scholarly journals Aerosol direct radiative effect in the Po Valley region derived from AERONET measurements

2008 ◽  
Vol 8 (16) ◽  
pp. 4925-4946 ◽  
Author(s):  
M. Clerici ◽  
F. Mélin
Keyword(s):  
Regional Climate ◽  
Single Scattering ◽  
Radiative Effect ◽  
Aerosol Model ◽  
Po Valley ◽  
Spatial Gradients ◽  
Clear Sky ◽  
Scattering Phase ◽  
Absorbing Aerosols ◽  
Scattering Phase Function

Abstract. The aerosol direct radiative effect (ADRE) affecting the Po Valley and the adjacent North Adriatic Sea is studied using 10-year series of measurements collected at two AERONET sites located in the western part of the Valley (Ispra), and on a platform (AAOT) offshore Venice. This region is characterized by a high, mostly continental, aerosol load with comparable average aerosol optical thickness τa at both locations (0.21 at 500 nm) and more absorbing aerosols at Ispra. A dynamic aerosol model accounting for the changes in scattering phase function with τa is used for radiative transfer calculations, together with boundary conditions representative of terrestrial and marine surfaces. A sensitivity analysis allows the construction of an error budget for the daily ADRE estimates, found to be of the order of 20% and mostly due to uncertainties on aerosol single scattering albedo and τa. The daily radiative efficiencies, normalized by τa at 500 nm, increase from December to June, from −17 to −24 W m−2 τa−1 at top-of-atmosphere (TOA) and −33 to −72 W m−2 τa−1 at surface for the Po Valley, and from −15 to −32 (TOA) and −35 to −65 W m−2 τa−1 (surface) for the AAOT site. The average of log-transformed ADRE for TOA, surface and atmosphere are −5.2, −12.2 and +6.8 W m−2 for the Po Valley case, and −6.5, −13.0 and +6.5 W m−2 for the AAOT site but these values can be much higher for individual days. Concurrent clear-sky days give indications on the regional atmospheric heating spatial gradients. Differences between the atmospheric ADRE at the two locations average 6.3 W m−2 with a gradient positive towards the inner valley in 65% of the cases. This study confirms the importance of duly considering the radiative impact of aerosols on the regional climate.

scholarly journals Aerosol direct radiative effect in the Po Valley region derived from AERONET measurements

2008 ◽  
Vol 8 (1) ◽  
pp. 3227-3285 ◽  
Author(s):  
M. Clerici ◽  
F. Mélin
Keyword(s):  
Regional Climate ◽  
Single Scattering ◽  
Radiative Effect ◽  
Aerosol Model ◽  
Po Valley ◽  
Spatial Gradients ◽  
Clear Sky ◽  
Scattering Phase ◽  
Absorbing Aerosols ◽  
Scattering Phase Function

Abstract. The aerosol direct radiative effect (ADRE) affecting the Po Valley and the adjacent North Adriatic Sea is studied using 10-year series of measurements collected at two AERONET sites located in the western part of the Valley (Ispra), and on a platform (AAOT) offshore Venice. This region is characterized by a high, mostly continental, aerosol load with comparable average aerosol optical thickness τa at both locations (0.21 at 500 nm) and more absorbing aerosols at Ispra. A dynamic aerosol model accounting for the changes in scattering phase function with τa is used for radiative transfer calculations, together with boundary conditions representative of terrestrial and marine surfaces. A sensitivity analysis allows the construction of an error budget for the daily ADRE estimates, found to be of the order of 20% and mostly due to uncertainties on aerosol single scattering albedo and τa. The daily radiative efficiencies, normalized by τa at 500 nm, increase from December to June, from −17 to −24 W m−2 τa−1 at top-of-atmosphere (TOA) and −33 to −72 W m−2 τa−1 at surface for the Po Valley, and from −15 to −32 (TOA) and −35 to −65 W m−2 τa−1 (surface) for the AAOT site. The average of log-transformed ADRE for TOA, surface and atmosphere are −5.2, −12.2 and +6.8 W m−2 for the Po Valley case, and −6.5, −13.0 and +6.5 W m−2 for the AAOT site but these values can be much higher for individual days. Concurrent clear-sky days give indications on the regional atmospheric heating spatial gradients. Differences between the atmospheric ADRE at the two locations average 6.3 W m−2 with a gradient positive towards the inner valley in 65% of the cases. This study confirms the importance of duly considering the radiative impact of aerosols on the regional climate.

scholarly journals Modeling of Aerosol Radiation-Relevant Parameters in the Troposphere of Siberia on the Basis of Empirical Data

Atmosphere ◽  
2018 ◽  
Vol 9 (11) ◽  
pp. 414 ◽  
Author(s):  
Mikhail Panchenko ◽  
Svetlana Terpugova ◽  
Victor Pol’kin ◽  
Valerii Kozlov ◽  
Dmitry Chernov
Keyword(s):  
Complex Refractive Index ◽  
West Siberia ◽  
Single Scattering ◽  
Single Scattering Albedo ◽  
Optical Characteristics ◽  
Asymmetry Factor ◽  
Size Spectrum ◽  
Scattering Phase ◽  
Scattering Phase Function ◽  
Modal Radius

The paper presents the generalized empirical model of the aerosol optical characteristics in the lower 5-km layer of the atmosphere of West Siberia. The model is based on the data of long-term airborne sensing of the vertical profiles of the angular scattering coefficient, aerosol disperse composition, as well as the content of absorbing particles. The model provides for retrieval of the aerosol optical characteristics in visible and near IR wavelength ranges (complex refractive index, scattering and absorption coefficients, optical depth, single scattering albedo, and asymmetry factor of the scattering phase function). The main attention in the presented version of the model is given to two aspects: The study of the effect of the size spectrum of the absorbing substance in the composition of aerosol particles on radiative-relevant parameters (the single scattering albedo (SSA) and the asymmetry factor (AF)) and the consideration of different algorithms for taking into account the relative humidity of air. The ranges of uncertainty of SSA and AF at variations in the modal radius of the absorbing fraction at different altitudes in the troposphere are estimated.

scholarly journals First correlated measurements of the shape and scattering properties of cloud particles using the new Particle Habit Imaging and Polar Scattering (PHIPS) probe

2011 ◽  
Vol 4 (3) ◽  
pp. 2883-2930
Author(s):  
A. Abdelmonem ◽  
M. Schnaiter ◽  
P. Amsler ◽  
E. Hesse ◽  
J. Meyer ◽  
...  
Keyword(s):  
Optical Sensor ◽  
Optical Resolution ◽  
Single Scattering ◽  
Cirrus Clouds ◽  
Size Distributions ◽  
Radiative Impact ◽  
Scattering Phase ◽  
Cloud Particles ◽  
Ice Crystal Size ◽  
Scattering Phase Function

Abstract. Studying the radiative impact of cirrus clouds requires the knowledge of the link between their microphysics and the single scattering properties of the cloud particles. Usually, this link is created by modeling the optical scattering properties from in situ measurements of ice crystal size distributions. The measured size distribution and the assumed particle shape might be erroneous in case of non-spherical ice particles. We present here a novel optical sensor (the Particle Habit Imaging and Polar Scattering probe, PHIPS) designed to measure the 3-D morphology and the corresponding optical and microphysical parameters of individual cloud particles, simultaneously. Clouds containing particles ranging in size from a few micrometers to about 800 μm diameter can be systematically characterized with an optical resolution power of 2 μm and polar scattering resolution of 1° for forward scattering directions (from 1° to 10°) and 8° for side and backscattering directions (from 18° to 170°). The maximum acquisition rates for scattering phase functions and images are 262 KHz and 10 Hz, respectively. Some preliminary results collected in two ice cloud campaigns which were conducted in the AIDA cloud simulation chamber are presented. PHIPS showed reliability in operation and produced comparable size distributions and images to those given by other certified cloud particles instruments. A 3-D model of a hexagonal ice plate is constructed and the corresponding scattering phase function is compared to that modeled using the Ray Tracing with Diffraction on Facets (RTDF) program. PHIPS is candidate to be a novel air borne optical sensor for studying the radiative impact of cirrus clouds and correlating the particle habit-scattering properties which will serve as a reference for other single, or multi-independent, measurements instruments.

scholarly journals Vertical variability of the properties of highly aged biomass burning aerosol transported over the southeast Atlantic during CLARIFY-2017

2020 ◽  
Author(s):  
Huihui Wu ◽  
Jonathan W. Taylor ◽  
Kate Szpek ◽  
Justin Langridge ◽  
Paul I. Williams ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Climate Models ◽  
Marine Boundary Layer ◽  
Regional Climate ◽  
Single Scattering ◽  
Important Region ◽  
Absorbing Aerosols ◽  
Lower Temperature ◽  
The Impact ◽  
Vertical Variability

Abstract. Seasonal biomass burning (BB) from June to October in central and southern Africa leads to absorbing aerosols being transported over the south Atlantic Ocean every year, and contributes significantly to the regional climate forcing. The vertical distribution of submicron aerosols and their properties were characterized over the remote southeast Atlantic for the first time, using airborne in-situ measurements made during the CLoud-Aerosol-Radiation Interactions and Forcing for Year 2017 (CLARIFY-2017) campaign. BB aerosols were intensively observed in the region surrounding Ascension Island, in the marine boundary layer (MBL) and free troposphere (FT) up to 5 km. We show that the aerosols had undergone a significant aging process during > 7 days transit from source, as indicated by highly oxidized organic aerosol and thickly coated black carbon (BC). The highly aged BB aerosols in the CLARIFY region were also especially rich in BC compared with those from other regions. We also found significant vertical variation in the single scattering albedos (SSA) of these aerosols, as a function of relative chemical composition and size. The lowest SSA was generally in the low FT layer around 2000 m altitude (medians: 0.83 at 405 nm and 0.80 at 658 nm). This finding is important since it means that BB aerosols across the east Atlantic region are more absorbing than is currently represented in climate models. Furthermore, in the FT, we show that SSA increased with altitude and this was associated with an enhanced inorganic nitrate mass fraction and aerosol size. This likely results from increased partitioning to the existing particles at higher altitude with lower temperature and higher relative humidity. After entrainment into the BL, aerosols were generally smaller in size than were observed in the FT, and had a larger fraction of scattering material with resultant higher average dry SSA, mostly due to marine emissions and aerosol removal by drizzle. Our results provide unique observational constraints on aerosol parameterizations used in modelling regional radiation interactions over this important region. We recommend that future work should consider the impact of this vertical variability on climate models.

Statistical estimates of the effect of the sea water scattering phase function on the characteristics of airborne hydrooptical lidar signals

2021 ◽  
pp. 171-177
Author(s):  
A.A. Lisenko ◽  
◽  
V.S. Shamanaev ◽  
Keyword(s):  
Sea Water ◽  
Water Layer ◽  
Single Scattering ◽  
Airborne Lidar ◽  
Statistical Estimates ◽  
Scattering Approximation ◽  
Coastal Sea ◽  
Scattering Phase ◽  
Scattering Phase Function ◽  
Phase Functions

The effect of the scattering phase functions of sea water types by the Petzold classification on the characteristics of signals of an airborne lidar is investigated using the Monte Carlo method. It is shown that for pure and coastal waters, the single scattering approximation is applicable for solving the laser sensing equation. Based on the analysis of the results obtained in the closed numerical experiment, the method of reconstruction of the extinction coefficient of lidar signals by pure and coastal sea waters in the mixing water layer is proposed and substantiated. The obtained results can be used to expand the possibilities of lidar signal interpretation, especially in complex and ambiguous situations.

scholarly journals Modelling Laboratory Data of Bidirectional Reflectance of a Regolith Surface Containing Alumina

2011 ◽  
Vol 28 (3) ◽  
pp. 261-265 ◽  
Author(s):  
C. Bhattacharjee ◽  
D. Deb ◽  
H. S. Das ◽  
A. K. Sen ◽  
R. Gupta
Keyword(s):  
Laboratory Data ◽  
Size Composition ◽  
Single Scattering ◽  
Bidirectional Reflectance ◽  
Reflection Function ◽  
Versus Phase ◽  
Scattering Phase ◽  
Scattering Phase Function ◽  
Phase Functions ◽  
Bidirectional Reflection

AbstractBidirectional reflectance of a surface is defined as the ratio of the scattered radiation at the detector to the incident irradiance as a function of geometry. Accurate knowledge of the bidirectional reflection function for layers composed of discrete, randomly positioned scattering particles is essential for many remote sensing, engineering, and biophysical applications, as well as for different areas of astrophysics. Computations of bidirectional reflection functions for plane parallel particulate layers are usually reduced to solving the radiative transfer equation by the existing techniques. In this work we present our laboratory data on bidirectional reflectance versus phase angle for two sample sizes of alumina, 0.3 and 1 μm, for the He–Ne laser at wavelengths of 632.8 nm (red) and 543.5 nm (green). The nature of the phase curves of the asteroids depends on the parameters like particle size, composition, porosity, roughness, etc. In the present study we analyze data which are being generated using a single scattering phase function, that is, Mie theory of treating particles as a compact sphere. The well-known Hapke formula, along with different particle phase functions such as Mie and Henyey–Greenstein, will be used to model the laboratory data obtained at the asteroid laboratory of Assam University.

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