scholarly journals Separation of aerosol fine- and coarse-mode radiative properties: Effect on the mineral dust longwave, direct radiative forcing

2014 ◽  
Vol 41 (19) ◽  
pp. 6978-6985 ◽  
Author(s):  
Michaël Sicard ◽  
Santi Bertolín ◽  
Constantino Muñoz ◽  
Alejandro Rodríguez ◽  
Francesc Rocadenbosch ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
Mineral Dust ◽  
Radiative Properties ◽  
Coarse Mode ◽  
Direct Radiative Forcing

scholarly journals Aerosol optical, microphysical and radiative properties at three regional background insular sites in the western Mediterranean Basin

2016 ◽  
Author(s):  
M. Sicard ◽  
R. Barragan ◽  
F. Dulac ◽  
L. Alados-Arboledas ◽  
M. Mallet
Keyword(s):  
Radiative Forcing ◽  
Mediterranean Basin ◽  
Mineral Dust ◽  
Western Mediterranean ◽  
Radiative Properties ◽  
Annual Cycles ◽  
Regional Background ◽  
Coarse Mode ◽  
Western Mediterranean Basin ◽  
Mode Volume

Abstract. In the framework of the ChArMEx (the Chemistry-Aerosol Mediterranean Experiment, http://charmex.lsce.ipsl.fr/) program, the seasonal variability of the aerosol optical, microphysical and radiative properties is examined in two regional background insular sites in the western Mediterranean Basin (WMB): Ersa (Corsica Island, France) and Palma de Mallorca (Mallorca Island, Spain). A third site in Alborán (Alborán Island, Spain) with only a few months of data is considered for exploring the possible Northeast–Southwest (NE–SW) gradient of the aforementioned aerosol properties. The dataset is exclusively composed of AERONET (Aerosol Robotic Network; http://aeronet.gsfc.nasa.gov/) products during a four-year period (2011–2014). AERONET fluxes are validated with ground- and satellite-based flux measurements. To the best of our knowledge this is the first time that AERONET fluxes are validated at the top of the atmosphere. Products such as the aerosol optical depth (AOD), the fraction fine mode to total AOD, the particle size distribution, the sphericity, the radiative forcing and the radiative forcing efficiency show a clear annual cycle. The main drivers of the observed annual cycles are mineral dust outbreaks in summer and the transport of European continental aerosols in spring. A NE–SW gradient is observed on 6 parameters (3 extensive and 3 intensive) out of the 18 discussed in the paper. The NE–SW gradient of the AOD, the Ångström exponent, the coarse mode volume concentration, the sphericity and the radiative forcing at the surface are related to mineral dust outbreaks, while the NE–SW gradient of the coarse mode volume median radius is related to the decreasing influence of European continental aerosols along the NE–SW axis. The fact that two thirds of the parameters discussed in the paper do not present a NE–SW gradient is partly explained by two relevant findings: (1) a homogeneous spatial distribution of the fine particle loads over the three sites in spite of the distances between the sites and the differences in local sources, and (2) low values and the absence of spectral dependency of the absorption found in the southwesternmost site.

scholarly journals The spatial distribution of mineral dust and its shortwave radiative forcing over North Africa: modeling sensitivities to dust emissions and aerosol size treatments

2010 ◽  
Vol 10 (18) ◽  
pp. 8821-8838 ◽  
Author(s):  
C. Zhao ◽  
X. Liu ◽  
L. R. Leung ◽  
B. Johnson ◽  
S. A. McFarlane ◽  
...  
Keyword(s):  
North Africa ◽  
Radiative Forcing ◽  
Mineral Dust ◽  
Regional Climate ◽  
Dust Emission ◽  
Radiative Properties ◽  
Lower Atmosphere ◽  
Dust Particles ◽  
Dust Emissions ◽  
Sahel Region

Abstract. A fully coupled meteorology-chemistry-aerosol model (WRF-Chem) is applied to simulate mineral dust and its shortwave (SW) radiative forcing over North Africa. Two dust emission schemes (GOCART and DUSTRAN) and two aerosol models (MADE/SORGAM and MOSAIC) are adopted in simulations to investigate the modeling sensitivities to dust emissions and aerosol size treatments. The modeled size distribution and spatial variability of mineral dust and its radiative properties are evaluated using measurements (ground-based, aircraft, and satellites) during the AMMA SOP0 campaign from 6 January to 3 February of 2006 (the SOP0 period) over North Africa. Two dust emission schemes generally simulate similar spatial distributions and temporal evolutions of dust emissions. Simulations using the GOCART scheme with different initial (emitted) dust size distributions require ~40% difference in total emitted dust mass to produce similar SW radiative forcing of dust over the Sahel region. The modal approach of MADE/SORGAM retains 25% more fine dust particles (radius<1.25 μm) but 8% less coarse dust particles (radius>1.25 μm) than the sectional approach of MOSAIC in simulations using the same size-resolved dust emissions. Consequently, MADE/SORGAM simulates 11% higher AOD, up to 13% lower SW dust heating rate, and 15% larger (more negative) SW dust radiative forcing at the surface than MOSAIC over the Sahel region. In the daytime of the SOP0 period, the model simulations show that the mineral dust heats the lower atmosphere with an average rate of 0.8 ± 0.5 K day−1 over the Niamey vicinity and 0.5 ± 0.2 K day−1 over North Africa and reduces the downwelling SW radiation at the surface by up to 58 W m−2 with an average of 22 W m−2 over North Africa. This highlights the importance of including dust radiative impact in understanding the regional climate of North Africa. When compared to the available measurements, the WRF-Chem simulations can generally capture the measured features of mineral dust and its radiative properties over North Africa, suggesting that the model is suitable for more extensive simulations of dust impact on regional climate over North Africa.

scholarly journals Retrieval of aerosol microphysical and optical properties above liquid clouds from POLDER/PARASOL polarization measurements

2013 ◽  
Vol 6 (4) ◽  
pp. 991-1016 ◽  
Author(s):  
F. Waquet ◽  
C. Cornet ◽  
J.-L. Deuzé ◽  
O. Dubovik ◽  
F. Ducos ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Radiative Forcing ◽  
Mineral Dust ◽  
Spherical Particles ◽  
Dust Particles ◽  
Polarization Measurements ◽  
Microphysical Properties ◽  
Coarse Mode ◽  
Fine Mode ◽  
Aerosol Properties

Abstract. Most of the current aerosol retrievals from passive sensors are restricted to cloud-free scenes, which strongly reduces our ability to monitor the aerosol properties at a global scale and to estimate their radiative forcing. The presence of aerosol above clouds (AAC) affects the polarized light reflected by the cloud layer, as shown by the spaceborne measurements provided by the POlarization and Directionality of Earth Reflectances (POLDER) instrument on the PARASOL satellite. In a previous work, a first retrieval method was developed for AAC scenes and evaluated for biomass-burning aerosols transported over stratocumulus clouds. The method was restricted to the use of observations acquired at forward scattering angles (90–120°) where polarized measurements are highly sensitive to fine-mode particle scattering. Non-spherical particles in the coarse mode, such as mineral dust particles, do not much polarize light and cannot be handled with this method. In this paper, we present new developments that allow retrieving also the properties of mineral dust particles above clouds. These particles do not much polarize light but strongly reduce the polarized cloud bow generated by the liquid cloud layer beneath and observed for scattering angles around 140°. The spectral attenuation can be used to qualitatively identify the nature of the particles (i.e. accumulation mode versus coarse mode, i.e. mineral dust particles versus biomass-burning aerosols), whereas the magnitude of the attenuation is related to the optical thickness of the aerosol layer. We also use the polarized measurements acquired in the cloud bow to improve the retrieval of both the biomass-burning aerosol properties and the cloud microphysical properties. We provide accurate polarized radiance calculations for AAC scenes and evaluate the contribution of the POLDER polarization measurements for the simultaneous retrieval of the aerosol and cloud properties. We investigate various scenes with mineral dust particles and biomass-burning aerosols above clouds. For clouds, our results confirm that the droplet size distribution is narrow in high-latitude ocean regions and that the droplet effective radii retrieved from both polarization measurements and from total radiance measurements are generally close for AAC scenes (departures smaller than 2 μm). We found that the magnitude of the primary cloud bow cannot be accurately estimated with a plane parallel transfer radiative code. The errors for the modeling of the polarized cloud bow are between 4 and 8% for homogenous cloudy scenes, as shown by a 3-D radiative transfer code. These effects only weakly impact the retrieval of the Aerosol Optical Thickness (AOT) performed with a mineral dust particle model for which the microphysical properties are entirely known (relative error smaller than 6%). We show that the POLDER polarization measurements allow retrieving the AOT, the fine-mode particle size, the Ångström exponent and the fraction of spherical particles. However, the complex refractive index and the coarse-mode particle size cannot be accurately retrieved with the present polarization measurements. Our complete and accurate algorithm cannot be applied to process large amounts of data, so a simpler algorithm was developed to retrieve the AOT and the Ångström exponent above clouds in an operational way. Illustrations are provided for July–August 2008 near the African coast. Large mean AOTs above clouds at 0.865 μm (>0.3) are retrieved for oceanic regions near the coasts of South Africa that correspond to biomass-burning aerosols, whereas even larger mean AOTs above clouds for mineral dust particles (>0.6) are also retrieved near the coasts of Senegal. For these regions and time period, the direct AAC radiative forcing is likely to be significant. The final aim of this work is the global monitoring of the AAC properties and the estimation of the direct aerosol radiative forcing in cloudy scenes.

Preliminary Simulation Research of Direct Radiative Forcing of Mineral Dust Aerosol Over East Asia Region

2005 ◽  
Vol 48 (6) ◽  
pp. 1336-1347 ◽  
Author(s):  
Jian WU ◽  
Cong-Bin FU ◽  
Wei-Mei JIANG ◽  
Hong-Nian LIU ◽  
Run-Hua ZHAO
Keyword(s):  
East Asia ◽  
Radiative Forcing ◽  
Mineral Dust ◽  
Dust Aerosol ◽  
Simulation Research ◽  
Direct Radiative Forcing ◽  
East Asia Region

scholarly journals Simulation of the spatial distribution of mineral dust and its direct radiative forcing over Australia

Tellus B ◽  
2013 ◽  
Vol 65 (1) ◽  
pp. 19856 ◽  
Author(s):  
Omid Alizadeh Choobari ◽  
Peyman Zawar-Reza ◽  
Andrew Sturman
Keyword(s):  
Spatial Distribution ◽  
Radiative Forcing ◽  
Mineral Dust ◽  
Direct Radiative Forcing

scholarly journals 2-D mineral dust radiative forcing calculations from CALIPSO observations over Europe

2019 ◽  
Author(s):  
Maria José Granados-Muñoz ◽  
Michaël Sicard ◽  
Nikolaos Papagiannopoulos ◽  
Rubén Barragán ◽  
Juan Antonio Bravo-Aranda ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
Mineral Dust ◽  
Single Point ◽  
Strong Dependence ◽  
Radiant Energy ◽  
Radiative Properties ◽  
Radiative Transfer Model ◽  
Orthogonal Polarization ◽  
Transfer Model ◽  
Radiative Effects

Abstract. A demonstration study to examine the feasibility to retrieve dust radiative effects based on combined satellite data from MODIS (Moderate Resolution Imaging Spectroradiometer), CERES (Clouds and the Earth’s Radiant Energy System) and CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) li-dar vertical profiles along their orbit is presented. The radiative transfer model GAME (Global Atmos-pheric Model) is used to estimate the shortwave and longwave dust radiative effects below the CALIP-SO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite) orbit assuming an aerosol parameterization based on CALIOP vertical distribution at a horizontal resolution of 5 km and additional AERONET (Aerosol Robotic Network) data. Two study cases are analysed; a strong long-range transport mineral dust event (AOD = 0.52) originated in the Sahara Desert and reaching the United Kingdom and a weaker event (AOD = 0.16) affecting Eastern Europe. The obtained radiative fluxes are first validated in terms of radiative forcing efficiency at a single point with space-time co-located lidar ground-based measurements from EARLINET (European Aerosol Research Lidar Network) stations below the orbit. The methodology is then applied to the full orbit. The obtained results indicate that the radiative effects show a strong dependence on the aerosol load, highlighting the need of accurate AOD measurements for forcing studies, and on the surface albedo. The calculated dust radiative effects and heating rates below the orbits are in good agreement with previous studies of mineral dust, with the forcing efficiency obtained at the surface ranging between −80.3 and −63.0 W m−2 for the weaker event and −119.1 and −79.3 W m−2 for the strong one. Results thus demonstrate the validity of the presented method to retrieve 2-D accurate radiative properties with large spatial and temporal coverage.

scholarly journals Optical Characteristics and Radiative Properties of Aerosols in Harbin, Heilongjiang Province during 2017

Atmosphere ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 463
Author(s):  
Jiemei Liu ◽  
Wenxiang Shen ◽  
Yuan Yuan ◽  
Shikui Dong
Keyword(s):  
Radiative Forcing ◽  
Radiative Properties ◽  
Santa Barbara ◽  
Mean Values ◽  
Aerosol Radiative Forcing ◽  
Direct Radiative Forcing ◽  
Different Seasons ◽  
Atmospheric Radiative Transfer ◽  
Aerosol Types ◽  
Aerosol Radiative

This study considers aerosol optical properties and direct radiative forcing over Harbin (126.63° E, 45.75° N), the highest latitude city in Northeast China, during 2017. Observations based on the CE-318 sun-photometer show that the annual mean values of the aerosol optical depth (AOD) at 500 nm and the Angstrom exponent (AE) at 440–870 nm over Harbin are respectively 0.26 ± 0.20 and 1.36 ± 0.26. Aerosol loading is the highest in the spring followed by winter, and the lowest loading is in autumn. AE440–870 is the highest in summer, second highest in winter, and lowest in autumn. The Santa Barbara DISORT Atmospheric Radiative Transfer (SBDART) model is used to estimate the shortwave aerosol radiative forcing at the top of the atmosphere, on the Earth’s surface and in the atmosphere, and the annual mean values are −16.36 ± 18.42 Wm−2, −71.01 ± 27.37 Wm−2 and 54.65 ± 30.62 Wm−2, respectively, which indicate that aerosols cause climate effects of cooling the earth-atmosphere system, cooling the earth’s surface and heating the atmosphere. Four main aerosol types in Harbin are classified via AOD and AE. Specifically, clean continental, mixed type, biomass burning and urban industry, and desert dust aerosols accounted for 51%, 38%, 9%, and 2% of the total, respectively. Aerosol radiative forcing varies greatly in different seasons, and the aerosol load and type from different emission sources have an important influence on the seasonal variation of radiative forcing.

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