Abstract:
NASA is measuring Earth radiation budget under the Clouds and the Earth's Radiant Energy System (CERES) project. The instruments measure top-of-atmosphere broadband shortwaves and longwave radiances. Radiances are converted to irradiances to monitor energy budget of the Earth. The CERES project also estimates surface and atmosphere radiation budgets. This presentation provides a summary of how the radiation budget is changing in the last 25 years. The CERES data indicate that the net shortwave irradiance is increasing at a rate of 0.87 W m-2 dec-1 (increasing absorption) and net longwave irradiance is decreasing at a rate of 0.43 W m-2 dec-1. Nearly 90% of the radiant energy absorbed by the Earth heats oceans. Reanalysis data show that water vapor amount in the atmosphere is increasing nearly following the Clausius-Clapeyron relationship. However, net atmospheric cooling by radiation has no statistically significant trend, which has an implication to the global hydrological cycle.