Simulating direct and semi-direct effect of aerosols on subseasonal prediction: climatology versus interactive aerosols in the UFS model

<p class="p1"><span class="s1">We investigate the aerosol direct and semi-direct effect on subseasonal prediction using NOAA&#8217;s fully coupled Unified Forecast System (UFS) model, which includes the atmospheric model FV3 with the Global Forecast System (GFS) physics package V17, MOM6 ocean model, WW3 wave model and CICE6 sea ice model. A systematic twin experiment is carried out: (i) UFS with prescribed aerosol climatology and (ii) UFS coupled to interactive aerosols from the GOCART aerosol module. Both experiments are deterministic 32-day hindcasts with monthly initialization over multiple years.</span></p> <p class="p1"><span class="s1">The modeled aerosol optical depth (AOD) in both experiments is in good agreement with the MODIS satellite observations. The AOD from the experiments with interactive aerosols captured the interannual variability seen in the observations. The estimated radiative forcing from the aerosol radiation interaction in these two sets of experiments is similar in the multi-year average. However, the advantage in the experiments with interactive aerosols can be seen clearly when simulating radiative forcing in the extreme dust storm and biomass burning events. Changes in cloud and precipitation are small between these two sets of experiments.</span></p>