Evaluation of TROPOMI Surface UV Irradiance in the Continental United States : Preliminary Results

Solar ultraviolet (UV) radiation at short wavelengths ranging from 280-400 nm is well known to cause harmful effects in humans. Sunburn, cataracts, and increased risk of skin cancers including melanoma are all possible effects of exposure to UV radiation. A steady increase in the amount of people diagnosed with serious skin cancers such as melanoma has been observed worldwide, with rates almost doubling since 1999. In order to understand and study the health effects of UV radiation, information on the geographical distribution of radiation reaching Earth’s surface is needed. As the successor of Ozone Monitoring Instrument (OMI), which has been used since 2004 to monitor surface UV radiation levels, the TROPOspheric Monitoring Instrument (TROPOMI) satellite, launched in 2017, will continue the efforts to monitor the surface UV radiation levels. Although TROPOMI is able to provide global measurement of UV levels, measurements can only be taken once per day and complications with cloud cover and aerosol levels can impact the accuracy of the measurement. Some efforts have been made to verify TROPOMI data in Europe and Australia; however, no organized effort has been taken to make this verification for the United States. In this work, we will use the ground-based sensor network through the Colorado State University Natural Resource Ecology Laboratory (NREL) to evaluate the TROPOMI surface UV radiation. This network records UV levels at 30 ground sites across the US every 15-20 seconds. This project looks to use Python to conduct the data analysis. As part of this effort, TROPOMI data was downloaded and regridded to more standard grids, which would also be convenient for the community to use. Ground data from the NREL was downloaded, and quality control was performed to refine the data. Time series plots were created for many of the ground sites. Maps were then created to visualize the levels of UV radiation across the US. Finally, we processed the TROPOMI data and spatially and temporally matched it to the corresponding ground sensor data to evaluate the TROPOMI data performances. Further analysis of the trends of the satellite and ground-based surface UV data is planned for the future.