Abstract: Sensitivities of Clouds and Atmospheric Energy Balance Simulation to Changes in Sea Surface Temperature over El Nino 3.4 Region

Amarech A. Addisuu and Titike K. Bahaga

This study presents a numerical sensitivity experiment, where the regional climate model is used over the El Niño 3.4 region to understand how changes in Sea Surface Temperature (SST) affect cloud properties and the atmospheric radiation budget. The Spatio-temporal variation of cloud radiative forcing response to control (CNTRL), warmer (SST+2K), and colder (SST-2K) SSTs are analyzed. It is shown that the SST+2K experiment led to a reduced low-level cloud fraction, while the SST-2K experiment caused an enhancement of cloud fraction in the lower troposphere. The decreased low-level cloud coverage in the SST+2K experiment acted to compensate for the improvement of high-cloud. The opposite occurred in the SST-2K experiment. Consistent with previous studies, both surface temperature and precipitation increase (decrease) as SST increases (decreases). Besides, changes in radiation on the top of the atmosphere are simulated, primarily because of changes in cloud coverage. The results have ramifications for the improvement of convective, radiative schemes, and regional climate simulations.

Atmospheric and surface energy balance, Cloud, Cloud radiative forcing, SST, Regional climate model.