Langley method applied in study of aerosol optical depth in the Brazilian semiarid region using 500, 670 and 870nm bands for sun photometer calibration

Fernandez, José Henrique; Hoelzemann, Judith J.; Leme, Neusa Maria Paes; Sousa, Cristina Tobler de

doi:10.1016/j.asr.2014.06.006

Cited by 11 publications

(14 citation statements)

References 28 publications

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“…For vertical measurements, aerosol extinction coefficient (AEC) is given as a function of altitude, z, and wavelength, λ, representing the light attenuation due to the combined effects of scattering and absorption [4] [5] [6]. Aerosol optical thickness (AOT) usually refers to the integration of extinction coefficient over the whole range of altitude, from the surface to the top of the atmosphere [6] [7] [8] [9] [10]. Values of AOT can be obtained from measurements using instruments such as a sunphotometer calibrated by means of the Langley extrapolation method [8] [9] [10], and the information on AOT with its wavelength dependence is valuable for monitoring the influence of aerosols and clouds [10] [11] [12].…”

Section: Introductionmentioning

confidence: 99%

“…Aerosol optical thickness (AOT) usually refers to the integration of extinction coefficient over the whole range of altitude, from the surface to the top of the atmosphere [6] [7] [8] [9] [10]. Values of AOT can be obtained from measurements using instruments such as a sunphotometer calibrated by means of the Langley extrapolation method [8] [9] [10], and the information on AOT with its wavelength dependence is valuable for monitoring the influence of aerosols and clouds [10] [11] [12]. The use of a sunphotometer, however, is limited to daytime under nearly cloud free conditions when the observation of the directly transmitted solar radiation is feasible.…”

Section: Introductionmentioning

confidence: 99%

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Real Time Derivation of Atmospheric Aerosol Optical Properties by Concurrent Measurements of Optical and Sampling Instruments

Aminuddin¹,

Okude²,

Lagrosas³

et al. 2018

OJAP

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The understanding of aerosol properties in troposphere, especially their behavior near the ground level, is indispensable for precise evaluation of their impact on the Earth's radiation studies. Although a sunphotometer or a skyradiometer can provide the aerosol optical thickness (AOT), their application is limited to daytime under near cloud free conditions. In order to attain the multi-wavelength observation for both day-and night-time including cloudy conditions, here we propose a novel monitoring technique by means of simultaneous measurement using a nephelometer (450, 550, and 700 nm), an aethalometer (370, 470, 520, 590, 660, 880, and 950 nm), and a visibility meter (550 nm). On the basis of the multi-wavelength data of scattering and absorption coefficients from the nephelometer and aethalometer, respectively, first we calculate the real-time values of aerosol extinction coefficient in addition to the Angstrom exponent (AE). Then, correction of these values is carried out by comparing the resulting extinction coefficient with the corresponding value obtained from the optical data of visibility-meter. The major reason for this correction is the loss of relatively coarse particles due to the aerodynamic effect as well as evaporation of water content from particles during the sampling procedure. Then, with the ancillary data of vertical aerosol profile obtained with a lidar (532 nm), the temporal change of AOT is estimated. In this way, information from the sampling can be converted to the ambient properties in the atmospheric boundary layer. Furthermore, daytime data from a

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Real Time Derivation of Atmospheric Aerosol Optical Properties by Concurrent Measurements of Optical and Sampling Instruments

Aminuddin¹,

Okude²,

Lagrosas³

et al. 2018

OJAP

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“…The measurement is made at the wavelengths of 368, 500, 678, and 778 nm. The Lambert-Beer law coupled with the Langley extrapolation method [5] [23] [24] is used to derive AOT:…”

Section: Aot and Angstrom Exponent From Sunphotometer Measurementmentioning

confidence: 99%

“…Here the variables A τ , G τ , and R τ represent the optical thickness due to aerosol, absorbing gas (ozone), and Rayleigh scattering, respectively; I 0 is the extra-terrestrial intensity of solar radiation (dependent on the seasonal change of the Sun-Earth distance), I is the solar radiation intensity measured by the sunphotometer, and m is the air mass dependent on the solar zenith angle, θ. The value of I 0 can be determined by implementing the Langley extrapolation method on a clear-sky day with small aerosol loading [24].…”

Section: Aot and Angstrom Exponent From Sunphotometer Measurementmentioning

confidence: 99%

Landsat-8 Satellite and Plan Position Indicator Lidar Observations for Retrieving Aerosol Optical Properties in the Lower Troposphere

Aminuddin¹,

Purbantoro²,

Lagrosas³

et al. 2018

ARS

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Observation of optical properties of atmospheric aerosols, especially their behavior near the surface level, is indispensable for better understanding of atmospheric environmental conditions. Concurrent observations of ground-based instruments and satellite-borne sensors are useful for attaining improved accuracy in the observation of relatively wide area. In the present paper, aerosol parameters in the lower troposphere are monitored using a plan position indicator (PPI) lidar, ground-sampling instruments (a nephelometer, an aethalometer, and optical particle counters), as well as a sunphotometer. The purpose of these observations is to retrieve the aerosol extinction coefficient (AEC) and aerosol optical thickness (AOT) simultaneously at the overpass time of Landsat-8 satellite. The PPI lidar, operated at 349 nm, provides nearly horizontal distribution of AEC in the lower part of the atmospheric boundary layer. For solving the lidar equation, the boundary condition and lidar ratio are determined from the data of ground sampling instruments. The value of AOT, on the other hand, is derived from sunphotometer, and used to analyze the visible band imagery of Landsat-8 satellite. The radiative transfer calculation is conducted using the MODTRAN code with the original aerosol type that has been determined from the ground sampling data coupled with the Mie scattering calculation. Reasonable agreement is found between the spatial distribution of AEC from the PPI lidar and that of AOT from the blue band (band 2) of Landsat-8. The influence of AOT on the values of apparent surface reflectance is also discussed.

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“…The AEC represents the light attenuation due to the combined e ects of scattering and absorption (Chen et al, 2014;Titos et al, 2014;Zieger et al, 2013). The time series values of AOT can be obtained through measurements using the sun-photometer and calibration using the Langley plot (Aminuddin et al, 2018a;Cerqueira et al, 2014;Chen et al, 2009;Chubarova et al, 2016;Qiu, 1998;Shaw, 1983).…”

Section: Introductionmentioning

confidence: 99%

Development and Testing a Method for Retrieving Atmospheric Aerosol Optical Thickness based on the Solar Intensity from the Sun-photometer Data

Aminuddin

Abdullatif

Mashuri

et al. 2022

Sci. Technol. Indones

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The context of atmospheric aerosols is an indispensable aspect in studying the Earth’s radiation budget, climate change, and air quality. Therefore, the quality technique in retrieving aerosol parameters is important for a better understanding their characteristics. The precise calculating of the aerosol physical parameter in the planetary boundary layer will increase the accuracy of evaluation of their impact on environmental conditions. In several atmospheric corrections of optical remote sensing using satellite sensors, the AOT’s values play an important role in arranging a Look Up Table (LUT) for scattering parameters. Therefore, this study aims to develop a method for processing and correcting the sun-photometer data to obtain the original AOT in the planetary boundary layer. In AOT calculation using the sun-photometer data, the solar radiation at the extraterritorial of the atmosphere is determined using the Langley plot. Then, using the target data at the same season as the data for the Langley plot, the temporal change of AOT is estimated by employing the Lambert-Beer Law with some corrections. The major correction for the AOT’s values computation in the measurement target is the contribution of molecule from the local station and Ozone (O3) from the GOME-2 satellite data. The result has been compared with an independent measurement using a sky-radiometer at the same time as the sun-photometer monitoring. From the overall procedure, the AOT’s values have uncertainties at approximately 2-5% compared to the sky-radiometer. Therefore, the procedure will be useful for studying aerosol optical properties in the lower troposphere.

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Langley method applied in study of aerosol optical depth in the Brazilian semiarid region using 500, 670 and 870nm bands for sun photometer calibration

Cited by 11 publications

References 28 publications

Real Time Derivation of Atmospheric Aerosol Optical Properties by Concurrent Measurements of Optical and Sampling Instruments

Real Time Derivation of Atmospheric Aerosol Optical Properties by Concurrent Measurements of Optical and Sampling Instruments

Landsat-8 Satellite and Plan Position Indicator Lidar Observations for Retrieving Aerosol Optical Properties in the Lower Troposphere

Development and Testing a Method for Retrieving Atmospheric Aerosol Optical Thickness based on the Solar Intensity from the Sun-photometer Data

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