Aerosol Impact on Subseasonal to Seasonal Prediction Using FIM-Chem-iHYCOM Coupled Model

The aerosol impact on subseasonal to seasonal (s2s) prediction is investigated using a global coupled atmosphere, chemistry and ocean system of FIM-Chem-iHYCOM. The online chemistry includes a simple suite with bulk aerosols only. The sources and sinks for aerosols, fire and anthropogenic emissions are prescribed during the model integration. The resulting aerosol optical depths from the model are shown to be in good agreement with observations. We also compare the model sensitivity with various aerosol emissions at different seasons in a multiyear study. Additional emphasis of this work is on the effect of aerosols on surface radiation, cloudiness and precipitation, to demonstrate the importance of using the correct aerosol optical properties at s2s time scale. Overall, these multiple case studies show that the biggest aerosol impact from online chemistry is on the radiation budget and less so on the cloudiness and precipitation.