scholarly journals Radiative forcing of the desert aerosol at Ouarzazate (Morocco)

2018 ◽  
Vol 37 ◽  
pp. 03004
Author(s):  
Abdelouahid Tahiri ◽  
Mohamed Diouri
Keyword(s):  
Optical Properties ◽  
Atmospheric Aerosol ◽  
Radiative Forcing ◽  
Cloud Formation ◽  
Optical Parameters ◽  
Aerosol Radiative Forcing ◽  
Daily Average ◽  
Definition Of ◽  
Aerosol Radiative

The atmospheric aerosol contributes to the definition of the climate with direct effect, the diffusion and absorption of solar and terrestrial radiations, and indirect, the cloud formation process where aerosols behave as condensation nuclei and alter the optical properties. Satellites and ground-based networks (solar photometers) allow the terrestrial aerosol observation and the determination of impact. Desert aerosol considered among the main types of tropospheric aerosols whose optical property uncertainties are still quite important. The analysis concerns the optical parameters recorded in 2015 at Ouarzazate solar photometric station (AERONET/PHOTONS network, http://aeronet.gsfc.nasa.gov/) close to Saharan zone. The daily average aerosol optical depthτaer at 0.5μm, are relatively high in summer and less degree in spring (from 0.01 to 1.82). Daily average of the Angstrom coefficients α vary between 0.01 and 1.55. The daily average of aerosol radiative forcing at the surface range between -150W/m2 and -10 W/m2 with peaks recorded in summer, characterized locally by large loads of desert aerosol in agreement with the advections of the Southeast of Morocco. Those recorded at the Top of the atmosphere show a variation from -74 W/m2 to +24 W/m2

scholarly journals Column aerosol optical properties and aerosol radiative forcing during a serious haze-fog month over North China Plain in 2013 based on ground-based sunphotometer measurements

2013 ◽  
Vol 13 (11) ◽  
pp. 29685-29720 ◽  
Author(s):  
H. Che ◽  
X. Xia ◽  
J. Zhu ◽  
Z. Li ◽  
O. Dubovic ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
North China Plain ◽  
North China ◽  
Optical Parameters ◽  
Aerosol Radiative Forcing ◽  
Coarse Mode ◽  
Fine Mode ◽  
Rural Sites ◽  
Urban Sites ◽  
Aerosol Radiative

Abstract. In January 2013, North China Plain experienced several serious haze events. Cimel sunphotometer measurements at seven sites over rural, suburban and urban regions of North China Plain from 1 to 30 January 2013 were used to further our understanding of spatial-temporal variation of aerosol optical parameters and aerosol radiative forcing (ARF). It was found that Aerosol Optical Depth at 500 nm (AOD500 nm) during non-pollution periods at all stations was lower than 0.30 and increased significantly to greater than 1.00 as pollution events developed. The Angstrom exponent (Alpha) was larger than 0.80 for all stations most of the time. AOD500 nm averages increased from north to south during both polluted and non-polluted periods on the three urban sites in Beijing. The fine mode AOD during pollution periods is about a factor of 2.5 times larger than that during the non-pollution period at urban sites but a factor of 5.0 at suburban and rural sites. The fine mode fraction of AOD675 nm was higher than 80% for all sites during January 2013. The absorption AOD675 nm at rural sites was only about 0.01 during pollution periods, while ~0.03–0.07 and 0.01–0.03 during pollution and non-pollution periods at other sites, respectively. Single scattering albedo varied between 0.87 and 0.95 during January 2013 over North China Plain. The size distribution showed an obvious tri-peak pattern during the most serious period. The fine mode effective radius in the pollution period was about 0.01–0.08 μm larger than during non-pollution periods, while the coarse mode radius in pollution periods was about 0.06–0.38 μm less than that during non-pollution periods. The total, fine and coarse mode particle volumes varied by about 0.06–0.34 μm3, 0.03–0.23 μm3, and 0.03–0.10 μm3, respectively, throughout January 2013. During the most intense period (1–16 January), aerosol radiative forcing (ARF) at the surface exceeded −50 W m−2, −180 W m−2, and −200 W m−2 at rural, suburban, and urban sites, respectively. The ARF readings at the top of the atmosphere were approximately −30 W m−2 in rural and −40–60 W m−2 in urban areas. Positive ARF at the top of the atmosphere at the Huimin suburban site was found to be different from others as a result of the high surface albedo due to snow cover.

scholarly journals MACv2-SP: a parameterization of anthropogenic aerosol optical properties and an associated Twomey effect for use in CMIP6

2017 ◽  
Vol 10 (1) ◽  
pp. 433-452 ◽  
Author(s):  
Bjorn Stevens ◽  
Stephanie Fiedler ◽  
Stefan Kinne ◽  
Karsten Peters ◽  
Sebastian Rast ◽  
...  
Keyword(s):  
Optical Properties ◽  
Radiative Forcing ◽  
Industrial Emissions ◽  
Max Planck ◽  
Aerosol Optical Properties ◽  
Anthropogenic Aerosol ◽  
Aerosol Radiative Forcing ◽  
Clear Sky ◽  
Aerosol Forcing ◽  
Aerosol Radiative

Abstract. A simple plume implementation of the second version (v2) of the Max Planck Institute Aerosol Climatology, MACv2-SP, is described. MACv2-SP provides a prescription of anthropogenic aerosol optical properties and an associated Twomey effect. It was created to provide a harmonized description of post-1850 anthropogenic aerosol radiative forcing for climate modeling studies. MACv2-SP has been designed to be easy to implement, change and use, and thereby enable studies exploring the climatic effects of different patterns of aerosol radiative forcing, including a Twomey effect. MACv2-SP is formulated in terms of nine spatial plumes associated with different major anthropogenic source regions. The shape of the plumes is fit to the Max Planck Institute Aerosol Climatology, version 2, whose present-day (2005) distribution is anchored by surface-based observations. Two types of plumes are considered: one predominantly associated with biomass burning, the other with industrial emissions. These differ in the prescription of their annual cycle and in their optical properties, thereby implicitly accounting for different contributions of absorbing aerosol to the different plumes. A Twomey effect for each plume is prescribed as a change in the host model's background cloud-droplet population density using relationships derived from satellite data. Year-to-year variations in the amplitude of the plumes over the historical period (1850–2016) are derived by scaling the plumes with associated national emission sources of SO2 and NH3. Experiments using MACv2-SP are performed with the Max Planck Institute Earth System Model. The globally and annually averaged instantaneous and effective aerosol radiative forcings are estimated to be −0.6 and −0.5 W m−2, respectively. Forcing from aerosol–cloud interactions (the Twomey effect) offsets the reduction of clear-sky forcing by clouds, so that the net effect of clouds on the aerosol forcing is small; hence, the clear-sky forcing, which is more readily measurable, provides a good estimate of the total aerosol forcing.

Composition Dependence of Stratospheric Aerosol Radiative Forcing

2021 ◽  
Author(s):  
Yaowei Li ◽  
John Dykema ◽  
Frank Keutsch
Keyword(s):  
Refractive Index ◽  
Optical Properties ◽  
Radiative Forcing ◽  
Complex Refractive Index ◽  
Stratospheric Aerosol ◽  
Organic Component ◽  
Aerosol Optical Properties ◽  
Aerosol Radiative Forcing ◽  
Aerosol Radiative

<p>Model results suggest organic aerosol represents a significant fraction of total stratospheric aerosol radiative forcing, which in itself could represent as much as a quarter of global radiative forcing. Other model investigations suggest that the radiative influence of organic aerosols and dust must be included to obtain consistency with satellite measurements of stratospheric aerosols. <em>In situ</em> observations suggest that stratospheric aerosol composition is strongly vertically dependent and contains a significant organic component in the lower stratosphere. Laboratory studies suggest a range of possible values for the complex refractive index of organic aerosols in the stratosphere. The real part of the refractive index could vary over a range that brackets the value of the real refractive index for pure sulfuric acid/water aerosols. The imaginary part of the refractive index of the organic component is highly uncertain, suggesting aerosols that range from being purely refractive to significantly absorbing (eg, brown carbon). The mixing state of these mixed composition aerosols is also uncertain; depending on the complex refractive index of the organic component, morphological variation could have a significant influence on aerosol radiative properties. In this work we perform a sensitivity study of shortwave radiative forcing of stratospheric aerosols, examining the influence of different plausible values of complex refractive index and particle morphologies. <em>In situ</em> measurements of aerosol size and composition are used to represent the size distribution, vertical profile, and organic mass fraction for the computation of aerosol optical properties. These profiles of aerosol optical properties are used as inputs to a radiative transfer model to calculate profiles of shortwave fluxes and radiative heating rates for standard model atmospheres. The implications of the variations in aerosol optical depth and resulting radiative forcing are interpreted in terms of implications for satellite measurements of stratospheric radiative forcing. The various radiative forcing results and remote sensing implications for different scenarios of organic complex refractive index and morphology call for better understandings of the effects of chemical evolution and transport dynamics on the aerosol optical properties in the stratosphere.</p>

scholarly journals Column aerosol optical properties and aerosol radiative forcing during a serious haze-fog month over North China Plain in 2013 based on ground-based sunphotometer measurements

2014 ◽  
Vol 14 (4) ◽  
pp. 2125-2138 ◽  
Author(s):  
H. Che ◽  
X. Xia ◽  
J. Zhu ◽  
Z. Li ◽  
O. Dubovik ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
North China Plain ◽  
North China ◽  
Optical Parameters ◽  
Aerosol Radiative Forcing ◽  
Coarse Mode ◽  
Fine Mode ◽  
Rural Sites ◽  
Urban Sites ◽  
Aerosol Radiative

Abstract. In January 2013, North China Plain experienced several serious haze events. Cimel sunphotometer measurements at seven sites over rural, suburban and urban regions of North China Plain from 1 to 30 January 2013 were used to further our understanding of spatial-temporal variation of aerosol optical parameters and aerosol radiative forcing (ARF). It was found that Aerosol Optical Depth at 500 nm (AOD500 nm) during non-pollution periods at all stations was lower than 0.30 and increased significantly to greater than 1.00 as pollution events developed. The Angstrom exponent (Alpha) was larger than 0.80 for all stations most of the time. AOD500 nm averages increased from north to south during both polluted and non-polluted periods on the three urban sites in Beijing. The fine mode AOD during pollution periods is about a factor of 2.5 times larger than that during the non-pollution period at urban sites but a factor of 5.0 at suburban and rural sites. The fine mode fraction of AOD675 nm was higher than 80% for all sites during January 2013. The absorption AOD675 nm at rural sites was only about 0.01 during pollution periods, while ~0.03–0.07 and 0.01–0.03 during pollution and non-pollution periods at other sites, respectively. Single scattering albedo varied between 0.87 and 0.95 during January 2013 over North China Plain. The size distribution showed an obvious tri-peak pattern during the most serious period. The fine mode effective radius in the pollution period was about 0.01–0.08 μm larger than during non-pollution periods, while the coarse mode radius in pollution periods was about 0.06–0.38 μm less than that during non-pollution periods. The total, fine and coarse mode particle volumes varied by about 0.06–0.34 μm3, 0.03–0.23 μm3, and 0.03–0.10 μm3, respectively, throughout January 2013. During the most intense period (1–16 January), ARF at the surface exceeded −50 W m−2, −180 W m−2, and −200 W m−2 at rural, suburban, and urban sites, respectively. The ARF readings at the top of the atmosphere were approximately −30 W m−2 in rural and −40–60 W m−2 in urban areas. Positive ARF at the top of the atmosphere at the Huimin suburban site was found to be different from others as a result of the high surface albedo due to snow cover.

scholarly journals Effect of Vertical Profile of Aerosols on the Local Shortwave Radiative Forcing Estimation

Atmosphere ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 187
Author(s):  
Francisco Molero ◽  
Alfonso Javier Fernández ◽  
María Aránzazu Revuelta ◽  
Isabel Martínez-Marco ◽  
Manuel Pujadas ◽  
...  
Keyword(s):  
Vertical Distribution ◽  
Vertical Profile ◽  
Radiative Forcing ◽  
Accurate Information ◽  
Optical Parameters ◽  
Aerosol Radiative Forcing ◽  
Radiative Forcings ◽  
Lidar Measurements ◽  
Aerosol Types ◽  
Aerosol Radiative

In this work, the effect of the aerosol vertical distribution on the local shortwave aerosol radiative forcing is studied. We computed the radiative forcing at the top and bottom of the atmosphere between 0.2 and 4 microns using the libRadTran package and compared the results with those provided by AERONET (AErosol RObotic NETwork). Lidar measurements were employed to characterize the aerosol vertical profile, and collocated AERONET measurements provided aerosol optical parameters required to calculate its radiative forcing. A good correlation between the calculated radiative forcings and those provide by AERONET, with differences smaller than 1 W m−2 (15% of estimated radiative forcing), is obtained when a gaussian vertical aerosol profile is assumed. Notwithstanding, when a measured aerosol profile is inserted into the model, differences between radiative forcings can vary up to 6.54 W m−2 (15%), with a mean of differences = −0.74 ± 3.06 W m−2 at BOA and −3.69 W m−2 (13%), with a mean of differences = −0.27 ± 1.32 W m−2 at TOA due to multiple aerosol layers and aerosol types. These results indicate that accurate information about aerosol vertical distribution must be incorporated in the radiative forcing calculation in order to reduce its uncertainties.

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