Influences of Aerosols on Global Radiance Data Assimilation

Recently, the aerosol impact on numerical weather prediction (NWP) is gaining more attention. Many studies focus on the physical representation of aerosols-cloud-radiation interaction, but the impact of the aerosols from the data assimilation aspect is rarely discussed. In the NOAA operational analysis system, the radiance observation operator determines the radiative properties based on atmosphere composition with background aerosols. In this case, spatial-temporal variations of aerosols are not considered during the derivation of brightness temperature from the model state variables in the radiance observation operator. Based on the stand-alone experiment of the radiative transfer model, the aloft aerosols could introduce the cooling effects over the infrared window channel. To investigate the impact and complexity of accounting for aerosols in the analysis system, three-dimensional gridded aerosol mixing ratio from NOAA global aerosol model is incorporated as part of the model variables. In this study, the impact of the aerosol fields on the meteorological and SST analysis, departure of brightness temperature, bias correction, quality control, and the observation usage for infrared sensors was assessed. The development toward improving the representation of aerosols in the analysis system is explored as well.