The study evaluates the simulation of the circulation and thermal response of the troposphere and stratosphere to the El Nino phenomenon for the winter period in the Northern Hemisphere and for the summer and winter periods in the Southern Hemisphere in two versions of the INM-CM model of the Marchuk Institute of Numerical Mathematics of the Russian Academy of Sciences (INM RAS). Taking into account the influence of the localization of the Pacific sea surface temperature anomalies (SSTAs) on the nature and amplitude of the response, two types of El Nino were considered: Eastern Pacific (EP) El Nino with the SSTA maximum in the eastern Pacific, and Central Pacific (CP) El Nino with the SSTA maximum in the central Pacific. The quality of the models was assessed by comparing with the data obtained from ERA5 reanalysis. It was shown that the simulation of the tropospheric circulation response to the two types of El Nino in polar and middle latitudes was improved in the new version of the model INM-CM6-M in both hemispheres as compared with INM-CM5-0 (except for EP El Nino during the austral winter). In the Northern Hemisphere’s lower stratosphere, the opposite situation occurs: the previous version of the model has a better skill in simulating the response to CP and EP El Ninos. The circulation response to CP El Nino in austral summer does not agree with the reanalysis in both model versions, while for EP events, the spatial correlation with the reanalysis fields exceeds 80%. In austral winter, the situation is opposite: the response to CP El Nino was simulated more correctly than to EP one. In the Northern Hemisphere’s middle stratosphere, the quality of the models significantly varies depending on the type of El Nino: version 5-0 much better reproduces the response to CP El Nino, while version 6-M is more consistent with the reanalysis during the EP type. In the Southern Hemisphere, the summer response of the middle troposphere to El Nino in the models is similar to the reanalysis, while the winter response is not correctly simulated. The thermal response is generally worse reproduced by both model versions as compared to the circulation one. The structure of the temperature response is consistent with the reanalysis only for the middle stratosphere in the Southern Hemisphere in summer, as well as in the Northern Hemisphere, but only for CP El Nino in version 5-0.
Gvozdeva et al. (Sat,) studied this question.