Application of the SKYRAD Improved Langley plot method for the in situ calibration of CIMEL Sun-sky photometers

Campanelli, Monica; Estellés, V.; Tomasi, Claudio; Nakajima, Teruyuki; Malvestuto, V.; Martínez‐Lozano, J. A.

doi:10.1364/ao.46.002688

Cited by 84 publications

(62 citation statements)

References 10 publications

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“…There are several reports that the AOT is obtained with high accuracy compared with that of the standard Langley method and with those from AERONET (Campanelli et al, 2007;Che et al, 2008). However, it is pointed out that the SSA values from SKYNET are 3 % to 8 % larger than those of AERONET at the Beijing site, although the retrieved AOT values from SKYNET agree with those from AERONET within about 1 % (Che et al, 2008).…”

Section: Hashimoto Et Al: Development Of a New Data-processing Mementioning

confidence: 86%

Development of a new data-processing method for SKYNET sky radiometer observations

et al. 2012

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Abstract. In order to reduce uncertainty in the estimation of Direct Aerosol Radiative Forcing (DARF), it is important to improve the estimation of the single scattering albedo (SSA). In this study, we propose a new data processing method to improve SSA retrievals for the SKYNET sky radiometer network, which is one of the growing number of networks of sun-sky photometers, such as NASA AERONET and others. There are several reports that SSA values from SKYNET have a bias compared to those from AERONET, which is regarded to be the most accurate due to its rigorous calibration routines and data quality and cloud screening algorithms. We investigated possible causes of errors in SSA that might explain the known biases through sensitivity experiments using a numerical model, and also using real data at the SKYNET sites at Pune (18.616 • N/73.800 • E) in India and Beijing (39.586 • N/116.229 • E) in China. Sensitivity experiments showed that an uncertainty of the order of ±0.03 in the SSA value can be caused by a possible error in the ground surface albedo or solid view angle assumed for each observation site. Another candidate for possible error in the SSA was found in cirrus contamination generated by imperfect cloud screening in the SKYNET data processing. Therefore, we developed a new data quality control method to get rid of low quality or cloud contamination data, and we applied this method to the real observation data at the Pune site in SKYNET. After applying this method to the observation data, we were able to screen out a large amount of cirruscontaminated data and to reduce the deviation in the SSA value from that of AERONET. We then estimated DARF using data screened by our new method. The result showed that the method significantly reduced the difference of 5 W m −2 that existed between the SKYNET and AERONET values of DARF before screening. The present study also suggests the necessity of preparing suitable a priori information on the distribution of coarse particles ranging in radius between 10 µm and 30 µm for the analysis of heavily dust-laden atmospheric cases.

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Section: Hashimoto Et Al: Development Of a New Data-processing Mementioning

confidence: 86%

Development of a new data-processing method for SKYNET sky radiometer observations

et al. 2012

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“…The columnar aerosol optical properties are extracted from direct solar irradiance and sky diffuse radiance data using the "SKYRAD.pack" (Version 4.2) software code developed by Nakajima et al (1996). It is worth noting that the calibration constants V 0 (λ) for the SKYNET sky radiometer data were inferred from an improved Langley plot (ILM; Campanelli et al 2007), in which the AOD was estimated in advance by an inversion procedure involving the direct solar irradiance and forward scattering radiance data (3°-30°). The calibration constants were then determined by linear best fitting to the ln…”

Section: Retrieval Of Aerosol Optical Depthmentioning

confidence: 99%

Dust Aerosol Characteristics and Shortwave Radiative Impact at a Gobi Desert of Northwest China during the Spring of 2012

Shi

Xie

et al. 2014

Journal of the Meteorological Society of Japan

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The Semi-Arid Climate and Environment Observatory of Lanzhou University (SACOL) project initiated an intensive field experiment on dust aerosols in Dunhuang from April 1 to June 12, 2012. Using sky radiometer measurements and conducting model simulations, we investigated the dust aerosol characteristics and its shortwave radiative impact on the regional climate. The daily averaged optical features of the aerosols markedly varied throughout the study period. High aerosol loading and predominantly coarse particulates were observed in the spring of 2012 ascribed to the influence of prevalent dust storm. The single scattering albedo at 500 nm (SSA 500 ) varied from 0.91 to 0.97 on dusty days and from 0.86 to 0.91 on dust-free days, indicating that the dust aerosols sourced from northwest China were not strongly absorbing. Surface radiation quantities estimated by the radiative transfer model excellently agreed with ground-based and satellite observations, with correlation coefficients exceeding 0.990 and mean differences ranging from −3.9 to 17.0 W m ), indicating strong cooling at the surface and moderate atmospheric warming. The monthly averaged ARFEs (ARFs per unit aerosol optical depth at 500 nm (AOD 500 )) at the surface were (−73.9 ± 11.6) W m ), comparable to previously obtained values in East Asia and India domains. The relations between the diurnal ARFs at the surface and top of the atmosphere (TOA) and the AOD 500 indicate that aerosol composition remained relatively stable at Dunhuang during the spring of 2012. The ARF at the TOA was positive for SSA 500 less than 0.85 or when the imaginary part at 500 nm exceeded 0.015.

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“…For the direct component calibration of the field Cimel sunphotometers, calibration transfers from a master radiometer are periodically performed (Holben et al, 1998) although the improved method has been also previously applied with good results (Campanelli et al, 2007). For the diffuse component calibration, the standard radiometric method can be used (Holben et al, 1998).…”

Section: Skynet and Aeronet Strategiesmentioning

confidence: 99%

Comparison of AERONET and SKYRAD4.2 inversion products retrieved from a Cimel CE318 sunphotometer

Estellés

Campanelli

Utrillas³

et al. 2012

Atmos. Meas. Tech.

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Abstract. SKYNET is an international research network of ground based sky -sunphotometers for the observation and monitoring of columnar aerosol properties. The algorithm developed by SKYNET is called SKYRAD.pack, and it is used on Prede instruments only. In this study, we have modified the SKYRAD.pack software in order to adapt it to Cimel sunphotometers. A one month database of Cimel data obtained at Burjassot (Valencia, Spain) has been processed with this program and the obtained inversion products have been compared with AERONET retrievals. In general, the differences found were consistent with the individual error assessments for both algorithms. Although the aerosol optical depth compared well for any aerosol burden situation (rmsd of 0.002-0.013 for all wavelengths), inversion products such as the single scattering albedo, refractive index and asymmetry parameter compared better for higher turbidity situations. The comparison performed for cases with an aerosol optical depth at 440 nm over 0.2 showed rms differences of 0.025-0.049 for single scattering albedo, 0.005-0.034 for the real part of refractive index, 0.004-0.007 for the imaginary part of the refractive index and 0.006-0.009 for the asymmetry parameter. With respect to the volume distributions, the comparison also showed a good agreement for high turbidity cases (mainly within the 0.01-7 µm interval) although the already known discrepancy in the extremes of the distribution was still found in 40 % of the cases, in spite of eliminating data and instrumental differences present in previous studies.

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Application of the SKYRAD Improved Langley plot method for the in situ calibration of CIMEL Sun-sky photometers

Cited by 84 publications

References 10 publications

Development of a new data-processing method for SKYNET sky radiometer observations

Development of a new data-processing method for SKYNET sky radiometer observations

Dust Aerosol Characteristics and Shortwave Radiative Impact at a Gobi Desert of Northwest China during the Spring of 2012

Comparison of AERONET and SKYRAD4.2 inversion products retrieved from a Cimel CE318 sunphotometer

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