Assessment of nocturnal Aerosol Optical Depth from lunar
photometry at Izaña high mountain Observatory

Barreto, África; Román, Roberto; Cuevas, E.; Berjón, A.; Almansa, A. Fernando; Toledano, Carlos; González, Ramiro; Hernandéz, Y.; Blarel, Luc; Goloub, Philippe; Yela, Margarita

doi:10.5194/amt-2016-423

Cited by 6 publications

(11 citation statements)

References 12 publications

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“…Here we make use of one implementation of the ROLO named as RIMO (ROLO Implementation for Moon's Observation; Barreto et al, 2019). The irradiance from these models is usually assumed as true for the AOD calculation, however different authors reported some uncertainties and biases in these models (e.g., Viticchie et al 2013;Lacherade et al 2014;Barreto et al 2017;Geogdzhayev and Marshak 2018).…”

Section: Introductionmentioning

confidence: 99%

Correction of a lunar irradiance model for aerosol optical depth retrieval and comparison with star photometer

Román¹,

González²,

Toledano³

et al. 2020

Preprint

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Abstract. The emergence of Moon photometers is allowing measurements of lunar irradiance over the world and increasing the potential to derive aerosol optical depth (AOD) at night-time, that is very relevant in polar areas. Actually, new photometers implement the latest technological advances that permit lunar irradiance measurements together with classical Sun photometry measurements. However, a proper use of these instruments for AOD retrieval requires accurate time-dependent knowledge of the extraterrestrial lunar irradiance over time, due to its fast change throughout the Moon's cycle. This paper uses the RIMO model (an implementation of the ROLO model) to estimate the AOD at night-time assuming that the calibration of the solar channels can be transferred to the Moon by a vicarious method. However, the obtained AOD values using a Cimel CE318-T Sun/sky/Moon photometer for 98 pristine nights with low and stable AOD at the Izaña Observatory (Tenerife, Spain) are not in agreement with the expected (low and stable) AOD values, estimated by linear interpolations from daytime values obtained during the previous evening and the following morning. Actually, AOD calculated using RIMO shows negative values and with a marked cycle dependent on the optical airmass. The differences between the AOD obtained using RIMO and the expected values are assumed to be associated with inaccuracies in the RIMO model, and these differences are used to calculate the RIMO correction factor (RCF). The RCF is a proposed correction factor that, multiplied by RIMO value, gives an effective extraterrestrial lunar irradiance that provides the expected AOD values. The RCF varies with the Moon phase angle (MPA) and with wavelength, ranging from 1.01 to 1.14, which reveals an overall underestimation of RIMO to the lunar irradiance. These obtained RCF values are modeled for each photometer wavelength to a second order polynomial as function of MPA. The AOD derived by this proposed method is compared with the independent AOD measurements obtained by a star photometer at Granada (Spain) for two years. The mean of the Moon-star AOD differences are between −0.015 and −0.005 and the standard deviation between 0.03 and 0.04 (which is reduced to about 0.01 if one month of data affected by instrumental issues is not included in the analysis), for 440, 500, 675 ad 870 nm; however, for 380 nm, the mean and standard deviation of these differences are higher. The Moon-star AOD differences are also analyzed as a function of MPA, showing no significant dependence.

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Section: Introductionmentioning

confidence: 99%

Correction of a lunar irradiance model for aerosol optical depth retrieval and comparison with star photometer

Román¹,

González²,

Toledano³

et al. 2020

Preprint

Self Cite

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“…As it has been shown in previous works (Barreto et al, 2017(Barreto et al, , 2019 it is important to assume that night-time AOD uncertainty is larger that the uncertainty of daytime retrievals, and that it will also depend on Moon phase angle. These facts also pose additional difficulty to the cloud screening, apart from the lack of the aureole radiance check to detect thin clouds.…”

Section: Night-time Aod Evaluationmentioning

confidence: 97%

Day- and night-time aerosol optical depth implementation in CÆLIS

González

Toledano

Román

et al. 2020

Preprint

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Abstract. The University of Valladolid (UVa, Spain) manages since 2006 a calibration center of the AErosol RObotic NETwork (AERONET). The CÆLIS software tool, developed by UVa, was created to manage the data generated by the AERONET photometers, for calibration, quality control and data processing purposes. This paper exploits the potential of this tool in order to obtain products like the aerosol optical depth (AOD) and Angstrom exponent (AE), which are of high interest for atmospheric and climate studies, as well as to enhance the quality control of the instruments and data managed by CÆLIS. The AOD and cloud screening algorithms implemented in CÆLIS, both based on AERONET version 3, are described in detail. The obtained products are compared with the AERONET database. In general, the differences in daytime AOD between CÆLIS and AERONET are far below the expected uncertainty of the instrument, ranging the mean differences between −1.3×10−4 at 870 nm and 6.2×10−4 at 380 nm. The standard deviations of the differences range from 2.8×10−4 at 675 nm to 8.1×10−4 at 340 nm. The AOD and AE at night-time calculated by CÆLIS from Moon observations are also presented, showing good continuity between day and night-time for different locations, aerosol loads and moon phase angles. Regarding cloud screening, around 99.9 % of the observations classified as cloud-free by CÆLIS are also assumed cloud-free by AERONET; this percentage is similar for the cases considered as cloud-contaminated by both databases. The obtained results point out the capability of CÆLIS as processing system. The AOD algorithm provides the opportunity to use this tool with other instrument types and to retrieve other aerosol products in the future.

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“…However, in Moon photometry this cycle, as equation (3.10) evidences, could be also caused by inaccuracies in the used E M 0 values. Barreto et al (2017) found a similar behaviour in these differences but being close to zero for MPA≈0 and increasing with the absolute phase, which could be explained because they used Lunar Langley calibration near to the full Moon and it masked the possible bias on RIMO at least close to MPA≈0. Assuming the Gain calibration and AOD ref are accurate, and all the differences between AOD and the reference are caused by RIMO inaccuracies, the ∆AOD G−r can be expressed as 1 :…”

Section: Resultsmentioning

confidence: 58%

“…However, the possible errors and uncertainties in E M 0 are propagated to the value of κ obtained by this method, although these uncertainties are partially masked in the AOD retrieval (equation (3.10)) because the E M 0 values are also used in the calculation. Recently, Barreto et al (2017) found a dependence on MPA and MZA of the AOD calculated by this Lunar Langley method.…”

Section: Gain Calibration Methodsmentioning

confidence: 93%

“…In this paper we have presented the CAELIS implementation of the latest improvements in lunar photometry that aims at providing good continuity between solar-and lunar-derived AOD observations. As has been shown in previous works (Barreto et al, 2017(Barreto et al, , 2019 it is important to assume that nighttime AOD uncertainty is larger that the uncertainty of daytime retrievals, and that it will also depend on Moon phase angle.…”

Section: Nighttime Aod Evaluationmentioning

confidence: 94%

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Desarrollo de nuevos métodos de procesado de datos de redes fotométricas para el análisis de propiedades del aerosol atmosférico

González¹

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Assessment of nocturnal Aerosol Optical Depth from lunar photometry at Izaña high mountain Observatory

Cited by 6 publications

References 12 publications

Correction of a lunar irradiance model for aerosol optical depth retrieval and comparison with star photometer

Correction of a lunar irradiance model for aerosol optical depth retrieval and comparison with star photometer

Day- and night-time aerosol optical depth implementation in CÆLIS

Desarrollo de nuevos métodos de procesado de datos de redes fotométricas para el análisis de propiedades del aerosol atmosférico

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