CESM experiments for intraseasonal oscillation intensity changes in El Niño and La Niña developing summers

Experiments are conducted using version 5.2 of Community Atmospheric Model (CAM-5.2; https://www.cesm.ucar.edu/models/cesm1.1/cam/). CAM is the atmosphere component of Community Earth System Model (CESM) developed by the National Center for Atmospheric Research (NCAR). The model resolution used in this study is f19_g16, with f19 finite volume grid (1.9º latitude by 2.5º longitude) for the atmosphere and land components combined with the gx1v6 displaced pole grid (approximately 1º) for the ocean and ice components.

   Four sets of numerical experiments are performed in this study:

Full SST forcing simulation (full-SST run): The CAM is forced by global monthly OI SST and integrated from January 1982 to December 2020.

Climatological SST forcing simulation (CLM-SST run): The CAM is integrated for 30 years forced by global climatological mean monthly SST obtained from OI SST data for the period of January 1982 to December 2020.

Tropical central-eastern Pacific SST forcing simulation (CEP-SST run): The SST forcing field is composed of two parts: total monthly SST in the domain of 15°S-15°N and 160°E-80°W and climatological mean monthly SST in the other regions. The CAM is integrated from January 1982 to December 2020.

Sensitivity experiments of tropical central-eastern Pacific SST anomalies during ENSO events: Composite SST anomalies in El Niño and La Niña events in the region of 15°S-15°N and 160°E-80°W and the above SST anomaly fields multiplied by -1 are added to climatological mean monthly SST from May to December. Climatological mean monthly SST is used in the other regions and months. The CAM is integrated for 30 years in these experiments. These experiments are referred to as EPEL, EPLA, EPEL-reverse and EPLA-reverse, respectively.