Analyzing the contribution of aerosols to an observed increase in direct normal irradiance in Oregon
Analyzing the contribution of aerosols to an observed increase in direct normal irradiance in Oregon
复制标题
分析气溶胶对俄勒冈州观测到的直接正常辐照度增加的贡献
DOI：
10.1029/2008jd010970
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发表时间：
2009
影响因子：
--
通讯作者：
W. Halliwell
中科院分区：
文献类型：
--
作者：
R. Vallerand;W. Halliwell
[1]从1980年到2007年，在俄勒冈州的三个监测站，年平均总辐照度每十年增加1-2%。在同一时期内，直接法向辐照度测量值每十年增加5%。测量结果显示，在1990年之前没有变暗的迹象。在测量中清楚地看到了El Chichon和Mount Pinatubo火山爆发后平流层气溶胶高浓度的影响。从年平均全天时间序列中删除这些年份会降低总正常辐照度和直接正常辐照度的趋势。从这个长期的直接正常时间序列的晴空周期与辐射传输计算一起使用，以测试是否部分的增加可能是由人为气溶胶。所有这三个网站都显示出相对较低的晴空测量在1982年的El Chichon火山爆发之前，这表明在此期间较高的气溶胶负荷。在去除受火山爆发影响最严重的时期后，其中两个站点显示从1987年到2007年晴空直接正常辐照度在统计上显著增加。对火山气溶胶和对流层水汽影响的辐射传输计算表明，皮纳图博火山爆发前后背景气溶胶期间的晴空增加只有约20%可以用这两个因素来解释。因此，在1987年至2007年期间，一个具有统计意义的晴空趋势仍然存在，这与地表辐照度的增加至少有一部分可能是由人为气溶胶减少引起的假设是一致的。
[1] Annual average total irradiance increases by 1–2% per decade at three monitoring stations in Oregon over the period from 1980 to 2007. Direct normal irradiance measurements increase by 5% per decade over the same time period. The measurements show no sign of a dimming before 1990. The impact of high concentrations of stratospheric aerosols following the volcanic eruptions of El Chichon and Mount 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 transfer calculations to test whether part of the increase could be caused by anthropogenic aerosols. All three sites show relatively low clear-sky measurements before the eruption of El Chichon 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 significant 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 Mount Pinatubo can be explained by these two factors. Thus a statistically significant 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.