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	Aerosoloptisk tjocklek	NDVI	Standardiserad nederbördsindex
Ämnesområde	Geofysik	Geofysik	Geofysik
Familj	Process / pipeline	Process / pipeline	Process / pipeline
Ursprungsår	1929	1973	1993
Upphovsperson	Anders Ångström	Rouse, Haas, Schell, and Deering	Thomas McKee, Neil Doesken, and John Kleist
Typ	Optical parameter for aerosol loading quantification	Spectral index for vegetation assessment	Probabilistic drought indicator
Ursprungskälla	Ångström, A. (1929). On the atmospheric transmission of sun radiation and on dust in the air. Geografiska Annaler, 11(2), 156-166.	Rouse, J. W., Haas, R. H., Schell, J. A., & Deering, D. W. (1973). Monitoring vegetation systems in the Great Plains with ERTS. Third Earth Resources Technology Satellite Symposium Proceedings, 1, 309-317.	McKee, T. B., Doesken, N. J., & Kleist, J. (1993). The relationship of drought frequency and duration to time scales. Proceedings of the Eighth Conference on Applied Climatology, 179-184.
Alias	AOD, Aerosol Optical Thickness	NDVI	SPI
Närliggande	3	3	3
Sammanfattning	Aerosol Optical Depth (AOD) is a dimensionless measure of aerosol light extinction in the atmosphere, quantifying how much sunlight is scattered and absorbed by particles suspended in air. Formalized by Ångström in 1929 and now routinely measured via satellite (MODIS, Sentinel-5P) and ground networks (AERONET), AOD is essential for air quality monitoring, climate forcing assessment, and visibility prediction.	The Normalized Difference Vegetation Index (NDVI) is a spectral index computed from satellite or aerial multispectral imagery that quantifies vegetation greenness and vigor. Introduced by Rouse and colleagues in 1973 using Landsat data, NDVI has become the most widely used remote sensing metric for vegetation monitoring, drought assessment, crop productivity forecasting, and land cover change detection.	The Standardized Precipitation Index (SPI) is a climate index that quantifies precipitation anomalies relative to historical norms, standardized to account for differences in precipitation climatology across regions. Introduced by McKee, Doesken, and Kleist in 1993, SPI has become a primary tool for drought detection and characterization, adopted by meteorological agencies worldwide for operational drought monitoring and early warning systems.