SAFARI 2000 TOMS AEROSOL INDEX DATA, SOUTHERN AFRICA, DRY SEASON 2000

Daily Aerosol Index (AI) data from Earth Probe (EP) Total Ozone Mapping Spectrometer (TOMS) for the period of August 12-September 25, 2000 were processed and provided by the Atmospheric Chemistry and Dynamics Branch at NASA/GSFC for the SAFARI 2000 Dry Season Aircraft Campaign.The TOMS AI is formed directly from measured TOMS radiances in two channels. It is a measure of how much the wavelength dependence of backscattered UV radiation from an atmosphere containing aerosols (Mie scattering, Rayleigh scattering, and absorption) differs from that of a pure molecular atmosphere (pure Rayleigh scattering). Quantitatively, the AI is defined at http://toms.gsfc.nasa.gov/aerosols/AI_definition/ai_ep_definition.pdf. Positive values represent absorbing aerosols (dust and smoke); negative values represent non-absorbing aerosols. The identification is not perfect because of geophysical reasons (e.g., when aerosols are too low to the ground).The data from TOMS records have been used increasingly to understand the behavior of aerosols within the atmosphere. The TOMS is the first instrument to allow observation of aerosols as the particles cross the land/sea boundary. Using these data it is possible to observe a wide range of phenomena such as desert dust storms, forest fires, and biomass burning.The TOMS AI data are a daily gridded Level-3 product (ASCII .dat format) that covers the area of 40 deg. S to the Equator and 40 deg. W to 80 deg. E. There is also a JPEG image of each data file.

2000年8月12日至9月25日期间的地球探测（Earth Probe, EP）总臭氧测绘光谱仪（Total Ozone Mapping Spectrometer, TOMS）每日气溶胶指数（Aerosol Index, AI）数据，由美国国家航空航天局戈达德航天飞行中心（NASA/GSFC）大气化学与动力学分支（Atmospheric Chemistry and Dynamics Branch）为SAFARI 2000旱季航空科考行动处理并提供。

TOMS气溶胶指数直接由两个通道测得的TOMS辐射亮度计算得到，用于表征含气溶胶的大气（存在米氏散射（Mie scattering）、瑞利散射（Rayleigh scattering）与吸收作用）的后向散射紫外辐射波长依赖性，与纯分子大气（仅存在瑞利散射）的差异程度。

气溶胶指数的定量定义可参见文档http://toms.gsfc.nasa.gov/aerosols/AI_definition/ai_ep_definition.pdf。其正值代表吸收性气溶胶（沙尘与烟尘），负值代表非吸收性气溶胶。但受地球物理因素影响（例如气溶胶离地高度过低时），该识别逻辑并非完美无缺。

TOMS气溶胶观测记录数据已被愈发广泛地用于解析大气中气溶胶的演化行为。TOMS是首款可实现气溶胶跨海陆边界迁移观测的科学仪器。依托该数据集，可观测到沙漠沙尘暴、森林火灾与生物质燃烧等诸多大气现象。

TOMS AI数据为每日网格化三级（Level-3）产品，格式为ASCII .dat文件，覆盖范围为南纬40度至赤道，西经40度至东经80度。每个数据文件均配有JPEG格式预览图像。