Cirrus and water vapor transport in the tropical tropopause layer – Part 1: A specific case modeling study
- ISSN: 1680-7324
- DOI: 10.5194/acp-12-9799-2012
In a simulation of a tropical-tropopause-layer (TTL) cirrus forced\nby a large-scale equatorial Kelvin wave, the radiatively induced\nmesoscale dynamics of the cloud actively contributes to the transport\nof water vapor in the vertical direction. \n\n\nIn a typical TTL cirrus, the heating that results from absorption\nof radiation by ice crystals induces a mesoscale circulation. Advection\nof water vapor by the radiatively induced circulation leads to upward\nadvection of the cloudy air. Upward advection of the cloudy air is\nequivalent to upward transport of water vapor when the air above\nthe cloud is drier than the cloudy air. On the other hand, ice nucleation\nand depositional growth, followed by sedimentation and sublimation\nlead to downward transport of water vapor.\n\n\nUnder the conditions specific to our simulation, the upward transport\nof water vapor by the mesoscale circulation dominates the downward\ntransport by microphysical processes. The net result is upward transport\nof water vapor, which is equivalent to hydration of the lower stratosphere.\nSensitivity to model conditions and parameters will be discussed\nin a follow-up paper.