Analysis on the impact of aerosol optical depth on surface solar radiation in the Shanghai megacity, China
Analysis on the impact of aerosol optical depth on surface solar radiation in the Shanghai megacity, China
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DOI：
10.5194/acp-11-3281-2011
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发表时间：
2011-04
影响因子：
6.3
通讯作者：
Jianzhong Xu;LI Chengcai;H. Shi;Q. He;L. Pan
中科院分区：
文献类型：
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作者：
Jianzhong Xu;LI Chengcai;H. Shi;Q. He;L. Pan
抽象。利用1961-2008年上海大城市地面太阳直接辐射（DiSR）和散射辐射（DfSR）的年代际变化特征，分析了晴天条件下上海大城市地面太阳直接辐射和散射辐射与气溶胶光学厚度（AOD）的关系。在晴空和全天空条件下，确定了三个连续的具有独特特征的DiSR长期变化的时期：从20世纪60年代末到80年代中期的“变暗”时期，从80年代中期到90年代中期的“稳定”/“轻微变亮”时期，以及此后的“重新变暗”时期。在DiSR的两个变暗期间，DfSR在晴空条件下显著增亮，表明气溶胶排放引起的大气透明度变化对该地区地面太阳辐射（SSR）的年代际变化有重要作用。在晴空条件下，对中分辨率成像光谱仪（MODIS）反演的气溶胶光学厚度（AOD）与相应的DiSR和DfSR逐时测量值的相关性分析表明，AOD与DfSR和DiSR的相关性和反相关性均在99%置信度以上，说明气溶胶通过吸收和/或散射对SSR有很大影响。此外，在卫星通过上海期间，气溶胶光学厚度和相应的DiSR和DfSR都有明显的周周期变化。在周末，AOD低于每周平均值，对应于较高的DiSR和较低的DfSR，而工作日则相反。由于交通运输和工业活动的减少，周末的气溶胶光学厚度减少，导致无云条件下大气透明度增加，从而使DiSR增加，DfSR减少。结果表明，人为排放的气溶胶负荷是上海SSR长期变化的重要调节因子。
Abstract. This study investigated the decadal variation of the direct surface solar radiation (DiSR) and the diffuse surface solar radiation (DfSR) during 1961–2008 in the Shanghai megacity as well as their relationships to Aerosol Optical Depth (AOD) under clear-sky conditions. Three successive periods with unique features of long term variation of DiSR were identified for both clear-sky and all-sky conditions: a "dimming" period from the late 1960s to the mid 1980s, a "stabilization"/"slight brightening" period from the mid 1980s to the mid 1990s, and a "renewed dimming" period thereafter. During the two dimming periods of DiSR, DfSR brightened significantly under clear-sky conditions, indicating that change in atmospheric transparency resulting from aerosol emission has an important role on decadal variation of surface solar radiation (SSR) over this area. The analysis on the relationship between the Moderate-resolution Imaging Spectroradiometer (MODIS) retrieved AOD and the corresponding hourly measurements of DiSR and DfSR under clear-sky conditions clearly revealed that AOD is significantly correlated and anti-correlated with DfSR and DiSR, respectively, both above 99% confidence in all seasons, indicating the great impact of aerosols on SSR through absorption and/or scattering in the atmosphere. In addition, both AOD and the corresponding DiSR and DfSR measured during the satellite passage over Shanghai show obvious weekly cycles. On weekends, AOD is lower than the weekly average, corresponding to higher DiSR and lower DfSR, while the opposite pattern was true for weekdays. Less AOD on weekends due to the reduction of transportation and industrial activities results in enhancement of atmospheric transparency under cloud free conditions so as to increase DiSR and decrease DfSR simultaneously. Results show that aerosol loading from the anthropogenic emissions is an important modulator for the long term variation of SSR in Shanghai.