The instrument constant of sky radiometers (POM-02) – Part 1: Calibration constant

Uchiyama, Akihiro; Matsunaga, Tsuneo; Yamazaki, Akihiro

doi:10.5194/amt-11-5363-2018

Cited by 14 publications

(23 citation statements)

References 48 publications

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“…The merit of the method is that we can narrow the size of the point source below 0.5° and can extend the CSD size beyond ±1° without significant effect of the sky light. Analyzing data from the solar disk scan and lamp scan methods, Uchiyama et al, (2018b) found an underestimation of SVA from the disk scan method of 0.5 % to 1.9 % and proposed a correction method by extending CSD size up to scattering angle of 2.5° assuming an extrapolation function as illustrated in Fig. 7.…”

Section: Sky Radiance Calibration For the Sky Radiometermentioning

confidence: 99%

An overview and issues of the sky radiometer technology and SKYNET

Nakajima¹,

Campanelli²,

Che³

et al. 2020

Preprint

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Abstract. This paper overviews the progress in the sky radiometer technology and development of the network called SKYNET. It is found that the technology has produced useful on-site calibration methods, retrieval algorithms, and data analyses from the sky radiometer observation of aerosol, cloud, water vapor and ozone. Increasing collaborations of users in the SKYNET community are becoming a useful platform for research and operation. The paper also presents issues of the technology for future development.

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Section: Sky Radiance Calibration For the Sky Radiometermentioning

confidence: 99%

An overview and issues of the sky radiometer technology and SKYNET

Nakajima¹,

Campanelli²,

Che³

et al. 2020

Preprint

Self Cite

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“…Several satellite programs provide aerosol optical depth data on a global scale: for example, the Moderate Resolution Imaging Spectroradiometer (MODIS) (Remer et al, 2005), Multiangle Imaging Spectroradiometer (MISR) (Kahn et al, 2005), Geostationary Operational Environmental Satellite (GOES) Aerosol/Smoke Product (GASP) (Prados et al, 2007), Sea-viewing Wide Field-of-view Sensor (SeaWiFS) (Wang et al, 2000), Advanced Himawari Imager (AHI) (Yoshida et al, 2018;Kikuchi et al, 2018), and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) (Winker et al, 2007).…”

Section: Introductionmentioning

confidence: 99%

Nocturnal aerosol optical depth measurements with modified sky radiometer POM-02 using the moon as a light source

et al. 2019

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Abstract. The majority of aerosol data are obtained from daytime measurements, and there are few datasets available for studying nighttime aerosol characteristics. In order to estimate the aerosol optical depth (AOD) and the precipitable water vapor (PWV) during the nighttime using the moon as a light source, a sky radiometer (POM-02, Prede Ltd., Japan) was modified. The amplifier was adjusted so that POM-02 could measure lower levels of input irradiance. In order to track the moon based on the calculated values, a simplified formula was incorporated into the firmware. A new position sensor with a four-quadrant detector to adjust the tracking of the Sun and moon was also developed. The calibration constant, which is the sensor output for the extraterrestrial solar and lunar irradiance at the mean Earth–Sun distance, was determined by using the Langley method. The measurements for the Langley calibration were conducted at the National Oceanic and Atmospheric Administration/Mauna Loa Observatory (NOAA/MLO) from 28 September 2017 to 7 November 2017. By assuming that the correct reflectance is proportional to the reflectance estimated by the Robotic Lunar Observatory (ROLO) irradiance model, the calibration constant for the lunar direct irradiance was successfully determined using the Langley method. The ratio of the calibration constant for the moon to that of the Sun was often greater than 1; the value of the ratio was 0.95 to 1.18 in the visible and near-infrared wavelength regions. This indicates that the ROLO model often underestimates the reflectance. In addition, this ratio depended on the phase angle. In this study, this ratio was approximated by a quadratic equation of the phase angle. By using this approximation, the reflectance of the moon can be calculated to within an accuracy of 1 % or less. In order to validate the estimates of the AOD and PWV, continuous measurements with POM-02 were conducted at the Japan Meteorological Agency/Meteorological Research Institute (JMA/MRI) from January 2018 to May 2018, and the AOD and PWV were estimated. The results were compared with the AOD and PWV obtained by independent methods. The AOD was compared with that estimated by the National Institute for Environmental Studies (NIES) High Spectral Resolution Lidar measurements (wavelength: 532 nm), and the PWV was compared with the PWV obtained from a radiosonde and the Global Positioning System. In addition, the continuity of the AOD (PWV) before and after sunrise and sunset in Tsukuba was examined, and the AOD (PWV) of AERONET and that of POM-02 at MLO were compared. In the results, the daytime and nighttime AOD (PWV) measurements are shown to be statistically almost equivalent. The AODs (PWVs) during the daytime and nighttime for POM-02 are presumed to have the same degree of precision and accuracy within the measurement uncertainty.

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“…This output at the mean earth-sun 307 distance (1 AU) at the reference temperature is called the calibration constant. In 308 this study, the calibration constant was determined by the Langley method 309 (Uchiyama et al 2018). Here, we do not consider the temperature dependence of the 310 sensor output for the POM-02.…”

mentioning

confidence: 99%

“…Here, we do not consider the temperature dependence of the 310 sensor output for the POM-02. Under these observation conditions in Tsukuba, the 311 temperature dependence of the sensor output can be ignored except for the 340, 380, 312 and 2200 nm channels (Uchiyama et al 2018). 313…”

mentioning

confidence: 99%

Nocturnal aerosol optical depth measurements with modified skyradiometer POM-02 using the moon as a light source

Uchiyama¹,

Shiobara²,

Kobayashi³

et al. 2019

Preprint

Self Cite

View full text Add to dashboard Cite

Abstract. The majority of aerosol data are obtained from daytime measurements, and there are few datasets available for studying nighttime aerosol characteristics. In order to estimate the aerosol optical depth (AOD) and the precipitable water vapor (PWV) during the nighttime using the moon as a light source, a skyradiometer POM-02 (Prede Ltd., Japan) was modified. The amplifier was adjusted so that POM-02 could measure lower levels of input irradiance. In order to track the moon based on the calculated values, a simplified formula was incorporated into the firmware. A new position sensor with a four-quadrant detector to adjust tracking of the sun and the moon was also developed. The calibration constant, which is the sensor output for the extra-terrestrial solar and lunar irradiance at the mean earth-sun distance, was determined by using the Langley method. The measurements for the Langley calibration were conducted at the NOAA/MLO in October and November 2017. By assuming that the relative variation of the reflectance of the Robotic Lunar Observatory (ROLO) irradiance model is correct, the calibration constant for the lunar direct irradiance was successfully determined using the Langley method. The ratio of the calibration constant for the moon to that for the sun was often greater than 1; the value of the ratio was 0.95 to 1.18 in the visible near-infrared wavelength region. This means that the ROLO model often underestimates the reflectance. In addition, this ratio depended on the phase angle. In this study, this ratio was approximated by a quadratic expression of the phase angle. By using this approximation, the reflectance of the moon can be calculated to within an accuracy of 1 % or less. In order to validate the estimates of the AOD and PWV, continuous measurements with POM-02 were conducted at MRI/JMA from January 2018 to May 2018, and the AOD and PWV were estimated. The results were compared with the AOD and PWV obtained by independent methods. The AOD was compared with that estimated from NIES High Spectral Resolution Lidar measurements (wavelength: 532 nm), and the PWV was compared with the PWV obtained from a radiosonde and the Global Positioning System. As a result, the estimations of the AOD and the PWV using the moon as the light source were made with the same degree of precision and accuracy as the estimates using the sun as the light source.

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The instrument constant of sky radiometers (POM-02) – Part 1: Calibration constant

Cited by 14 publications

References 48 publications

An overview and issues of the sky radiometer technology and SKYNET

An overview and issues of the sky radiometer technology and SKYNET

Nocturnal aerosol optical depth measurements with modified sky radiometer POM-02 using the moon as a light source

Nocturnal aerosol optical depth measurements with modified skyradiometer POM-02 using the moon as a light source

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