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Development of near-sea-level Langley calibration algorithm for aerosol optical depth measurement

Aerosol optical depth (AOD) represents the total attenuation of solar terrestrial radiation caused by aerosol. In long-term monitoring networks, accurate measurement of AOD is difficult due to the lack of frequent calibration of the spectrometer. This is because conventional Langley calibration is u...

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Main Author: Chang, Jackson Hian Wui
Format: Thesis
Language:English
English
Published: 2014
Subjects:
QC851-999 Meteorology. Climatology Including the earth's atmosphere
Online Access:https://eprints.ums.edu.my/id/eprint/40568/1/24%20PAGES.pdf
https://eprints.ums.edu.my/id/eprint/40568/2/FULLTEXT.pdf
https://eprints.ums.edu.my/id/eprint/40568/
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spelling my.ums.eprints.405682024-08-16T02:23:08Z https://eprints.ums.edu.my/id/eprint/40568/ Development of near-sea-level Langley calibration algorithm for aerosol optical depth measurement Chang, Jackson Hian Wui QC851-999 Meteorology. Climatology Including the earth's atmosphere Aerosol optical depth (AOD) represents the total attenuation of solar terrestrial radiation caused by aerosol. In long-term monitoring networks, accurate measurement of AOD is difficult due to the lack of frequent calibration of the spectrometer. This is because conventional Langley calibration is usually performed at high mountains for clear and stable atmosphere and regular access to high altitudes is inefficient in terms of accessibility and economical prospects. Therefore, a near-sea-level Langley calibration algorithm is developed to allow frequent calibration feasible even at low altitude. It uses the combination of Perez-Du Mortier (PDM) model and statistical filter to constrain the Langley extrapolation to get closest possible extraterrestrial constant over a wide range of wavelengths. To further contain the wavelength-dependent error due to varying extraterrestrial constant, the Ratio Langley method is combined with the proposed algorithm to improve the prediction accuracy. In this way, more accurate AOD can be estimated by reanalysis of the calibrated volume spectrum using Beer-Lambert law. A total of 568 useful solar spectral data had been collected using ground-based spectrometer for the validation purposes. It is found that the AODs predicted by the proposed algorithm agree well to the reference values obtained from i-SMARTS model with high linearity and small error <3% for all wavelengths. The consistency of the proposed method is also validated with good resultsover two study areas (n=241) with different location, day, and time. Overall results implied that the application of the proposed algorithm in near-sea-level Langley calibration is proven feasible for AOD measurement. 2014 Thesis NonPeerReviewed text en https://eprints.ums.edu.my/id/eprint/40568/1/24%20PAGES.pdf text en https://eprints.ums.edu.my/id/eprint/40568/2/FULLTEXT.pdf Chang, Jackson Hian Wui (2014) Development of near-sea-level Langley calibration algorithm for aerosol optical depth measurement. Masters thesis, Universiti Malaysia Sabah.
institution Universiti Malaysia Sabah
building UMS Library
collection Institutional Repository
continent Asia
country Malaysia
content_provider Universiti Malaysia Sabah
content_source UMS Institutional Repository
url_provider http://eprints.ums.edu.my/
language English
English
topic QC851-999 Meteorology. Climatology Including the earth's atmosphere
spellingShingle QC851-999 Meteorology. Climatology Including the earth's atmosphere
Chang, Jackson Hian Wui
Development of near-sea-level Langley calibration algorithm for aerosol optical depth measurement
description Aerosol optical depth (AOD) represents the total attenuation of solar terrestrial radiation caused by aerosol. In long-term monitoring networks, accurate measurement of AOD is difficult due to the lack of frequent calibration of the spectrometer. This is because conventional Langley calibration is usually performed at high mountains for clear and stable atmosphere and regular access to high altitudes is inefficient in terms of accessibility and economical prospects. Therefore, a near-sea-level Langley calibration algorithm is developed to allow frequent calibration feasible even at low altitude. It uses the combination of Perez-Du Mortier (PDM) model and statistical filter to constrain the Langley extrapolation to get closest possible extraterrestrial constant over a wide range of wavelengths. To further contain the wavelength-dependent error due to varying extraterrestrial constant, the Ratio Langley method is combined with the proposed algorithm to improve the prediction accuracy. In this way, more accurate AOD can be estimated by reanalysis of the calibrated volume spectrum using Beer-Lambert law. A total of 568 useful solar spectral data had been collected using ground-based spectrometer for the validation purposes. It is found that the AODs predicted by the proposed algorithm agree well to the reference values obtained from i-SMARTS model with high linearity and small error <3% for all wavelengths. The consistency of the proposed method is also validated with good resultsover two study areas (n=241) with different location, day, and time. Overall results implied that the application of the proposed algorithm in near-sea-level Langley calibration is proven feasible for AOD measurement.
format Thesis
author Chang, Jackson Hian Wui
author_facet Chang, Jackson Hian Wui
author_sort Chang, Jackson Hian Wui
title Development of near-sea-level Langley calibration algorithm for aerosol optical depth measurement
title_short Development of near-sea-level Langley calibration algorithm for aerosol optical depth measurement
title_full Development of near-sea-level Langley calibration algorithm for aerosol optical depth measurement
title_fullStr Development of near-sea-level Langley calibration algorithm for aerosol optical depth measurement
title_full_unstemmed Development of near-sea-level Langley calibration algorithm for aerosol optical depth measurement
title_sort development of near-sea-level langley calibration algorithm for aerosol optical depth measurement
publishDate 2014
url https://eprints.ums.edu.my/id/eprint/40568/1/24%20PAGES.pdf
https://eprints.ums.edu.my/id/eprint/40568/2/FULLTEXT.pdf
https://eprints.ums.edu.my/id/eprint/40568/
_version_ 1809140076179881984
score 13.211869

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