Diurnal Dependence of Boreal Winter Surface Air Temperature Responses to ENSO Across Global Land Areas

Abstract The El Niño‐Southern Oscillation (ENSO) significantly influences the seasonal‐to‐interannual variability of surface air temperature (SAT) over global land areas. Using the high temporal resolution ERA5 data set, we identify eight land regions where ENSO's impact on boreal winter SAT exhibits a pronounced diurnal dependence: southern North America (SNA), southern Africa (SA), western Australia (WA), southeastern South America (SESA), eastern Africa (EA), India (IN), Maritime Continent (MC), and southeastern China (SEC). In SNA, SA, and WA, ENSO effects are pronounced only during the afternoon, coinciding with daily SAT maxima. Conversely, in SESA, EA, IN, MC, and SEC, ENSO's influence is significant for seasonal‐mean SAT minima. These diurnal variations are primarily driven by the ENSO‐induced cloud‐solar radiation effect, which modulates daytime land surface heating. Additionally, temperature advection and downward longwave radiation anomalies associated with ENSO‐driven atmospheric changes contribute to the SAT responses in SESA, EA, IN, MC, and SEC.