Choi, YS, Ho, CH (2006). Radiative effect of cirrus with different optical properties over the tropics in MODIS and CERES observations. GEOPHYSICAL RESEARCH LETTERS, 33(21), L21811.

The radiative effects of cirrus clouds are evaluated based on observations extending over a period of six years (2000-2005) from the Moderate Resolution Imaging Spectroradiometer (MODIS) and the Clouds and the Earth's Radiant Energy System (CERES) over the Tropics (25 degrees S-25 degrees N). The cloud radiative effect (CRE) shows a positive sign for optically thin cirrus (total-column cloud optical depth: tau < 10) and a negative sign for thicker clouds (t >= 10), regardless of the region and season. Since a considerable portion of tropical ice clouds consists in thin cirrus clouds (>60%), their net effective CRE (net CRE x cloud amount) is roughly twice as strong as that of thicker clouds; the modulation of the net radiative flux by variations in thin cirrus (particularly with 1 <= t < 9) dominates-up to 15 W m(-2)-that by thicker clouds. These results suggest that thin cirrus has a significant effect on the tropical energy balance.