Browsing by Autor "B. N. Holben"

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Evaluation of AERONET precipitable water vapor versus microwave radiometry, GPS, and radiosondes at ARM sites
(Wiley, 2014) Daniel Pérez‐Ramírez; David N. Whiteman; A. Smirnov; H. Lyamani; B. N. Holben; R. T. Pinker; Marcos Andrade; Lucas Alados‐Arboledas
Abstract In this paper we present comparisons of Aerosol Robotic Network (AERONET) precipitable water vapor ( W ) retrievals from Sun photometers versus radiosonde observations and other ground‐based retrieval techniques such as microwave radiometry (MWR) and GPS. The comparisons make use of the extensive measurements made within the U.S. Department of Energy Atmospheric Radiation Measurement Program (ARM), mainly at their permanent sites located at the Southern Great Plains (Oklahoma, U.S.), Nauru Islands, and Barrow (Alaska, U.S.). These places experience different types of weather which allows the comparison of W under different conditions. Radiosonde and microwave radiometry data were provided by the ARM program while the GPS data were obtained from the SOUMINET network. In general, W obtained by AERONET is lower than those obtained by MWR and GPS by ~6.0–9.0% and ~6.0–8.0%, respectively. The AERONET values are also lower by approximately 5% than those obtained from the numerous balloon‐borne radiosondes launched at the Southern Great Plains. These results point toward a consistent dry bias in the retrievals of W by AERONET of approximately 5–6% and a total estimated uncertainty of 12–15%. Differences with respect to MWR retrievals are a function of solar zenith angle pointing toward a possible bias in the MWR retrievals. Finally, the ability of AERONET precipitable water vapor retrievals to provide long‐term records of W in diverse climate regimes is demonstrated.
GOES-16 ABI solar reflective channel validation for earth science application
(Elsevier BV, 2019) Joel McCorkel; Boryana Efremova; Jason Hair; Marcos Andrade; B. N. Holben
This paper presents the validation results of GOES-16 Satellite's Advanced Baseline Imager (ABI) obtained from a reflectance-based field campaign undertaken at the Salar de Uyuni in Bolivia in June 2017. In situ ground measurements are used to characterize the surface reflectance and the atmosphere in order to constrain the radiative transfer code and predict at-sensor reflectance (also referred to as top-of-atmosphere (TOA) reflectance) to compare with concurrent GOES-16 ABI measurements. The five-day field campaign provided repeated TOA reflectance estimates, allowing assessment not only of the calibration accuracy of the ABI reflective channels 1, 2, 3, 5 and 6, but also of its stability over the duration of the campaign. The results show that the accuracy of the ABI reflective channels calibration is within specification for channels 1, 3, 5, and 6 - average biases within 2%; for channel 2 the bias is 5%. The estimated uncertainty on the derived biases is 2–2.4%. Some calibration stability issues were present in the ABI calibration at the time of the campaign: (i) a jump on the order of 2% in channels 1 and 6, coincident with an ABI solar calibration event, reflects an instability of the ABI gains in these channels, and (ii) short-term variability in channels 1 and 2 is due to striping (ABI detector-to-detector calibration differences). Continued validation and subsequent reprocessing of ABI reflectance imagery would allow Earth scientists to fully benefit from the high spatial and spectral fidelity of the GOES-16 ABI diurnal measurements at the continental scale.