Global distributions of multi-layer and multi-phase clouds and their cloud radiative effects

Abstract

Accurate and reliable knowledge about how clouds with various layers and phases are vertically and horizontally distributed over the globe has been lacking, which hinders the understanding about the impacts of various sub-types of clouds. This study utilizes the cloud retrieval products from the CloudSat/CALIPSO satellite observations from 2007 to 2010 to analyze the global distributions of multi-layer and multi-phase clouds as well as their cloud radiative effects (CRE) at the top of the atmosphere (TOA), at the surface, and within the atmosphere. We separate and aggregate cloudy satellite footprints by the number of cloud layers, and further consider the different combinations of cloud phases for the one-layer and multi-layer clouds. The globally averaged total cloud fraction is 72.52 %, with the one-layer and multi-layer clouds take up 49.39 % and 23.13 %, respectively. The one-layer water, ice, and mixed-phase cloud fractions are 21.93 %, 19.42 %, and 8.04 %, respectively. The two-layer and three-layer clouds most frequently occur with one ice layer at the top. The heights of cloud top and bottom as well as the cloud thickness are correspondingly derived for all sub-types of clouds. The globally averaged TOA net total CRE is −18.25 W m−2, with −14.63 W m−2 attributed to one-layer clouds and −3.62 W m−2 to multi-layer clouds. At the surface, the global annual average net total CRE is −25.01 W m−2, and the one-layer and multi-layer clouds contribute −17.24 W m−2 and −7.77 W m−2, respectively. Clouds generally exert a net heating effect within the atmosphere. Our findings provide valuable insights into the detailed layer and phase structures of clouds and could serve as the reference for evaluating cloud structure and radiation simulations.