Abstract. This paper presents the new photometer CE318-T, able to perform daytime and night-time photometric measurements using the sun and the moon as light source. Therefore, this new device permits a complete cycle of diurnal aerosol and water vapour measurements valuable to enhance atmospheric monitoring to be extracted. In this study we have found significantly higher precision of triplets when comparing the CE318-T master instrument and the Cimel AErosol RObotic NETwork (AERONET) master (CE318-AERONET) triplets as a result of the new CE318-T tracking system. Regarding the instrument calibration, two new methodologies to transfer the calibration from a reference instrument using only daytime measurements (Sun Ratio and Sun-Moon gain factor techniques) are presented and discussed. These methods allow the reduction of the previous complexities inherent to nocturnal calibration. A quantitative estimation of CE318-T AOD uncertainty by means of error propagation theory during daytime revealed AOD uncertainties (u D AOD ) for Langley-calibrated instruments similar to the expected values for other reference instruments (0.002-0.009). We have also found u D AOD values similar to the values reported in sun photometry for field instruments (∼ 0.015). In the case of the night-time period, the CE318-T-estimated standard combined uncertainty (u N AOD ) is dependent not only on the calibration technique but also on illumination conditions and the instrumental noise. These values range from 0.011-0.018 for Lunar Langley-calibrated instruments to 0.012-0.021 for instruments calibrated using the Sun Ratio technique. In the case of moon-calibrated instruments using the Sun-Moon gain factor method and suncalibrated using the Langley technique, we found u N AOD ranging from 0.016 to 0.017 (up to 0.019 in 440 nm channel), not dependent on any lunar irradiance model.A subsequent performance evaluation including CE318-T and collocated measurements from independent reference instruments has served to assess the CE318-T performance as well as to confirm its estimated uncertainty. Daytime AOD evaluation, performed at Izaña station from March to June 2014, encompassed measurements from a reference CE318-T, a CE318-AERONET master instrument, a Precision Filter Radiometer (PFR) and a Precision Spectroradiometer (PSR) prototype, reporting low AOD discrepancies between the four instruments (up to 0.006). The nocturnal AOD evaluation was performed using CE318-T-and starphotometer-collocated measurements and also by means of a day/night coherence transition test using the CE318-T masPublished by Copernicus Publications on behalf of the European Geosciences Union. Á. Barreto et al.: The new sun-sky-lunar Cimel CE318-T multiband photometerter instrument and the CE318 daytime data from the CE318-AERONET master instrument. Results showed low discrepancies with the star photometer at 870 and 500 nm channels (≤ 0.013) and differences with AERONET daytime data (1 h after and before sunset and sunrise) in agreement with the estimated u N AOD value...
30The use of sky cameras for nocturnal aerosol characterization is discussed in this study. 31Two sky cameras are configured to take High Dynamic Range (HDR) images at and thermal radiation (direct effect), and acting as cloud droplet nuclei that leads to 60 changes in the cloud properties and lifetime (indirect effect). 61At night there is no solar radiation, but aerosol radiative forcing in the longwave 62 range can be significant for large particles like desert dust and sea salt [Stier et al., 2007; 63 Sicard et al., 2014]. In addition, at night the aerosol indirect effect still works and could 64 provide changes on nocturnal cloud properties [Ramanathan et al., 2001; Kaufman et al. 65 2005; Rosenfeld et al. 2006]. These changes could contribute to global warming since 66 clouds at night absorb part of the longwave radiation emitted by Earth, and then, they 67 re-emit radiation back to the Earth surface [Ramanathan et al., 1989; NASA Facts, 68 1999; Wild, 2012]. Moreover, the knowledge of aerosol properties at night is important 69 for the aerosol characterization in polar areas and in winter seasons, which present low 70 sunshine duration values [Stone et al., 2010; Tomasi et al., 2015]. 71Some instruments and techniques are used for the characterization of aerosol 72 properties at night: lidar systems provide backscatter and extinction profiles using Fernald-Sasano retrievals [Klett, 1981[Klett, , 1985 Fernald, 1984;Sasano, 1984] [Ansmann et al., 2001;Pérez-Ramírez et al., 2008Berkoff et al., 2011; Barreto et 79 al., 2013 Barreto et 79 al., , 2016 Barreto et 79 al., , 2017. The AOD measurements at night provide information to 80 discriminate between the extinction of fine and coarse mode [O'Neill et al., 2003] brighter. This information could be combined with the spectral AOD, also obtained 91 from the Moon (lunar photometry) to retrieve aerosol characteristics. 92A sky camera can be used to obtain relative sky radiance near the Moon since it 93 records the full hemispherical sky radiance measuring different wavelength intervals 94 and it can operate at night with an appropriate exposure time (ET). It should be noted 95 also that sky cameras usually present a low signal to noise ratio. Cloud detection is the 96 most spread use of sky cameras [Long et al., 2006; Calbó and Sabburg, 2008; Cazorla et 97 al., 2008a; Ghonima et al., 2012;Kazantzidis et al., 2012; Mandat et al., 2014, Alonso 98 et al., 2014 though they have been used with other purposes [Horváth et al., 2002; 99 Cazorla et al., 2008b;Kreuter et al., 2009; Sigernes et al., 2014], including the 100 retrieval of sky radiances in daytime [Voss and Zibordi, 1989; López-Alvarez et al., 101 2008; Román et al., 2012; Toshing et al., 2013; Chauvin et al., 2015]. The CCD spectral response, given by the manufacturer, is shown in Fig. 1a. This 183 response is only available up to 700 nm, but red channel seems to have certain 184 sensitivity to longer wavelengths. As mentioned above, the camera also co...
In this paper we present an approach for the profiling of aerosol microphysical and optical properties combining ceilometer and sun/sky photometer measurements in the GRASP code (General Retrieval of Aerosol and Surface Properties). For this objective, GRASP is used with sun/sky photometer measurements of aerosol optical depth (AOD) and sky radiances, both at four wavelengths and obtained from AErosol RObotic NETwork (AERONET), and ceilometer measurements of range corrected signal (RCS) at 1064 nm. A sensitivity study with synthetic data evidences the capability of the method to retrieve aerosol properties such as size distribution and profiles of volume concentration (VC), especially for coarse particles. Aerosol properties obtained by the mentioned method are compared with airborne in-situ measurements acquired during two flights over Granada (Spain) within the framework of ChArMEx/ADRIMED (Chemistry-Aerosol Mediterranean Experiment/Aerosol Direct Radiative Impact on the regional climate in the MEDiterranean region) 2013 campaign. The retrieved aerosol VC profiles agree well with the airborne measurements, showing a mean bias error (MBE) and a mean absolute bias error (MABE) of 0.3 µm 3 /cm 3 (12%) and 5.8 µm 3 /cm 3 (25%), respectively. The differences between retrieved VC and airborne in-situ measurements are within the uncertainty of GRASP retrievals. In addition, the retrieved VC at 2500 m a.s.l. is shown and compared with in-situ measurements obtained during summer 2016 at a high-atitude mountain station in the framework of the SLOPE I campaign (Sierra Nevada Lidar AerOsol Profiling Experiment). VC from GRASP presents high correlation (r=0.91) with the in-situ measurements, but overestimates them, MBE and MABE being equal to 23% and 43%.
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