Water Vapor, Clouds, and Saturation in the Tropical Tropopause Layer
Aura…AuraWater Vapor, Clouds, and…HomeAboutSpacecraft and InstrumentsWhy Aura?Science and DataEducationNewsroom A recent study used relative humidity (RHi) and cloud fraction (CF) observations from Aura’s Microwave Limb Sounder (MLS) and Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) instruments, in conjunction with observations from NASA and other field experiments and 1D and Lagrangian models. The study shows that the high humidity is due to both horizontal transport of air into colder regions, and slow ascent due to radiative heating, both of which lead to cloud formation. In contrast with some previous studies, the study also found that convection is not important in maintaining this high humidity environment. The radiative impacts of water vapor, the strongest greenhouse gas, are greatest at these altitudes. Better understanding of the processes controlling the humidity of this region is essential for understanding its role in climate feedbacks and for improving climate projections. MLS RHi (colors) and CALIOP CF (black contours). During DJF (December–February),...