Characterization of an EKO MS-711 spectroradiometer: aerosol retrieval from spectral direct irradiance measurements and corrections of the circumsolar radiation

Abstract. Spectral direct UV-Visible normal solar irradiance (DNI) measured with an EKO MS-711 spectroradiometer at the Izaña Atmospheric Observatory (IZO, Spain) 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 that have been compared with synchronous AOD measurements from a reference Cimel-AERONET (Aerosol RObotic NETwork) sunphotometer. The EKO MS-711 has been calibrated at Izaña Observatory 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 that recommended in solar photometry for AOD determination, the AOD differences compared against the AERONET Cimel reference instrument (FOV ∼ 1.2°), are fairly small. The comparison results between AOD Cimel and EKO MS-711 present 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, resulting 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, obtaining RMS of 0.006 (14.9 %) at 340 and 380 nm, and 0.005 (11.1 %) for longer wavelengths. The percentage of 2-minute synchronous EKO AOD–Cimel AOD differences within the World Meteorological Organization (WMO) traceability limits were ≥ 96 % at 500 nm, 675 nm 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 %.

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Aerosol retrievals from the EKO MS-711 spectral direct irradiance measurements and corrections of the circumsolar radiation

Atmospheric Measurement Techniques ◽

10.5194/amt-13-2601-2020 ◽

2020 ◽

Vol 13 (5) ◽

pp. 2601-2621

Author(s):

Rosa Delia García-Cabrera ◽

Emilio Cuevas-Agulló ◽

África Barreto ◽

Victoria Eugenia Cachorro ◽

Mario Pó ◽

...

Keyword(s):

Field Of View ◽

Radiative Transfer Model ◽

Transfer Model ◽

Mean Square ◽

Aerosol Scattering ◽

The World ◽

Uv Visible ◽

Sun Photometer ◽

Comparison Of The Results ◽

Uv Range

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 %.

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Study of the effect of different type of aerosols on UV-B radiation from measurements during EARLINET

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-3-4671-2003 ◽

2003 ◽

Vol 3 (5) ◽

pp. 4671-4700

Author(s):

D. S. Balis ◽

V. Amiridis ◽

C. Zerefos ◽

A. Kazantzidis ◽

S. Kazadzis ◽

...

Keyword(s):

Total Ozone ◽

Single Scattering ◽

Single Scattering Albedo ◽

Radiative Transfer Model ◽

Transfer Model ◽

Combined Use ◽

Lidar Measurements ◽

The Vertical Distribution ◽

Aerosol Type

Abstract. Routine lidar measurements of the vertical distribution of the aerosol extinction coefficient and the extinction-to-backscatter ratio have been performed at Thessaloniki, Greece using a Raman lidar system in the frame of the EARLINET project since 2000. Spectral and broadband UV-B irradiance measurements, as well as total ozone observations, were available whenever lidar measurements were obtained. From the available measurements several cases could be identified that allowed the study of the effect of different types of aerosol on the levels of the UV-B solar irradiance at the Earth's surface. The TUV radiative transfer model has been used to simulate the irradiance measurements, using total ozone and the lidar aerosol data as input. From the comparison of the model results with the measured spectra the effective single scattering albedo was determined using an iterative procedure, which has been verified against results from the 1998 Lindenberg Aerosol Characterization Experiment. It is shown that the same aerosol optical depth and same total ozone values can show differences up to 10% in the UV-B irradiance at the Earth's surface, which can be attributed to differences in the aerosol type. It is shown that the combined use of the estimated single scattering albedo and the measured extinction-to-backscatter ratio leads to a better characterization of the aerosol type probed.

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Relative sky radiance from multi-exposure all-sky camera images

Atmospheric Measurement Techniques ◽

10.5194/amt-14-2201-2021 ◽

2021 ◽

Vol 14 (3) ◽

pp. 2201-2217

Author(s):

Juan C. Antuña-Sánchez ◽

Roberto Román ◽

Victoria E. Cachorro ◽

Carlos Toledano ◽

César López ◽

...

Keyword(s):

Dynamic Range ◽

Quality Criteria ◽

High Dynamic Range ◽

Radiative Transfer Model ◽

Transfer Model ◽

High Dynamic ◽

Sky Radiance ◽

Black Level ◽

Hdr Image

Abstract. All-sky cameras are frequently used to detect cloud cover; however, this work explores the use of these instruments for the more complex purpose of extracting relative sky radiances. An all-sky camera (SONA202-NF model) with three colour filters narrower than usual for this kind of cameras is configured to capture raw images at seven exposure times. A detailed camera characterization of the black level, readout noise, hot pixels and linear response is carried out. A methodology is proposed to obtain a linear high dynamic range (HDR) image and its uncertainty, which represents the relative sky radiance (in arbitrary units) maps at three effective wavelengths. The relative sky radiances are extracted from these maps and normalized by dividing every radiance of one channel by the sum of all radiances at this channel. Then, the normalized radiances are compared with the sky radiance measured at different sky points by a sun and sky photometer belonging to the Aerosol Robotic Network (AERONET). The camera radiances correlate with photometer ones except for scattering angles below 10∘, which is probably due to some light reflections on the fisheye lens and camera dome. Camera and photometer wavelengths are not coincident; hence, camera radiances are also compared with sky radiances simulated by a radiative transfer model at the same camera effective wavelengths. This comparison reveals an uncertainty on the normalized camera radiances of about 3.3 %, 4.3 % and 5.3 % for 467, 536 and 605 nm, respectively, if specific quality criteria are applied.

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Description of the Baseline Surface Radiation Network (BSRN) station at the Izaña Observatory (2009–2017): measurements and quality control/assurance procedures

Geoscientific Instrumentation Methods and Data Systems ◽

10.5194/gi-8-77-2019 ◽

2019 ◽

Vol 8 (1) ◽

pp. 77-96 ◽

Cited By ~ 4

Author(s):

Rosa Delia García ◽

Emilio Cuevas ◽

Ramón Ramos ◽

Victoria Eugenia Cachorro ◽

Alberto Redondas ◽

...

Keyword(s):

Quality Control ◽

Research Programme ◽

Surface Radiation ◽

Shortwave Radiation ◽

Radiative Transfer Model ◽

Transfer Model ◽

High Mountain ◽

Total Column Ozone ◽

The World ◽

Instantaneous Values

Abstract. The Baseline Surface Radiation Network (BSRN) was implemented by the World Climate Research Programme (WCRP) starting observations with nine stations in 1992, under the auspices of the World Meteorological Organization (WMO). Currently, 59 BSRN stations submit their data to the WCRP. One of these stations is the Izaña station (station IZA, no. 61) that enrolled in this network in 2009. This is a high-mountain station located in Tenerife (Canary Islands, Spain, at 28.3∘ N, 16.5∘ W; 2373 m a.s.l.) and is a representative site of the subtropical North Atlantic free troposphere. It contributes with basic-BSRN radiation measurements, such as global shortwave radiation (SWD), direct radiation (DIR), diffuse radiation (DIF) and longwave downward radiation (LWD), and extended-BSRN measurements, including ultraviolet ranges (UV-A and UV-B), shortwave upward radiation (SWU) and longwave upward radiation (LWU), and other ancillary measurements, such as vertical profiles of temperature, humidity and wind obtained from radiosonde profiles (WMO station no. 60018) and total column ozone from the Brewer spectrophotometer. The IZA measurements present high-quality standards since more than 98 % of the data are within the limits recommended by the BSRN. There is an excellent agreement in the comparison between SWD, DIR and DIF (instantaneous and daily) measurements with simulations obtained with the LibRadtran radiative transfer model. The root mean square error (RMSE) for SWD is 2.28 % for instantaneous values and 1.58 % for daily values, while the RMSE for DIR is 2.00 % for instantaneous values and 2.07 % for daily values. IZA is a unique station that provides very accurate solar radiation data in very contrasting scenarios: most of the time under pristine sky conditions and periodically under the effects of the Saharan air layer characterized by a high content of mineral dust. A detailed description of the BSRN program at IZA, including quality control and quality assurance activities, is given in this work.

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Characterization of milk properties with a radiative transfer model

Applied Optics ◽

10.1364/ao.41.002028 ◽

2002 ◽

Vol 41 (10) ◽

pp. 2028 ◽

Cited By ~ 20

Author(s):

Czarena L. Crofcheck ◽

Fred A. Payne ◽

M. Pinar Mengüç

Keyword(s):

Radiative Transfer ◽

Radiative Transfer Model ◽

Transfer Model

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Aerosol absorption retrieval at ultraviolet wavelengths in a complex environment

10.5194/amt-2016-273 ◽

2016 ◽

Author(s):

Stelios Kazadzis ◽

Panagiotis Ι. Raptis ◽

Natalia Kouremeti ◽

Vassilis Amiridis ◽

Antti Arola ◽

...

Keyword(s):

Wavelength Dependence ◽

Single Scattering ◽

Radiative Transfer Model ◽

Transfer Model ◽

Aerosol Composition ◽

Data Set ◽

Aerosol Absorption ◽

Uv Irradiance ◽

Band Radiometer ◽

Uv Range

Abstract. We have used total and diffuse UV irradiance measurements with a multi-filter rotating shadow-band radiometer (UVMFR), in order to calculate aerosol absorption properties (Single Scattering Albedo – SSA) in the UV range, for a 5 years period in Athens, Greece. Τhis data set was used as input to a radiative transfer model and the SSA for 368 nm and 332 nm has been calculated. Retrievals from a collocated CIMEL sun-photometer were used to validate the products and study absorption spectral behavior SSA values at these wavelengths. UVMFR SSA together with synchronous,CIMEL-derived, retrievals at 440 nm, show a mean of 0.90, 0.87 and 0.83, with lowest values (higher absorption) towards lower wavelengths. In addition, noticeable diurnal variations of the SSA in all wavelengths are revealed, with amplitudes in up to 0.05. High SSA wavelength dependence is found for cases of low Ångström exponents and also an SSA decrease with decreasing extinction optical depth, suggesting an effect of the different aerosol composition. Dust and Brown Carbon UV absorbing properties were investigated to understand seasonal variability of the results.

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Relative sky radiance from multi-exposure all-sky camera images

10.5194/amt-2020-421 ◽

2020 ◽

Author(s):

Juan C. Antuña-Sánchez ◽

Roberto Román ◽

Victoria E. Cachorro ◽

Carlos Toledano ◽

César López ◽

...

Keyword(s):

Dynamic Range ◽

Quality Criteria ◽

High Dynamic Range ◽

Radiative Transfer Model ◽

Transfer Model ◽

High Dynamic ◽

Sky Radiance ◽

Black Level ◽

Hdr Image

Abstract. All-sky cameras are frequently used to detect cloud cover; however, this work explores the use of these instruments for the more complex purpose of extracting relative sky radiances. An all-sky camera (SONA202-NF model) with three colour filters, narrower than usual for this kind of cameras, is configured to capture raw images at seven exposure times. A detailed camera characterization of the black level, readout noise, hot pixels and linear response is carried out. A methodology is proposed to obtain a linear high dynamic range (HDR) image and its uncertainty, which represents the relative sky radiance map at three effective wavelengths. The relative sky radiance (normalized by the sum of all radiances) is extracted from these maps and compared with the sky radiance measured at different sky points by a sun/sky photometer belonging to the Aerosol Robotic Network (AERONET). The camera radiances are in line with photometer ones excepting for scattering angles below 10º, which is probably due to some light reflections on the fisheye lens and camera dome. Camera and photometer wavelengths are not coincident, hence camera radiances are also compared with sky radiances simulated by a radiative transfer model at the same camera effective wavelengths. This comparison reveals an uncertainty on the normalized camera radiances about 3.3 %, 4.3 % and 5.3 % for 467, 536 and 605 nm, respectively, if specific quality criteria are applied.

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RADIOMETRIC CHARACTERIZATION OF A MARSH SITE AT THE ARGENTINIAN PAMPAS IN THE CONTEXT OF HYPERNETS PROJECT (A NEW AUTONOMOUS HYPERSPECTRAL RADIOMETER)

ISPRS Annals of Photogrammetry Remote Sensing and Spatial Information Sciences ◽

10.5194/isprs-annals-iv-3-w2-2020-95-2020 ◽

2020 ◽

Vol IV-3/W2-2020 ◽

pp. 95-100

Author(s):

E. Piegari ◽

J. I. Gossn ◽

Á. Juárez ◽

V. Barraza ◽

G. González Trilla ◽

...

Keyword(s):

Biochemical Characterization ◽

Low Cost ◽

Photosynthetic Apparatus ◽

Test Site ◽

Coastal Marsh ◽

Radiative Transfer Model ◽

Transfer Model ◽

Coastal Habitat

Abstract. In the context of HYPERNETS project, which is developing a relatively low cost hyperspectral radiometer (and associated pointing system and embedded calibration device for automated measurement of water and land bidirectional reflectance), the tidal coastal marsh in the Mar Chiquita (Argentina) lagoon is being characterized as a test site for validation of radiometric variables. High quality in situ measurements will be available at all spectral bands at this site (and other sites over land and water around the world) for the validation of the surface reflectance data issued from all earth observation missions. This site, dominanted by Sporobolus densiflorus vegetation, is a coastal habitat that provides ecosystem services essential to people and the environment. There is evidence that growth and photosynthetic apparatus of S. densiflorus is negatively affected by the herbicide glyphosate, which is extensively used in the Argentinian agricultural production. As a way to monitor this risk, in this work a theoretical study was performed to establish if it is possible to estimate the chlorophyll content (Ca+b in S. densiflorus), which concentrations are known to be affected by the herbicide, using hyperspectral reflectance. Signatures recorded in situ plus other parameters obtained from a biochemical characterization of the plant were used to obtain a simulated reflectance with the radiative transfer model PROSAIL. Then, a BaseLine Residual approach, based on close band triplets, was proposed to retrieve Ca+b. As a result, we found that it is possible to distinguish between two levels of Ca+b.

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Aerosol absorption retrieval at ultraviolet wavelengths in a complex environment

Atmospheric Measurement Techniques ◽

10.5194/amt-9-5997-2016 ◽

2016 ◽

Vol 9 (12) ◽

pp. 5997-6011 ◽

Cited By ~ 12

Author(s):

Stelios Kazadzis ◽

Panagiotis Raptis ◽

Natalia Kouremeti ◽

Vassilis Amiridis ◽

Antti Arola ◽

...

Keyword(s):

Wavelength Dependence ◽

Single Scattering ◽

Radiative Transfer Model ◽

Transfer Model ◽

Complex Environment ◽

Aerosol Composition ◽

Aerosol Absorption ◽

Uv Irradiance ◽

Band Radiometer ◽

Uv Range

Abstract. We have used total and diffuse UV irradiance measurements from a multi-filter rotating shadow-band radiometer (UVMFR) in order to investigate aerosol absorption in the UV range for a 5-year period in Athens, Greece. This dataset was used as input to a radiative transfer model and the single scattering albedo (SSA) at 368 and 332 nm was calculated. Retrievals from a collocated CIMEL sun photometer were used to evaluate the products and study the absorption spectral behavior of retrieved SSA values. The UVMFR SSA, together with synchronous, CIMEL-derived retrievals of SSA at 440 nm, had a mean of 0.90, 0.87 and 0.83, with lowest values (higher absorption) encountered at the shorter wavelengths. In addition, noticeable diurnal variation of the SSA in all wavelengths is shown, with amplitudes up to 0.05. Strong SSA wavelength dependence is revealed for cases of low Ångström exponents, accompanied by a SSA decrease with decreasing extinction optical depth, suggesting varying influence under different aerosol composition. However, part of this dependence for low aerosol optical depths is masked by the enhanced SSA retrieval uncertainty. Dust and brown carbon UV absorbing properties were also investigated to explain seasonal patterns.

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Atmospheric Science with Visible/Near-Infrared Spectra from the Mars 2020 Perseverance Rover

10.5194/egusphere-egu21-1986 ◽

2021 ◽

Author(s):

Timothy McConnochie ◽

Thierry Fouchet ◽

Franck Montmessin ◽

Pierre Beck ◽

Baptiste Chide ◽

...

Keyword(s):

Near Infrared ◽

Solar Spectrum ◽

Atmospheric Science ◽

Tunable Filter ◽

Radiative Transfer Model ◽

Discrete Ordinates ◽

Transfer Model ◽

Absorption Bands ◽

Aerosol Scattering ◽

Remote Sensing Techniques

The Mars 2020 &#8220;Perseverance&#8221; rover&#8217;s SuperCam instrument suite [1,2,3] provides a wide variety of active and passive remote sensing techniques [4, 5, 6, 7] including passive visible & near-infrared (&#8220;VISIR&#8221;) spectroscopy [8]. Here we present our plans to use the VISIR technique for atmospheric science by observing solar radiation scattered by the Martian sky, similar to the &#8220;passive sky&#8221; technique demonstrated with ChemCam on the Mars Science Laboratory (MSL) rover [9]. Our presentation will focus on the objectives and techniques of SuperCam VISIR atmospheric science, but we will also present initial atmospheric science results or relevant instrument performance validation results to the extent that such are available at the time of the conference.The objectives of VISIR atmospheric science are O2, CO, and H2O vapor column abundances, and aerosol particle sizes and composition. These objectives are motivated by unexpected seasonal and interannual variability in the O2mixing ratio that is argued to be so large as to require O2 sources and sinks in surface soils [10], by evidence of surface-atmosphere exchange of H2O [11], by the potential significance of O2 and H2O volatiles as field context for returned samples due to their active exchanges with surface materials, and by the Mars 2020 mission [12] objectives of characterizing dust and validating global atmospheric models to prepare for human explorationThe SuperCam spectrometers used for VISIR mode are a ChemCam-heritage reflection spectrometer covering 385&#8211;465 nm with < 0.2 nm res. [2], an intensified transmission spectrometer covering 536&#8211;853 nm with 0.3&#8211;0.7 nm res. [2], and an acousto-optic-tunable-filter (AOTF) -based IR spectrometer covering 1300&#8211;2600 nm with 20&#8211;30 cm-1 res. [1, 8]. Our primary observing strategy is the same approach used for MSL ChemCam &#8220;passive sky&#8221; observations [9]: ratioing instrument signals from the two pointing positions with different elevation angles eliminates solar spectrum and instrument response uncertainties that are ~100x and ~10x larger than signals of interest for the transmission and AOTF IR spectrometers, respectively. We will also make use of single pointings directed at the white SuperCam calibration target for less-resource-intensive water vapor and aerosol monitoring, and of multiple-pointing lower-signal-to-noise sky scans to better constrain aerosol size and shape. Sky radiance is fit with a discrete ordinates multiple scattering radiative transfer model identical to that of [9]. As in [9] gas abundances are made robust to aerosol scattering uncertainties by fitting CO2 absorption bands with an aerosol vertical profile parameter.References: [1] Maurice S. et al. (2020) SSR, in press. [2] Wiens R.C. et al. (2021) SSR 217, 4. [3] Manrique J.-A. et al. (2020) SSR 216, 138. [4] Ollila A.M. et al. (2021), this meeting. [5] Ollila A.M. et al. (2018) LPSC 49, 2786. [6] Forni O. et al. (2021), this meeting. [7] Lanza N. L. et al. (2021), this meeting. [8] Johnson J.R et al. (2021), this meeting. [9] McConnochie T.H et al. (2018), Icarus 307, 294. [10] Trainer M.G. et al. (2019), JGR 124, 3000. [11] Savij&#228;rvi H. et al. (2016), Icarus 265, 63. [12] Farley K.A. et al. (2020), SSR 216, 142.

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