title: Validation of ozone monitoring instrument ultraviolet index against ground-based UV index in Kampala, Uganda.
abstract: The Ozone Monitoring Instrument (OMI) overpass solar ultraviolet (UV) indices have been validated against the ground-based UV indices derived from Norwegian Institute for Air Research UV measurements in Kampala (0.31° N, 32.58° E, 1200 m), Uganda for the period between 2005 and 2014. An excessive use of old cars, which would imply a high loading of absorbing aerosols, could cause the OMI retrieval algorithm to overestimate the surface UV irradiances. The UV index values were found to follow a seasonal pattern with maximum values in March and October. Under all-sky conditions, the OMI retrieval algorithm was found to overestimate the UV index values with a mean bias of about 28%. When only days with radiation modification factor greater than or equal to 65%, 70%, 75%, and 80% were considered, the mean bias between ground-based and OMI overpass UV index values was reduced to 8%, 5%, 3%, and 1%, respectively. The overestimation of the UV index by the OMI retrieval algorithm was found to be mainly due to clouds and aerosols.
authors.forename: Dennis
authors.initials: D
authors.lastname: Muyimbwa
authors.forename: Arne
authors.initials: A
authors.lastname: Dahlback
authors.forename: Taddeo
authors.initials: T
authors.lastname: Ssenyonga
authors.forename: Yi-Chun
authors.initials: YC
authors.lastname: Chen
authors.forename: Jakob J
authors.initials: JJ
authors.lastname: Stamnes
authors.forename: Øyvind
authors.initials: Ø
authors.lastname: Frette
authors.forename: Børge
authors.initials: B
authors.lastname: Hamre
mesh_terms: D000336:Aerosols; D000393:Air Pollutants / Q000032:analysis*; D000465:Algorithms; D001336:Automobiles; D002138:Calibration; D003198:Computer Simulation; D004784:Environmental Monitoring / Q000379:methods*; D010126:Ozone / Q000032:analysis*; D015203:Reproducibility of Results; D012621:Seasons; D018531:Spacecraft; D013056:Spectrophotometry, Ultraviolet; D013472:Sunlight; D014454:Uganda; D014466:Ultraviolet Rays
chemical_list: D000336:Aerosols; D000393:Air Pollutants; D010126:Ozone