scholarly journals Monitoring aerosol optical properties over the Mediterranean from SeaWiFS images using a neural network inversion

2004 ◽  
Vol 31 (13) ◽  
pp. n/a-n/a ◽  
Author(s):  
C. Jamet ◽  
C. Moulin ◽  
S. Thiria
Keyword(s):  
Neural Network ◽  
Optical Properties ◽  
Aerosol Optical Properties ◽  
Neural Network Inversion ◽  
The Mediterranean

scholarly journals Calibrated sky imager for aerosol optical properties determination

2008 ◽  
Vol 8 (6) ◽  
pp. 19989-20018
Author(s):  
A. Cazorla ◽  
J. E. Shields ◽  
M. E. Karr ◽  
A. Burden ◽  
F. J. Olmo ◽  
...  
Keyword(s):  
Neural Network ◽  
Optical Properties ◽  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Standard Method ◽  
Atmospheric Aerosol ◽  
Aerosol Optical Properties ◽  
The Neural Network ◽  
Physical Laboratory ◽  
Sky Imager

Abstract. The calibrated ground-based sky imager developed in the Marine Physical Laboratory, the Whole Sky Imager (WSI), has been tested to determine optical properties of the atmospheric aerosol. Different neural network-based models calculate the aerosol optical depth (AOD) for three wavelengths using the radiance extracted from the principal plane of sky images from the WSI as input parameters. The models use data from a CIMEL CE318 photometer for training and validation and the wavelengths used correspond to the closest wavelengths in both instruments. The spectral dependency of the AOD, characterized by the Ångström exponent α in the interval 440–870, is also derived using the standard AERONET procedure and also with a neural network-based model using the values obtained with a CIMEL CE318. The deviations between the WSI derived AOD and the AOD retrieved by AERONET are within the nominal uncertainty assigned to the AERONET AOD calculation (±0.01), in 80% of the cases. The explanation of data variance by the model is over 92% in all cases. In the case of α, the deviation is within the uncertainty assigned to the AERONET α (±0.1) in 50% for the standard method and 84% for the neural network-based model. The explanation of data variance by the model is 63% for the standard method and 77% for the neural network-based model.

scholarly journals Sensitivity of aerosol optical properties to the aerosol size distribution over central Europe and the Mediterranean Basin using the WRF-Chem v.3.9.1.1 coupled model

2020 ◽  
Vol 13 (12) ◽  
pp. 5897-5915
Author(s):  
Laura Palacios-Peña ◽  
Jerome D. Fast ◽  
Enrique Pravia-Sarabia ◽  
Pedro Jiménez-Guerrero
Keyword(s):  
Optical Properties ◽  
Standard Deviation ◽  
Size Distribution ◽  
Central Europe ◽  
Mediterranean Basin ◽  
Aerosol Size Distribution ◽  
Aerosol Optical Properties ◽  
Accumulation Mode ◽  
The Mediterranean ◽  
The Mediterranean Basin

Abstract. The size distribution of atmospheric aerosols plays a key role for understanding and quantifying the uncertainties related to aerosol–radiation and aerosol–cloud interactions. These interactions ultimately depend on the size distribution through optical properties (such as aerosol optical depth, AOD) or cloud microphysical properties. Hence, the main objective of this contribution is to disentangle the impact of the representation of aerosol size distribution on aerosol optical properties over central Europe, particularly over the Mediterranean Basin, during a summertime aerosol episode. To fulfill this objective, a sensitivity test has been conducted using the coupled chemistry–meteorology model WRF-Chem (Weather Research Forecast model coupled with Chemistry). The test modified the parameters defining a lognormal size distribution (geometric diameter and standard deviation) by 10 %, 20 %, and 50 %. Results reveal that the reduction in the standard deviation of the accumulation mode leads to the largest impacts on AOD due to a transfer of particles from the accumulation mode to the coarse mode. A reduction in the geometric diameter of the accumulation mode also has an influence on AOD representation since particles in this mode are assumed to be smaller. In addition, an increase in the geometric diameter of the coarse mode produces a redistribution through the total size distribution by relocating particles from the finer modes to the coarse.

scholarly journals Sensitivity of aerosol optical properties to the aerosol size distribution over central Europe and the Mediterranean Basin

2020 ◽  
Author(s):  
Laura Palacios-Peña ◽  
Jerome D. Fast ◽  
Enrique Pravia-Sarabia ◽  
Pedro Jiménez-Guerrero
Keyword(s):  
Optical Properties ◽  
Size Distribution ◽  
Central Europe ◽  
Mediterranean Basin ◽  
Aerosol Size Distribution ◽  
Aerosol Optical Properties ◽  
Accumulation Mode ◽  
Coarse Mode ◽  
The Mediterranean ◽  
The Mediterranean Basin

Abstract. Aerosol size distribution is, among others, a key property of atmospheric aerosols when trying to establish the uncertainties related to aerosol-radiation (ARI) and aerosol-clouds (ACI) interactions. These interactions ultimately depend on the size distribution through optical properties as aerosol optical depth (AOD) or cloud microphysical properties. Hence, the main objective of this work is to study the impact of the representation of aerosol size distribution on aerosol optical properties over Central Europe, and particularly over the Mediterranean Basin during a summertime aerosol episode. To fulfill this objective, a sensitivity test has been carried out using the WRF-Chem on-line model. The test consisted on modifying the parameters which define a log-normal size distribution (the geometric diameter, from now on DG, and the standard deviation, SG) by 10, 20 and 50 %. Results reveal that the reduction in the SG of the accumulation mode leads to the largest impacts in the AOD representation due to a transfer of particles from the accumulation mode to the coarse mode. A reduction in the DG of the accumulation mode has also an influence on AOD representation since particles in this mode are assumed to be smaller. In addition, an increase in the DG of the coarse mode produces a redistribution through the total size distribution by relocating particles from the finer modes to the coarse.

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