How accurate are aerosol measurements made with the GLOBE sun photometer?
The accuracy of sun photometer measurements has been studied for decades by atmospheric scientists, and it remains a topic of some debate. There are some inherent limitations to measuring atmospheric aerosols from Earth’s surface, and there are also some limitations imposed by the design of the GLOBE sun photometer. Measurements made carefully according to the protocols should be accurate to within less than about 0.02 AOT units. For very clear skies, with AOT values of perhaps less than 0.05, this is a significant percentage error. However, even operational “professional” sun photometers claim accuracies of no better than 0.01 AOT units. Thus, the accuracy of measurements made carefully with a GLOBE sun photometer are comparable to measurements made with other sun photometers. Unlike some other GLOBE measurements, there is no easily accessible standard against which to check the accuracy of AOT calculations. GLOBE aerosol measurements will be subjected to scrutiny by the GLOBE science
