A modeling study of the ENSO influence on the terrestrial energy profile in North America

The influence of the El Niño-Southern Oscillation (ENSO) on the terrestrial energy profile over North America is studied using a 15-yr model simulation. A large-area basin scale (LABs) land surface model is driven using the European Centre for Medium-Range Weather Forecasts 15-yr Re-Analyses (1979-93) dataset. It is found that the fluctuations of the soil temperature anomalies at different soil depths, in certain geographic regions, are correlated with the ENSO signal. In other words, the temperature anomaly can penetrate into the deeper soil layers due to the long wavelength associated with the ENSO signal. Using a simplified theoretical method, it is shown that the propagation of the ENSO-related long-wavelength temperature anomaly from the land surface to deep soil needs several months. In addition, it is found that the variation of the anomaly of the terrestrial enthalpy, consisting of the soil water enthalpy and soil particle enthalpy, in the shallow soil zone is dominated by the variation of the soil water storage, while that in the deep soil zone is determined by the variation of the soil temperature.