Evaluating trends using TROPOMI and OMI aerosol index

With more than 5 years of operational aerosol index data from the TROPOMI instrument onboard the Sentinel 5-precursor (S5P), the seasonal cycle can be characterized and trends in global aerosol index can be investigated in more depth. Positive values of the aerosol index are driven by strong emission and transport events of ultraviolet (UV) absobring aerosols including desert dust outbreaks, biomass burning smoke, and volcanic ash eruptions. Near-zero values of the aerosol index however can also be useful to understand the dependency and sensitivity of calculated reflectances on precision and nature of the calibration of the instrument. Since the reprocessing of the dataset carried out in 2023, the largest effects of observed degradation in radiance and irradiance have been well characterized and are removed. A discussion will be presented addressing the delineation of variability due to changes in the global emission of absorbing aerosols as well as observed and characterized changes in insturment sensitivity and calibration.  As a comparison the soon-to-be released OMI aerosol index data (Collection 4) extending back to 2004 will be appended to lend additional insights about long-term variability seasonal variability of UV-absorbing aerosol presence.