scholarly journals Ship borne rotating shadow band radiometer observations for the determination of multi spectral irradiance components and direct sun products for aerosol

2016 ◽  
Author(s):  
Jonas Witthuhn ◽  
Hartwig Deneke ◽  
Andreas Macke ◽  
Germar Bernhard
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Precipitable Water ◽  
Gas Absorption ◽  
Spectral Irradiance ◽  
Total Uncertainty ◽  
Direct Beam ◽  
Sun Photometer ◽  
Beam Transmittance ◽  
Band Radiometer

Abstract. The 19 channel rotating shadow band radiometer GUVis-3511 built by Biospherical Instruments is introduced as an instrument which is able to provide automated ship borne measurements of the direct, diffuse and global spectral irradiance components without a requirement for stabilization. Several direct sun products, including spectral direct beam transmittance, aerosol optical depth, Angström exponent, and precipitable water can be derived from these observations. The individual steps of the data analysis are described, and the different sources of uncertainty are discussed. The total uncertainty of the observed direct beam transmittances is estimated to be 4.24 % at 95 % CI for ship borne operation. The calibration is identified as the dominating contribution to the total uncertainty. A comparison of direct beam transmittance with those obtained from a Cimel sun photometer at a land site and a manually operated Microtops II sun photometer on a ship is presented, yielding relative deviations of less than 3 % and 4 % on land and on ship, respectively, for most channels and in agreement with our previous uncertainty estimate. These numbers demonstrate that the instrument is well suited for ship borne operation, and the applied methods for motion correction work accurately. Based on spectral direct beam transmittance, aerosol optical depth at 510 nm can be retrieved with an uncertainty of 0.0032 for a 95 % CI. Only minor deviations occur due to the different methods used for estimating Rayleigh scattering and gas absorption optical depths, as implemented by AERONET and in our processing. Relying on the cross-calibration of the 940 nm water vapor channel with the Cimel sun photometer, the column amount of precipitable water has been estimated with an uncertainty of +−0.034 cm. More research is needed to estimate the accuracy of the instrument for low sun (solar zenith angles larger than 70°) and during periods with strong swell.

scholarly journals Algorithms and uncertainties for the determination of multispectral irradiance components and aerosol optical depth from a shipborne rotating shadowband radiometer

2017 ◽  
Vol 10 (2) ◽  
pp. 709-730 ◽  
Author(s):  
Jonas Witthuhn ◽  
Hartwig Deneke ◽  
Andreas Macke ◽  
Germar Bernhard
Keyword(s):  
Confidence Interval ◽  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Rayleigh Scattering ◽  
Precipitable Water ◽  
Gas Absorption ◽  
Spectral Irradiance ◽  
Total Uncertainty ◽  
Direct Beam ◽  
Beam Transmittance

Abstract. The 19-channel rotating shadowband radiometer GUVis-3511 built by Biospherical Instruments provides automated shipborne measurements of the direct, diffuse and global spectral irradiance components without a requirement for platform stabilization. Several direct sun products, including spectral direct beam transmittance, aerosol optical depth, Ångström exponent and precipitable water, can be derived from these observations. The individual steps of the data analysis are described, and the different sources of uncertainty are discussed. The total uncertainty of the observed direct beam transmittances is estimated to be about 4 % for most channels within a 95 % confidence interval for shipborne operation. The calibration is identified as the dominating contribution to the total uncertainty. A comparison of direct beam transmittance with those obtained from a Cimel sunphotometer at a land site and a manually operated Microtops II sunphotometer on a ship is presented. Measurements deviate by less than 3 and 4 % on land and on ship, respectively, for most channels and in agreement with our previous uncertainty estimate. These numbers demonstrate that the instrument is well suited for shipborne operation, and the applied methods for motion correction work accurately. Based on spectral direct beam transmittance, aerosol optical depth can be retrieved with an uncertainty of 0.02 for all channels within a 95 % confidence interval. The different methods to account for Rayleigh scattering and gas absorption in our scheme and in the Aerosol Robotic Network processing for Cimel sunphotometers lead to minor deviations. Relying on the cross calibration of the 940 nm water vapor channel with the Cimel sunphotometer, the column amount of precipitable water can be estimated with an uncertainty of ±0.034 cm.

scholarly journals Above-aircraft cirrus cloud and aerosol optical depth from hyperspectral irradiances measured by a total-diffuse radiometer

2021 ◽  
Author(s):  
Matthew S. Norgren ◽  
John Wood ◽  
K. Sebastian Schmidt ◽  
Bastiaan van Diedenhoven ◽  
Snorre A. Stamnes ◽  
...  
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Low Cost ◽  
In Situ Measurements ◽  
Cirrus Cloud ◽  
Optical Extinction ◽  
Direct Beam ◽  
Diffuse Irradiance ◽  
Sun Photometer

Abstract. This study develops the use of spectral total and diffuse irradiance measurements, made from a prototype hyperspectral total-diffuse Sunshine Pyranometer (SPN-S), to retrieve layer fine-mode aerosol (τaer) and total optical depths from airborne platforms. Additionally, we use spectral analysis in an attempt to partition the total optical depth it into its τaer and cirrus cloud optical depth (τcld) components in the absence of coarse-mode aerosols. Two retrieval methods are developed: one leveraging information in the diffuse irradiance, and the other using spectral characteristics of the transmitted direct beam, with each approach best suited for specific cloud and aerosol conditions. SPN-S has advantages over traditional sun-photometer systems including no moving parts and a low cost. However, a significant drawback of the instrument is that it is unable to measure the direct beam irradiance as accurately as sun-photometers. To compensate for the greater measurement uncertainty of the radiometric irradiances these retrieval techniques employ ratioed inputs or spectral information to reduce output uncertainty. This analysis uses irradiance measurements from SPN-S and the Solar Spectral Flux Radiometer (SSFR) aboard the National Aeronautics and Space Administration’s (NASA) P-3 aircraft during the 2018 deployment of the ObseRvations of Aerosols above CLouds and their intEractionS (ORACLES) campaign and the 2019 Cloud, Aerosol and Monsoon Processes Philippines Experiment (CAMP2Ex) mission to quantify above-aircraft cirrus τcld and derive vertical profiles of layer τaer. Validation of the τaer retrieval is accomplished by comparison with collocated measurements of direct solar irradiance made by the Sky-Scanning Sun-Tracking Atmospheric Research (4STAR) and in situ measurements of aerosol optical depth. For the aggregated 2018 ORACLES results, regression between the SPN-S based method and sun-photometer τaer values yield a slope of 0.96 with an R2 of 0.96, while the root-mean-square error (RMSE) is 3.0 × 10−2. When comparing the retrieved τaer to profiles of integrated in situ measurements of optical extinction, the slope, R2, and RMSE values for ORACLES are 0.90, 0.96, 3.4 × 10−2, and for CAMP2Ex are 0.94, 0.97, 3.4 × 10−2 respectively. This paper is a demonstration of methods for deriving cloud and aerosol optical properties in environments where both atmospheric constituents may be present. With improvements to the low-cost SPN-S radiometer instrument, it may be possible to extend these methods to a broader set of sampling applications, such as ground-based settings.

scholarly journals Retrieval of aerosol single-scattering albedo and polarized phase function from polarized sun-photometer measurements for Zanjan's atmosphere

2013 ◽  
Vol 6 (10) ◽  
pp. 2659-2669 ◽  
Author(s):  
A. Bayat ◽  
H. R. Khalesifard ◽  
A. Masoumi
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Atmospheric Aerosols ◽  
Phase Function ◽  
Single Scattering ◽  
Single Scattering Albedo ◽  
Angstrom Exponent ◽  
Ångström Exponent ◽  
Sun Photometer ◽  
Ångstrom Exponent

Abstract. The polarized phase function of atmospheric aerosols has been investigated for the atmosphere of Zanjan, a city in northwest Iran. To do this, aerosol optical depth, Ångström exponent, single-scattering albedo, and polarized phase function have been retrieved from the measurements of a Cimel CE 318-2 polarized sun-photometer from February 2010 to December 2012. The results show that the maximum value of aerosol polarized phase function as well as the polarized phase function retrieved for a specific scattering angle (i.e., 60°) are strongly correlated (R = 0.95 and 0.95, respectively) with the Ångström exponent. The latter has a meaningful variation with respect to the changes in the complex refractive index of the atmospheric aerosols. Furthermore the polarized phase function shows a moderate negative correlation with respect to the atmospheric aerosol optical depth and single-scattering albedo (R = −0.76 and −0.33, respectively). Therefore the polarized phase function can be regarded as a key parameter to characterize the atmospheric particles of the region – a populated city in the semi-arid area and surrounded by some dust sources of the Earth's dust belt.

scholarly journals Aerosol optical depth retrievals in central Amazonia from a multi-filter rotating shadow-band radiometer calibrated on-site

2019 ◽  
Vol 12 (2) ◽  
pp. 921-934
Author(s):  
Nilton E. Rosário ◽  
Thamara Sauini ◽  
Theotonio Pauliquevis ◽  
Henrique M. J. Barbosa ◽  
Marcia A. Yamasoe ◽  
...  
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Spectral Response ◽  
Monitoring Site ◽  
Direct Normal Irradiance ◽  
Central Amazonia ◽  
Long Term Monitoring ◽  
Term Monitoring ◽  
Band Radiometer

Abstract. Extraterrestrial spectral response calibration of a multi-filter rotating shadow band radiometer (MFRSR) under pristine Amazonian Forest atmosphere conditions was performed using the Langley plot method. The MFRSR is installed in central Amazonia as part of a long-term monitoring site, which was used in the context of the GoAmazon2014/5 experiment. It has been operating continuously since 2011 without regular extraterrestrial calibration, preventing its application to accurate monitoring of aerosol particles. Once calibrated, the MFRSR measurements were applied to retrieve aerosol particle columnar optical properties, specifically aerosol optical depth (AODλ) and Ångström exponent (AE), which were evaluated against retrievals from a collocated Cimel Sun photometer belonging to the AErosol RObotic NETwork (AERONET). Results obtained revealed that pristine Amazonian conditions are able to provide MFRSR extraterrestrial spectral response with relative uncertainty lower than 1.0 % in visible channels. The worst estimate (air mass =1) for absolute uncertainty in AODλ retrieval varied from ≈0.02 to ≈0.03, depending on the assumption regarding uncertainty for MFRSR direct normal irradiance measured at the surface. The obtained root mean square error (RMSE ≈0.025) from the evaluation of MFRSR retrievals against AERONET AODλ was, in general, lower than estimated MFRSR AODλ uncertainty, and close to the uncertainty of AERONET field Sun photometers (≈0.02).

Validation of satellite and model aerosol optical depth and precipitable water vapour observations with AERONET data over Pune, India

2018 ◽  
Vol 39 (21) ◽  
pp. 7643-7663 ◽  
Author(s):  
K. Vijayakumar ◽  
P. C. S. Devara ◽  
David M. Giles ◽  
Brent N. Holben ◽  
S. Vijaya Bhaskara Rao ◽  
...  
Keyword(s):  
Water Vapour ◽  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Precipitable Water ◽  
Precipitable Water Vapour ◽  
Model Aerosol

Evaluating Aerosol Optical Depth From Himawari‐8 With Sun Photometer Network

2019 ◽  
Vol 124 (10) ◽  
pp. 5516-5538 ◽  
Author(s):  
Wei Wang ◽  
Feiyue Mao ◽  
Zengxin Pan ◽  
Wei Gong ◽  
Mayumi Yoshida ◽  
...  
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Sun Photometer

scholarly journals A Multi Linear Regression Model to Derive Dust PM10 in the Sahel Using AERONET Aerosol Optical Depth and CALIOP Aerosol Layer Products

2020 ◽  
Vol 12 (18) ◽  
pp. 3099
Author(s):  
Jean-François Léon ◽  
Nadège Martiny ◽  
Sébastien Merlet
Keyword(s):  
Linear Regression ◽  
Regression Model ◽  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Linear Regression Model ◽  
Population Exposure ◽  
Aerosol Layer ◽  
Multi Linear Regression ◽  
Sun Photometer ◽  
The Impact

Due to a limited number of monitoring stations in Western Africa, the impact of mineral dust on PM10 surface concentrations is still poorly known. We propose a new method to retrieve PM10 dust surface concentrations from sun photometer aerosol optical depth (AOD) and CALIPSO/CALIOP Level 2 aerosol layer products. The method is based on a multi linear regression model that is trained using co-located PM10, AERONET and CALIOP observations at 3 different locations in the Sahel. In addition to the sun photometer AOD, the regression model uses the CALIOP-derived base and top altitude of the lowermost dust layer, its AOD, the columnar total and columnar dust AOD. Due to the low revisit period of the CALIPSO satellite, the monthly mean annual cycles of the parameters are used as predictor variables rather than instantaneous observations. The regression model improves the correlation coefficient between monthly mean PM10 and AOD from 0.15 (AERONET AOD only) to 0.75 (AERONET AOD and CALIOP parameters). The respective high and low PM10 concentration during the winter dry season and summer season are well produced. Days with surface PM10 above 100 μg/m3 are better identified when using the CALIOP parameters in the multi linear regression model. The number of true positives (actual and predicted concentrations above the threshold) is increased and leads to an improvement in the classification sensitivity (recall) by a factor 1.8. Our methodology can be extrapolated to the whole Sahel area provided that satellite derived AOD maps are used in order to create a new dataset on population exposure to dust events in this area.

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