Retrieval of the single scattering albedo in the El Paso-Juarez Airshed using the TUV model and a UV-MFRSR radiometer

Abstract

A methodology to retrieve Single Scattering Albedo (SSA) values employing the ratio of Direct to Diffuse Irradiances (DDR) is used and applied to the El Paso-Juarez Airshed, a challenging region where air masses interact. The TUV model was used to obtain the calculated DDR irradiances, and the experimental irradiances were obtained from a UV-MFRSR instrument located in the city of El Paso, Texas. The wavelengths used were 332 nm and 368 nm. The retrieved SSA values at both 332 nm and 368 nm were higher in a lightly polluted day (0.66–0.81 at 332 nm, and 0.61 to 0.80 at 368 nm) than in a heavier polluted day (0.56–0.70 at 332 nm and 0.53–0.66 at 368 nm). A sensitivity study of the ground albedo and the asymmetry parameter was performed, which indicated that the variation of the asymmetry parameter is a secondary effect in the retrievals of SSA. In addition, the variation of SSA values during the day was also analyzed for the El Paso-Juarez Airshed and linked to the flow of air masses into the region using HYSPLIT trajectories. A presence of absorptive aerosols was observed during the late morning and the middle of the day. This methodology can be applied in any area, and is particularly useful for cities that experience episodes of high PM concentrations. ► Retrieval of the single scattering albedo, SSA, to characterize aerosols in situ. ► The methodology used is robust and can be applied to any region. ► It is applied to the El Paso-Juarez Airshed, a very challenging region to model. ► A sensitivity study of the relevant optical, physical parameters was also performed. ► The evolution of the SSA throughout the day for this region was analyzed.