View-angle dependent AIRS cloud radiances: Implications for tropical anvil structures

Tropical anvil clouds play important roles in redistributing energy, water in the troposphere. Interacting with dynamics at a wide range of spatial and temporal scales, they can become organized internally and form structured cells, transporting momentum vertically and laterally. To quantify small-scale structures inside cirrus and anvils, we study view-dependence of the cloud-induced radiance from Atmospheric Infrared Sounder (AIRS) using channels near CO2 absorption line. The analysis of tropical eight-year (30 degrees S-30 degrees N, 2003-2010) data suggests that AIRS east-views observe 10% more anvil clouds than west-views during day (13:30 LST), whereas east-views and west-views observe equally amount of clouds at midnight (1:30 LST). For entire tropical averages, AIRS oblique views observe more anvils than the nadir views, while the opposite is true for deep convective clouds. The dominance of cloudiness in the east-view cannot be explained by AIRS sampling and cloud microphysical differences. Tilted and banded anvil structures from convective scale to mesoscale are likely the cause of the observed view-dependent cloudiness, and gravity wave-cloud interaction is a plausible explanation for the observed structures. Effects of the tilted and banded cloud features need to be further evaluated and taken into account potentially in large-scale model parameterizations because of the vertical momentum transport through cloud wave breaking. Citation: Gong, J., and D. L. Wu (2011), View-angle dependent AIRS cloud radiances: Implications for tropical anvil structures, Geophys. Res. Lett., 38, L14802, doi:10.1029/2011GL047910.