Please use this identifier to cite or link to this item: http://hdl.handle.net/20.500.11765/11870
Aerosol retrievals from the EKO MS-711 spectral direct irradiance measurements and corrections of the circumsolar radiation
Title: Aerosol retrievals from the EKO MS-711 spectral direct irradiance measurements and corrections of the circumsolar radiation
Authors: García Cabrera, Rosa Delia ORCID RESEARCHERID Cuevas Agulló, Emilio ORCID RESEARCHERID SCOPUSID Autor AEMETBarreto, África RESEARCHERID Cachorro, Victoria E.Pó, MarioRamos López, RamónAutor AEMETHoogendijk, Kees
Keywords: Spectroradiometer; Sunphotometer; Solar irradiance; Aerosol optical depth
Issue Date: 2020
Publisher: European Geosciences Union
Citation: Atmospheric Measurement Techniques. 2020, 13(5), p. 2601–2621
Publisher version: https://dx.doi.org/10.5194/amt-13-2601-2020
Abstract: Spectral direct UV–visible normal solar irradiance (DNI) has been measured with an EKO MS-711 grating spectroradiometer, which has a spectral range of 300–1100 nm, and 0.4 nm step, at the Izaña Atmospheric Observatory (IZO, Spain). It has been used to determine aerosol optical depth (AOD) at several wavelengths (340, 380, 440, 500, 675, and 870 nm) between April and September 2019, which has been compared with synchronous AOD measurements from a reference Cimel and Aerosol RObotic NETwork (AERONET) sun photometer. The EKO MS-711 has been calibrated at the Izaña Atmospheric Observatory by using the Langley plot method during the study period. Although this instrument has been designed for spectral solar DNI measurements, and therefore has a field of view (FOV) of 5∘ that is twice the recommended amount in solar photometry for AOD determination, the AOD differences compared to the AERONET–Cimel reference instrument (FOV ∼1.2∘) are fairly small. A comparison of the results from the Cimel AOD and EKO MS-711 AOD presents a root mean square (rms) of 0.013 (24.6 %) at 340 and 380 nm, and 0.029 (19.5 %) for longer wavelengths (440, 500, 675, and 870 nm). However, under relatively high AOD, near-forward aerosol scattering might be significant because of the relatively large circumsolar radiation (CSR) due to the large EKO MS-711 FOV, which results in a small but significant AOD underestimation in the UV range. The AOD differences decrease considerably when CSR corrections, estimated from libRadtran radiative transfer model simulations, are performed and obtain an rms of 0.006 (14.9 %) at 340 and 380 nm, and 0.005 (11.1 %) for longer wavelengths. The percentage of 2 min synchronous EKO AOD–Cimel AOD differences within the World Meteorological Organization (WMO) traceability limits were ≥96 % at 500, 675, and 870 nm with no CSR corrections. After applying the CSR corrections, the percentage of AOD differences within the WMO traceability limits increased to >95 % for 380, 440, 500, 675, and 870 nm, while for 340 nm the percentage of AOD differences showed a poorer increase from 67 % to a modest 86 %.
Sponsorship : This research has received funding from the European Union’s Horizon 2020 Research and Innovation Programme (grant no. 654109; ACTRIS-2). The funding from MINECO (grant no. CTM2015-66742-R) and Junta de Castilla y León (grant no. VA100P17) is also gratefully acknowledged. Much of this study has been performed in the framework of the WMO–CIMO Izaña test bed for aerosols and water vapour remote-sensing instruments and has been funded by the State Meteorological Agency of Spain (AEMET).
URI: http://hdl.handle.net/20.500.11765/11870
ISSN: 1867-1381
1867-8548
Appears in Collections:Artículos científicos 2019-2020


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