di Sarra Alcide, Sferlazzo Damiano, Meloni Daniela, Anello Fabrizio, Bommarito Carlo, Corradini Stefano, De Silvestri Lorenzo, Di Iorio Tatiana, Monteleone Francesco, Pace Giandomenico, Piacentino Salvatore, Pugnaghi Sergio
Appl Opt. 2015 Apr 1;54(10):2725-37. doi: 10.1364/AO.54.002725.
Aerosol optical properties have been measured on the island of Lampedusa (35.5°N, 12.6°E) with seven-band multifilter rotating shadowband radiometers (MFRSRs) and a CE 318 Cimel sunphotometer (part of the AERONET network) since 1999. Four different MFRSRs have operated since 1999. The Cimel sunphotometer has been operational for a short period in 2000 and in 2003-2006 and 2010-present. Simultaneous determinations of the aerosol optical depth (AOD) from the two instruments were compared over a period of almost 4 years at several wavelengths between 415 and 870 nm. This is the first long-term comparison at a site strongly influenced by desert dust and marine aerosols and characterized by frequent cases of elevated AOD. The datasets show a good agreement, with MFRSR underestimating the Cimel AOD in cases with low Ångström exponent; the underestimate decreases for increasing wavelength and increases with AOD. This underestimate is attributed to the effect of aerosol forward scattering on the relatively wide field of view of the MFRSR. An empirical correction of the MFRSR data was implemented. After correction, the mean bias (MB) between MFRSR and Cimel simultaneous AOD determinations is always smaller than 0.004, and the root mean square difference is ≤0.031 at all wavelengths. The MB between MFRSR and Cimel monthly averages (for months with at least 20 days with AOD determinations) is 0.0052. Thus, by combining the MFRSR and Cimel observations, an integrated long-term series is obtained, covering the period 1999-present, with almost continuous measurements since early 2002. The long-term data show a small (nonstatistically significant) decreasing trend over the period 2002-2013, in agreement with independent observations in the Mediterranean. The integrated Lampedusa dataset will be used for aerosol climatological studies and for verification of satellite observations and model analyses.
自1999年以来，在兰佩杜萨岛（北纬35.5°，东经12.6°）使用七波段多滤光片旋转阴影带辐射计（MFRSR）和一台CE 318 Cimel太阳光度计（AERONET网络的一部分）对气溶胶光学特性进行了测量。自1999年以来，有四台不同的MFRSR投入使用。Cimel太阳光度计在2000年、2003 - 2006年以及2010年至今的时间段内短期运行。在415至870纳米的几个波长下，对这两种仪器同时测定的气溶胶光学厚度（AOD）进行了近4年的比较。这是在一个受沙漠尘埃和海洋气溶胶强烈影响且AOD经常升高的站点进行的首次长期比较。数据集显示出良好的一致性，在Ångström指数较低的情况下，MFRSR低估了Cimel AOD；随着波长增加，这种低估减小，并且随着AOD增大而增大。这种低估归因于气溶胶前向散射对MFRSR相对较宽视场的影响。对MFRSR数据实施了经验校正。校正后，MFRSR和Cimel同时测定的AOD之间的平均偏差（MB）始终小于0.004，并且在所有波长下均方根差≤0.031。MFRSR和Cimel月平均值（对于至少有20天进行AOD测定的月份）之间的MB为0.0052。因此，通过结合MFRSR和Cimel的观测数据，获得了一个涵盖1999年至今的综合长期序列，自2002年初以来几乎是连续测量。长期数据显示在2002 - 2013年期间有一个小的（无统计学显著意义的）下降趋势，这与地中海地区的独立观测结果一致。兰佩杜萨岛的综合数据集将用于气溶胶气候学研究以及卫星观测和模型分析的验证。
