Validation of TOA radiation and clouds simulated by different versions of LMD GCM in comparison to satellite and ground-based data amg

The vali­dat­ion of clou­din­ess and radi­ative fluxes simu­lated by three vers­ions of the Labo­rato­ire de Mete­orol­ogie Dyna­mique (LMD) general circ­ulat­ion model (GCM) is perf­ormed against sate­llite and ground- based obse­rvat­ions. These GCM vers­ions include quite diff­erent cloud schemes and surface albedo repr­ese­nta- tions. One model version impl­eme­nts the solar radi­ation diurnal cycle, while the others do not. Addi­tion­ally, model vers­ions are run with diff­erent spatial reso­luti­ons. Model vali­dat­ion is based on quite simple meth­odol- ogy to analyze the simu­lati­ons for only three prec­hosen cross-sect­ions in equa­tor­ial and middle lati­tudes, instead of stud­ying the whole model field. It is shown that over middle lati­tudes simu­lated disc­repa­ncies exhibit a strong seas­onal depe­nde­nce. This is closely related to the repr­esen­tat­ion of water vapor, clou­din­ess, and sur- face albedo in the model. In part­icu­lar, errors in the simu­lated cloud radi­ative forcing (CRF) portray those for low-level clou­din­ess (for short-wave radi­ation) or high-level clou­din­ess (for long-wave radi­ation). As a whole, the errors in short-wave CRF are larger than those of the long-wave CRF, and are stro­ngly ampl­ified in summer. In the simu­lated total cloud amount, main errors are related to low-level clou­din­ess. It is also shown that the causes of the model defi­cien­cies differ between vers­ions. In some cases, errors coming from diff­erent origins could comp­ens­ate each other. Alth­ough quite simple, the meth­odol­ogy foll­owed in this inte­rcom­pari­son proved to be an effe­ctive appr­oach for trac­king syst­ema­tic errors in a set of diff­erent model vers­ions.