. The relative distance between the AERONET site and the plume, the assumption of homogeneous and static plume properties, the lack of the aerosol profile information, and the uncertainties in observations are primarily responsible for this discrepancy. Except for the observational errors, the impact of remaining error sources on ω0 retrieval is difficult to quantify.

Clinical Conundrums When Integrating the QbTest into a Standard ADHD Assessment of Children and Young People

2021 ◽  
Author(s):  
Carsten Vogt
Keyword(s):  
Clinical Practice ◽  
Clinical Decision Making ◽  
Ecological Validity ◽  
Neuropsychological Test ◽  
Real Life ◽  
Clinical Decision ◽  
Hyperactivity Disorder ◽  
Standard Clinical Practice ◽  
Novel Method ◽  
The Impact

AbstractThe uptake of the QbTest in clinical practice is increasing and has recently been supported by research evidence proposing its effectiveness in relation to clinical decision-making. However, the exact underlying process leading to this clinical benefit is currently not well established and requires further clarification. For the clinician, certain challenges arise when adding the QbTest as a novel method to standard clinical practice, such as having the skills required to interpret neuropsychological test information and assess for diagnostically relevant neurocognitive domains that are related to attention-deficit hyperactivity disorder (ADHD), or how neurocognitive domains express themselves within the behavioral classifications of ADHD and how the quantitative measurement of activity in a laboratory setting compares with real-life (ecological validity) situations as well as the impact of comorbidity on test results. This article aims to address these clinical conundrums in aid of developing a consistent approach and future guidelines in clinical practice.

scholarly journals Retrieval of aerosol single-scattering albedo and polarized phase function from polarized sun-photometer measurements for Zanjan's atmosphere

2013 ◽  
Vol 6 (10) ◽  
pp. 2659-2669 ◽  
Author(s):  
A. Bayat ◽  
H. R. Khalesifard ◽  
A. Masoumi
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Atmospheric Aerosols ◽  
Phase Function ◽  
Single Scattering ◽  
Single Scattering Albedo ◽  
Angstrom Exponent ◽  
Ångström Exponent ◽  
Sun Photometer ◽  
Ångstrom Exponent

Abstract. The polarized phase function of atmospheric aerosols has been investigated for the atmosphere of Zanjan, a city in northwest Iran. To do this, aerosol optical depth, Ångström exponent, single-scattering albedo, and polarized phase function have been retrieved from the measurements of a Cimel CE 318-2 polarized sun-photometer from February 2010 to December 2012. The results show that the maximum value of aerosol polarized phase function as well as the polarized phase function retrieved for a specific scattering angle (i.e., 60°) are strongly correlated (R = 0.95 and 0.95, respectively) with the Ångström exponent. The latter has a meaningful variation with respect to the changes in the complex refractive index of the atmospheric aerosols. Furthermore the polarized phase function shows a moderate negative correlation with respect to the atmospheric aerosol optical depth and single-scattering albedo (R = −0.76 and −0.33, respectively). Therefore the polarized phase function can be regarded as a key parameter to characterize the atmospheric particles of the region – a populated city in the semi-arid area and surrounded by some dust sources of the Earth's dust belt.

Sign in / Sign up

Export Citation Format

Share Document