scholarly journals Simultaneous retrieval of aerosol and surface optical properties from combined airborne- and ground-based direct and diffuse radiometric measurements

2010 ◽  
Vol 10 (6) ◽  
pp. 2777-2794 ◽  
Author(s):  
C. K. Gatebe ◽  
O. Dubovik ◽  
M. D. King ◽  
A. Sinyuk
Keyword(s):  
Optical Properties ◽  
Land Surface ◽  
Surface Characteristics ◽  
Index Of Refraction ◽  
The Arctic ◽  
Aerosol Size Distribution ◽  
Inversion Method ◽  
Good Test ◽  
Radiometric Measurements ◽  
Surface Optical

Abstract. This paper presents a new method for simultaneously retrieving aerosol and surface reflectance properties from combined airborne and ground-based direct and diffuse radiometric measurements. The method is based on the standard Aerosol Robotic Network (AERONET) method for retrieving aerosol size distribution, complex index of refraction, and single scattering albedo, but modified to retrieve aerosol properties in two layers, below and above the aircraft, and parameters on surface optical properties from combined datasets (Cloud Absorption Radiometer (CAR) and AERONET data). A key advantage of this method is the inversion of all available spectral and angular data at the same time, while accounting for the influence of noise in the inversion procedure using statistical optimization. The wide spectral (0.34–2.30 μm) and angular range (180°) of the CAR instrument, combined with observations from an AERONET sunphotometer, provide sufficient measurement constraints for characterizing aerosol and surface properties with minimal assumptions. The robustness of the method was tested on observations made during four different field campaigns: (a) the Southern African Regional Science Initiative 2000 over Mongu, Zambia, (b) the Intercontinental Transport Experiment-Phase B over Mexico City, Mexico (c) Cloud and Land Surface Interaction Campaign over the Atmospheric Radiation Measurement (ARM) Central Facility, Oklahoma, USA, and (d) the Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) over Elson Lagoon in Barrow, Alaska, USA. The four areas are dominated by different surface characteristics and aerosol types, and therefore provide good test cases for the new inversion method.

scholarly journals Simultaneous retrieval of aerosol and surface optical properties from combined airborne- and ground-based direct and diffuse radiometric measurements

2009 ◽  
Vol 9 (6) ◽  
pp. 26491-26538 ◽  
Author(s):  
C. K. Gatebe ◽  
O. Dubovik ◽  
M. D. King ◽  
A. Sinyuk
Keyword(s):  
Optical Properties ◽  
Land Surface ◽  
Surface Characteristics ◽  
Index Of Refraction ◽  
The Arctic ◽  
Aerosol Size Distribution ◽  
Inversion Method ◽  
Good Test ◽  
Radiometric Measurements ◽  
Surface Optical

Abstract. This paper presents a new method for simultaneously retrieving aerosol and surface reflectance properties from combined airborne and ground-based direct and diffuse radiometric measurements. The method is based on the standard Aerosol Robotic Network (AERONET) method for retrieving aerosol size distribution, complex index of refraction, and single scattering albedo, but modified to retrieve aerosol properties in two layers, below and above the aircraft, and parameters on surface optical properties from combined datasets (Cloud Absorption Radiometer, CAR, and AERONET data). A key advantage of this method is the inversion of all available spectral and angular data at the same time, while accounting for the influence of noise in the inversion procedure using statistical optimization. The wide spectral (0.34–2.30 μm) and angular range (180°) of the CAR instrument, combined with observations from an AERONET sunphotometer, provide sufficient measurement constraints for characterizing aerosol and surface properties with minimal assumptions. The robustness of the method was tested on observations made during four different field campaigns: (a) the Southern African Regional Science Initiative 2000 over Mongu, Zambia, (b) the Intercontinental Transport Experiment-Phase B over Mexico City, Mexico (c) Cloud and Land Surface Interaction Campaign over the Atmospheric Radiation Measurement (ARM) Central Facility, Oklahoma, USA, and (d) the Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) over Elson Lagoon in Barrow, Alaska, USA. The four areas are dominated by different surface characteristics and aerosol types, and therefore provide good test cases for the new inversion method.

scholarly journals Toward a minimal representation of aerosols in climate models: description and evaluation in the Community Atmosphere Model CAM5

2012 ◽  
Vol 5 (3) ◽  
pp. 709-739 ◽  
Author(s):  
X. Liu ◽  
R. C. Easter ◽  
S. J. Ghan ◽  
R. Zaveri ◽  
P. Rasch ◽  
...  
Keyword(s):  
Developing Countries ◽  
Optical Properties ◽  
Size Distribution ◽  
Sea Salt ◽  
The Arctic ◽  
Aerosol Size Distribution ◽  
Model Version ◽  
Community Atmosphere Model ◽  
Atmosphere Model ◽  
Aerosol Module

Abstract. A modal aerosol module (MAM) has been developed for the Community Atmosphere Model version 5 (CAM5), the atmospheric component of the Community Earth System Model version 1 (CESM1). MAM is capable of simulating the aerosol size distribution and both internal and external mixing between aerosol components, treating numerous complicated aerosol processes and aerosol physical, chemical and optical properties in a physically-based manner. Two MAM versions were developed: a more complete version with seven lognormal modes (MAM7), and a version with three lognormal modes (MAM3) for the purpose of long-term (decades to centuries) simulations. In this paper a description and evaluation of the aerosol module and its two representations are provided. Sensitivity of the aerosol lifecycle to simplifications in the representation of aerosol is discussed. Simulated sulfate and secondary organic aerosol (SOA) mass concentrations are remarkably similar between MAM3 and MAM7. Differences in primary organic matter (POM) and black carbon (BC) concentrations between MAM3 and MAM7 are also small (mostly within 10%). The mineral dust global burden differs by 10% and sea salt burden by 30–40% between MAM3 and MAM7, mainly due to the different size ranges for dust and sea salt modes and different standard deviations of the log-normal size distribution for sea salt modes between MAM3 and MAM7. The model is able to qualitatively capture the observed geographical and temporal variations of aerosol mass and number concentrations, size distributions, and aerosol optical properties. However, there are noticeable biases; e.g., simulated BC concentrations are significantly lower than measurements in the Arctic. There is a low bias in modeled aerosol optical depth on the global scale, especially in the developing countries. These biases in aerosol simulations clearly indicate the need for improvements of aerosol processes (e.g., emission fluxes of anthropogenic aerosols and precursor gases in developing countries, boundary layer nucleation) and properties (e.g., primary aerosol emission size, POM hygroscopicity). In addition, the critical role of cloud properties (e.g., liquid water content, cloud fraction) responsible for the wet scavenging of aerosol is highlighted.

scholarly journals Toward a minimal representation of aerosol direct and indirect effects: model description and evaluation

2011 ◽  
Vol 4 (4) ◽  
pp. 3485-3598 ◽  
Author(s):  
X. Liu ◽  
R. C. Easter ◽  
S. J. Ghan ◽  
R. Zaveri ◽  
P. Rasch ◽  
...  
Keyword(s):  
Developing Countries ◽  
Optical Properties ◽  
Size Distribution ◽  
Mineral Dust ◽  
Sea Salt ◽  
The Arctic ◽  
Aerosol Size Distribution ◽  
Model Description ◽  
Accumulation Mode ◽  
Model Version

Abstract. A modal aerosol module (MAM) has been developed for the Community Atmosphere Model version 5 (CAM5), the atmospheric component of the Community Earth System Model version 1 (CESM1). MAM is capable of simulating the aerosol size distribution and both internal and external mixing between aerosol components, treating numerous complicated aerosol processes and aerosol physical, chemical and optical properties in a physically based manner. Two MAM versions were developed: a more complete version with seven lognormal modes (MAM7), and a version with three lognormal modes (MAM3) for the purpose of long-term (decades to centuries) simulations. Major approximations in MAM3 include assuming immediate mixing of primary organic matter (POM) and black carbon (BC) with other aerosol components, merging of the MAM7 fine dust and fine sea salt modes into the accumulation mode, merging of the MAM7 coarse dust and coarse sea salt modes into the single coarse mode, and neglecting the explicit treatment of ammonia and ammonium cycles. Simulated sulfate and secondary organic aerosol (SOA) mass concentrations are remarkably similar between MAM3 and MAM7 as most (~90%) of these aerosol species are in the accumulation mode. Differences of POM and BC concentrations between MAM3 and MAM7 are also small (mostly within 10%) because of the assumed hygroscopic nature of POM, so that much of the freshly emitted POM and BC is wet-removed before mixing internally with soluble aerosol species. Sensitivity tests with the POM assumed to be hydrophobic and with slower aging increase the POM and BC concentrations, especially at high latitudes (by several times). The mineral dust global burden differs by 10% and sea salt burden by 30–40% between MAM3 and MAM7 mainly due to the different size ranges for dust and sea salt modes and different standard deviations of the log-normal size distribution for sea salt modes between MAM3 and MAM7. The model is able to qualitatively capture the observed geographical and temporal variations of aerosol mass and number concentrations, size distributions, and aerosol optical properties. However, there are noticeable biases, e.g., simulated sulfate and mineral dust concentrations at surface over the oceans are too low. Simulated BC concentrations are significantly lower than measurements in the Arctic. There is a low bias in modeled aerosol optical depth on the global scale, especially in the developing countries. There biases in aerosol simulations clearly indicate the need for improvements of aerosol processes (e.g., emission fluxes of anthropogenic aerosols and precursor gases in developing countries, boundary layer nucleation) and properties (e.g., primary aerosol emission size, POM hygroscopicity). In addition the critical role of cloud properties (e.g., liquid water content, cloud fraction) responsible for the wet scavenging of aerosol is highlighted.

scholarly journals Standardized monitoring of permafrost thaw: a user-friendly, multi-parameter protocol

2021 ◽  
Author(s):  
Julia Boike ◽  
Sarah Chadburn ◽  
Julia Martin ◽  
Simon Zwieback ◽  
Inge H.J. Althuizen ◽  
...  
Keyword(s):  
Land Surface ◽  
Ground Surface ◽  
Surface Characteristics ◽  
The Arctic ◽  
Vegetation Height ◽  
Permafrost Thaw ◽  
Standardized Protocol ◽  
Indigenous Groups ◽  
Thaw Depth ◽  
User Friendly

Climate change is destabilizing permafrost landscapes, affecting infrastructure, ecosystems and human livelihoods. The rate of permafrost thaw is controlled by surface and subsurface properties and processes, all of which are potentially linked with each other. Yet, no standardized protocol exists for measuring permafrost thaw and related processes and properties in a linked manner. The permafrost thaw action group of the Terrestrial Multidisciplinary distributed Observatories for the Study of the Arctic Connections (T-MOSAiC) project has developed a protocol, for use by non-specialist scientists and technicians, citizen scientists and indigenous groups, to collect standardized metadata and data on permafrost thaw. The protocol introduced here addresses the need to jointly measure permafrost thaw and the associated surface and subsurface environmental conditions. The parameters measured along transects are: snow depth, thaw depth, vegetation height, soil texture, and water level. The metadata collection includes data on timing of data collection, geographical coordinates, land surface characteristics (vegetation, ground surface, water conditions), as well as photographs. Our hope is that this openly available dataset will also be highly valuable for validation and parameterization of numerical and conceptual models, thus to the broad community represented by the T-MOSAIC project.

Optical properties of a thin layer of the Vanadium dioxide at the metal state

2015 ◽  
Vol 9 (1) ◽  
pp. 2303-2310
Author(s):  
Abderrahim Benchaib ◽  
Abdesselam Mdaa ◽  
Izeddine Zorkani ◽  
Anouar Jorio
Keyword(s):  
Optical Properties ◽  
Thin Layer ◽  
Vanadium Dioxide ◽  
Ultra Violet ◽  
Index Of Refraction ◽  
Cost Of Energy ◽  
Infra Red ◽  
Metal State ◽  
The Cost ◽  
Reversible Phase

The vanadium dioxide VO₂ currently became very motivating for the nanotechnologies’ researchers. It makes party of the intelligent materials because these optical properties abruptly change semiconductor state with metal at a critical  temperature θ = 68°C. This transition from reversible phase is carried out from a monoclinical structure characterizing its semiconductor state at low temperature towards the metal state of this material which becomes tétragonal rutile for  θ ˃ 68°C ; it is done during a few nanoseconds. Several studies were made on this material in a massive state and a thin layer. We will simulate by Maple the constant optics of a thin layer of VO₂ thickness z = 82 nm for the metal state according to the energy ω of the incidental photons in the energy interval: 0.001242 ≤ ω(ev) ≤ 6, from the infra-red (I.R) to the ultra-violet (U.V) so as to be able to control the various technological nano applications, like the detectors I.R or the U.V,  the intelligent windows to  increase  the energy efficiency in the buildings in order to save the cost of energy consumption by electric air-conditioning and the paintings containing nano crystals of this material. The constant optics, which we will simulate, is: the index of refraction, the reflectivity, the transmittivity, the coefficient of extinction, the dielectric functions ԑ₁ real part and  ԑ₂  imaginary part of the permittivity complexes ԑ of this material and the coefficient absorption. 

Optical properties of the Vanadium dioxide

2015 ◽  
Vol 8 (2) ◽  
pp. 2148-2155 ◽  
Author(s):  
Abderrahim Benchaib ◽  
Abdesselam Mdaa ◽  
Izeddine Zorkani ◽  
Anouar Jorio
Keyword(s):  
Energy Efficiency ◽  
Optical Properties ◽  
Critical Temperature ◽  
Thin Layer ◽  
Dielectric Function ◽  
Vanadium Dioxide ◽  
Ultra Violet ◽  
Index Of Refraction ◽  
Practical Utility ◽  
Infra Red

The vanadium dioxide is a material thermo chromium which sees its optical properties changing at the time of the transition from the phase of semiconductor state ↔ metal, at a critical temperature of 68°C. The study of the optical properties of a thin layer of VO₂ thickness 82 nm, such as the dielectric function, the index of refraction, the coefficient ofextinction, the absorption’s coefficient, the reflectivity, the transmittivity, in the photonic spectrum of energy ω located inthe interval: 0.001242 ≤ ω (ev) ≤ 6, enables us to control well its practical utility in various applications, like the intelligentpanes, the photovoltaic, paintings for increasing energy efficiency in buildings, detectors of infra-red (I.R) or ultra-violet(U.V). We will make simulations with Maple and compare our results with those of the literature

scholarly journals The Gradient Effect on the Relationship between the Underlying Factor and Land Surface Temperature in Large Urbanized Region

Land ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 20
Author(s):  
Yixu Wang ◽  
Mingxue Xu ◽  
Jun Li ◽  
Nan Jiang ◽  
Dongchuan Wang ◽  
...  
Keyword(s):  
Surface Temperature ◽  
Land Surface Temperature ◽  
Land Surface ◽  
Landscape Planning ◽  
Potential Gradient ◽  
Surface Characteristics ◽  
Ordinary Least Squares ◽  
Urban Agglomeration ◽  
Spatial Gradient ◽  
Gradient Effect

Although research relating to the urban heat island (UHI) phenomenon has been significantly increasing in recent years, there is still a lack of a continuous and clear recognition of the potential gradient effect on the UHI—landscape relationship within large urbanized regions. In this study, we chose the Beijing-Tianjin-Hebei (BTH) region, which is a large scaled urban agglomeration in China, as the case study area. We examined the causal relationship between the LST variation and underlying surface characteristics using multi-temporal land cover and summer average land surface temperature (LST) data as the analyzed variables. This study then further discussed the modeling performance when quantifying their relationship from a spatial gradient perspective (the grid size ranged from 6 to 24 km), by comparing the ordinary least squares (OLS) and geographically weighted regression (GWR) methods. The results indicate that: (1) both the OLS and GWR analysis confirmed that the composition of built-up land contributes as an essential factor that is responsible for the UHI phenomenon in a large urban agglomeration region; (2) for the OLS, the modeled relationship between the LST and its drive factor showed a significant spatial gradient effect, changing with different spatial analysis grids; and, (3) in contrast, using the GWR model revealed a considerably robust and better performance for accommodating the spatial non-stationarity with a lower scale dependence than that of the OLS model. This study highlights the significant spatial heterogeneity that is related to the UHI effect in large-extent urban agglomeration areas, and it suggests that the potential gradient effect and uncertainty induced by different spatial scale and methodology usage should be considered when modeling the UHI effect with urbanization. This would supplement current UHI study and be beneficial for deepening the cognition and enlightenment of landscape planning for UHI regulation.

scholarly journals Evaluating model parameterizations of submicron aerosol scattering and absorption with in situ data from ARCTAS 2008

2016 ◽  
Vol 16 (14) ◽  
pp. 9435-9455 ◽  
Author(s):  
Matthew J. Alvarado ◽  
Chantelle R. Lonsdale ◽  
Helen L. Macintyre ◽  
Huisheng Bian ◽  
Mian Chin ◽  
...  
Keyword(s):  
Optical Properties ◽  
Size Distribution ◽  
Aerosol Size Distribution ◽  
Visible Radiation ◽  
Submicron Aerosol ◽  
In Situ Data ◽  
Aerosol Absorption ◽  
Aerosol Scattering ◽  
The Impact

Abstract. Accurate modeling of the scattering and absorption of ultraviolet and visible radiation by aerosols is essential for accurate simulations of atmospheric chemistry and climate. Closure studies using in situ measurements of aerosol scattering and absorption can be used to evaluate and improve models of aerosol optical properties without interference from model errors in aerosol emissions, transport, chemistry, or deposition rates. Here we evaluate the ability of four externally mixed, fixed size distribution parameterizations used in global models to simulate submicron aerosol scattering and absorption at three wavelengths using in situ data gathered during the 2008 Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) campaign. The four models are the NASA Global Modeling Initiative (GMI) Combo model, GEOS-Chem v9-02, the baseline configuration of a version of GEOS-Chem with online radiative transfer calculations (called GC-RT), and the Optical Properties of Aerosol and Clouds (OPAC v3.1) package. We also use the ARCTAS data to perform the first evaluation of the ability of the Aerosol Simulation Program (ASP v2.1) to simulate submicron aerosol scattering and absorption when in situ data on the aerosol size distribution are used, and examine the impact of different mixing rules for black carbon (BC) on the results. We find that the GMI model tends to overestimate submicron scattering and absorption at shorter wavelengths by 10–23 %, and that GMI has smaller absolute mean biases for submicron absorption than OPAC v3.1, GEOS-Chem v9-02, or GC-RT. However, the changes to the density and refractive index of BC in GC-RT improve the simulation of submicron aerosol absorption at all wavelengths relative to GEOS-Chem v9-02. Adding a variable size distribution, as in ASP v2.1, improves model performance for scattering but not for absorption, likely due to the assumption in ASP v2.1 that BC is present at a constant mass fraction throughout the aerosol size distribution. Using a core-shell mixing rule in ASP overestimates aerosol absorption, especially for the fresh biomass burning aerosol measured in ARCTAS-B, suggesting the need for modeling the time-varying mixing states of aerosols in future versions of ASP.

scholarly journals Aerosol chemical and optical properties over the Paris area within ESQUIF project

2006 ◽  
Vol 6 (11) ◽  
pp. 3257-3280 ◽  
Author(s):  
A. Hodzic ◽  
R. Vautard ◽  
P. Chazette ◽  
L. Menut ◽  
B. Bessagnet
Keyword(s):  
Optical Properties ◽  
Secondary Organic Aerosols ◽  
Organic Aerosols ◽  
Dust Particles ◽  
Aerosol Size Distribution ◽  
Aerosol Composition ◽  
Aerosol Mass ◽  
Coarse Mode ◽  
Paris Area ◽  
Flight Trajectories

Abstract. Aerosol chemical and optical properties are extensively investigated for the first time over the Paris Basin in July 2000 within the ESQUIF project. The measurement campaign offers an exceptional framework to evaluate the performances of the chemistry-transport model CHIMERE in simulating concentrations of gaseous and aerosol pollutants, as well as the aerosol-size distribution and composition in polluted urban environments against ground-based and airborne measurements. A detailed comparison of measured and simulated variables during the second half of July with particular focus on 19 and 31 pollution episodes reveals an overall good agreement for gas-species and aerosol components both at the ground level and along flight trajectories, and the absence of systematic biases in simulated meteorological variables such as wind speed, relative humidity and boundary layer height as computed by the MM5 model. A good consistency in ozone and NO concentrations demonstrates the ability of the model to reproduce the plume structure and location fairly well both on 19 and 31 July, despite an underestimation of the amplitude of ozone concentrations on 31 July. The spatial and vertical aerosol distributions are also examined by comparing simulated and observed lidar vertical profiles along flight trajectories on 31 July and confirm the model capacity to simulate the plume characteristics. The comparison of observed and modeled aerosol components in the southwest suburb of Paris during the second half of July indicates that the aerosol composition is rather correctly reproduced, although the total aerosol mass is underestimated by about 20%. The simulated Parisian aerosol is dominated by primary particulate matter that accounts for anthropogenic and biogenic primary particles (40%), and inorganic aerosol fraction (40%) including nitrate (8%), sulfate (22%) and ammonium (10%). The secondary organic aerosols (SOA) represent 12% of the total aerosol mass, while the mineral dust accounts for 8%. The comparison demonstrates the absence of systematic errors in the simulated sulfate, ammonium and nitrates total concentrations. However, for nitrates the observed partition between fine and coarse mode is not reproduced. In CHIMERE there is a clear lack of coarse-mode nitrates. This calls for additional parameterizations in order to account for the heterogeneous formation of nitrate onto dust particles. Larger discrepancies are obtained for the secondary organic aerosols due to both inconsistencies in the SOA formation processes in the model leading to an underestimation of their mass and large uncertainties in the determination of the measured aerosol organic fraction. The observed mass distribution of aerosols is not well reproduced, although no clear explanation can be given.

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