Abstract
Method for error analysis of aerosol parameter estimation with assumed noises which are included in the measured solar direct and diffuse irradiance is proposed. The noises included in the measured solar direct and diffuse irradiance are assumed to be Chi-Square probability density function due to the fact that the measured irradiance is represented as output power which is square of output voltage which corresponds to the measured irradiance which is assumed to be normal distribution of probability density function. Aerosol parameters (refractive index which consists of real and imaginary parts, size distribution which is represented by Junge parameter) are estimated with the measured solar direct and diffuse irradiance which corresponds to the acquired output power of the measuring instrument which allows measurement of solar direct and diffuse irradiance. Through experiments with the measured solar direct and diffuse irradiance, it is found that the estimation accuracy of imaginary part of aerosol refractive index is the most sensitive to the added noises followed by size distribution of Junge parameter and real part of aerosol refractive index.
Highlights
The largest uncertainty in estimation of the effects of atmospheric aerosols on climate systems is from uncertainties in the determination of their microphysical properties, including the aerosol complex index of refraction that in turn determines their optical properties
Through the experiments for investigation of influence due to Chi-Square distributed additive noises included in the measured solar direct and diffuse irradiance on estimations of aerosol refractive index and size distribution, it is found that the influence is getting increased according to shortening of the wavelength and is decreasing in accordance with increasing of DOF of Chi-Square probability density function
When the Chi-Square noises are added to the solar direct irradiance, the estimation error of real part of refractive index is getting large in accordance with increasing of solar direct pointing angle errors because of aerosol scattering factor is over estimated
Summary
The largest uncertainty in estimation of the effects of atmospheric aerosols on climate systems is from uncertainties in the determination of their microphysical properties, including the aerosol complex index of refraction that in turn determines their optical properties. The methodology for estimation of a complete set of vertically resolved aerosol size distribution and refractive index data, yielding the vertical distribution of aerosol optical properties required for the determination of aerosol-induced radiative flux changes is proposed [6]. Laboratory based refractive indices estimation methods with spectral extinction measurements are proposed [8], [9]. All these existing methods are based on radiance from the sun and the atmosphere. In order to assess the estimation accuracy of refractive index with the proposed method, sensitivity analysis is conducted with a variety of parameters of the atmosphere. It is conducted to assess influences due to observation angle on estimation accuracies of refractive index and size distribution.
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