The Sentinel-5P TROPOMI Near Real Time (NRT) Aerosol Index 1-Orbit L2 5.5km x 3.5km V2 (S5P_L2__AER_AI_HiR_NRT) at GES DISC is the near real time version of the offline S5P_L2__AER_AI_HiR data product. These data are typically available within three hours of measurement as required by the Land Atmosphere NRT Capability Earth Observing System (LANCE). These data are intended for a rapid turnaround assessment and are only archived for up to ten days. Users who require a longer data record, or wish to conduct rigorous analysis should use the offline version of this product S5P_L2__AER_AI_HiR.

The Copernicus Sentinel-5 Precursor (Sentinel-5P or S5P) satellite mission is one of the European Space Agency's (ESA) new mission family - Sentinels, and it is a joint initiative between the Kingdom of the Netherlands and the ESA. The sole payload on Sentinel-5P is the TROPOspheric Monitoring Instrument (TROPOMI), which is a nadir-viewing 108 degree Field-of-View push-broom grating hyperspectral spectrometer, covering the wavelength of ultraviolet-visible (UV-VIS, 270nm to 495nm), near infrared (NIR, 675nm to 775nm), and shortwave infrared (SWIR, 2305nm-2385nm). Sentinel-5P is the first of the Atmospheric Composition Sentinels and is expected to provide measurements of ozone, NO2, SO2, CH4, CO, formaldehyde, aerosols and cloud at high spatial, temporal and spectral resolutions.

The TROPOMI UV Aerosol Index has been calculated based on wavelength dependent changes in Rayleigh scattering in the UV spectral range where ozone absorption is weak. A residual value is calculated from measured top-of-atmosphere (TOA) reflectance and per-calculated theoretical reflectance for a Rayleigh scattering-only atmosphere given a wavelength pair. TROPOMI UVAI products use the classical wavelength pair of 340/380 nm, and the OMI chosen 354/388 nm pair for the long-term continuous AI record. Figure 1 shows TROPOMI UVAI of orbit# 4060. Data are stored in individual files, or granules, that contain one orbit of information. The data are stored in netCDF4 data format and files and complete files are ~20 MB.