Tendency Bias Correction in the GEOS AGCM

In this report, we summarize the results of global and regional TBC applied to the GEOS AGCM(the same model used to generate MERRA-2 though run at lower resolution, referred to as the M2_AGCM) employing the analysis increments (analysis minus forecast) generated by MERRA-2 to calculate the TBC terms. Extending the results of Chang et al. (2019)and Schubert et al. (2019), we examine in more detail the seasonality of the TBC impacts, including a deeper look into the reasons for why TBC appears to be least effective during boreal winter. We also look into the ability of TBC to correct other diagnostic fields such as cloudiness and surface fluxes and, more generally, attempt to provide some insight into why TBC is effective in correcting long term climate biases. Looking beyond TBC, we also present some preliminary results from an extension of the TBC approach in which we include a state-dependent term