Mao and Robock (1995) Mao, Jianping and Alan Robock, 1995: Report of AMIP Diagnostic Subproject 19, Part 2: The surface air temperature record in the AMIP simulations and the influence of El Chichón. Proceedings of the First International AMIP Scientific Conference, WCRP-92, WMO/TD-No. 732, W. L. Gates, Ed., (World Climate Research Programme, Geneva), 471-476.


We have examined the AMIP model output to investigate the impact of the April 1982 El Chichón volcanic eruption on surface air temperature. First we compared the temperature fields of the 28 available models to each other and found that 3 had serious errors. By comparing the average of the 25 remaining models to the surface temperature observations, we found that the model-average temperatures over the oceans are too cold for the first 3 years, a consequence of the sea surface temperature (SST) specification at high latitudes of climatology rather than observations. Even though the SST fields are specified from observations in the AMIP experiment, and SSTs were influenced by the El Chichón aerosols, there is a lag for the oceans to respond. The model- average temperatures over land are higher than observations during 1982, a signal of the cooling due to El Chichón, and this difference lasts for almost a year. The Northern Hemisphere winters over land exhibit large differences between the model average and the observations. In particular, 1980-81 was much warmer than the models, and 1981-82 and 1984-85 were much colder, suggesting that part of this winter variability is chaotic and produced by internal atmospheric dynamics-not forced by global SST patterns. The winters of 1982-82 and 1986-87, however, show warming patterns over northwestern North America due to the El Niños those years, and these patterns are simulated by most of the models. By choosing the models with the best El Niño simulation, and comparing their simulations to the observations, we delineate a clear winter warming pattern over North America and Eurasia in the winter of 1982-83 which agrees with previous observational, theoretical, and climate model simulations of a pattern forced by the volcanic eruption as distinct from El Niño.

Prepared by Alan Robock ( ) - Last updated on April 21, 1999