Updated Quantification of ENSO Influence on Statistical Distribution of Surface Variables

Ropelewski and Halpert (1996) attempted to quantify ENSO-precipitation relationships in several regions of the world based on shifts in the statistical distribution of rainfall during warm (El Niño) and cold (La Niña) phases of the Southern Oscillation. Their goal was to provide long-range forecasters with a typical ENSO response in precipitation amounts over regions that are known to be affected by the oscillation. The authors used a 91-year record spanning the period 1901-1992 for 19 ENSO-sensitive regions around the world. In North America, these regions were the Gulf Coast (dry-EN and wet-LN from Oct-Mar) and the Great Basin of the US (wet-EN from Apr-Oct). In India, the authors found wet-LN and dry-EN for the Jun-Sep period during the ENSO event year. Here, we have updated their study for North America and India using a different base-period (1973-2016) and a denser network of weather stations. The analysis also stratified ENSO years to include Central Pacific warming episodes. We also look at how distinct ENSO events affect the statistical distribution of surface air temperature across the CONUS and the Indian subcontinent. Finally, we discuss how these updated results can add value to real time forecast, using the ECMWF Seasonal Forecast System 4 and the NOAA CFSv2 system.