Séminaire
Most coupled general circulation models fail to reproduce observed features of the tropical Atlantic climate. Previous studies have attributed these coupled biases to the erroneous precipitation distribution in the atmospheric component of the models. In this talk, I would be presenting results from the analysis of precipitation from 22 atmospheric models under CMIP5. It is found that the models can be separated into two groups. The first group misplaces the ocean precipitation maximum westward, instead of the central Atlantic as observed. The second group misplaces the oceanic maximum eastward, and has intense orographic precipitation. These two distinct model behaviors appear to be related to the employed horizontal resolution. A reduction in west Atlantic precipitation is apparent as the resolution in ECHAM is increased from T63 to T255. To investigate this further, sensitivity studies are performed using ECHAM 6.2 to test the effect of resolving orography. First results show that orography plays a major role in the east-west partitioning of precipitation. By prescribing T63 orography into T255, increased precipitation over the west Atlantic and decreased precipitation over the east Atlantic are observed.
MP Lefebvre 0144272799