Morphology of CALIPSO Laminar Cirrus and Its Role in the Cross-Tropopause Water Vapor Transport

Laminar cirrus is a unique type of ice cloud in the tropical tropopause layer (TTL) that can effectively store mass of water vapor (WV) as temperature changes. It dominates the TTL cloud fraction because its extensiveness and longevity, but the understanding of its formation mechanisms and roles in TTL dehydration and cross-tropopause WV transport remain lacking. The process of laminar cirrus is poorly represented in weather and climate models.

The Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) onboard the CALIPSO satellite has been continuously observing the laminar cirrus with unprecedented details since 2006. In this presentation, we will apply newly developed semi-automatic tool, called CALIPSO Interactive Digitization Interface (CINDI), to extract laminar characteristics (length, height, location, shape, mass, etc.) from CALIPSO Level-1 532 nm backscatter data.

With CINDI we are able to investigate for the first time the laminar cirrus global morphology on a monthly basis. Initial results show a diurnal difference in the occurring frequency and formation height of laminar cirrus in the TTL. By sorting laminar cirrus into isolated and convective cases, we are able to quantify their formation mechanisms and their roles on depleting the upper troposphere WV. We will present our study on the derived relationship between the total water mass of laminar cirrus and WV amount retrieved from Aura Microwave Limb Sounder (MLS) observations in proximity of the laminar cirrus. We will also show our analysis of inertial gravity waves and their impacts on laminar cirrus formation.