How Well Do Models Reproduce the Ocean-Forced Teleconnections Associated with Droughts in Central-Southwest Asia and the Middle East?

Previous work has shown that cold season precipitation over much of Central-Southwest Asia and the Middle East (35E-80E, 12N-45N) is linked via atmospheric teleconnections to tropical sea surface temperatures (SSTs) in the Pacific and Indian Oceans. Here we examine how well those teleconnections are reproduced in a range of atmospheric models for the region as a whole, as well as for subdomains of the region, including the coastal Middle East and the high mountains of Afghanistan. The models considered include the GEOS 5, GFS V2, ECHAM 5, CAM 4, and CAM 5.

For the region as a whole, model representation of the season cycle is generally realistic, although some models still struggle with over-extending the monsoon into Afghanistan. In terms of interannual variability, there is a wide range in the ability of the atmospheric models considered here to reproduce the observed influence of SSTs on the average precipitation of the region. Some models capture both the pattern and the magnitude of the teleconnections in upper-level winds fairly closely while some models reproduce almost none of the relationship. Even the most realistic models do not fully capture the strength of the relationship. The teleconnections to the eastern and central parts of the region are better represented than for the western parts (coastal Middle East), where the observed precipitation during recent decades shows a strong connection to Pacific SSTs that the models only weakly reproduce, at best.

All the models produce a vigorous tropical response in convection to the SST anomalies but the atmospheric response to the tropical convection extends broadly over southern Asia in some models, in good correspondence with observations, whereas it appears blocked over east Asia in several models, in a way clearly different from observations. The relationship between the northwestward extent of the teleconnection and the mean jetstream structure of individual models is investigated in a two-layer model and a barotropic model, both linearized about the zonally-varying mean state of the full atmospheric models.

The large differences in the ability of individual models to represent the dominant seasonal teleconnection for the region has important implications both for seasonal predictions and for future climate projections.