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Title: Analyzing the Contribution of Aerosols to an Observed Increase in Direct Normal Irradiance in Oregon

Abstract

Annual average total irradiance increases by 1-2% per decade at three mon- itoring stations in Oregon over the period from 1980 to 2007. Direct normal irradiance measurements increase by 5% per decade over the same time pe- riod. The measurements show no sign of a dimming before 1990. The impact of high concentrations of stratospheric aerosols following the volcanic erup- tions of El Chich¶on and Mt. Pinatubo are clearly seen in the measurements. Removing these years from the annual average all-sky time series reduces the trends in both total and direct normal irradiance. Clear-sky periods from this long direct normal time series are used in conjunction with radiative trans- fer calculations to test whether part of the increase could be caused by an- thropogenic aerosols. All three sites show relatively low clear-sky measure- ments before the eruption of El Chich¶on in 1982, suggesting higher aerosol loads during this period. After removing the periods most strongly impacted by volcanic eruptions, two of the sites show statistically signi¯cant increases in clear-sky direct normal irradiance from 1987 to 2007. Radiative transfer calculations of the impact of volcanic aerosols and tropospheric water vapor indicate that only about 20% of that clear-sky increase between backgroundmore » aerosol periods before and after the eruption of Mt. Pinatubo can be explained by these two factors. Thus, a statistically signi¯cant clear-sky trend remains between 1987 and 2007 that is consistent with the hypothesis that at least some of the increase in surface irradiance could be caused by a reduction of anthropogenic aerosols. D« less

Authors:
; ;
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
947045
Report Number(s):
PNNL-SA-63742
400409900; TRN: US200904%%319
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article
Journal Name:
Journal of Geophysical Research. D. (Atmospheres), 114:D00D02
Additional Journal Information:
Journal Volume: 114
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; AEROSOLS; MONITORING; OREGON; RADIANT FLUX DENSITY; RADIANT HEAT TRANSFER; WATER VAPOR; SOLAR RADIATION; ATMOSPHERIC CHEMISTRY

Citation Formats

Riihimaki, Laura D, Vignola, F, and Long, Charles N. Analyzing the Contribution of Aerosols to an Observed Increase in Direct Normal Irradiance in Oregon. United States: N. p., 2009. Web. doi:10.1029/2008JD010970.
Riihimaki, Laura D, Vignola, F, & Long, Charles N. Analyzing the Contribution of Aerosols to an Observed Increase in Direct Normal Irradiance in Oregon. United States. https://doi.org/10.1029/2008JD010970
Riihimaki, Laura D, Vignola, F, and Long, Charles N. 2009. "Analyzing the Contribution of Aerosols to an Observed Increase in Direct Normal Irradiance in Oregon". United States. https://doi.org/10.1029/2008JD010970.
@article{osti_947045,
title = {Analyzing the Contribution of Aerosols to an Observed Increase in Direct Normal Irradiance in Oregon},
author = {Riihimaki, Laura D and Vignola, F and Long, Charles N},
abstractNote = {Annual average total irradiance increases by 1-2% per decade at three mon- itoring stations in Oregon over the period from 1980 to 2007. Direct normal irradiance measurements increase by 5% per decade over the same time pe- riod. The measurements show no sign of a dimming before 1990. The impact of high concentrations of stratospheric aerosols following the volcanic erup- tions of El Chich¶on and Mt. Pinatubo are clearly seen in the measurements. Removing these years from the annual average all-sky time series reduces the trends in both total and direct normal irradiance. Clear-sky periods from this long direct normal time series are used in conjunction with radiative trans- fer calculations to test whether part of the increase could be caused by an- thropogenic aerosols. All three sites show relatively low clear-sky measure- ments before the eruption of El Chich¶on in 1982, suggesting higher aerosol loads during this period. After removing the periods most strongly impacted by volcanic eruptions, two of the sites show statistically signi¯cant increases in clear-sky direct normal irradiance from 1987 to 2007. Radiative transfer calculations of the impact of volcanic aerosols and tropospheric water vapor indicate that only about 20% of that clear-sky increase between background aerosol periods before and after the eruption of Mt. Pinatubo can be explained by these two factors. Thus, a statistically signi¯cant clear-sky trend remains between 1987 and 2007 that is consistent with the hypothesis that at least some of the increase in surface irradiance could be caused by a reduction of anthropogenic aerosols. D},
doi = {10.1029/2008JD010970},
url = {https://www.osti.gov/biblio/947045}, journal = {Journal of Geophysical Research. D. (Atmospheres), 114:D00D02},
number = ,
volume = 114,
place = {United States},
year = {Thu Jan 22 00:00:00 EST 2009},
month = {Thu Jan 22 00:00:00 EST 2009}
}