Review of "Aerosol optical depth determination in the UV using a four-channel precision filter radiometer" by Carlund et al.

2017 ◽  
Author(s):  
Anonymous
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Filter Radiometer ◽  
Depth Determination

scholarly journals Aerosol optical depth retrievals at the Izaña Atmospheric Observatory from 1941 to 2013 by using artificial neural networks

2016 ◽  
Vol 9 (1) ◽  
pp. 53-62 ◽  
Author(s):  
R. D. García ◽  
O. E. García ◽  
E. Cuevas ◽  
V. E. Cachorro ◽  
A. Barreto ◽  
...  
Keyword(s):  
Neural Networks ◽  
Time Series ◽  
Artificial Neural Networks ◽  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Mineral Dust ◽  
Dust Particles ◽  
Filter Radiometer ◽  
Artificial Neural

Abstract. This paper presents the reconstruction of a 73-year time series of the aerosol optical depth (AOD) at 500 nm at the subtropical high-mountain Izaña Atmospheric Observatory (IZO) located in Tenerife (Canary Islands, Spain). For this purpose, we have combined AOD estimates from artificial neural networks (ANNs) from 1941 to 2001 and AOD measurements directly obtained with a Precision Filter Radiometer (PFR) between 2003 and 2013. The analysis is limited to summer months (July–August–September), when the largest aerosol load is observed at IZO (Saharan mineral dust particles). The ANN AOD time series has been comprehensively validated against coincident AOD measurements performed with a solar spectrometer Mark-I (1984–2009) and AERONET (AErosol RObotic NETwork) CIMEL photometers (2004–2009) at IZO, obtaining a rather good agreement on a daily basis: Pearson coefficient, R, of 0.97 between AERONET and ANN AOD, and 0.93 between Mark-I and ANN AOD estimates. In addition, we have analysed the long-term consistency between ANN AOD time series and long-term meteorological records identifying Saharan mineral dust events at IZO (synoptical observations and local wind records). Both analyses provide consistent results, with correlations  >  85 %. Therefore, we can conclude that the reconstructed AOD time series captures well the AOD variations and dust-laden Saharan air mass outbreaks on short-term and long-term timescales and, thus, it is suitable to be used in climate analysis.

scholarly journals Aerosol optical depth retrievals at the Izaña Atmospheric Observatory from 1941 to 2013 by using artificial neural networks

2015 ◽  
Vol 8 (9) ◽  
pp. 9075-9103 ◽  
Author(s):  
R. D. García ◽  
O. E. García ◽  
E. Cuevas ◽  
V. E. Cachorro ◽  
A. Barreto ◽  
...  
Keyword(s):  
Neural Networks ◽  
Time Series ◽  
Artificial Neural Networks ◽  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Mineral Dust ◽  
Dust Particles ◽  
Filter Radiometer ◽  
Artificial Neural

Abstract. This paper presents the reconstruction of the 73 year time series of the aerosol optical depth (AOD) at 500 nm at the subtropical high-mountain Izaña Atmospheric Observatory (IZO) located in Tenerife (Canary Islands, Spain). For this purpose, we have combined AOD estimates from artificial neural networks (ANNs) from 1941 to 2001 and AOD measurements directly obtained with a Precision Filter Radiometer (PFR) between 2003 and 2013. The analysis is limited to summer months (July–August–September), when the largest aerosol load is observed at IZO (Saharan mineral dust particles). The ANN AOD time series has been comprehensively validated against coincident AOD measurements performed with a solar spectrometer Mark-I (1984–2009) and AERONET (AErosol RObotic NETwork) CIMEL photometers (2004–2009) at IZO, obtaining a rather good agreement on a daily basis: Pearson coefficient, R, of 0.97 between AERONET and ANN AOD, and 0.93 between Mark-I and ANN AOD estimates. In addition, we have analyzed the long-term consistency between ANN AOD time series and long-term meteorological records identifying Saharan mineral dust events at IZO (synoptical observations and local wind records). Both analyses provide consistent results, with correlations larger than 85 %. Therefore, we can conclude the reconstructed AOD time series captures well the AOD variations and dust-laden Saharan air mass outbreaks at short-term and long-term time scales and, thus, it is suitable to be used in climate analysis.

scholarly journals Results from the Fourth WMO Filter Radiometer Comparison for aerosol optical depth measurements

2018 ◽  
Vol 18 (5) ◽  
pp. 3185-3201 ◽  
Author(s):  
Stelios Kazadzis ◽  
Natalia Kouremeti ◽  
Henri Diémoz ◽  
Julian Gröbner ◽  
Bruce W. Forgan ◽  
...  
Keyword(s):  
Water Vapor ◽  
Individual Differences ◽  
Aerosol Optical Depth ◽  
Optical Depth ◽  
High Accuracy ◽  
Measured Data ◽  
Air Mass ◽  
Filter Radiometer ◽  
The World ◽  
Near Future

Abstract. This study presents the results of the Fourth Filter Radiometer Comparison that was held in Davos, Switzerland, between 28 September and 16 October 2015. Thirty filter radiometers and spectroradiometers from 12 countries participated including reference instruments from global aerosol networks. The absolute differences of all instruments compared to the reference have been based on the World Meteorological Organization (WMO) criterion defined as follows: 95% of the measured data has to be within 0.005 ± 0.001∕m (where m is the air mass). At least 24 out of 29 instruments achieved this goal at both 500 and 865 nm, while 12 out of 17 and 13 out of 21 achieved this at 368 and 412 nm, respectively. While searching for sources of differences among different instruments, it was found that all individual differences linked to Rayleigh, NO2, ozone, water vapor calculations and related optical depths and air mass calculations were smaller than 0.01 in aerosol optical depth (AOD) at 500 and 865 nm. Different cloud-detecting algorithms used have been compared. Ångström exponent calculations showed relatively large differences among different instruments, partly because of the high calculation uncertainty of this parameter in low AOD conditions. The overall low deviations of these AOD results and the high accuracy of reference aerosol network instruments demonstrated a promising framework to achieve homogeneity, compatibility and harmonization among the different spectral AOD networks in the near future.

scholarly journals Recovering Long-term Aerosol Optical Depth Series (1976–2012) from an Astronomical Potassium-based Resonance Scattering Spectrometer

2014 ◽  
Vol 7 (4) ◽  
pp. 4093-4121 ◽  
Author(s):  
A. Barreto ◽  
E. Cuevas ◽  
P. Pallé ◽  
P. M. Romero ◽  
F. Almansa ◽  
...  
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Correlation Coefficients ◽  
Resonant Scattering ◽  
Resonance Scattering ◽  
Data Series ◽  
Long Term Stability ◽  
Filter Radiometer ◽  
Scattered Component

Abstract. A 37 year long-term series of monochromatic Aerosol Optical Depth (AOD) has been recovered from solar irradiance measurements performed with the solar spectrometer Mark-I, deployed at Izaña mountain since 1976. The instrument operation is based on the method of resonant scattering, which presents a long-term stability and high precision in comparison to other instruments based on interference filters. However, it has been specifically designed as a reference instrument for helioseismology, and its ability to determine AOD from transmitted and scattered monochromatic radiation at 769.9 nm inside a potassium vapor cell in the presence of a permanent magnetic field is evaluated in this paper. Particularly, the use of an exposed mirrors arrangement to collect sunlight as well as the Sun-laboratory velocity dependence of the scattered component introduces some inconveniences when we perform the instrument's calibration. We have solved this problem using a quasi-continuous Langley calibration technique and a refinement procedure to correct for calibration errors as well as for the fictitious diurnal cycle on AOD data. Our results showed that calibration errors associated to the quasi-continuous Langley technique are not dependent on aerosol load, provided aerosol concentration remains constant throughout the day, assuring the validity of this technique for those periods with relatively high aerosol content required to calibrate the scattered component. The comparative analysis between the recovered AOD dataset from Mark-I and collocated quasi-simultaneous data from Cimel AErosol RObotic NETwork (AERONET) and Precision Filter Radiometer (PFR) instruments showed an absolute mean bias ≤ 0.01 in the 11 year and 12 year comparison, respectively. High correlation coefficients between AERONET/Mark-I and PFR/Mark-I pairs confirmed a very good linear relationship between instruments, proving that recovered AOD data series from Mark-I can be used together PFR and AERONET AOD data to build a long-term AOD data series at Izaña site (1976–now), suitable for future analysis of aerosols trends and inter-annual variability. Finally, the AOD preliminary trend analysis in the 29 year period from 1984 to 2012 with Mark-I AOD revealed no significant trends. However, we detected a negative significant trend of 0.047 decade−1 during the period 1984–1993.

Aerosol optical depth determination from ground based irradiance ratios

1989 ◽  
Vol 28 (15) ◽  
pp. 3092 ◽  
Author(s):  
Norman T. O’Neill ◽  
Alain Royer ◽  
John R. Miller
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Depth Determination

scholarly journals Supplementary material to "Results from the 4<sup>th</sup> WMO Filter Radiometer Comparison for aerosol optical depth measurements"

2017 ◽  
Author(s):  
Stelios Kazadzis ◽  
Natalia Kouremeti ◽  
Henri Diémoz ◽  
Julian Gröbner ◽  
Bruce W. Forgan ◽  
...  
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Filter Radiometer ◽  
Supplementary Material

scholarly journals Aerosol optical depth determination in the UV using a four-channel precision filter radiometer

2016 ◽  
Author(s):  
Thomas Carlund ◽  
Natalia Kouremeti ◽  
Stelios Kazadzis ◽  
Julian Gröbner
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Spectral Response ◽  
Wavelength Region ◽  
Measuring Instruments ◽  
Response Functions ◽  
Total Column Ozone ◽  
Total Uncertainty ◽  
Air Mass ◽  
Filter Radiometer

Abstract. The determination of aerosol properties, especially the aerosol optical depth (AOD) in the UV wavelength region is of great importance to understand the climatological variability of UV radiation. However, operational retrievals of AOD at the biological most harmful wavelengths in the UVB are currently only made at very few places. This paper reports on the UVPFR sunphotometer, a stable and robust instrument that can be used for AOD retrievals at four UV wavelengths. Instrument characteristics and results of Langley calibrations at a high altitude site were presented. It was shown that due to the relatively wide spectral response functions of the UVPFR, the calibration constants (V0) from Langley plot calibrations underestimate the true extra-terrestrial signals. Accordingly, correction factors were introduced. In addition, the instrument spectral response functions also result in an apparent airmass dependent decrease in ozone optical depth used in the AOD determinations. An adjusted formula for the calculation of AOD, with a correction term dependent on total column ozone amount and ozone air mass, was therefore developed. Langley calibrations performed 13–14 months apart resulted in sensitivity changes of ≤ 1.1 %, indicating good instrument stability. Comparison with a standard PFR, measuring AOD at 368–862 nm wavelengths with high accuracy, showed consistent results. Also very good agreement was achieved comparing the UVPFR with AOD at UVB wavelengths derived with a Brewer spectrophotometer, which was calibrated against the UVPFR at an earlier date. Mainly due to non-instrumental uncertainties connected with ozone optical depth, the total uncertainty of AOD in the UVB are higher than the ones reported from UVA and visible AOD measuring instruments. However, the precision can be high between instruments using harmonized algorithms for ozone and Rayleigh optical depth as well as for air mass terms. For several months of comparison measurements with the UVPFR and a Brewer the root mean squared AOD differences were

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